条件查询-分页查询-条件分页查询
条件查询（参考）
设计图：
参考代码：
创建数据表：
#创建班级表
create table classInfo
(
classId int primary key auto_increment,
className varchar(20)
)
insert into classInfo
(className)
select 'AAA01' UNION
select 'AAA02' UNION
select 'AAA03'
insert into classInfo
(className)
select 'AAA04' UNION
select 'AAA05' UNION
select 'AAA06' UNION
select 'AAA07'
select * from classInfo
drop table studentInfo
#创建学生信息表
create table studentInfo
(
studentId int primary key auto_increment,
name varchar(20),
sex char(1),
birthday date,
tall decimal(3,2),
classId int
)
insert into studentInfo
(name,sex,birthday,tall,classId)
select '张三','男','2001-01-01',1.7,1 union
select '李四','女','2002-01-01',1.7,2
select * from studentInfo
BaseDAO:
package com.util;
import javax.sql.DataSource;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.sql.*;
import java.util.*;
public class BaseDAO {
//四大金刚
//驱动类
private static final String DRIVER="com.mysql.cj.jdbc.Driver";
//连接地址
private static final String URL="jdbc:mysql://192.168.0.115:3306/0801_db?useSSL=false&characterEncoding=utf8&serverTimezone=Asia/Shanghai";
//用户名
private static final String USER="root";
//密码
private static final String PASSWORD="123456";
//获取连接
public static Connection getConnection(){
Connection con = null;
try{
//加载驱动类
Class.forName(DRIVER);
//获取连接
con = DriverManager.getConnection(URL,USER,PASSWORD);
}catch(Exception ex){
ex.printStackTrace();
}
return con;
}
//关闭数据库对象
public static void closeAll(Connection con,Statement st,ResultSet rs){
if(rs!=null){
try{
rs.close();
}catch(Exception ex){
ex.printStackTrace();
}
}
if(st!=null){
try{
st.close();
}catch(Exception ex){
ex.printStackTrace();
}
}
if(con!=null){
try{
con.close();
}catch(Exception ex){
ex.printStackTrace();
}
}
}
//通用设置参数方法
public static void setParams(PreparedStatement pst,Object[] params){
if(params==null){
return;
}
for(int i=0;i<params.length;i++){
try{
pst.setObject(i+1,params[i]);
}catch(Exception ex){
ex.printStackTrace();
}
}
}
//通用增删改
public static int executeUpdate(String sql,Object[] params){
Connection con = null;
PreparedStatement pst = null;
int res = -1;
try{
//获取连接
con = getConnection();
//创建预编译命令执行对象
pst = con.prepareStatement(sql);
//设置参数
setParams(pst,params);
//执行
res = pst.executeUpdate();
}catch(Exception ex){
ex.printStackTrace();
}finally{
closeAll(con,pst,null);
}
return res;
}
//通用查询
public static List<Map<String,Object>> executeQuery(String sql,Object[] params) {
List<Map<String,Object>> rows = new ArrayList<>();
Connection con = null;
PreparedStatement pst = null;
ResultSet rs = null;
try{
//获取连接
con = getConnection();
//获取命令对象
pst = con.prepareStatement(sql);
//设置参数
setParams(pst,params);
//执行查询
rs = pst.executeQuery();
//通过rs获取结果集的结构信息
ResultSetMetaData rsmd = rs.getMetaData();
//获取结果集的列数
int colCount = rsmd.getColumnCount();
//遍历查询结果，并封装到List<Map>中
while(rs.next()){
//用Map存储当前行的各个列数据
Map<String,Object> map = new HashMap<>();
//循环获取每一列的信息
for(int i=1;i<=colCount;i++){
//获取列名(使用rsmd)
String colName = rsmd.getColumnLabel(i);
//获取列值(使用rs)
Object colVal = rs.getObject(i);
//将当前列存储到map中
map.put(colName,colVal);
}
//将遍历的当前行的数据存储到List中
rows.add(map);
}
}catch(Exception ex){
ex.printStackTrace();
}finally{
closeAll(con,pst,rs);
}
return rows;
}
}
ClassInfo:
package com.entity;
/**
* @author: hy
* @create: 2022-08-01 10:52:43
*/
public class ClassInfo {
private Integer classId;
private String className;
public ClassInfo() {
}
public ClassInfo(Integer classId, String className) {
this.classId = classId;
this.className = className;
}
public ClassInfo(String className) {
this.className = className;
}
public Integer getClassId() {
return classId;
}
public void setClassId(Integer classId) {
this.classId = classId;
}
public String getClassName() {
return className;
}
public void setClassName(String className) {
this.className = className;
}
@Override
public String toString() {
return "ClassInfo{" +
"classId=" + classId +
", className='" + className + '\'' +
'}';
}
}
IClassInfoDAO:
package com.dao;
import com.entity.ClassInfo;
import java.util.List;
import java.util.Map;
public interface IClassInfoDAO {
/**
* 查询所有
* @return
*/
List<Map<String,Object>> listAll();
//带条件查询
List<Map<String,Object>> listByCon(String searchClassName);
ClassInfo getByClassId(Integer classId);
int insert(ClassInfo classInfo);
int update(ClassInfo classInfo);
int delete(Integer classId);
}
ClassInfoDAOImpl:
package com.dao.impl;
import com.dao.IClassInfoDAO;
import com.entity.ClassInfo;
import com.mysql.cj.util.StringUtils;
import com.util.BaseDAO;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
/**
* @author: hy
* @create: 2022-08-01 10:54:26
*/
public class ClassInfoDAOImpl implements IClassInfoDAO {
@Override
public List<Map<String, Object>> listAll() {
String sql ="select classId,className from classInfo ";
return BaseDAO.executeQuery(sql,null);
}
@Override
public List<Map<String, Object>> listByCon(String searchClassName) {
//where sql语句
StringBuilder whereSql = new StringBuilder();
//sql中的参数
List<Object> params = new ArrayList<>();
//如果条件不为空，则拼接where ，同时添加参数
if(!StringUtils.isNullOrEmpty(searchClassName)){
whereSql.append(" where className like ? ");
params.add("%"+searchClassName+"%");
}
String sql ="select classId,className " +
" from classInfo " + whereSql;
return BaseDAO.executeQuery(sql,params.toArray());
}
/**
* 根据编号查询数据对象
* @param classId
* @return
*/
@Override
public ClassInfo getByClassId(Integer classId) {
String sql ="select classId,className from classInfo " +
" where classId = ? ";
Object[] params = {classId};
List<Map<String,Object>> rows = BaseDAO.executeQuery(sql,params);
if(rows.size()>0){
Map<String,Object> map = rows.get(0);
ClassInfo c = new ClassInfo(
(Integer)map.get("classId"),
(String)map.get("className")
);
System.out.println(c);
return c;
}
return null;
}
@Override
public int insert(ClassInfo classInfo) {
String sql = "insert into classInfo" +
" (className)" +
" values" +
" (?)";
Object[] params = {classInfo.getClassName()};
return BaseDAO.executeUpdate(sql,params);
}
@Override
public int update(ClassInfo classInfo) {
String sql = "update classInfo " +
" set className = ? " +
" where classId = ? ";
Object[] params = {
classInfo.getClassName(),
classInfo.getClassId()
};
return BaseDAO.executeUpdate(sql,params);
}
@Override
public int delete(Integer classId) {
String sql = "delete from classInfo where classId = ? ";
Object[] params = {classId};
return BaseDAO.executeUpdate(sql,params);
}
}
IClassInfoService:
package com.service;
import com.entity.ClassInfo;
import java.util.List;
import java.util.Map;
public interface IClassInfoService {
//查询所有班级数据
List<Map<String,Object>> listAll();
//带条件查询
List<Map<String,Object>> listByCon(String searchClassName);
//根据编号查询班级对象
ClassInfo getByClassId(Integer classId);
int insert(ClassInfo classInfo);
int update(ClassInfo classInfo);
int delete(Integer classId);
}
ClassInfoServiceImpl:
package com.service.impl;
import com.dao.IClassInfoDAO;
import com.dao.impl.ClassInfoDAOImpl;
import com.entity.ClassInfo;
import com.service.IClassInfoService;
import java.util.List;
import java.util.Map;
/**
* @author: hy
* @create: 2022-08-01 10:55:41
*/
public class ClassInfoServiceImpl implements IClassInfoService {
//数据访问层对象
private IClassInfoDAO classInfoDAO = new ClassInfoDAOImpl();
@Override
public List<Map<String, Object>> listAll() {
return classInfoDAO.listAll();
}
@Override
public List<Map<String, Object>> listByCon(String searchClassName) {
return classInfoDAO.listByCon(searchClassName);
}
@Override
public ClassInfo getByClassId(Integer classId) {
return classInfoDAO.getByClassId(classId);
}
@Override
public int insert(ClassInfo classInfo) {
return classInfoDAO.insert(classInfo);
}
@Override
public int update(ClassInfo classInfo) {
return classInfoDAO.update(classInfo);
}
@Override
public int delete(Integer classId) {
return classInfoDAO.delete(classId);
}
}
ClassInfoServlet:
package com.servlet;
import com.entity.ClassInfo;
import com.service.IClassInfoService;
import com.service.impl.ClassInfoServiceImpl;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.List;
import java.util.Map;
/**
* @author: hy
* @create: 2022-08-01 10:57:07
*/
@WebServlet(urlPatterns = "/ClassInfoServlet/*")
public class ClassInfoServlet extends HttpServlet {
//定义业务层对象
IClassInfoService classInfoService = new ClassInfoServiceImpl();
@Override
protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//设置请求和响应对象的编码
req.setCharacterEncoding("utf-8");
resp.setContentType("text/html;charset=utf-8");
//获取请求路径，截取请求处理的字符串
// uri: /lesson0801_crud/ClassInfoServlet/query
String uri = req.getRequestURI();
// process: query
String process = uri.substring(uri.lastIndexOf("/")+1);
//针对增删改查的请求做处理
switch (process){
case "query":
this.query(req,resp); //查询处理
break;
case "toAdd":
this.toAdd(req,resp); //跳转到添加
break;
case "add":
this.add(req,resp); //添加处理
break;
case "toUpdate":
this.toUpdate(req,resp);//跳转到修改
break;
case "update":
this.update(req,resp);//修改处理
break;
case "delete":
this.delete(req,resp); //删除处理
break;
}
}
private void delete(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//获取班级编号
Integer classId = Integer.parseInt(req.getParameter("classId"));
int count = classInfoService.delete(classId);
if(count==1){
//删除成功，重新显示
this.query(req,resp);
}else{
//失败，跳转到失败页面
}
}
private void update(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//获取提交的表单数据
Integer classId = Integer.parseInt(req.getParameter("classId"));
String className = req.getParameter("className");
ClassInfo classInfo = new ClassInfo(classId,className);
//调用修改
int count = classInfoService.update(classInfo);
if(count==1){
//修改成功，则重新显示
this.query(req,resp);
}else{
//跳转到失败
}
}
private void toUpdate(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//获取要修改的编号:如果此时没有获取到编号，会爆出数字格式异常
System.out.println("classId:"+req.getParameter("classId"));
Integer classId = Integer.parseInt(req.getParameter("classId"));
//根据编号，查询要修改的班级对象
ClassInfo classInfo = classInfoService.getByClassId(classId);
//将要修改的班级对象，存储到request中，带到页面上，呈现出来
req.setAttribute("classInfo",classInfo);
//跳转到修改页面
req.getRequestDispatcher("/classUpdate.jsp").forward(req,resp);
}
/**
* 添加班级数据
* @param req
* @param resp
*/
private void add(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//获取添加页面提交的数据
String className = req.getParameter("className");
ClassInfo ci = new ClassInfo(className);
//构建班级对象
int count = classInfoService.insert(ci);
if(count==1){
//添加成功，跳转到查询页面
//resp.sendRedirect(req.getContextPath()+"/ClassInfoServlet/query");
//直接调用查询逻辑
this.query(req,resp);
}else{
//跳转到失败页面
System.out.println("添加记录不等于1，失败了......");
}
}
/**
* 跳转到添加页面
* @param req
* @param resp
*/
private void toAdd(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
req.getRequestDispatcher("/classAdd.jsp").forward(req,resp);
}
/**
* 查询处理
* @param req
* @param resp
*/
private void query(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//获取查询条件
String searchClassName = req.getParameter("searchClassName");
//List<Map<String,Object>> classInfoList = classInfoService.listAll();
//条件查询
List<Map<String, Object>> classInfoList = classInfoService.listByCon(searchClassName);
req.setAttribute("classInfoList",classInfoList);
//设置查询条件，存储到req,返回到页面
//req.setAttribute("searchClassName",searchClassName);
req.getRequestDispatcher("/classList.jsp").forward(req,resp);
}
}
index.jsp:
<%--
Created by IntelliJ IDEA.
User: henry
Date: 2022/8/1
Time: 9:56
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>$Title$</title>
</head>
<body>
<a href="${pageContext.request.contextPath}/StudentInfoServlet">学生信息</a>
<a href="${pageContext.request.contextPath}/ClassInfoServlet/query">班级信息</a>
</body>
</html>
classList.jsp:
<%--
Created by IntelliJ IDEA.
User: henry
Date: 2022/8/1
Time: 10:58
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@taglib prefix="c" uri="http://java.sun.com/jstl/core_rt" %>
<html>
<head>
<title>Title</title>
</head>
<body>
班级数据:${classInfoList}
<hr/>
<table border="1" align="center" width="50%">
<tr>
<td colspan="3">
<a href="${pageContext.request.contextPath}/ClassInfoServlet/toAdd">添加</a>
</td>
</tr>
<tr>
<td colspan="3">
<form id="searchFrm" action="" method="get">
班级:
<!--param: el 隐式对象，能够存储页面提交到服务器端的参数数据-->
<input type="text" id="searchCls" name="searchClassName" value="${param.searchClassName}"/>
<input type="submit" value="搜索"/>
</form>
</td>
</tr>
<tr>
<th>班级编号</th>
<th>班级名称</th>
<th>操作</th>
</tr>
<!--items:数据集合
注意:items关联的一定是个对象集合(el表达式)，不是纯粹的字符串
var:用于定义变量名字，临时存储遍历集合中的某个对象
-->
<c:forEach items="${classInfoList}" var="c">
<tr>
<td>${c.classId}</td>
<td>${c.className}</td>
<td>
<a href="${pageContext.request.contextPath}/ClassInfoServlet/toUpdate?classId=${c.classId}">修改</a>
<a href="${pageContext.request.contextPath}/ClassInfoServlet/delete?classId=${c.classId}"
onclick="return confirm('确定要删除么?')">
删除
</a>
</td>
</tr>
</c:forEach>
</table>
</body>
</html>
classAdd.jsp:
<%--
Created by IntelliJ IDEA.
User: henry
Date: 2022/8/1
Time: 11:20
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>Title</title>
</head>
<body>
<form method="post" action="${pageContext.request.contextPath}/ClassInfoServlet/add">
<table border="1" align="center">
<tr>
<td>班级名称</td>
<td>
<input type="text" name="className"/>
</td>
</tr>
<tr>
<td></td>
<td>
<input type="submit" value="添加"/>
</td>
</tr>
</table>
</form>
</body>
</html>
classUpdate.jsp:
<%--
Created by IntelliJ IDEA.
User: henry
Date: 2022/8/1
Time: 11:20
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>Title</title>
</head>
<body>
${classInfo}
<hr/>
<form method="post" action="${pageContext.request.contextPath}/ClassInfoServlet/update">
<table border="1" align="center">
<!--type=hidden : 隐藏文本框-->
<input type="hidden" name="classId" value="${classInfo.classId}"/>
<tr>
<td>班级名称</td>
<td>
<input type="text" name="className" value="${classInfo.className}"/>
</td>
</tr>
<tr>
<td></td>
<td>
<input type="submit" value="修改"/>
</td>
</tr>
</table>
</form>
</body>
</html>
// A code block
var foo = 'bar';
// A code block
var foo = 'bar';
分页查询(参考）
参考代码：
BaseDAO:
package com.util;
import javax.sql.DataSource;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.sql.*;
import java.util.*;
public class BaseDAO {
//四大金刚
//驱动类
private static final String DRIVER="com.mysql.cj.jdbc.Driver";
//连接地址
private static final String URL="jdbc:mysql://192.168.0.115:3306/0801_db?useSSL=false&characterEncoding=utf8&serverTimezone=Asia/Shanghai";
//用户名
private static final String USER="root";
//密码
private static final String PASSWORD="123456";
//获取连接
public static Connection getConnection(){
Connection con = null;
try{
//加载驱动类
Class.forName(DRIVER);
//获取连接
con = DriverManager.getConnection(URL,USER,PASSWORD);
}catch(Exception ex){
ex.printStackTrace();
}
return con;
}
//关闭数据库对象
public static void closeAll(Connection con,Statement st,ResultSet rs){
if(rs!=null){
try{
rs.close();
}catch(Exception ex){
ex.printStackTrace();
}
}
if(st!=null){
try{
st.close();
}catch(Exception ex){
ex.printStackTrace();
}
}
if(con!=null){
try{
con.close();
}catch(Exception ex){
ex.printStackTrace();
}
}
}
//通用设置参数方法
public static void setParams(PreparedStatement pst,Object[] params){
if(params==null){
return;
}
for(int i=0;i<params.length;i++){
try{
pst.setObject(i+1,params[i]);
}catch(Exception ex){
ex.printStackTrace();
}
}
}
//通用增删改
public static int executeUpdate(String sql,Object[] params){
Connection con = null;
PreparedStatement pst = null;
int res = -1;
try{
//获取连接
con = getConnection();
//创建预编译命令执行对象
pst = con.prepareStatement(sql);
//设置参数
setParams(pst,params);
//执行
res = pst.executeUpdate();
}catch(Exception ex){
ex.printStackTrace();
}finally{
closeAll(con,pst,null);
}
return res;
}
//获取总记录数的查询:select count(*) from ..
public static int getTotal(String sql,Object[] params){
int total = 0;
Connection con = null;
PreparedStatement pst = null;
ResultSet rs = null;
try{
con = getConnection();
pst = con.prepareStatement(sql);
setParams(pst,params);
rs = pst.executeQuery();
//判断是否查询除了一个记录
if(rs.next()){
total = rs.getInt(1);
}
}catch (Exception ex){
ex.printStackTrace();
}finally {
closeAll(con,pst,rs);
}
return total;
}
//通用查询
public static List<Map<String,Object>> executeQuery(String sql,Object[] params) {
List<Map<String,Object>> rows = new ArrayList<>();
Connection con = null;
PreparedStatement pst = null;
ResultSet rs = null;
try{
//获取连接
con = getConnection();
//获取命令对象
pst = con.prepareStatement(sql);
//设置参数
setParams(pst,params);
//执行查询
rs = pst.executeQuery();
//通过rs获取结果集的结构信息
ResultSetMetaData rsmd = rs.getMetaData();
//获取结果集的列数
int colCount = rsmd.getColumnCount();
//遍历查询结果，并封装到List<Map>中
while(rs.next()){
//用Map存储当前行的各个列数据
Map<String,Object> map = new HashMap<>();
//循环获取每一列的信息
for(int i=1;i<=colCount;i++){
//获取列名(使用rsmd)
String colName = rsmd.getColumnLabel(i);
//获取列值(使用rs)
Object colVal = rs.getObject(i);
//将当前列存储到map中
map.put(colName,colVal);
}
//将遍历的当前行的数据存储到List中
rows.add(map);
}
}catch(Exception ex){
ex.printStackTrace();
}finally{
closeAll(con,pst,rs);
}
return rows;
}
}
ClassInfo：
package com.entity;
/**
* @author: hy
* @create: 2022-08-01 10:52:43
*/
public class ClassInfo {
private Integer classId;
private String className;
public ClassInfo() {
}
public ClassInfo(Integer classId, String className) {
this.classId = classId;
this.className = className;
}
public ClassInfo(String className) {
this.className = className;
}
public Integer getClassId() {
return classId;
}
public void setClassId(Integer classId) {
this.classId = classId;
}
public String getClassName() {
return className;
}
public void setClassName(String className) {
this.className = className;
}
@Override
public String toString() {
return "ClassInfo{" +
"classId=" + classId +
", className='" + className + '\'' +
'}';
}
}
PageData：
package com.entity;
import java.util.List;
/**
* 用于封装分页数据的实体类
* @author: hy
* @create: 2022-08-02 11:05:21
*/
public class PageData {
//1.当前页码
private Integer pageNo;
//2.每页条数
private Integer pageSize;
//3.总记录数
private Integer totalCount;
//4.总页数
private Integer totalPage;
//5.当前页的记录
private Object data;
public PageData() {
}
public PageData(Integer pageNo, Integer pageSize, Integer totalCount, Integer totalPage, Object data) {
this.pageNo = pageNo;
this.pageSize = pageSize;
this.totalCount = totalCount;
this.totalPage = totalPage;
this.data = data;
}
public Integer getPageNo() {
return pageNo;
}
public void setPageNo(Integer pageNo) {
this.pageNo = pageNo;
}
public Integer getPageSize() {
return pageSize;
}
public void setPageSize(Integer pageSize) {
this.pageSize = pageSize;
}
public Integer getTotalCount() {
return totalCount;
}
public void setTotalCount(Integer totalCount) {
this.totalCount = totalCount;
}
public Integer getTotalPage() {
return totalPage;
}
public void setTotalPage(Integer totalPage) {
this.totalPage = totalPage;
}
public Object getData() {
return data;
}
public void setData(Object data) {
this.data = data;
}
@Override
public String toString() {
return "PageData{" +
"pageNo=" + pageNo +
", pageSize=" + pageSize +
", totalCount=" + totalCount +
", totalPage=" + totalPage +
", data=" + data +
'}';
}
}
IClassInfoDAO：
package com.dao;
import com.entity.ClassInfo;
import com.entity.PageData;
import java.util.List;
import java.util.Map;
public interface IClassInfoDAO {
/**
* 查询所有
* @return
*/
List<Map<String,Object>> listAll();
//带条件查询
List<Map<String,Object>> listByCon(String searchClassName);
//分页查询:pageNo 当前页码 pagesize 每页几条
PageData listByPage(Integer pageNo,Integer pageSize);
ClassInfo getByClassId(Integer classId);
int insert(ClassInfo classInfo);
int update(ClassInfo classInfo);
int delete(Integer classId);
}
ClassInfoDAOImpl：
package com.dao.impl;
import com.dao.IClassInfoDAO;
import com.entity.ClassInfo;
import com.entity.PageData;
import com.mysql.cj.util.StringUtils;
import com.util.BaseDAO;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
/**
* @author: hy
* @create: 2022-08-01 10:54:26
*/
public class ClassInfoDAOImpl implements IClassInfoDAO {
@Override
public List<Map<String, Object>> listAll() {
String sql ="select classId,className from classInfo ";
return BaseDAO.executeQuery(sql,null);
}
@Override
public List<Map<String, Object>> listByCon(String searchClassName) {
//where sql语句
StringBuilder whereSql = new StringBuilder();
//sql中的参数
List<Object> params = new ArrayList<>();
//如果条件不为空，则拼接where ，同时添加参数
if(!StringUtils.isNullOrEmpty(searchClassName)){
whereSql.append(" where className like ? ");
params.add("%"+searchClassName+"%");
}
String sql ="select classId,className " +
" from classInfo " + whereSql;
return BaseDAO.executeQuery(sql,params.toArray());
}
/**
* 分页查询数据
* @param pageNo
* @param pageSize
* @return
*/
@Override
public PageData listByPage(Integer pageNo, Integer pageSize) {
//查询总记录数
String totalSql = "select count(*) from classInfo ";
Integer totalCount = BaseDAO.getTotal(totalSql,null);
//获取总页数: 10 2 3
Integer totalPage = totalCount%pageSize==0?totalCount/pageSize
:totalCount/pageSize+1;
// limit ?,?：从哪一条之后，取若干条
String sql ="select classId,className " +
" from classInfo " +
" order by classId " +
" limit ?,? ";
//计算分页开始位置
int start = (pageNo-1)*pageSize;
//构建分页参数
Object[] params = {
start,pageSize
};
//分页查询：查询当前页若干条的记录数
List<Map<String,Object>> rows = BaseDAO.executeQuery(sql,params);
//将5项数据封装到PageData中
PageData pd = new PageData();
pd.setPageNo(pageNo); //当前页码
pd.setPageSize(pageSize); //每页记录数
pd.setTotalCount(totalCount); //总记录数
pd.setTotalPage(totalPage); //总页数
pd.setData(rows); //当前页记录
return pd;
}
/**
* 根据编号查询数据对象
* @param classId
* @return
*/
@Override
public ClassInfo getByClassId(Integer classId) {
String sql ="select classId,className from classInfo " +
" where classId = ? ";
Object[] params = {classId};
List<Map<String,Object>> rows = BaseDAO.executeQuery(sql,params);
if(rows.size()>0){
Map<String,Object> map = rows.get(0);
ClassInfo c = new ClassInfo(
(Integer)map.get("classId"),
(String)map.get("className")
);
System.out.println(c);
return c;
}
return null;
}
@Override
public int insert(ClassInfo classInfo) {
String sql = "insert into classInfo" +
" (className)" +
" values" +
" (?)";
Object[] params = {classInfo.getClassName()};
return BaseDAO.executeUpdate(sql,params);
}
@Override
public int update(ClassInfo classInfo) {
String sql = "update classInfo " +
" set className = ? " +
" where classId = ? ";
Object[] params = {
classInfo.getClassName(),
classInfo.getClassId()
};
return BaseDAO.executeUpdate(sql,params);
}
@Override
public int delete(Integer classId) {
String sql = "delete from classInfo where classId = ? ";
Object[] params = {classId};
return BaseDAO.executeUpdate(sql,params);
}
}
IClassInfoService：
package com.service;
import com.entity.ClassInfo;
import com.entity.PageData;
import java.util.List;
import java.util.Map;
public interface IClassInfoService {
//查询所有班级数据
List<Map<String,Object>> listAll();
//带条件查询
List<Map<String,Object>> listByCon(String searchClassName);
//分页查询:pageNo 当前页码 pagesize 每页几条
PageData listByPage(Integer pageNo, Integer pageSize);
//根据编号查询班级对象
ClassInfo getByClassId(Integer classId);
int insert(ClassInfo classInfo);
int update(ClassInfo classInfo);
int delete(Integer classId);
}
ClassInfoServiceImpl：
package com.service.impl;
import com.dao.IClassInfoDAO;
import com.dao.impl.ClassInfoDAOImpl;
import com.entity.ClassInfo;
import com.entity.PageData;
import com.service.IClassInfoService;
import java.util.List;
import java.util.Map;
/**
* @author: hy
* @create: 2022-08-01 10:55:41
*/
public class ClassInfoServiceImpl implements IClassInfoService {
//数据访问层对象
private IClassInfoDAO classInfoDAO = new ClassInfoDAOImpl();
@Override
public List<Map<String, Object>> listAll() {
return classInfoDAO.listAll();
}
@Override
public List<Map<String, Object>> listByCon(String searchClassName) {
return classInfoDAO.listByCon(searchClassName);
}
@Override
public PageData listByPage(Integer pageNo, Integer pageSize) {
return classInfoDAO.listByPage(pageNo,pageSize);
}
@Override
public ClassInfo getByClassId(Integer classId) {
return classInfoDAO.getByClassId(classId);
}
@Override
public int insert(ClassInfo classInfo) {
return classInfoDAO.insert(classInfo);
}
@Override
public int update(ClassInfo classInfo) {
return classInfoDAO.update(classInfo);
}
@Override
public int delete(Integer classId) {
return classInfoDAO.delete(classId);
}
}
ClassInfoServlet ：
package com.servlet;
import com.entity.ClassInfo;
import com.entity.PageData;
import com.service.IClassInfoService;
import com.service.impl.ClassInfoServiceImpl;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.List;
import java.util.Map;
/**
* @author: hy
* @create: 2022-08-01 10:57:07
*/
@WebServlet(urlPatterns = "/ClassInfoServlet/*")
public class ClassInfoServlet extends HttpServlet {
//定义业务层对象
IClassInfoService classInfoService = new ClassInfoServiceImpl();
@Override
protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//设置请求和响应对象的编码
req.setCharacterEncoding("utf-8");
resp.setContentType("text/html;charset=utf-8");
//获取请求路径，截取请求处理的字符串
// uri: /lesson0801_crud/ClassInfoServlet/query
String uri = req.getRequestURI();
// process: query
String process = uri.substring(uri.lastIndexOf("/")+1);
//针对增删改查的请求做处理
switch (process){
case "query":
this.query(req,resp); //查询处理
break;
case "queryByPage":
this.queryByPage(req,resp);
break;
case "toAdd":
this.toAdd(req,resp); //跳转到添加
break;
case "add":
this.add(req,resp); //添加处理
break;
case "toUpdate":
this.toUpdate(req,resp);//跳转到修改
break;
case "update":
this.update(req,resp);//修改处理
break;
case "delete":
this.delete(req,resp); //删除处理
break;
}
}
//分页查询
private void queryByPage(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//获取当前页页码
Integer pageNo = 1;
Integer pageSize = 3;
if(req.getParameter("pageNo")!=null){
pageNo = Integer.parseInt(req.getParameter("pageNo"));
}
if(req.getParameter("pageSize")!=null){
pageSize = Integer.parseInt(req.getParameter("pageSize"));
}
//获取查询条件
String searchClassName = req.getParameter("searchClassName");
System.out.println("searchClassName:"+searchClassName);
System.out.println("pageNo:"+pageNo);
System.out.println("pageSize:"+pageSize);
//调用分页查询
PageData pageData = classInfoService.listByPage(pageNo, pageSize);
System.out.println("pagedata:"+pageData);
//存储到req，跳转到页面
req.setAttribute("pd",pageData);
req.getRequestDispatcher("/classList.jsp").forward(req,resp);
}
private void delete(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//获取班级编号
Integer classId = Integer.parseInt(req.getParameter("classId"));
int count = classInfoService.delete(classId);
if(count==1){
//删除成功，重新显示
this.query(req,resp);
}else{
//失败，跳转到失败页面
}
}
private void update(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//获取提交的表单数据
Integer classId = Integer.parseInt(req.getParameter("classId"));
String className = req.getParameter("className");
ClassInfo classInfo = new ClassInfo(classId,className);
//调用修改
int count = classInfoService.update(classInfo);
if(count==1){
//修改成功，则重新显示
this.query(req,resp);
}else{
//跳转到失败
}
}
private void toUpdate(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//获取要修改的编号:如果此时没有获取到编号，会爆出数字格式异常
System.out.println("classId:"+req.getParameter("classId"));
Integer classId = Integer.parseInt(req.getParameter("classId"));
//根据编号，查询要修改的班级对象
ClassInfo classInfo = classInfoService.getByClassId(classId);
//将要修改的班级对象，存储到request中，带到页面上，呈现出来
req.setAttribute("classInfo",classInfo);
//跳转到修改页面
req.getRequestDispatcher("/classUpdate.jsp").forward(req,resp);
}
/**
* 添加班级数据
* @param req
* @param resp
*/
private void add(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//获取添加页面提交的数据
String className = req.getParameter("className");
ClassInfo ci = new ClassInfo(className);
//构建班级对象
int count = classInfoService.insert(ci);
if(count==1){
//添加成功，跳转到查询页面
//resp.sendRedirect(req.getContextPath()+"/ClassInfoServlet/query");
//直接调用查询逻辑
this.query(req,resp);
}else{
//跳转到失败页面
System.out.println("添加记录不等于1，失败了......");
}
}
/**
* 跳转到添加页面
* @param req
* @param resp
*/
private void toAdd(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
req.getRequestDispatcher("/classAdd.jsp").forward(req,resp);
}
/**
* 查询处理
* @param req
* @param resp
*/
private void query(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//获取查询条件
String searchClassName = req.getParameter("searchClassName");
//List<Map<String,Object>> classInfoList = classInfoService.listAll();
//条件查询
List<Map<String, Object>> classInfoList = classInfoService.listByCon(searchClassName);
req.setAttribute("classInfoList",classInfoList);
//设置查询条件，存储到req,返回到页面
//req.setAttribute("searchClassName",searchClassName);
req.getRequestDispatcher("/classList.jsp").forward(req,resp);
}
}
index.jsp:
<%--
Created by IntelliJ IDEA.
User: henry
Date: 2022/8/1
Time: 9:56
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>$Title$</title>
</head>
<body>
<a href="${pageContext.request.contextPath}/StudentInfoServlet">学生信息</a>
<a href="${pageContext.request.contextPath}/ClassInfoServlet/query">班级信息</a>
<a href="${pageContext.request.contextPath}/ClassInfoServlet/queryByPage">班级分页</a>
</body>
</html>
classList.jsp:
<%--
Created by IntelliJ IDEA.
User: henry
Date: 2022/8/1
Time: 10:58
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@taglib prefix="c" uri="http://java.sun.com/jstl/core_rt" %>
<html>
<head>
<title>Title</title>
</head>
<body>
班级数据:${classInfoList}
<hr/>
<table border="1" align="center" width="50%">
<tr>
<td colspan="3">
<a href="${pageContext.request.contextPath}/ClassInfoServlet/toAdd">添加</a>
</td>
</tr>
<tr>
<td colspan="3">
<form id="searchFrm" action="${pageContext.request.contextPath}/ClassInfoServlet/queryByPage" method="get">
班级:
<!--param: el 隐式对象，能够存储页面提交到服务器端的参数数据-->
<input type="text" id="searchCls" name="searchClassName" value="${param.searchClassName}"/>
<input type="submit" value="搜索"/>
<!--不管是条件查询，还是分页处理，需要将两种情况的数据放在一起条件-->
<input type="hidden" name="pageNo" id="pageNo"/>
<input type="hidden" name="pageSize" id="pageSize"/>
</form>
</td>
</tr>
<tr>
<th>班级编号</th>
<th>班级名称</th>
<th>操作</th>
</tr>
<!--items:数据集合
注意:items关联的一定是个对象集合(el表达式)，不是纯粹的字符串
var:用于定义变量名字，临时存储遍历集合中的某个对象
-->
<c:forEach items="${pd.data}" var="c">
<tr>
<td>${c.classId}</td>
<td>${c.className}</td>
<td>
<a href="${pageContext.request.contextPath}/ClassInfoServlet/toUpdate?classId=${c.classId}">修改</a>
<a href="${pageContext.request.contextPath}/ClassInfoServlet/delete?classId=${c.classId}"
onclick="return confirm('确定要删除么?')">
删除
</a>
</td>
</tr>
</c:forEach>
<!--生成分页信息-->
<tr>
<td colspan="3">
当前第${pd.pageNo}页/共${pd.totalPage}页 |
总记录数:${pd.totalCount} |
<c:forEach begin="1" end="${pd.totalPage}" var="i">
<c:if test="${pd.pageNo==i}">
<span>${i}</span>
</c:if>
<c:if test="${pd.pageNo!=i}">
<a href="javascript:jumpPage(${i})">${i}</a>
</c:if>
</c:forEach> |
每页
<select name="pageSize" id="ps" onchange="changePageSize(this.value)">
<option value="2" ${pd.pageSize==2?'selected':''}>2</option>
<option value="3" ${pd.pageSize==3?'selected':''}>3</option>
<option value="5" ${pd.pageSize==5?'selected':''}>5</option>
</select>
条
</td>
</tr>
</table>
<script type="text/javascript">
//切换每页记录数
function changePageSize(size){
window.location.href="${pageContext.request.contextPath}/ClassInfoServlet/queryByPage?pageSize="+size;
}
//跳转分页
function jumpPage(no){
//设置查询表单中的分页页码
document.getElementById("pageNo").value=no;
//设置查询表单中的每页记录数
document.getElementById("pageSize").value=ps.value;
//提交表单
searchFrm.submit();
}
</script>
</body>
</html>
classAdd.jsp:
<%--
Created by IntelliJ IDEA.
User: henry
Date: 2022/8/1
Time: 11:20
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>Title</title>
</head>
<body>
<form method="post" action="${pageContext.request.contextPath}/ClassInfoServlet/add">
<table border="1" align="center">
<tr>
<td>班级名称</td>
<td>
<input type="text" name="className"/>
</td>
</tr>
<tr>
<td></td>
<td>
<input type="submit" value="添加"/>
</td>
</tr>
</table>
</form>
</body>
</html>
classUpdate.jsp:
<%--
Created by IntelliJ IDEA.
User: henry
Date: 2022/8/1
Time: 11:20
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>Title</title>
</head>
<body>
${classInfo}
<hr/>
<form method="post" action="${pageContext.request.contextPath}/ClassInfoServlet/update">
<table border="1" align="center">
<!--type=hidden : 隐藏文本框-->
<input type="hidden" name="classId" value="${classInfo.classId}"/>
<tr>
<td>班级名称</td>
<td>
<input type="text" name="className" value="${classInfo.className}"/>
</td>
</tr>
<tr>
<td></td>
<td>
<input type="submit" value="修改"/>
</td>
</tr>
</table>
</form>
</body>
</html>
1.条件查询(标准)
设计图：
实现效果：
代码整体布局：（class部分）
代码：
创建数据库/表格：
#创建数据库
create database 70730_db
default character set utf8mb4 #设置字符集
default collate utf8mb4_general_ci #设置排序规则
#创建班级表
create table class
(
classId int primary key auto_increment,
className varchar(20)
);
insert into class
(className)
values
('菜鸟1班'),
('菜鸟2班'),
('菜鸟3班'),
('菜鸟4班'),
('菜鸡1班'),
('菜鸡2班'),
('菜鸡3班'),
('菜鸡4班');
select * from class;
BaseDAO：
package com.util;
import java.sql.*;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
public class BaseDAO {
//四大金刚
//驱动类
private static final String DRIVER="com.mysql.cj.jdbc.Driver";
//连接地址
private static final String URL="jdbc:mysql://localhost:3306/70730_db?useSSL=false&characterEncoding=utf8&serverTimezone=Asia/Shanghai";
//用户名
private static final String USER="root";
//密码
private static final String PASSWORD="123456";
//获取连接
public static Connection getConnection(){
Connection con = null;
try{
//加载驱动类
Class.forName(DRIVER);
//获取连接
con = DriverManager.getConnection(URL,USER,PASSWORD);
}catch(Exception ex){
ex.printStackTrace();
}
return con;
}
//关闭数据库对象
public static void closeAll(Connection con,Statement st,ResultSet rs){
if(rs!=null){
try{
rs.close();
}catch(Exception ex){
ex.printStackTrace();
}
}
if(st!=null){
try{
st.close();
}catch(Exception ex){
ex.printStackTrace();
}
}
if(con!=null){
try{
con.close();
}catch(Exception ex){
ex.printStackTrace();
}
}
}
//通用设置参数方法
public static void setParams(PreparedStatement pst,Object[] params){
if(params==null){
return;
}
for(int i=0;i<params.length;i++){
try{
pst.setObject(i+1,params[i]);
}catch(Exception ex){
ex.printStackTrace();
}
}
}
//通用增删改
public static int executeUpdate(String sql,Object[] params){
Connection con = null;
PreparedStatement pst = null;
int res = -1;
try{
//获取连接
con = getConnection();
//创建预编译命令执行对象
pst = con.prepareStatement(sql);
//设置参数
setParams(pst,params);
//执行
res = pst.executeUpdate();
}catch(Exception ex){
ex.printStackTrace();
}finally{
closeAll(con,pst,null);
}
return res;
}
//通用查询
public static List<Map<String,Object>> executeQuery(String sql,Object[] params) {
List<Map<String,Object>> rows = new ArrayList<>();
Connection con = null;
PreparedStatement pst = null;
ResultSet rs = null;
try{
//获取连接
con = getConnection();
//获取命令对象
pst = con.prepareStatement(sql);
//设置参数
setParams(pst,params);
//执行查询
rs = pst.executeQuery();
//通过rs获取结果集的结构信息
ResultSetMetaData rsmd = rs.getMetaData();
//获取结果集的列数
int colCount = rsmd.getColumnCount();
//遍历查询结果，并封装到List<Map>中
while(rs.next()){
//用Map存储当前行的各个列数据
Map<String,Object> map = new HashMap<>();
//循环获取每一列的信息
for(int i=1;i<=colCount;i++){
//获取列名(使用rsmd)
String colName = rsmd.getColumnLabel(i);
//获取列值(使用rs)
Object colVal = rs.getObject(i);
//将当前列存储到map中
map.put(colName,colVal);
}
//将遍历的当前行的数据存储到List中
rows.add(map);
}
}catch(Exception ex){
ex.printStackTrace();
}finally{
closeAll(con,pst,rs);
}
return rows;
}
}
ClassInfo：
package com.entity;
public class ClassInfo {
private Integer classId;
private String className;
public ClassInfo() {
}
public ClassInfo(String className) {
this.className = className;
}
public ClassInfo(Integer classId, String className) {
this.classId = classId;
this.className = className;
}
public Integer getClassId() {
return classId;
}
public void setClassId(Integer classId) {
this.classId = classId;
}
public String getClassName() {
return className;
}
public void setClassName(String className) {
this.className = className;
}
@Override
public String toString() {
return "Class{" +
"classId=" + classId +
", className='" + className + '\'' +
'}';
}
}
IClassDAO：
package com.dao;
import com.entity.ClassInfo;
import java.util.List;
import java.util.Map;
public interface IClassDAO {
List<Map<String,Object>> listAll();
ClassInfo getByClassId(Integer classId);
List<Map<String,Object>> listByCon(String searchClassName);
int insert(ClassInfo classInfo);
int update(ClassInfo classInfo);
int delete(Integer classId);
}
ClassDAOImpl：
package com.dao.impl;
import com.dao.IClassDAO;
import com.entity.ClassInfo;
import com.mysql.cj.util.StringUtils;
import com.util.BaseDAO;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
public class ClassDAOImpl implements IClassDAO {
@Override
public List<Map<String, Object>> listByCon(String searchClassName) {
StringBuilder whereSql=new StringBuilder();
List<Object> sparams=new ArrayList<>();
if(!StringUtils.isNullOrEmpty(searchClassName)){
whereSql.append(" where className like ? ");
sparams.add("%"+searchClassName+"%");
}
String sql="select classId,className " +
" from class "+whereSql;
System.out.println("sql:"+sql);
System.out.println(sparams);
System.out.println("sparams.toArray():"+sparams.toArray());
return BaseDAO.executeQuery(sql,sparams.toArray());
}
@Override
public ClassInfo getByClassId(Integer classId) {
String sql="select classId,className from class"+
" where classId=?";
Object[] params={classId};
List<Map<String,Object>> rows = BaseDAO.executeQuery(sql,params);
if(rows.size()>0){
Map<String,Object> map= rows.get(0);
ClassInfo classInfo=new ClassInfo(
(Integer) map.get("classId"), //注意强转化 get得到的是Object类型（鼠标放在get上看）
(String) map.get("className")
);
System.out.println(classInfo);
return classInfo;
}
return null;
}
@Override
public List<Map<String, Object>> listAll() {
String sql="select * from class";
return BaseDAO.executeQuery(sql,null);
}
@Override
public int insert(ClassInfo classInfo) {
String sql="insert into class"+
" (className)"+
" values"+
" (?)";
Object[] params={classInfo.getClassName()};
return BaseDAO.executeUpdate(sql,params);
}
@Override
public int update(ClassInfo classInfo) {
String sql="update class"+
" set className=?"+
" where classId=?";
Object[] params={
classInfo.getClassName(),
classInfo.getClassId()
};
return BaseDAO.executeUpdate(sql,params);
}
@Override
public int delete(Integer classId) {
String sql="delete from class"+ //注意delete写法
" where classId=?";
Object[] params={classId};
return BaseDAO.executeUpdate(sql,params);
}
}
IClassService：
package com.service;
import com.entity.ClassInfo;
import java.util.List;
import java.util.Map;
public interface IClassService {
List<Map<String,Object>> listAll();
ClassInfo getByClassId(Integer classId);
List<Map<String,Object>> listByCon(String searchClassName);
int insert(ClassInfo classInfo);
int update(ClassInfo classInfo);
int delete(Integer classId);
}
ClassServiceImpl：
package com.service.impl;
import com.dao.IClassDAO;
import com.dao.impl.ClassDAOImpl;
import com.entity.ClassInfo;
import com.service.IClassService;
import java.util.List;
import java.util.Map;
public class ClassServiceImpl implements IClassService {
IClassDAO classDAO=new ClassDAOImpl();
@Override
public List<Map<String, Object>> listByCon(String searchClassName) {
return classDAO.listByCon(searchClassName);
}
@Override
public ClassInfo getByClassId(Integer classId) {
return classDAO.getByClassId(classId);
}
@Override
public List<Map<String, Object>> listAll() {
return classDAO.listAll();
}
@Override
public int insert(ClassInfo classInfo) {
return classDAO.insert(classInfo);
}
@Override
public int update(ClassInfo classInfo) {
return classDAO.update(classInfo);
}
@Override
public int delete(Integer classId) {
return classDAO.delete(classId);
}
}
ClassInfoServlet ：
package com.servlet;
import com.entity.ClassInfo;
import com.service.IClassService;
import com.service.impl.ClassServiceImpl;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.List;
import java.util.Map;
@WebServlet(urlPatterns = "/ClassInfoServlet/*")
public class ClassInfoServlet extends HttpServlet {
IClassService classService=new ClassServiceImpl();
@Override
protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
req.setCharacterEncoding("utf-8");
String uri=req.getRequestURI();
String process=uri.substring(uri.lastIndexOf("/")+1);
System.out.println("截取字段："+process);
switch (process){
case "query":
this.query(req,resp);
break;
case "toAdd":
this.toAdd(req,resp);
break;
case "add":
this.add(req,resp);
break;
case "toUpdate":
this.toUpdate(req,resp);
break;
case "update":
this.update(req,resp);
break;
case "delete":
this.delete(req,resp);
break;
}
}
// private void query(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
// List<Map<String,Object>> classList=classService.listAll();
//
// req.setAttribute("classList",classList);
// req.getRequestDispatcher("/classList.jsp").forward(req,resp);
// }
private void query(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
String searchClassName=req.getParameter("searchClassName");
List<Map<String,Object>> classList=classService.listByCon(searchClassName);
//用的特别巧妙，如果searchClassName为空，将查询所有；如果不为空，将模糊查询得相关的数据
System.out.println(classList);
req.setAttribute("classList",classList);
req.getRequestDispatcher("/classList.jsp").forward(req,resp);
}
private void toAdd(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
req.getRequestDispatcher("/classAdd.jsp").forward(req,resp);
}
private void add(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
String className=req.getParameter("className"); //注意 设置值关键字 从输入框获取值的关键字
ClassInfo ci=new ClassInfo(className);
int count=classService.insert(ci);
if(count==1){
System.out.println("插入成功！");
this.query(req,resp);
}else{
System.out.println("插入失败！");
}
}
private void toUpdate(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
Integer classId = Integer.parseInt(req.getParameter("classId"));
//根据编号，查询要修改的班级对象
ClassInfo classInfo = classService.getByClassId(classId);
//将要修改的班级对象，存储到request中，带到页面上，呈现出来
req.setAttribute("classInfo",classInfo);
//跳转到修改页面
req.getRequestDispatcher("/classUpdate.jsp").forward(req,resp);
req.setAttribute("classInfo",classInfo);
req.getRequestDispatcher("/classUpdate.jsp").forward(req,resp);
}
private void update(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
Integer classId = Integer.parseInt(req.getParameter("classId"));
String className = req.getParameter("className");
ClassInfo classInfo = new ClassInfo(classId,className);
//调用修改
int count = classService.update(classInfo);
if(count==1){
//修改成功，则重新显示
this.query(req,resp);
}else{
//跳转到失败
}
}
private void delete(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
Integer classId= Integer.parseInt(req.getParameter("classId"));
int count =classService.delete(classId);
if(count==1){
System.out.println("删除成功！");
this.query(req,resp);
}else{
System.out.println("删除失败！");
}
}
}
index.jsp:
<%--
Created by IntelliJ IDEA.
User: 33154
Date: 2022/8/1
Time: 20:26
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>$Title$</title>
</head>
<body>
$END$
<a href="${pageContext.request.contextPath}/StudentInfoServlet ">学生信息</a>
<a href="${pageContext.request.contextPath}/ClassInfoServlet/query">班级信息</a>
</body>
</html>
classList.jsp:
<%--
Created by IntelliJ IDEA.
User: 33154
Date: 2022/8/2
Time: 1:18
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<html>
<head>
<title>Title</title>
<%=request.getAttribute("classList")%>
</head>
<body>
班级数据：${classList}
<hr/>
<table border="1" align="center" width="50%">
<tr>
<td colspan="3">
<a href="${pageContext.request.contextPath}/ClassInfoServlet/toAdd">添加</a>
</td>
</tr>
<tr>
<td colspan="3">
<form id="searchFrm" action="${pageContext.request.contextPath}/ClassInfoServlet/query" method="get">
班级：<input type="text" id="searchCls" name="searchClassName" value="${param.searchClassName}"/>
<input type="submit" value="搜索" />
</form>
</td>
</tr>
<tr>
<th>班级编号</th>
<th>班级名称</th>
<th>操作</th>
</tr>
<c:forEach items="${classList}" var="clas">
<tr>
<td>${clas.classId}</td>
<td>${clas.className}</td>
<td>
<a href="${pageContext.request.contextPath}/ClassInfoServlet/toUpdate?classId=${clas.classId}">修改</a>
<a href="${pageContext.request.contextPath}/ClassInfoServlet/delete?classId=${clas.classId}"
onclick="return confirm('你确定要删除吗？')">
删除
</a>
</td>
</tr>
</c:forEach>
</table>
</body>
</html>
2.分页查询：（这时的分页查询完好，条件查询异常）
实现效果：
代码整体布局：
代码：
创建数据库/表：
#创建班级表
create table class
(
classId int primary key auto_increment,
className varchar(20)
);
insert into class
(className)
values
('菜鸟1班'),
('菜鸟2班'),
('菜鸟3班'),
('菜鸟4班'),
('菜鸡1班'),
('菜鸡2班'),
('菜鸡3班'),
('菜鸡4班');
select * from class;
select count(*) from class;
BaseDAO：
package com.util;
import java.sql.*;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
public class BaseDAO {
//四大金刚
//驱动类
private static final String DRIVER="com.mysql.cj.jdbc.Driver";
//连接地址
private static final String URL="jdbc:mysql://localhost:3306/70730_db?useSSL=false&characterEncoding=utf8&serverTimezone=Asia/Shanghai";
//用户名
private static final String USER="root";
//密码
private static final String PASSWORD="123456";
//获取连接
public static Connection getConnection(){
Connection con = null;
try{
//加载驱动类
Class.forName(DRIVER);
//获取连接
con = DriverManager.getConnection(URL,USER,PASSWORD);
}catch(Exception ex){
ex.printStackTrace();
}
return con;
}
//关闭数据库对象
public static void closeAll(Connection con,Statement st,ResultSet rs){
if(rs!=null){
try{
rs.close();
}catch(Exception ex){
ex.printStackTrace();
}
}
if(st!=null){
try{
st.close();
}catch(Exception ex){
ex.printStackTrace();
}
}
if(con!=null){
try{
con.close();
}catch(Exception ex){
ex.printStackTrace();
}
}
}
//通用设置参数方法
public static void setParams(PreparedStatement pst,Object[] params){
if(params==null){
return;
}
for(int i=0;i<params.length;i++){
try{
pst.setObject(i+1,params[i]);
}catch(Exception ex){
ex.printStackTrace();
}
}
}
//获取总记录数的查询 :select count(*) from ..
public static int getTotal(String sql,Object[] params){
int total=0;
Connection con=null;
PreparedStatement pst=null;
ResultSet rs=null;
try { //手动添加try-catch: ctrl+alt+t
con=getConnection();
pst=con.prepareStatement(sql);
setParams(pst,params);
rs=pst.executeQuery();
if(rs.next()){
total=rs.getInt(1); //获取第一列的值（具体解释请看详细图解）
}
} catch (SQLException throwables) {
throwables.printStackTrace();
} finally {
closeAll(con,pst,rs);
}
return total;
}
//通用增删改
public static int executeUpdate(String sql,Object[] params){
Connection con = null;
PreparedStatement pst = null;
int res = -1;
try{
//获取连接
con = getConnection();
//创建预编译命令执行对象
pst = con.prepareStatement(sql);
//设置参数
setParams(pst,params);
//执行
res = pst.executeUpdate();
}catch(Exception ex){
ex.printStackTrace();
}finally{
closeAll(con,pst,null);
}
return res;
}
//通用查询
public static List<Map<String,Object>> executeQuery(String sql,Object[] params) {
List<Map<String,Object>> rows = new ArrayList<>();
Connection con = null;
PreparedStatement pst = null;
ResultSet rs = null;
try{
//获取连接
con = getConnection();
//获取命令对象
pst = con.prepareStatement(sql);
//设置参数
setParams(pst,params);
//执行查询
rs = pst.executeQuery();
//通过rs获取结果集的结构信息
ResultSetMetaData rsmd = rs.getMetaData();
//获取结果集的列数
int colCount = rsmd.getColumnCount();
//遍历查询结果，并封装到List<Map>中
while(rs.next()){
//用Map存储当前行的各个列数据
Map<String,Object> map = new HashMap<>();
//循环获取每一列的信息
for(int i=1;i<=colCount;i++){
//获取列名(使用rsmd)
String colName = rsmd.getColumnLabel(i);
//获取列值(使用rs)
Object colVal = rs.getObject(i);
//将当前列存储到map中
map.put(colName,colVal);
}
//将遍历的当前行的数据存储到List中
rows.add(map);
}
}catch(Exception ex){
ex.printStackTrace();
}finally{
closeAll(con,pst,rs);
}
return rows;
}
}
ClassInfo：
package com.entity;
public class ClassInfo {
private Integer classId;
private String className;
public ClassInfo() {
}
public ClassInfo(String className) {
this.className = className;
}
public ClassInfo(Integer classId, String className) {
this.classId = classId;
this.className = className;
}
public Integer getClassId() {
return classId;
}
public void setClassId(Integer classId) {
this.classId = classId;
}
public String getClassName() {
return className;
}
public void setClassName(String className) {
this.className = className;
}
@Override
public String toString() {
return "Class{" +
"classId=" + classId +
", className='" + className + '\'' +
'}';
}
}
PageDate ：
package com.entity;
public class PageDate {
//当前页码
private Integer pageNo;
//每页条数
private Integer pageSize;
//总记录数
private Integer totalCount;
//总页数
private Integer totalPage;
//当前页的记录
private Object data;
public PageDate() {
}
public PageDate(Integer pageSize, Integer totalCount, Integer totalPage, Object data) {
this.pageSize = pageSize;
this.totalCount = totalCount;
this.totalPage = totalPage;
this.data = data;
}
public PageDate(Integer pageNo, Integer pageSize, Integer totalCount, Integer totalPage, Object data) {
this.pageNo = pageNo;
this.pageSize = pageSize;
this.totalCount = totalCount;
this.totalPage = totalPage;
this.data = data;
}
public Integer getPageNo() {
return pageNo;
}
public void setPageNo(Integer pageNo) {
this.pageNo = pageNo;
}
public Integer getPageSize() {
return pageSize;
}
public void setPageSize(Integer pageSize) {
this.pageSize = pageSize;
}
public Integer getTotalCount() {
return totalCount;
}
public void setTotalCount(Integer totalCount) {
this.totalCount = totalCount;
}
public Integer getTotalPage() {
return totalPage;
}
public void setTotalPage(Integer totalPage) {
this.totalPage = totalPage;
}
public Object getData() {
return data;
}
public void setData(Object data) {
this.data = data;
}
@Override
public String toString() {
return "PageDate{" +
"pageNo=" + pageNo +
", pageSize=" + pageSize +
", totalCount=" + totalCount +
", totalPage=" + totalPage +
", data=" + data +
'}';
}
}
IClassDAO：
package com.dao;
import com.entity.ClassInfo;
import com.entity.PageDate;
import java.util.List;
import java.util.Map;
public interface IClassDAO {
List<Map<String,Object>> listAll();
ClassInfo getByClassId(Integer classId);
List<Map<String,Object>> listByCon(String searchClassName);
PageDate listByPage(Integer pageNo,Integer pageSize);
int insert(ClassInfo classInfo);
int update(ClassInfo classInfo);
int delete(Integer classId);
}
ClassDAOImpl：
package com.dao.impl;
import com.dao.IClassDAO;
import com.entity.ClassInfo;
import com.entity.PageDate;
import com.mysql.cj.util.StringUtils;
import com.util.BaseDAO;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
public class ClassDAOImpl implements IClassDAO {
@Override
public PageDate listByPage(Integer pageNo, Integer pageSize) {
//查询总记录数
String totalSql="select count(*) from class";
Integer totalCount=BaseDAO.getTotal(totalSql,null);
//获取总页数
Integer totalPage=totalCount%pageSize==0?totalCount/pageSize:totalCount/pageSize+1;
//limit ?,?; 从哪一条开始，取若干条
String sql="select * from class "+
" order by classId "+
" limit ?,? ";
//计算分页开始的位置
int start=(pageNo-1)*pageSize;
//构建分页参数
Object[] params={
start,
pageSize
};
//分页查询：查询当前页若干条的记录数
List<Map<String,Object>> rows=BaseDAO.executeQuery(sql,params);
//将5项数据封装到PageData中
PageDate pd=new PageDate();
pd.setPageNo(pageNo);
pd.setPageSize(pageSize);
pd.setTotalCount(totalCount);
pd.setTotalPage(totalPage);
pd.setData(rows);
return pd;
}
@Override
public List<Map<String, Object>> listByCon(String searchClassName) {
StringBuilder whereSql=new StringBuilder();
List<Object> sparams=new ArrayList<>();
if(!StringUtils.isNullOrEmpty(searchClassName)){
whereSql.append(" where className like ? ");
sparams.add("%"+searchClassName+"%");
}
String sql="select classId,className " +
" from class "+whereSql;
System.out.println("sql:"+sql);
System.out.println(sparams);
System.out.println("sparams.toArray():"+sparams.toArray());
return BaseDAO.executeQuery(sql,sparams.toArray());
}
@Override
public ClassInfo getByClassId(Integer classId) {
String sql="select classId,className from class"+
" where classId=?";
Object[] params={classId};
List<Map<String,Object>> rows = BaseDAO.executeQuery(sql,params);
if(rows.size()>0){
Map<String,Object> map= rows.get(0);
ClassInfo classInfo=new ClassInfo(
(Integer) map.get("classId"), //注意强转化 get得到的是Object类型（鼠标放在get上看）
(String) map.get("className")
);
System.out.println(classInfo);
return classInfo;
}
return null;
}
@Override
public List<Map<String, Object>> listAll() {
String sql="select * from class";
return BaseDAO.executeQuery(sql,null);
}
@Override
public int insert(ClassInfo classInfo) {
String sql="insert into class"+
" (className)"+
" values"+
" (?)";
Object[] params={classInfo.getClassName()};
return BaseDAO.executeUpdate(sql,params);
}
@Override
public int update(ClassInfo classInfo) {
String sql="update class"+
" set className=?"+
" where classId=?";
Object[] params={
classInfo.getClassName(),
classInfo.getClassId()
};
return BaseDAO.executeUpdate(sql,params);
}
@Override
public int delete(Integer classId) {
String sql="delete from class"+ //注意delete写法
" where classId=?";
Object[] params={classId};
return BaseDAO.executeUpdate(sql,params);
}
}
IClassService：
package com.service;
import com.entity.ClassInfo;
import com.entity.PageDate;
import java.util.List;
import java.util.Map;
public interface IClassService {
List<Map<String,Object>> listAll();
ClassInfo getByClassId(Integer classId);
List<Map<String,Object>> listByCon(String searchClassName);
PageDate listByPage(Integer pageNo,Integer pageSize);
int insert(ClassInfo classInfo);
int update(ClassInfo classInfo);
int delete(Integer classId);
}
ClassServiceImpl:
package com.service.impl;
import com.dao.IClassDAO;
import com.dao.impl.ClassDAOImpl;
import com.entity.ClassInfo;
import com.entity.PageDate;
import com.service.IClassService;
import java.util.List;
import java.util.Map;
public class ClassServiceImpl implements IClassService {
IClassDAO classDAO=new ClassDAOImpl();
@Override
public PageDate listByPage(Integer pageNo, Integer pageSize) {
return classDAO.listByPage(pageNo,pageSize);
}
@Override
public List<Map<String, Object>> listByCon(String searchClassName) {
return classDAO.listByCon(searchClassName);
}
@Override
public ClassInfo getByClassId(Integer classId) {
return classDAO.getByClassId(classId);
}
@Override
public List<Map<String, Object>> listAll() {
return classDAO.listAll();
}
@Override
public int insert(ClassInfo classInfo) {
return classDAO.insert(classInfo);
}
@Override
public int update(ClassInfo classInfo) {
return classDAO.update(classInfo);
}
@Override
public int delete(Integer classId) {
return classDAO.delete(classId);
}
}
ClassInfoServlet:
package com.servlet;
import com.entity.ClassInfo;
import com.entity.PageDate;
import com.mysql.cj.util.StringUtils;
import com.service.IClassService;
import com.service.impl.ClassServiceImpl;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.List;
import java.util.Map;
@WebServlet(urlPatterns = "/ClassInfoServlet/*")
public class ClassInfoServlet extends HttpServlet {
IClassService classService=new ClassServiceImpl();
@Override
protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
req.setCharacterEncoding("utf-8");
String uri=req.getRequestURI();
String process=uri.substring(uri.lastIndexOf("/")+1);
System.out.println("截取字段："+process);
switch (process){
case "query":
this.query(req,resp);
break;
case "queryByPage":
this.queryByPage(req,resp);
break;
case "toAdd":
this.toAdd(req,resp);
break;
case "add":
this.add(req,resp);
break;
case "toUpdate":
this.toUpdate(req,resp);
break;
case "update":
this.update(req,resp);
break;
case "delete":
this.delete(req,resp);
break;
}
}
private void queryByPage(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
Integer pageNo=1;
Integer pageSize=3;
if(req.getParameter("pageNo")!=null){
pageNo=Integer.parseInt(req.getParameter("pageNo"));
}
if(req.getParameter("pageSize")!=null){
pageSize= Integer.parseInt(req.getParameter("pageSize")); //Integet.valueOf()和Integet.parseInt()
}
//获取查询条件
String searchClassName=req.getParameter("searchClassName");
System.out.println("searchClassName:"+searchClassName);
System.out.println("pageNo:"+pageNo);
System.out.println("pageSize:"+pageSize);
//调用分页查询
PageDate pageDate=classService.listByPage(pageNo,pageSize);
System.out.println("pageDate"+pageDate);
//存储到req,跳转到页面
req.setAttribute("pd",pageDate);
req.getRequestDispatcher("/classList.jsp").forward(req,resp);
}
// private void query(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
// List<Map<String,Object>> classList=classService.listAll();
//
// req.setAttribute("classList",classList);
// req.getRequestDispatcher("/classList.jsp").forward(req,resp);
// }
private void query(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
String searchClassName=req.getParameter("searchClassName");
List<Map<String,Object>> classList=classService.listByCon(searchClassName);
//用的特别巧妙，如果searchClassName为空，将查询所有；如果不为空，将模糊查询得相关的数据
System.out.println(classList);
req.setAttribute("classList",classList);
req.getRequestDispatcher("/classList.jsp").forward(req,resp);
}
private void toAdd(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
req.getRequestDispatcher("/classAdd.jsp").forward(req,resp);
}
private void add(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
String className=req.getParameter("className"); //注意 设置值关键字 从输入框获取值的关键字
ClassInfo ci=new ClassInfo(className);
int count=classService.insert(ci);
if(count==1){
System.out.println("插入成功！");
this.query(req,resp);
}else{
System.out.println("插入失败！");
}
}
private void toUpdate(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
Integer classId = Integer.parseInt(req.getParameter("classId"));
//根据编号，查询要修改的班级对象
ClassInfo classInfo = classService.getByClassId(classId);
//将要修改的班级对象，存储到request中，带到页面上，呈现出来
req.setAttribute("classInfo",classInfo);
//跳转到修改页面
req.getRequestDispatcher("/classUpdate.jsp").forward(req,resp);
req.setAttribute("classInfo",classInfo);
req.getRequestDispatcher("/classUpdate.jsp").forward(req,resp);
}
private void update(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
Integer classId = Integer.parseInt(req.getParameter("classId"));
String className = req.getParameter("className");
ClassInfo classInfo = new ClassInfo(classId,className);
//调用修改
int count = classService.update(classInfo);
if(count==1){
//修改成功，则重新显示
this.query(req,resp);
}else{
//跳转到失败
}
}
private void delete(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
Integer classId= Integer.parseInt(req.getParameter("classId"));
int count =classService.delete(classId);
if(count==1){
System.out.println("删除成功！");
this.query(req,resp);
}else{
System.out.println("删除失败！");
}
}
}
index.jsp:
<%--
Created by IntelliJ IDEA.
User: 33154
Date: 2022/8/1
Time: 20:26
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>$Title$</title>
</head>
<body>
$END$
<a href="${pageContext.request.contextPath}/StudentInfoServlet ">学生信息</a>
<a href="${pageContext.request.contextPath}/ClassInfoServlet/query">班级信息</a>
<a href="${pageContext.request.contextPath}/ClassInfoServlet/queryByPage">分页信息</a>
</body>
</html>
classList.jsp:
<%--
Created by IntelliJ IDEA.
User: 33154
Date: 2022/8/2
Time: 1:18
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<html>
<head>
<title>Title</title>
<%-- <%=request.getAttribute("classList")%>--%>
</head>
<body>
班级数据：${classList}
<table border="1" align="center" width="50%">
<tr>
<td colspan="3">
<a href="${pageContext.request.contextPath}/ClassInfoServlet/toAdd">添加</a>
</td>
</tr>
<tr>
<td colspan="3">
<form id="searchFrm" action="${pageContext.request.contextPath}/ClassInfoServlet/queryByPage" method="get">
班级：<input type="text" id="searchCls" name="searchClassName" value="${param.searchClassName}"/> <%--value--%>
<input type="submit" value="搜索" />
<input type="hidden" name="pageNo" id="pageNo" />
<input type="hidden" name="pageSize" id="pageSize" />
</form>
</td>
</tr>
<tr>
<th>班级编号</th>
<th>班级名称</th>
<th>操作</th>
</tr>
<c:forEach items="${pd.data}" var="pdd">
<tr>
<td>${pdd.classId}</td>
<td>${pdd.className}</td>
<td>
<a href="${pageContext.request.contextPath}/ClassInfoServlet/toUpdate?classId=${pdd.classId}">修改</a>
<a href="${pageContext.request.contextPath}/ClassInfoServlet/delete?classId=${pdd.classId}"
onclick="return confirm('你确定要删除吗？')">
删除
</a>
</td>
</tr>
</c:forEach>
<%--生成分页信息--%>
<tr>
<td colspan="3">
当前页${pd.pageNo}/共${pd.totalPage}页 |
总记录数：${pd.totalCount} |
<c:forEach begin="1" end="${pd.totalPage}" var="i">
<c:if test="${pd.pageNo==i}">
<span>${i}</span>
</c:if>
<c:if test="${pd.pageNo!=i}">
<a href="javascript:jumpPage(${i})">${i}</a>
</c:if>
</c:forEach>
每页
<select name="pageSize" id="ps" onchange="changePageSize(this.value)"> <%--onchange--%>
<option value="2" ${pd.pageSize==2?'selected':''}>2</option> <%--option value="2"和2哪个在起作用？--%>
<option value="3" ${pd.pageSize==3?'selected':''}>3</option> <%--注意：代码运行到这里出错了--%>
<option value="5" ${pd.pageSize==5?'selected':''}>5</option>
</select>
条
</td>
</tr>
</table>
<script type="text/javascript">
//切换每页记录数
function changePageSize(size){
window.location.href="${pageContext.request.contextPath}/ClassInfoServlet/queryByPage?pageSize="+size;
}
//跳转分页
function jumpPage(no){
document.getElementById("pageNo").value=no;
document.getElementById("pageSize").value=ps.value; //ps在 （每页。。条） 下一行的位置
searchFrm.submit();
}
</script>
</body>
</html>
// A code block
var foo = 'bar';
// A code block
var foo = 'bar';
// A code block
var foo = 'bar';
// A code block
var foo = 'bar';
// A code block
var foo = 'bar';
// A code block
var foo = 'bar';
KQC 0803 条件查询（待补充）
图书条件查询：创建图书表，编号，书名，作者，价格，出版日期。
要求可以按照书名和作者进行模糊查询。
// A code block
var foo = 'bar';
// A code block
var foo = 'bar';
// A code block
var foo = 'bar';
// A code block
var foo = 'bar';
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