SpringDataJpa自定义投影映射
前言
今天为大家分享：SpringDataJpa自定义投影映射。
前面讲了SpringDataJpa自定义查询语句(JPQL)，请查看博主的SpringDataJpa系列文章。欢迎关注！
为什么需要自定义投影映射
回忆我之前的文章使用Spring Data Jpa 持久层框架进行数据的查询操作时，只能获取一个对象或者对象集合，并不能获取对象中的指定的某个或者几个属性。但是在实际项目开发过程中，我们往往会有这种需求，那么我们应该怎
么办呢？不用担心，Spring Data Jpa框架也考虑到这种问题了，所以给我们提供了自定义投影映射来解决这种问题。
自定义投影映射的步骤
案例下载
github地址 https://github.com/chenxiban/SpringBoot-Simple.git
创建maven项目，搭建项目环境，项目目录如下：
配置pom.xml文件，代码如下：
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.ysd</groupId>
<artifactId>spring-boot-jpa-simple</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>
<name>spring-boot-jpa-simple</name>
<url>http://maven.apache.org</url>
<!-- Spring Boot 启动父依赖 -->
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>1.5.1.RELEASE</version>
</parent>
<!-- 项目全局属性 -->
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
<java.version>1.8</java.version>
<mybatis-spring-boot>1.2.0</mybatis-spring-boot>
<mysql-connector>5.1.39</mysql-connector>
<junit-version>4.12</junit-version>
</properties>
<dependencies>
<!-- Spring Boot Web 依赖 -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<!-- Spring Boot Test 依赖 -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<!-- Spring Boot devtools 热部署 依赖 -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-devtools</artifactId>
</dependency>
<!-- Spring Boot JPA 依赖 -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<!-- MySQL 连接驱动依赖 -->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>${mysql-connector}</version>
</dependency>
<!-- Junit 单元测试 依赖 -->
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>${junit-version}</version>
</dependency>
</dependencies>
<!-- SpringBoot 项目发布 打jar包 依赖 -->
<build>
<plugins>
<!-- SpringBoot 项目发布 打jar包 依赖 -->
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
<!-- Maven test junit 报告中文UTF-8编码 插件 -->
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-surefire-plugin</artifactId>
<version>2.6</version>
<configuration>
<forkMode>once</forkMode>
<argLine>-Dfile.encoding=UTF-8</argLine>
</configuration>
</plugin>
</plugins>
</build>
</project>
配置属性文件
在src/main/resources下配置application.properties，代码如下：
server:
port: 8090
context-path: /mydemo
tomcat:
uri-encoding: UTF-8
spring:
datasource:
url: jdbc:mysql://localhost:3306/springbootjpasimple?useUnicode=true&characterEncoding=utf8
username: root
password: root
driver-class-name: com.mysql.jdbc.Driver
jpa:
database-platform: org.hibernate.dialect.MySQL5InnoDBDialect #不加这句则默认为myisam引擎
##运行时输出jpa执行的sql语句
show-sql: true
## spring-boot-starter-data-jpa自动映射创建表动作 配置: 有表更新,无表创建
hibernate:
ddl-auto: update
#集中解决各种编码问题
banner:
charset: UTF-8
http:
encoding:
charset: UTF-8
enabled: true
force: true
messages:
encoding: UTF-8
# spring mvc 视图解析器
mvc:
view:
prefix: /
suffix: .html
# 时间格式化
jackson:
date-format: yyyy-MM-dd HH:mm:ss
# 时区设置
time-zone: GMT+8
编写实体类
在com.ysd.springboot.entity下编写cat实体，代码如下：（这里没有用lombok，各位可以引入进去使用）
package com.ysd.springboot.entity;
import java.io.Serializable;
import java.sql.Timestamp;
import java.util.Date;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.OrderBy;
import javax.persistence.Table;
import javax.persistence.Transient;
@Entity // HQL 使用,默认类名
@Table(name = "cattb") // 数据库原生SQL使用,默认表名
public class Cat implements Serializable {
@Id // 实体类的主键
@GeneratedValue // 自动增长列
@OrderBy // 数据加载顺序
@Column(columnDefinition = "int unsigned NOT NULL comment '备注:猫自动增长主键' ")
private Integer id;
@Column(length = 20) // 字符长度20
private String name;
@Column(columnDefinition = "char(1) comment '备注:猫姓名' ")
private String sex;
@Column(columnDefinition = "int unsigned DEFAULT 0 comment '备注:猫年龄' ")
private Integer age;
private Date birthday;
@Column(columnDefinition = "TIMESTAMP", nullable = false, updatable = false, insertable = false)
private Timestamp updateTime;
@Transient // 临时参数,不映射到数据库表字段
private String catParam;
// ----------------------------- 以下是构造方法 ------------------------
public Cat(String name, String sex, Integer age, String catParam) {
super();
this.name = name;
this.sex = sex;
this.age = age;
this.birthday = new Date();
this.catParam = catParam;
}
public Cat(String name, String sex, Integer age, Date birthday, String catParam) {
super();
this.name = name;
this.sex = sex;
this.age = age;
this.birthday = birthday;
this.catParam = catParam;
}
public Cat() {
super();
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getSex() {
return sex;
}
public void setSex(String sex) {
this.sex = sex;
}
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
public Date getBirthday() {
return birthday;
}
public void setBirthday(Date birthday) {
this.birthday = birthday;
}
public Timestamp getUpdateTime() {
return updateTime;
}
public void setUpdateTime(Timestamp updateTime) {
this.updateTime = updateTime;
}
public String getCatParam() {
return catParam;
}
public void setCatParam(String catParam) {
this.catParam = catParam;
}
// ----------------------------- 以下是Getter和setter方法 ------------------------
// 省略getter和setter方法
// ----------------------------- 以下是重写的toString方法 ------------------------
@Override
public String toString() {
return "Cat [id=" + id + ", name=" + name + ", sex=" + sex + ", age=" + age + ", birthday=" + birthday
+ ", updateTime=" + updateTime + ", catParam=" + catParam + "]";
}
}
编写dao类
在com.ysd.springboot.dao下编写CatRepository接口，代码如下：
package com.ysd.springboot.dao;
import java.util.List;
import org.springframework.data.domain.Page;
import org.springframework.data.domain.Pageable;
import org.springframework.data.domain.Sort;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.Query;
import org.springframework.data.repository.query.Param;
import com.ysd.springboot.entity.Cat;
public interface CatRepository extends JpaRepository<Cat, Integer> {
// ******************** []JPQL或者HQL 方式 ] 序号参数*******************
@Query(" SELECT MAX(c.age) FROM Cat c ")
public Long maxAge();
@Query("select c from Cat c where c.name like %:name% ")
List<Cat> queryByname(@Param(value = "name") String name);
// ----------------------------以下是自定义条件查询--------------------------------------
// Like --- 等价于 SQL 中的 "like"，比如 findByNameLike(String name);
public List<Cat> findByNameLike(String name);
// Like --- 等价于 SQL 中的 "like"，比如 findByNameLike(String name);
public List<Cat> findByNameLike(String name, Sort sort);
public Page<Cat> findByNameLike(String name, Pageable pageable);
// **************** 原生SQL********************
@Query(value = " SELECT * FROM cattb WHERE NAME LIKE %:name% ", nativeQuery = true)
List<Cat> queryBynameSQL(@Param(value = "name") String name);
}
编写业务接口
在com.ysd.springboot.service下，编写CatService接口，代码如下：
package com.ysd.springboot.service;
import java.util.List;
import org.springframework.data.domain.Page;
import org.springframework.data.domain.PageRequest;
import org.springframework.data.domain.Pageable;
import org.springframework.data.domain.Sort;
import com.ysd.springboot.entity.Cat;
public interface CatService {
public Cat insert(Cat cat);
public List<Cat> insert(List<Cat> list);
public void delete(Integer id);
public void delete(Cat cat);
public void delete(List<Cat> list);
public void deleteAll();
public Cat update(Cat cat);
public List<Cat> update(List<Cat> list);
public Boolean exists(Integer id);
public Long count();
public Cat queryById(Integer id);
public List<Cat> queryAll();
public List<Cat> queryByNameLike(String name);
public List<Cat> queryByName(String name);
public List<Cat> queryByNameSQL(String name);
public Long queryMaxAge();
public List<Cat> queryAllSort(String fieldName);// 排序
public Page<Cat> queryAllPage(Integer page, Integer size);// 分页,排序
public List<Cat> queryNameLikeAllSort(String nameLike, String fieldName);// 带条件的排序
public Page<Cat> queryNameLikeAllPage(String nameLike, Integer page, Integer size);// 带条件的分页
}
编写业务实现类
在com.ysd.springboot.ServiceImpl下，编写CatServiceImpl，代码如下
package com.ysd.springboot.ServiceImpl;
import java.util.List;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.domain.Page;
import org.springframework.data.domain.PageRequest;
import org.springframework.data.domain.Pageable;
import org.springframework.data.domain.Sort;
import org.springframework.stereotype.Service;
import com.ysd.springboot.dao.CatRepository;
import com.ysd.springboot.entity.Cat;
import com.ysd.springboot.service.CatService;
@Service
public class CatServiceImpl implements CatService {
@Autowired
private CatRepository repository;
@Override
public Cat insert(Cat cat) {
return repository.save(cat);
}
@Override
public List<Cat> insert(List<Cat> list) {
return repository.save(list);
}
@Override
public void delete(Integer id) {
repository.delete(id);
}
@Override
public void delete(Cat cat) {
repository.delete(cat);
}
@Override
public void delete(List<Cat> list) {
repository.delete(list);
}
@Override
public void deleteAll() {
repository.deleteAll();
}
@Override
public Cat update(Cat cat) {
return repository.save(cat);
}
@Override
public List<Cat> update(List<Cat> list) {
return repository.save(list);
}
@Override
public Boolean exists(Integer id) {
return repository.exists(id);
}
@Override
public Long count() {
return repository.count();
}
@Override
public Cat queryById(Integer id) {
return repository.findOne(id);
}
@Override
public List<Cat> queryAll() {
return repository.findAll();
}
@Override
public List<Cat> queryAllSort(String fieldName) {// 排序
// Sort sort = new Sort(Sort.Direction.DESC, "id");
// Pageable pageable = new PageRequest(page, size, sort);
Sort sort = new Sort(Sort.Direction.DESC, fieldName, "id");
return repository.findAll(sort);
}
@Override
public Page<Cat> queryAllPage(Integer page, Integer size) {// 分页
Sort sort = new Sort(Sort.Direction.ASC, "id");
Pageable pageable = new PageRequest(page, size, null);
return repository.findAll(pageable);
}
// ----------------------------以上是JpaRepository已经实现好的基本增删改查-----------------
@Override
public Long queryMaxAge() {
return repository.maxAge();
}
@Override
public List<Cat> queryByNameLike(String name) {
return repository.findByNameLike("%" + name + "%");
}
@Override
public List<Cat> queryByName(String name) {
return repository.queryByname(name);
}
@Override
public List<Cat> queryByNameSQL(String name) {
return repository.queryBynameSQL(name);
}
@Override
public List<Cat> queryNameLikeAllSort(String nameLike, String fieldName) {// 带条件的排序
// Sort sort = new Sort(Sort.Direction.DESC, "id");
// Pageable pageable = new PageRequest(page, size, sort);
Sort sort = new Sort(Sort.Direction.DESC, fieldName, "id");
return repository.findByNameLike("%" + nameLike + "%", sort);
}
@Override
public Page<Cat> queryNameLikeAllPage(String nameLike, Integer page, Integer size) {// 带条件的分页
Sort sort = new Sort(Sort.Direction.ASC, "id");
Pageable pageable = new PageRequest(page, size, sort);
return repository.findByNameLike("%" + nameLike + "%", pageable);
}
}
编写controller层
在com.ysd.springboot.controller下，编写CatController类，代码如下：
package com.ysd.springboot.controller;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.domain.Page;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import com.ysd.springboot.entity.Cat;
import com.ysd.springboot.service.CatService;
/**
* SpringMVC控制器
*
* @Description: 子模块
*
*/
@RestController
public class CatController {
@Autowired
private CatService service;
// 默认静态资源目录:http://localhost:8080/springbootjpasimple.sql
/**
* 测试项目环境是否正常 http://localhost:8080/index
*
* @return
*/
@RequestMapping("/index")
public Cat index() {
Cat cat = new Cat("张三", "男", 18, "预留参数");
return cat;
}
/**
* 新增 http://localhost:8080/insertOne
*
* @return
*/
@RequestMapping("/insertOne")
public Cat add() {
Cat cat = new Cat("张三", "男", 18, "预留参数");
return service.insert(cat);
}
/**
* 排序 http://localhost:8080/orderBy
*
* @return
*/
@RequestMapping("/orderBy")
public List<Cat> orderBy() {
return service.queryAllSort("age");
}
/**
* 条件模糊查询:[JPA关键字形式] http://localhost:8080/nameLike?name=m
* http://localhost:8080/nameLike?name=七
*
* @return
*/
@RequestMapping("/nameLike")
public List<Cat> nameLike(String name) {
return service.queryByNameLike(name);
}
/**
* 条件模糊查询:[HQL形式] http://localhost:8080/queryName?name=m
*
* @return
*/
@RequestMapping("/queryName")
public List<Cat> queryName(String name) {
return service.queryByName(name);
}
/**
* 条件模糊查询:[原生SQL形式] http://localhost:8080/queryNameSQL?name=m
*
* @return
*/
@RequestMapping("/queryNameSQL")
public List<Cat> queryNameSQL(String name) {
return service.queryByNameSQL(name);
}
/**
* http://localhost:8080/queryMaxAge
*
* @return
*/
@RequestMapping("/queryMaxAge")
public Long queryMaxAge() {
return service.queryMaxAge();
}
/**
* 分页查询 http://localhost:8080/queryPage
*
* @return
*/
@RequestMapping("/queryPage")
public Object queryPage() {
Page<Cat> page = null;
page = service.queryAllPage(1, 3);// 第2页,每页3条;第几页从零开始,每页显示几条.
System.out.println("queryPage page=>" + page);
Long total = page.getTotalElements();
List<Cat> list = page.getContent();
Map<String, Object> map = new HashMap<>();
map.put("total", total);
map.put("rows", list);
return map;
}
/**
* 带条件的排序查询 http://localhost:8080/nameLikeorderBy?name=m
*
* @return
*/
@RequestMapping("/nameLikeorderBy")
public List<Cat> nameLikeorderBy(String name) {
return service.queryNameLikeAllSort(name, "age");
}
/**
* 带条件的分页查询 http://localhost:8080/queryNameLikePage?name=m
*
* @return
*/
@RequestMapping("/queryNameLikePage")
public Object queryNameLikePage(String name) {
Page<Cat> page = null;
page = service.queryNameLikeAllPage(name, 0, 3);// 第1页,每页3条;第几页从零开始,每页显示几条.
System.out.println("page=>" + page);
Long total = page.getTotalElements();
List<Cat> list = page.getContent();
Map<String, Object> map = new HashMap<>();
map.put("total", total);
map.put("rows", list);
return map;
}
}
编写主项目类
在com.ysd.springboot下，编写主项目类，代码如下：
package com.ysd.springboot;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.autoconfigure.domain.EntityScan;
import org.springframework.data.jpa.repository.config.EnableJpaRepositories;
@EnableJpaRepositories(basePackages = "com.ysd.springboot.dao") // Spring Jpa 启用注解
@EntityScan(basePackages = "com.ysd.springboot.entity") // 扫描Jpa实体对象
@SpringBootApplication // Spring Boot 应用的标识
public class Application {
public static void main(String[] args) {
SpringApplication.run(Application.class, args);// 程序启动入口 启动嵌入式的 Tomcat 并初始化 Spring 环境及其各 Spring 组件
}
}
启动项目，查看运行结果，测试路径可根据controller层给出的提示进行测试。
好了到这里也该结束了，各位要自己多动手才能学到真正的东西。加油各位
最后
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更多参考精彩博文请看这里：《陈永佳的博客》
-
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