Mybatis 实现查询功能
1. 新建数据库
1.1 新建数据库 mybatis
1.2 新建 tb_user 表
SET NAMES utf8mb4;
SET FOREIGN_KEY_CHECKS = 0;
-- ----------------------------
-- Table structure for tb_user
-- ----------------------------
DROP TABLE IF EXISTS `tb_user`;
CREATE TABLE `tb_user` (
`id` bigint NOT NULL AUTO_INCREMENT COMMENT '主键ID',
`user_name` varchar(20) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL COMMENT '用户名',
`password` varchar(20) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL COMMENT '密码',
`name` varchar(30) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL COMMENT '姓名',
`age` int NULL DEFAULT NULL COMMENT '年龄',
`email` varchar(50) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL COMMENT '邮箱',
PRIMARY KEY (`id`) USING BTREE
) ENGINE = InnoDB CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Dynamic;
-- ----------------------------
-- Records of tb_user
-- ----------------------------
INSERT INTO `tb_user` VALUES (1, 'Messi', '123', '梅西', 34, 'test1@163.com');
INSERT INTO `tb_user` VALUES (2, 'C Ronaldo', '1234', 'C罗', 36, 'test2@163.com');
INSERT INTO `tb_user` VALUES (3, 'Dybala', '12345', '迪巴拉', 28, 'test3@163.com');
INSERT INTO `tb_user` VALUES (4, 'Mbappé', '123456', '姆巴佩', 23, 'test4@163.com');
INSERT INTO `tb_user` VALUES (5, 'Neymar', '1234567', '内马尔', 29, 'test5@just.cn')
SET FOREIGN_KEY_CHECKS = 1;
2. 新建maven工程 mybatis-test
2.1 配置文件 pom.xml
<?xml version="1.0" encoding="UTF-8"?>
<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.czh</groupId>
<artifactId>mybatis-test</artifactId>
<packaging>pom</packaging>
<version>1.0-SNAPSHOT</version>
<dependencies>
<dependency>
<groupId>com.baomidou</groupId>
<artifactId>mybatis-plus</artifactId>
<version>3.1.1</version>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>8.0.25</version>
</dependency>
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>druid</artifactId>
<version>1.0.11</version>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.12</version>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>1.18.4</version>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-log4j12</artifactId>
<version>1.6.4</version>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<configuration>
<source>1.8</source>
<target>1.8</target>
</configuration>
</plugin>
</plugins>
</build>
</project>
2.2 新建实体类 User 和接口 UserMapper
2.2.1 实体类 User
package com.czh.pojo;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
@Data
@NoArgsConstructor
@AllArgsConstructor
public class User {
private Long id;
private String userName;
private String password;
private String name;
private Integer age;
private String email;
}
2.2.2 接口 UserMapper
package com.czh.mapper;
import com.czh.pojo.User;
import java.util.List;
public interface UserMapper {
// 查询所有用户信息
public List<User> findAll();
}
2.3 配置 resource 文件夹
2.3.1 新建日志配置文件 log4j.properties
log4j.rootLogger=DEBUG,A1
log4j.appender.A1=org.apache.log4j.ConsoleAppender
log4j.appender.A1.layout=org.apache.log4j.PatternLayout
log4j.appender.A1.layout.ConversionPattern=[%t] [%c] - [%p] %m%n
2.3.2 新建 UserMapper.xml
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.czh.mapper.UserMapper">
<!--查询所有用户信息-->
<select id="findAll" resultType="com.czh.pojo.User">
select * from tb_user
</select>
</mapper>
2.3.3 新建 mybatis-config.xml 文件
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
<environments default="development">
<environment id="development">
<transactionManager type="JDBC"/>
<dataSource type="POOLED">
<property name="driver" value="com.mysql.cj.jdbc.Driver"/>
<property name="url" value="jdbc:mysql://127.0.0.1:3306/mp?useUnicode=true&characterEncoding=utf8&autoReconnect=true&allowMultiQueries=true&useSSL=false"/>
<property name="username" value="root"/>
<property name="password" value="root"/>
</dataSource>
</environment>
</environments>
<mappers>
<mapper resource="UserMapper.xml"/>
</mappers>
</configuration>
3. 测试查询功能
3.1 新建测试类 TestMybatis
package com.czh;
import com.czh.mapper.UserMapper;
import com.czh.pojo.User;
import jdk.management.resource.ResourceContext;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Test;
import java.io.InputStream;
import java.util.List;
public class TestMybatis {
@Test
public void testFindAll() throws Exception{
String config = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(config);
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
SqlSession sqlSession = sqlSessionFactory.openSession();
UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
// 测试查询
List<User> users = userMapper.findAll();
for (User user : users) {
System.out.println(user);
}
}
}
3.2 输出结果
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