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MyBatis详解
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一、案例
1.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>org.example</groupId>
<artifactId>MyBatis-Demo1</artifactId>
<version>1.0-SNAPSHOT</version>
<dependencies>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.32</version>
</dependency>
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.4.6</version>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.12</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
<version>1.2.17</version>
</dependency>
</dependencies>
</project>
2.User
package com.jkj.domain;
public class User {
private int id;
private String username;
private String password;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
@Override
public String toString() {
return "User{" +
"id=" + id +
", username='" + username + '\'' +
", password='" + password + '\'' +
'}';
}
}
3.user数据表
4.mybatis-config.xml
<?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 core file-->
<configuration>
<environments default="development">
<environment id="development">
<transactionManager type="JDBC"/>
<dataSource type="POOLED">
<property name="driver" value="com.mysql.jdbc.Driver"/>
<property name="url" value="jdbc:mysql://localhost:3306/mybatisthree?useSSL=false&useUnicode=true&characterEncoding=UTF-8"/>
<property name="username" value="root"/>
<property name="password" value="root"/>
</dataSource>
</environment>
</environments>
<!--加载sql映射文件-->
<mappers>
<mapper resource="com/jkj/mapper/UserMapper.xml"/>
</mappers>
</configuration>
5.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="userMapper">
<!-- 查询-->
<select id="findAll" resultType="com.jkj.domain.User">
select * from user
</select>
<!-- 插入-->
<insert id="save" parameterType="com.jkj.domain.User">
insert into user values(#{id},#{username},#{password})
</insert>
<!-- 修改-->
<update id="update" parameterType="com.jkj.domain.User">
update user set username=#{username},password=#{password} where id=#{id}
</update>
<!-- 删除-->
<delete id="delete" parameterType="com.jkj.domain.User">
delete from user where id=#{id}
</delete>
</mapper>
6.MyBatisTest测试类
package com.jkj.test;
import com.jkj.domain.User;
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.IOException;
import java.io.InputStream;
import java.util.List;
public class MyBatisTest {
//查询
@Test
public void test() throws IOException {
//1.加载MyBatis的核心配置文件获取sqlSessionFactory
InputStream inputStream = Resources.getResourceAsStream("mybatis-config.xml");
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
//2.获取sqlSession,执行sql
SqlSession sqlSession = sqlSessionFactory.openSession();
//3.执行sql
List<User> users = sqlSession.selectList("userMapper.findAll");
System.out.println(users);
//4.释放资源
sqlSession.close();
}
//插入
@Test
public void save() throws IOException {
//模拟User对象
User user = new User();
user.setUsername("科比");
user.setPassword("123456");
//1.加载MyBatis的核心配置文件获取sqlSessionFactory
InputStream inputStream = Resources.getResourceAsStream("mybatis-config.xml");
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
//2.获取sqlSession,执行sql
SqlSession sqlSession = sqlSessionFactory.openSession();
//3.执行sql
sqlSession.insert("userMapper.save",user);
//4.提交事务
sqlSession.commit();
//5.释放资源
sqlSession.close();
}
//修改
@Test
public void update() throws IOException {
//模拟User对象
User user = new User();
user.setId(5);
user.setUsername("RC");
user.setPassword("555555");
//1.加载MyBatis的核心配置文件获取sqlSessionFactory
InputStream inputStream = Resources.getResourceAsStream("mybatis-config.xml");
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
//2.获取sqlSession,执行sql
SqlSession sqlSession = sqlSessionFactory.openSession();
//3.执行sql
sqlSession.update("userMapper.update",user);
//4.提交事务
sqlSession.commit();
//5.释放资源
sqlSession.close();
}
//删除
//修改
@Test
public void delete() throws IOException {
//1.加载MyBatis的核心配置文件获取sqlSessionFactory
InputStream inputStream = Resources.getResourceAsStream("mybatis-config.xml");
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
//2.获取sqlSession,执行sql
SqlSession sqlSession = sqlSessionFactory.openSession();
//3.执行sql
sqlSession.delete("userMapper.delete",5);
//4.提交事务
sqlSession.commit();
//5.释放资源
sqlSession.close();
}
}
二、sql操作注意的问题
- 删除语句使用delete标签
- Sql语句中使用#{任意字符串}方式引用传递的单个参数
- 删除操作使用的API是sqlSession.delete(“命名空间.id”,Object)
- 修改语句使用update标签
- 修改操作使用的API是sqlSession.update(“命名空间.id”,实体对象)
- 插入语句使用insert标签
- 在映射文件中使用parameterType属性指定要插入的数据类型
- Sql语句中使用#{实体属性名}方式引用实体中的属性值
- 插入操作使用的API是sqlSession.insert(“命名空间.id”,实体对象);
- 插入操作涉及数据库数据变化，所以要使用sqlSession对象显示的提交事务，即sqlSession.commit(）
