Mybatis（一）--基础教程

一、Mybatis

MyBatis 是支持定制化 SQL、存储过程以及高级映射的优秀的持久层框架。MyBatis 避免了几乎所有的 JDBC 代码和手动设置参数以及获取结果集。MyBatis 可以对配置和原生Map使用简单的 XML 或注解，将接口和 Java 的 POJOs(Plain Old Java Objects,普通的 Java对象)映射成数据库中的记录。

二、入门实例

2.1 环境搭建

引入数据库jar包及Mybatis的核心jar包和依赖包

2.2 数据库创建

CREATE DATABASE mybatisdemo;
USE mybatisdemo;
CREATE TABLE USER(
	id INT PRIMARY KEY AUTO_INCREMENT,
	username VARCHAR(10),
	sex VARCHAR(4),
	birthday DATE
);

INSERT INTO USER(username,sex,birthday) VALUES ('陈星星','男','1992/06/16');
INSERT INTO USER(username,sex,birthday) VALUES ('小逗逗','女','1993/11/25');

2.3 创建配置文件

src下新建sqlMapConfig.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>
 	<!-- 环境配置 -->
	<environments default="development">
		<environment id="development">
			<!-- 使用jdbc事务管理 -->
			<transactionManager type="JDBC" />
			<!-- 数据库连接池 -->
			<dataSource type="POOLED">
				<property name="driver" value="com.mysql.jdbc.Driver" />
				<property name="url"
					value="jdbc:mysql://localhost:3305/mybatisdemo" />
				<property name="username" value="root" />
				<property name="password" value="root" />
			</dataSource>
		</environment>
	</environments>
	
	<!-- 引入mapper文件的位置 -->
	<mappers>
		<mapper resource="sqlmap/User.xml"/>
	</mappers>
	
</configuration>

sqlmap package下新建User.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">
  <!-- 写sql语句的位置-->
  <!-- 命名空间 ,方便和其他JavaBean类的语句名称区分-->
  <mapper namespace="users">
  		<!-- 通过id查询用户 -->
  		<select id="findUserById" parameterType="Integer" resultType="cn.cf.domain.User">
  			select * from user where id = #{id}
  		</select>
  </mapper>

2.4 实体类创建

User.java

package cn.cf.domain;

import java.util.Date;

public class User {

	private Integer id;
	private String username;
	private String sex;
	private Date birthday;

	public Integer getId() {
		return id;
	}

	public void setId(Integer id) {
		this.id = id;
	}

	public String getUsername() {
		return username;
	}

	public void setUsername(String username) {
		this.username = username;
	}

	public String getSex() {
		return sex;
	}

	public void setSex(String sex) {
		this.sex = sex;
	}

	public Date getBirthday() {
		return birthday;
	}

	public void setBirthday(Date birthday) {
		this.birthday = birthday;
	}

	@Override
	public String toString() {
		return "User [id=" + id + ", username=" + username + ", sex=" + sex + ", birthday=" + birthday + "]";
	}

}

2.5 测试类创建

TestDemo.java

package cn.cf.test;

import java.io.IOException;
import java.io.InputStream;

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 cn.cf.domain.User;

/**
 * 测试类
 * @author cf
 *
 */
public class TestDemo {
	
	@Test
	public void test() throws IOException {
		//1.加载核心配置文件
		String resource = "sqlMapConfig.xml";
		InputStream inputStream = Resources.getResourceAsStream(resource);
		//2.创建工厂
		SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
		//3.创建sesion
		SqlSession sqlSession = sqlSessionFactory.openSession();
		//4.执行sql语句
		User user = sqlSession.selectOne("users.findUserById", 1);
		
		System.out.println(user);
	}
}

结果如下：

三、其他CRUD语句

3.1 插入数据

User.xml

	<!-- 添加用户 -->
	<insert id="insertUser" parameterType="cn.cf.domain.User">
		insert into user(username, sex, birthday) 
		values(#{username}, #{sex}, #{birthday});
	</insert>

TestDemo.java

// 插入新用户
	@Test
	public void testInsertUser() throws Exception {
		// 1.加载核心配置文件
		String resource = "sqlMapConfig.xml";
		InputStream inputStream = Resources.getResourceAsStream(resource);
		// 2.创建工厂
		SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
		// 3.创建sesion
		SqlSession sqlSession = sqlSessionFactory.openSession();
		// 创建新的实体类实例
		User user = new User();
		user.setUsername("斯密");
		user.setSex("男");
		String date = "1900-10-02";
		SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
		Date birthday = sdf.parse(date);
		user.setBirthday(birthday);
		// 4.执行sql语句
		sqlSession.insert("users.insertUser", user);
		// 提交事务
		sqlSession.commit();
	}

3.2 修改数据

User.xml

	<!-- 修改数据 -->
	<update id="updateUserById" parameterType="cn.cf.domain.User">
		update user
		set username = #{username}, sex = #{sex}, birthday = #{birthday}
		where id = #{id}
	</update>

TestDemo.java

// 更新用户
	@Test
	public void testUpdateUser() throws Exception {
		// 1.加载核心配置文件
		String resource = "sqlMapConfig.xml";
		InputStream inputStream = Resources.getResourceAsStream(resource);
		// 2.创建工厂
		SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
		// 3.创建sesion
		SqlSession sqlSession = sqlSessionFactory.openSession();
		// 根据id查找user
		User user = sqlSession.selectOne("users.findUserById", 3);
		//修改user信息
		user.setUsername("亚当斯密");
		// 4.执行sql语句
		sqlSession.update("users.updateUserById", user);
		// 提交事务
		sqlSession.commit();
	}

3.3 删除数据

命名空间还是改回包名，上述，不改为包名出错了。

User.xml

	<!-- 删除数据 -->
	<delete id="deleteUserById" parameterType="Integer">
		delete from user where id = #{v}
	</delete>

TestDemo.java

// 删除用户
@Test
public void testDeleteUser() throws Exception {
	// 1.加载核心配置文件
	String resource = "sqlMapConfig.xml";
	InputStream inputStream = Resources.getResourceAsStream(resource);
	// 2.创建工厂
	SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
	// 3.创建sesion
	SqlSession sqlSession = sqlSessionFactory.openSession();
	// 4.执行sql语句,删除用户
	sqlSession.delete("cn.cf.domain.User.deleteUserById", 3);
	// 提交事务
	sqlSession.commit();
}

结果：

可以看到SQL语句是写在配置文件中的，方便维护。结果集也是定义配置文件中。