Mybatis（一），使用三种方式实现对数据库表的增删改查

    MyBatis实现对数据库表的增删改查主要有三种方式，分别为“基于配置文件方式”、“基于接口方式”和“基于注解方式”，下面主要介绍一下这三种方式是如何实现的。推荐使用接口方式。

（一）基于配置文件方式

涉及三个文件：核心配置文件，映射文件和测试类。核心配置文件主要是配置与数据库相关的信息和注册映射文件；映射文件中涉及SQL语句；测试类是SQL真正执行的地方。

1.核心配置文件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">
<!-- 配置跟数据库相关的信息 -->
<configuration>
	<environments default="development">
		<environment id="development">
			<!-- 配置事务 -->
			<transactionManager type="JDBC"></transactionManager>
			<!-- 配置数据源 -->
			<dataSource type="POOLED">
				<property name="driver" value="com.mysql.jdbc.Driver"/>
				<property name="url" value="jdbc:mysql://localhost:3306/mybatis"/>
				<property name="username" value="root"/>
				<property name="password" value="123"/>
			</dataSource>
		</environment>
	</environments>
	<!-- 注册映射文件 -->
	<mappers>
		<mapper resource="mapper/BlogMapper1.xml"/>
	</mappers>
</configuration>

2.映射文件BlogMapper1.xml，放置于mapper包下

<?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="BlogMapper">
	<!-- 查询 -->
	<select id="selectOne" parameterType="int" resultType="entity.Blog">
		select * from blog where id = #{id}
	</select>
	
	<!-- 插入 --> 
	<insert id="insert" parameterType="entity.Blog">
		INSERT INTO blog(id,title,author_id) VALUES(#{id},#{title},#{author_id})
	</insert>
	
	<!-- 删除 -->
	<delete id="delete" parameterType="int">
		delete from blog where id = #{id}
	</delete>
	
	<!-- 更新 -->
	<update id="update" parameterType="entity.Blog">
		update blog set title = #{title} where id = #{id}
	</update>
</mapper>

3.测试类test1.java

package test;

import java.io.InputStream;
import java.util.List;

import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

import com.mysql.jdbc.Blob;

import entity.Blog;

/**
 * 通过配置文件实现对blog表的增删改查
 * @author baka
 *
 */
public class test1 {

	public static void main(String[] args) {
		//1.获取配置文件名
		String resource = "SqlMapConfig.xml";
		
		//2.得到数据源
		InputStream is = test1.class.getClassLoader().getResourceAsStream(resource);
		
		//3.提供连接，建立工厂
		SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(is);
		
		//4.得到真正的连接
		SqlSession session = factory.openSession();
		
		//5.执行SQL语句
		
		//查询
		String statement = "BlogMapper.selectOne";
		Blog blog = session.selectOne(statement, 2);
		System.out.println(blog);
		
		//插入
		String statement2 = "BlogMapper.insert";
		Blog blog2 = new Blog(8, "wawa", 1);
		session.insert(statement2, blog2);
		
		//修改
		String statement3 = "BlogMapper.update";
		Blog blog3 = new Blog(8, "wawahh", 2);
		session.update(statement3, blog3);
		
		//删除
		String statement4 = "BlogMapper.delete";
		session.update(statement4, 8);
		
		//6、提交事务，关闭连接
		session.commit();
		session.close();
	}
}

(二)基于接口方式，涉及四个文件，核心配置文件、映射文件、测试类和接口类

1.核心配置文件

<mapper resource="mapper/BlogMapper2.xml"/>

2.接口类BlogDao2.java

package dao;

import java.util.List;

import entity.Blog;

public interface BlogDao2 {
	public Blog selectOne(int id);
	public int insert(Blog blog);
	public int delete(int id);
	public int update(Blog blog);
}

3.映射文件BlogMapper2.xml，使用的是上面的映射文件，但有两点需要注意

（1）命名空间必须是接口所在的位置

<mapper namespace="dao.BlogDao2">

我的接口类是“BlogDao.java”，位于"dao"包下

（2）命名空间中的id必须和接口中的方法同名

（3）完整代码

<?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="dao.BlogDao2">
	<!-- 查询 -->
	<select id="selectOne" parameterType="int" resultType="entity.Blog">
		select * from blog where id = #{id}
	</select>
	
	<!-- 插入 --> 
	<insert id="insert" parameterType="entity.Blog">
		INSERT INTO blog(id,title,author_id) VALUES(#{id},#{title},#{author_id})
	</insert>
	
	<!-- 删除 -->
	<delete id="delete" parameterType="int">
		delete from blog where id = #{id}
	</delete>
	
	<!-- 更新 -->
	<update id="update" parameterType="entity.Blog">
		update blog set title = #{title} where id = #{id}
	</update>
</mapper>

4.测试类test2.java

package test;

import java.io.InputStream;
import java.util.List;

import javax.naming.spi.ObjectFactory;

import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

import dao.BlogDao2;
import entity.Blog;

/**
 * 基于接口方式实现blog表的增删改查
 * @author baka
 *
 */
public class test2 {
	public static void main(String[] args) {
		//1.获得配置文件名
		String resource = "SqlMapConfig.xml";
		
		//2.获得数据流
		InputStream is = test2.class.getClassLoader().getResourceAsStream(resource);
		
		//3.提供连接，建立工厂
		SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(is);
		
		//4.获得真正的连接
		SqlSession session = factory.openSession();
		
		//5.实例化接口
		BlogDao2 blogDao = session.getMapper(BlogDao2.class);
		
		//6.执行SQL语句
		
		//查询
		Blog blog = blogDao.selectOne(2);
		System.out.println(blog);
		
		//插入
		Blog blog2 = new Blog(9, "xxx", 4);
		blogDao.insert(blog2);
		
		//修改
		Blog blog3 = new Blog(9, "xxxL", 4);
		blogDao.update(blog3);
		
		//删除
		blogDao.delete(9);
		
		//7.提交事务，关闭连接
		session.commit();
		session.close();
	}
}

（三）基于注解方式

涉及三个文件，核心配置文件，接口类和测试类，没有映射文件，SQL语句注解写在接口方法中

1.核心配置文件

<mapper class="dao.BlogDao3"/>

2.接口类BlogDao3.java

package dao;

import java.util.List;

import org.apache.ibatis.annotations.Delete;
import org.apache.ibatis.annotations.Insert;
import org.apache.ibatis.annotations.Select;
import org.apache.ibatis.annotations.Update;

import entity.Blog;

/**
 * 注解方式
 * @author baka
 *
 */

public interface BlogDao3 {
	@Select("select * from blog where id = #{id}")
	public Blog selectOne(int id);
	
	@Insert("INSERT INTO blog(id,title,author_id) VALUES(#{id},#{title},#{author_id})")
	public int insert(Blog blog);
	
	@Delete("delete from blog where id = #{id}")
	public int delete(int id);
	
	@Update("update blog set title = #{title} where id = #{id}")
	public int update(Blog blog);
}

3.测试类test3.java

package test;

import java.io.IOException;
import java.io.InputStream;
import java.util.List;

import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

import dao.BlogDao2;
import dao.BlogDao3;
import entity.Blog;

/**
 * 基于注解方式实现对blog表的增删改查
 * 
 * @author baka
 *
 */
public class test3 {

	public static void main(String[] args) throws IOException {
		// 1.获得配置文件名
		String resource = "SqlMapConfig.xml";

		// 2.获得数据流
		InputStream is = test3.class.getClassLoader().getResourceAsStream(resource);

		// 3.提供连接，建立工厂
		SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(is);

		// 4.获得真正的连接
		SqlSession session = factory.openSession();

		// 5.实例化接口
		BlogDao3 blogDao = session.getMapper(BlogDao3.class);

		// 6.执行SQL语句
		
		//查询
		Blog blog = blogDao.selectOne(1);
		System.out.println(blog);
		
		//增加
		Blog blog1 = new Blog(9, "xxx", 4);
		blogDao.insert(blog1);
		
		//修改
		Blog blog3 = new Blog(9, "xxxL", 4);
		blogDao.update(blog3);
		
		//删除
		blogDao.delete(9);
		
		// 7.提交事务，关闭连接
		session.commit();
		session.close();
	}

}