MyBatis学习练习（1）

昨天晚上学习了Mybatis文档，今天编写了一个简单练习。

基本目的：利用Mybatis完成对一个表简单的select、insert、update、delete操作。达到熟悉MyBatis基本用法的目的。
用到的jar：MyBatis.jar,数据库驱动.jar（如mysql-connector.jar）


MyBatis的配置文件MyBatisConfig.xml。可以进行数据源和事务管理器的配置，以及其他影响MyBatis执行的变量。

<?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> 
<!-- 导入属性文件，采用类路径方式 -->
<properties resource="com/chl/mybatis/properties/config.properties"> 
</properties> 

<!-- 简称  -->
<typeAliases>
	<typeAlias alias="User" type="com.chl.mybatis.domain.User"></typeAlias>
</typeAliases>

<!-- 环境设置 -->
<environments default="development"> 
	<environment id="development"> 
		<transactionManager type="JDBC"/> 
		<dataSource type="POOLED"> 
			<property name="driver" value="${driver}"/> 
			<property name="url" value="${url}"/> 
			<property name="username" value="${username}"/> 
			<property name="password" value="${password}"/> 
		</dataSource> 
	</environment> 
	<!-- 可以继续配置environment -->
</environments> 

<!-- 导入映射的文件，采用类路径方式 -->
<mappers> 
	<mapper resource="com/chl/mybatis/data/UserMapper.xml"/> 
</mappers> 


</configuration>

MyBatis的映射文件UserMapper.xml。文档中评价这个文件时奇迹发生的地方。

<?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.chl.mybatis.data.UserMapper">

	<select id="selectUsers" resultType="User">
		select username, sex from t_user;
	</select>
	
	<insert id="insertUser" parameterType="User">
		insert into t_user (username, sex) values (#{userName},#{sex});
	</insert>
	
	<update id="updateUser" parameterType="User">
		update t_user set username=#{userName}, sex=#{sex} where username=#{userName};
	</update>
	
	<delete id="deleteUser" parameterType="User">
		delete from t_user where username=#{userName} and sex=#{sex}
	</delete>
</mapper>

UserMapper接口文件，该文件与UserMapper.xml有着某些地方一一对应的关系，注意哦。

package com.chl.mybatis.data;

import java.util.List;

import com.chl.mybatis.domain.User;

/**
 * @author chl
 * 定义User的映射器接口，
 * 接口名称与命名空间的名称同，
 * 方法名称与映射配置中映射方法的id同。
 *
 */
public interface UserMapper {
	public List<User> selectUsers();
	public void insertUser(User user);
	public void updateUser(User user);
	public void deleteUser(User user);
}

MyBatis文件，其中定义了产生SqlSessionFactory的工厂单例类。

package com.chl.mybatis;

import java.io.IOException;
import java.io.Reader;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

/**
 * @author chl
 * 工厂单例模式，生成SqlSessionFactory实例。
 *
 */
public class MyBatis {
	private MyBatis(){};
	private static SqlSessionFactory ssf = null;
	public static SqlSessionFactory getSessionFactory() throws IOException{
		if(null == ssf){
			String resource = "com/chl/mybatis/data/mybatisConfig.xml";
			Reader reader = Resources.getResourceAsReader(resource);
			ssf = new SqlSessionFactoryBuilder().build(reader);		
		}//if
		return ssf;
	}
}

User文件，定义了User javabean实体类。

package com.chl.mybatis.domain;

public class User {
	private String userName = "";
	private String sex = "";
	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;
	}
}

userAction类，方法体中获取SqlSessionFactory实例，获得SqlSession，获取SqlMapper，然后调用映射的方法。

package com.chl.mybatis.action;

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

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

import com.chl.mybatis.MyBatis;
import com.chl.mybatis.data.UserMapper;
import com.chl.mybatis.domain.User;

/**
 * @author chl
 * 对user的操作。
 * 其中将SqlSession放于方法级范围。
 */
public class UserAction {
	public void insert(User user){
		SqlSessionFactory ssf = null;
		SqlSession session = null;
		try {
			ssf = MyBatis.getSessionFactory();
			session = ssf.openSession();
			UserMapper userMapper = session.getMapper(UserMapper.class);
			
			userMapper.insertUser(user);
			
			selectAll();
			System.out.println("==================================");
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} finally{
			if(null != session){
				session.close();
				session = null;
			}
		}
		
	}
	
	public void update(User user){
		SqlSessionFactory ssf = null;
		SqlSession session = null;
		try {
			ssf = MyBatis.getSessionFactory();
			session = ssf.openSession();
			UserMapper userMapper = session.getMapper(UserMapper.class);
			
			userMapper.updateUser(user);
			
			selectAll();
			System.out.println("==================================");
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} finally{
			if(null != session){
				session.close();
				session = null;
			}
		}
	}
	
	public void selectAll(){
		SqlSessionFactory ssf = null;
		SqlSession session = null;
		try {
			ssf = MyBatis.getSessionFactory();
			session = ssf.openSession();
			UserMapper userMapper = session.getMapper(UserMapper.class);
			
			List<User> users = userMapper.selectUsers();
			for(User u : users){
				System.out.println(u.getUserName()+"    "+u.getSex());
			}
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} finally{
			if(null != session){
				session.close();
				session = null;
			}
		}
	}
	
	public void delete(User user){
		SqlSessionFactory ssf = null;
		SqlSession session = null;
		
		try {
			ssf = MyBatis.getSessionFactory();
			session = ssf.openSession();
			UserMapper um = session.getMapper(UserMapper.class);
			um.deleteUser(user);
			
			selectAll();
			System.out.println("==================================");
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} finally{
			if(null != session){
				session.close();
				session = null;
			}
		}
	}
}