MyBatis入门实例

关于MyBatis，不作太多介绍，在google一搜索，有很多资料，我也是参考别人的例子，MyBatis入门非常容易，希望我现在发的代码对大家有用。

实体类：

package bean;

public class User {
	private String name;
	private Integer age;

	public User() {

	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public Integer getAge() {
		return age;
	}

	public void setAge(Integer age) {
		this.age = age;
	}

	public User(String name, Integer age) {
		super();
		this.name = name;
		this.age = age;
	}

}

映射器，这是一个接口，这个接口不需要实现类

package mapper;

import org.apache.ibatis.annotations.Select;

import bean.User;
/**
 * 映射器
 *
 */
public interface UserMapper {
	public void insertUser(User user); 

	//可以使用Java注解来替换XML
	@Select("select * from user where name=#{name}")
    public User getUser(String name); 

}

SQL映射的XML文件

<?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="mapper.UserMapper"> 
<!-- 这里namespace必须是UserMapper接口的路径，不然要运行的时候要报错 “is not known to the MapperRegistry”--> 
    <insert id="insertUser" parameterType="User"> 
       insert into user(name,age) values(#{name},#{age}) 
       <!-- 这里sql结尾不能加分号，否则报“ORA-00911”的错误 --> 
    </insert> 

    <!-- 这里的id必须和UserMapper接口中的接口方法名相同，不然运行的时候也要报错 --> 
<!--    <select id="getUser" resultType="User" parameterType="java.lang.String"> -->
<!--        select * from user where name=#{name} -->
<!--    </select> -->

</mapper>

XML映射配置文件

<?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> 
    <settings> 
        <!-- changes from the defaults for testing --> 
        <setting name="cacheEnabled" value="false" /> 
        <setting name="useGeneratedKeys" value="true" /> 
        <setting name="defaultExecutorType" value="REUSE" /> 
    </settings> 
    <typeAliases> 
       <typeAlias alias="User" type="bean.User"/> 
    </typeAliases> 

    <environments default="development"> 
	   <!-- environment元素体中包含对事务管理和连接池的环境配置 -->
	   <!-- 你可以配置多种环境，但你只能为每个SqlSessionFactory实例选择一个。 -->
       <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/test"/> 
              <property name="username" value="root"/> 
              <property name="password" value="123"/> 
           </dataSource> 
       </environment> 
    </environments> 
    <mappers> 
        <mapper resource="resource/UserMapper.xml" /> 
    </mappers> 
</configuration>

创建SqlSessionFactory的工具类

package utils;

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;

public class MyBatisUtil {
	//每一个MyBatis的应用程序都以一个SqlSessionFactory对象的实例为核心
	//使用SqlSessionFactory的最佳实践是在应用运行期间不要重复创建多次,最佳范围是应用范围
	 private  final static SqlSessionFactory sqlSessionFactory; 
	    static { 
	       String resource = "resource/configuration.xml"; 
	       Reader reader = null; 
	       try { 
	           reader = Resources.getResourceAsReader(resource); 
	       } catch (IOException e) { 
	           System.out.println(e.getMessage()); 

	       } 
	       //SqlSessionFactory对象的实例可以通过SqlSessionFactoryBuilder对象来获得
	       //SqlSessionFactoryBuilder实例的最佳范围是方法范围（也就是本地方法变量）。
	       sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader); 
	    } 

	    public static SqlSessionFactory getSqlSessionFactory() { 
	       return sqlSessionFactory; 
	    } 

}

测试类

package testMapper;

import mapper.UserMapper;

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

import utils.MyBatisUtil;
import bean.User;

public class TestMapper {
	static SqlSessionFactory sqlSessionFactory = null; 
    static { 
       sqlSessionFactory = MyBatisUtil.getSqlSessionFactory(); 
    } 

    @Test 
    public void addUser() { 
    	//获得SqlSession的实例
    	//每个线程都应该有它自己的SqlSession实例。SqlSession的实例不能被共享，也是线程不安全的。因此最佳的范围是请求或方法范围。
       SqlSession sqlSession = sqlSessionFactory.openSession(); 
       try { 
    	   //映射器实例的最佳范围是方法范围。
           UserMapper userMapper = sqlSession.getMapper(UserMapper.class); 
           User user = new User("neng",new Integer(5)); 
           userMapper.insertUser(user); 
           sqlSession.commit();//这里一定要提交，不然数据进不去数据库中 
       } finally { 
    	   //确保SqlSession关闭
           sqlSession.close(); 
       } 
    } 

    @Test 
    public void getUser() { 
       SqlSession sqlSession = sqlSessionFactory.openSession(); 
       try { 
           UserMapper userMapper = sqlSession.getMapper(UserMapper.class); 
           User user = userMapper.getUser("neng"); 
           System.out.println("name: "+user.getName()+"|age: "+user.getAge()); 
       } finally { 
           sqlSession.close(); 
       } 
    } 

}