sqlSession.getMapper(UserMapper.class)的使用方式

说明：

1，本文采用的Mybatis框架版本为： mybatis-3.0.4.jar

2， 以持久化一个简单的User bean为例

User实体类的代码如下：

 package bean;
     
    public class User {
        private String name;
        private Integer age;
       
        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;
        }
       
        public User() {
           super();
        }  //必须要有这个无参构造方法，不然根据UserMapper.xml中的配置，在查询数据库时，将不能反射构造出User实例
    } 

 
User实体的映射器取名为UserMapper(接口)，其代码如下

   package Mapper;
    import bean.User;
     
    public interface UserMapper {
        public void insertUser(User user);
        public User getUser(String name);
    } 

 

注意，该接口类似于Hibernate中的DAO层接口，唯一不同的是，MyBatis中，只声明该接口就可以，不需要去实现.

UserMapper映射器对应的配置文件如下(相当于Hibernate中的User.hbm.xml,当然这里面不是属性映射字段，而是直接是映射器中各种方法对应的sql语句)：

 <?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 vincent_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 vincent_user where name=#{name}
        </select>
    </mapper>

 

MyBatis的配置文件这里取名为mybatis-config.xml其配置代码如下(相当与Hibernate的hibernate.cfg.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>
        <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 id="development">
               <transactionManager type="jdbc"/>
               <dataSource type="POOLED">
                  <property name="driver" value="oracle.jdbc.driver.OracleDriver"/>
                  <property name="url" value="jdbc:oracle:thin:@192.168.56.201:1521:system"/>
                  <property name="username" value="vincent"/>
                  <property name="password" value="1234"/>
               </dataSource>
           </environment>
        </environments>
        <mappers>
            <mapper resource="resource/UserMapper.xml" />
        </mappers>
    </configuration> 

 

加载配置文件得到sqlSessionFactory的工具类

package Util;
     
    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  {
        private  final static SqlSessionFactory sqlSessionFactory;
        static {
           String resource = "resource/mybatis-config.xml";
           Reader reader = null;
           try {
               reader = Resources.getResourceAsReader(resource);
           } catch (IOException e) {
               System.out.println(e.getMessage());
              
           }
           sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
        }
       
        public static SqlSessionFactory getSqlSessionFactory() {
           return sqlSessionFactory;
        }
    }

 

测试代码如下：

 package TestMapper;
    import org.apache.ibatis.session.SqlSession;
    import org.apache.ibatis.session.SqlSessionFactory;
    import org.junit.Test;
     
    public class TestMapper {
        static SqlSessionFactory sqlSessionFactory = null;
        static {
           sqlSessionFactory = MyBatisUtil.getSqlSessionFactory();
        }
       
        @Test
        public void testAdd() {
           SqlSession sqlSession = sqlSessionFactory.openSession();
           try {
               UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
               User user = new User("tom",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 {
               sqlSession.close();
           }
        }
       
        @Test
        public void getUser() {
           SqlSession sqlSession = sqlSessionFactory.openSession();
           try {
               UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
               User user = userMapper.getUser("jun");
               System.out.println("name: "+user.getName()+"|age: "+user.getAge());
           } finally {
               sqlSession.close();
           }
        }
     
    }