myBatis系列之二：以接口方式交互数据

超、凢脫俗 2022-04-11 06:22 190阅读 0赞

myBatis系列之一：搭建开发环境是采用SqlSession的通用方法并强制转换的方式，存在着转换安全的问题：

User user = (User) session.selectOne("com.bijian.study.model.UserMapper.getUserById", 1);

可以采用接口加sql语句的方式来解决，sql语句理解为是接口的实现：

**一.新建接口类**

package com.bijian.study.dao;
    
    import java.util.List;
    
    import com.bijian.study.model.Article;
    import com.bijian.study.model.User;
    
    public interface IUserMapper {
    
        User getUserById(int id);
    }

**二.修改User.xml文件**

确保namespace属性值和接口的全限定名相同，且id属性值和接口方法名相同：

<?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.bijian.study.dao.IUserMapper">
    	<select id="getUserById" parameterType="int" resultType="User">
    		select *
    		from `user` where id = #{id}
    	</select>
    </mapper>

**三.在MyBatisBasicTest类中添加测试方法**

@Test
    public void queryInInterfaceWayTest() {
    	
    	SqlSession session = sqlSessionFactory.openSession();
    	// 如果namespace和接口全限定名不一致，报org.apache.ibatis.binding.BindingException: Type interface com..IUserMapper is not known to the MapperRegistry异常。  
    	IUserMapper mapper = session.getMapper(IUserMapper.class);
    	User user = mapper.getUserById(1);
    	log.info("{}:{}", user.getName(), user.getAddress());
    }

**附： **

上面的实现是把sql语句放在XML文件中，并通过一定的约束来保证接口能够在XML中找到对应的SQL语句；还有一种方式是通过接口+注解SQL方式来交互数据：

**1.新建接口类**

package com.bijian.study.dao;
    
    import org.apache.ibatis.annotations.Select;
    
    import com.bijian.study.model.User;
    
    public interface IUserMapper2 {
    
        @Select({ "select * from `user` where id = #{id}" })
        User getUserById(int id);
    }

**2.在Configuration.xml文件中加入**

<?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>
    	<typeAliases>
    		<typeAlias alias="User" type="com.bijian.study.model.User" />
    	</typeAliases>
    	
    	<environments default="development">
    	  <environment id="development">
    		<transactionManager type="JDBC"/>
    		<dataSource type="POOLED">
    			<property name="driver" value="com.mysql.jdbc.Driver" />
    			<property name="url" value="jdbc:mysql://10.60.222.65:3306/test" />
    			<property name="username" value="test" />
    			<property name="password" value="test" />
    		</dataSource>
    	  </environment>
    	</environments>
    	
    	<mappers>
    		<mapper class="com.bijian.study.dao.IUserMapper2" />
    	</mappers>
    </configuration>

或在初始化语句中加入：

sqlSessionFactory.getConfiguration().addMapper(IUserMapper2.class);

如下所示：

@BeforeClass
    public static void initial() {
    	try {
    		reader = Resources.getResourceAsReader("Configuration.xml");
    		sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
    		sqlSessionFactory.getConfiguration().addMapper(IUserMapper2.class);
    	} catch (IOException e) {
    		log.error("Error thrown while reading the configuration: {}", e);
    	} finally {
    		if (reader != null) {
    			try {
    				reader.close();
    			} catch (IOException e) {
    				log.error("Error thrown while closing the reader: {}", e);
    			}
    		}
    	}
    }

**3.相应修改上面的测试方法 **

@Test
    public void queryInInterfaceWayTest2() {
    	
    	SqlSession session = sqlSessionFactory.openSession();
    	// 如果namespace和接口全限定名不一致，报org.apache.ibatis.binding.BindingException: Type interface com..IUserMapper is not known to the MapperRegistry异常。  
    	IUserMapper2 mapper = session.getMapper(IUserMapper2.class);
    	User user = mapper.getUserById(1);
    	log.info("{}:{}", user.getName(), user.getAddress());
    }

文章来源：[http://czj4451.iteye.com/blog/1980569][http_czj4451.iteye.com_blog_1980569]

[http_czj4451.iteye.com_blog_1980569]: http://czj4451.iteye.com/blog/1980569