使用MyBatis(二)使用java注解查询单行数据

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第二种读取数据库user表的方法是使用java注解的方式。

1.去掉前面文章中的UserMapper.xml，将需要查询数据库表的sql语句加入interface中。

package com.yw.test02;import org.apache.ibatis.annotations.Select;public interface UserMapper{    @Select("SELECT * FROM user WHERE id = #{id}")    User selectUser(int id);}

2.修改mybatis-config.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><properties resource="config.properties"></properties><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></environments><mappers><mapper class="com.yw.test02.UserMapper"/></mappers></configuration>

注意修改了下面的部分：

<mappers><mapper class="com.yw.test02.UserMapper"/></mappers>

3.修改测试类

package com.yw.test02;import java.io.IOException;import java.io.InputStream;import org.apache.ibatis.io.Resources;import org.apache.ibatis.session.SqlSession;import org.apache.ibatis.session.SqlSessionFactory;import org.apache.ibatis.session.SqlSessionFactoryBuilder;public class Test01{    public static void main(String[] args) throws IOException    {        String resource = "com/yw/test02/mybatis-config.xml";        InputStream inputStream = Resources.getResourceAsStream(resource);        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);        SqlSession session = sqlSessionFactory.openSession();        try        {            // User user = (User) session.selectOne("com.yw.test01.UserMapper.selectUser", 1);            UserMapper mapper = session.getMapper(UserMapper.class);            User user = mapper.selectUser(1);            System.out.println(user);        }        finally        {            session.close();        }    }}

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