三、Mybatis 操作数据库

男娘i 2023-01-20 04:00 7阅读 0赞

*  源码地址：https://github.com/RononoaZoro/mybatis-book/tree/master 的 mybatis-book ( mybatis-chapter04 )
 *  文章内容出自《Mybatis 3 源码深度解析》第四章

## 1、使用 Mybatis 操作数据库 ##

### 1）、Mybatis 的主配置文件 ###

**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>
    	<settings>
    		<setting name="useGeneratedKeys" value="true"/>
    		<setting name="mapUnderscoreToCamelCase" value="true"/>
    		<setting name="logImpl" value="LOG4J"/>
    	</settings>
    
    	<environments default="dev" >
    		<environment id="dev">
    			<transactionManager type="JDBC">
    				<property name="" value="" />
    			</transactionManager>
    			<dataSource type="UNPOOLED">
    				<property name="driver" value="org.hsqldb.jdbcDriver" />
    				<property name="url" value="jdbc:hsqldb:mem:mybatis" />
    				<property name="username" value="sa" />
    				<property name="password" value="" />
    			</dataSource>
    		</environment>
    		<environment id="qa">
    			<transactionManager type="JDBC">
    				<property name="" value="" />
    			</transactionManager>
    			<dataSource type="UNPOOLED">
    				<property name="driver" value="org.hsqldb.jdbcDriver" />
    				<property name="url" value="jdbc:hsqldb:mem:mybatis_qa" />
    				<property name="username" value="admin" />
    				<property name="password" value="admin" />
    			</dataSource>
    		</environment>
    	</environments>
    
    	<mappers>
    		<mapper resource="com/blog4java/mybatis/example/mapper/UserMapper.xml"/>
    		
    	</mappers>
    </configuration>

### 2）、Java 实体 ###

package com.blog4java.mybatis.example.entity;
    
    import lombok.Data;
    
    import java.util.Date;
    
    @Data
    public class UserEntity {
        private Long id;
        private String name;
        private Date createTime;
        private String password;
        private String phone;
        private String nickName;
    }

### 3）、Mapper 文件 ###

package com.blog4java.mybatis.example.mapper;
    
    import com.blog4java.mybatis.example.entity.UserEntity;
    import org.apache.ibatis.annotations.Param;
    import org.apache.ibatis.annotations.Select;
    
    import java.util.List;
    
    public interface UserMapper {
    
        List<UserEntity> listAllUser();
    
        @Select("select * from user where id=#{userId,jdbcType=INTEGER}")
        UserEntity getUserById(@Param("userId") String userId);
    
        List<UserEntity> getUserByEntity( UserEntity user);
    
        UserEntity getUserByPhone(@Param("phone") String phone);
    
    }

<?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.blog4java.mybatis.example.mapper.UserMapper">
        <sql id="userAllField">
          id,create_time, name, password, phone, nick_name
        </sql>
    
        <select id="listAllUser"  resultType="com.blog4java.mybatis.example.entity.UserEntity" >
            select
            <include refid="userAllField"/>
            from user
        </select>
    
        <select id="getUserByEntity"  resultType="com.blog4java.mybatis.example.entity.UserEntity">
            select
            <include refid="userAllField"/>
            from user
            <where>
                <if test="id != null">
                    AND id = #{id}
                </if>
                <if test="name != null">
                    AND name = #{name}
                </if>
                <if test="phone != null">
                    AND phone = #{phone}
                </if>
            </where>
        </select>
    
        <select id="getUserByPhone" resultType="com.blog4java.mybatis.example.entity.UserEntity">
            select
            <include refid="userAllField"/>
            from user
            where phone = ${phone}
        </select>
    </mapper>

### 4）、通过 Mybatis 提供的 API 执行 ###

package com.blog4java.mybatis.example;
    
    import com.alibaba.fastjson.JSON;
    import com.blog4java.common.DbUtils;
    import com.blog4java.mybatis.example.entity.UserEntity;
    import com.blog4java.mybatis.example.mapper.UserMapper;
    import org.apache.ibatis.io.Resources;
    import org.apache.ibatis.session.SqlSession;
    import org.apache.ibatis.session.SqlSessionFactory;
    import org.apache.ibatis.session.SqlSessionFactoryBuilder;
    import org.apache.ibatis.session.SqlSessionManager;
    import org.junit.Before;
    import org.junit.Test;
    
    import java.io.IOException;
    import java.io.InputStream;
    import java.io.Reader;
    import java.util.List;
    
    public class MybatisExample {
        
    
        @Before
        public void initData() {
        
            DbUtils.initData();
        }
    
        @Test
        public  void testMybatis () throws IOException {
        
            // 获取配置文件输入流
            InputStream inputStream = Resources.getResourceAsStream("mybatis-config.xml");
            // 通过SqlSessionFactoryBuilder的build()方法创建SqlSessionFactory实例
            SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
            // 调用openSession()方法创建SqlSession实例
            SqlSession sqlSession = sqlSessionFactory.openSession();
            // 获取UserMapper代理对象
            UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
            // 执行Mapper方法，获取执行结果
            List<UserEntity> userList = userMapper.listAllUser();
             /*
            // 兼容Ibatis，通过Mapper Id执行SQL操作
            List<UserEntity> userList = sqlSession.selectList(
                    "com.blog4java.mybatis.com.blog4java.mybatis.example.mapper.UserMapper.listAllUser");
            */
            System.out.println(JSON.toJSONString(userList));
        }
    
        @Test
        public void testSessionManager() throws IOException {
        
            Reader mybatisConfig = Resources.getResourceAsReader("mybatis-config.xml");
            SqlSessionManager sqlSessionManager = SqlSessionManager.newInstance(mybatisConfig);
            sqlSessionManager.startManagedSession();
            UserMapper userMapper = sqlSessionManager.getMapper(UserMapper.class);
            List<UserEntity> userList = userMapper.listAllUser();
            System.out.println(JSON.toJSONString(userList));
        }
    }