mybatis——配置文件中mapper的namespace绑定接口

在mybatis中，映射文件中的namespace是用于绑定Dao接口的，即面向接口编程。

当你的namespace绑定接口后，你可以不用写接口实现类，mybatis会通过该绑定自动帮你找到对应要执行的SQL语句

以下为项目图和数据库表

    

mybatis-config

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "mybatis-3-config.dtd">
<configuration>
    <settings>
        <!-- 指定使用LOG4J输出日志 -->
        <setting name="logImpl" value="LOG4J"/>
    </settings>
    <typeAliases>
        <!-- 配置包的别名，通常在使用类时需要使用类的全限定名称，使用该配置后只要直接使用类名即可 -->
        <package name="com.etc.model"/>
    </typeAliases>
    <!-- 数据库环境 -->
    <environments default="development">
        <environment id="development">
            <!-- 采用JDBC管理器方式 -->
            <transactionManager type="JDBC"/>
            <!-- POOLED采用mybabtis内部连接池方式 -->
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis"/>
                <property name="username" value="root"/>
                <property name="password" value="1234"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="userMapping.xml"/>
    </mappers>
</configuration>

mapper中namespace绑定接口

<?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.etc.dao.UserDao">
    <insert id="insert" parameterType="User" useGeneratedKeys="true" keyProperty="id">
        insert into
        users(name,password)
        values(#{name},#{password})
    </insert>

    <insert id="insert2" parameterType="User" >
        insert into
        users(name,password)
        values(#{name},#{password})
        <selectKey keyProperty="id" keyColumn="id" resultType="int" order="AFTER">
            SELECT  LAST_INSERT_ID()
        </selectKey>
    </insert>

    <select id="getById" parameterType="int" resultType="User">
        select * from
        users where id=#{id}
    </select>

    <delete id="deleteById" parameterType="int">
        delete from
        users where id=#{id}
    </delete>

    <select id="queryAll" resultType="User">
        select * from users
    </select>

    <update id="updateById" parameterType="User">
        update users
        set
        name=#{name},password=#{password}
        where id=#{id}
    </update>

</mapper>

log4j.properties

#全局配置
log4j.rootLogger=ERROR,stdout

#MyBatis日志配置
log4j.logger.com.etc.dao=TRACE

#控制台输出配置
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%5p [%t] - %m%n

UserDao

package com.etc.dao;

import com.etc.model.User;

import java.util.List;

public interface UserDao {

    List<User> queryAll();

    int insert(User user);
  
}

BaseMapper

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.junit.Before;

import java.io.IOException;
import java.io.InputStream;

public class BaseMapper {

    private  SqlSessionFactory sqlSessionFactory;

    @Before
    public  void init() throws IOException {
        InputStream inputStream = null;
        try {
            String resource = "mybatis-config.xml";
            inputStream = Resources.getResourceAsStream(resource);
            this.sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

        }catch (Exception e){
            e.printStackTrace();
        }finally {
            if (inputStream!=null){
                inputStream.close();
            }
        }
    }

    public SqlSession getSqlSession(){
        return this.sqlSessionFactory.openSession();
    }
}

UserTest

import com.etc.model.User;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.List;

public class UserTest extends BaseMapper {


    @Test
    public void testSelectAll(){
        try {
            SqlSession sqlSession = this.getSqlSession();
            List<User> list = sqlSession.selectList("queryAll");
            sqlSession.close();
            for (User user : list){
                System.out.println(user.getName()+"__"+user.getPassword());
            }
        }catch (Exception e){
            e.printStackTrace();
        }
    }

    @Test
    public void testInsert(){
        try {
            User user = new User();
            user.setName("龙宫");
            user.setPassword("456");
            SqlSession sqlSession  = this.getSqlSession();
            sqlSession.insert("insert",user);
            sqlSession.commit();
            sqlSession.close();
        }catch (Exception e){
            e.printStackTrace();
        }
    }
}

效果图