Mybatis + MP

下面演示，通过纯Mybatis与Mybatis-Plus整合。

创建子Module

log4j.properties：

log4j.rootLogger=DEBUG,A1

log4j.appender.A1=org.apache.log4j.ConsoleAppender
log4j.appender.A1.layout=org.apache.log4j.PatternLayout
log4j.appender.A1.layout.ConversionPattern=[%t] [%c]-[%p] %m%n

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Mybatis实现查询User

第一步，编写mybatis-config.xml文件：

<?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>
    <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://127.0.0.1:3306/mp?useUnicode=true&amp;characterEncoding=utf8&amp;autoReconnect=true&amp;allowMultiQueries=true&amp;useSSL=false"/>
                <property name="username" value="root"/>
                <property name="password" value="1234"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="UserMapper.xml"/>
    </mappers>
</configuration>

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第二步，编写User实体对象：（这里使用lombok进行了简化bean操作）

package org.hong.pojo;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

@Data
@NoArgsConstructor
@AllArgsConstructor
public class User {
    private Long id;
    private String userName;
    private String password;
    private String name;
    private Integer age;
    private String email;
}

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第三步，编写UserMapper接口：

package org.hong.mapper;

import org.hong.pojo.User;

import java.util.List;

public interface UserMapper {
    List<User> findAll();
}

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第四步，编写UserMapper.xml文件：

<?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="cn.itcast.mp.simple.mapper.UserMapper">
    <select id="findAll" resultType="org.hong.pojo.User">
        select * from tb_user
    </select>
</mapper>

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第五步，编写TestMybatis测试用例：

package org.hong;

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.hong.mapper.UserMapper;
import org.hong.pojo.User;
import org.junit.Test;

import java.io.IOException;
import java.io.InputStream;
import java.util.List;

public class TestMyBatis {

    public SqlSessionFactory getSqlSessionFactory() {
        try {
            String config = "mybatis-config.xml";
            InputStream resourceAsStream = Resources.getResourceAsStream(config);
            SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream);
            return sqlSessionFactory;
        } catch (IOException e) {
            e.printStackTrace();
            return null;
        }
    }

    @Test
    public void testFindAll() {
        SqlSession sqlSession = getSqlSessionFactory().openSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        List<User> users = mapper.findAll();
        for (User user : users) {
            System.out.println(user);
        }
    }
}

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测试结果：

[main] [org.hong.mapper.UserMapper.findAll]-[DEBUG] ==> Parameters:
[main] [org.hong.mapper.UserMapper.findAll]-[DEBUG] <== Total: 5
User(id=1, userName=null, password=123456, name=张三, age=18, email=test1@itcast.cn)
User(id=2, userName=null, password=123456, name=李四, age=20, email=test2@itcast.cn)
User(id=3, userName=null, password=123456, name=王五, age=28, email=test3@itcast.cn)
User(id=4, userName=null, password=123456, name=赵六, age=21, email=test4@itcast.cn)
User(id=5, userName=null, password=123456, name=孙七, age=24, email=test5@itcast.cn)

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Mybatis+MP实现查询User

第一步，将UserMapper继承BaseMapper，将拥有了BaseMapper中的所有方法：

package org.hong.mapper;

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import org.hong.pojo.User;

import java.util.List;

public interface UserMapper extends BaseMapper<User> {
    List<User> findAll();
}

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第二步，使用MP中的MybatisSqlSessionFactoryBuilder进程构建：

package org.hong;

import com.baomidou.mybatisplus.core.MybatisSqlSessionFactoryBuilder;
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.hong.mapper.UserMapper;
import org.hong.pojo.User;
import org.junit.Test;

import java.io.IOException;
import java.io.InputStream;
import java.util.List;

public class TestMyBatis {

    public SqlSessionFactory getSqlSessionFactory() {
        try {
            String config = "mybatis-config.xml";
            InputStream resourceAsStream = Resources.getResourceAsStream(config);
            // 这里使用的是MP中的MybatisSqlSessionFactoryBuilder
            SqlSessionFactory sqlSessionFactory = new MybatisSqlSessionFactoryBuilder().build(resourceAsStream);
            return sqlSessionFactory;
        } catch (IOException e) {
            e.printStackTrace();
            return null;
        }
    }

    @Test
    public void testFindAll() {
        SqlSession sqlSession = getSqlSessionFactory().openSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        // 可以调用BaseMapper中定义的方法
        List<User> users = mapper.selectList(null);
        for (User user : users) {
            System.out.println(user);
        }
    }
}

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运行报错：

解决：在User类中添加@TableName，指定数据库表名

package org.hong.pojo;

import com.baomidou.mybatisplus.annotation.TableName;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

@Data
@NoArgsConstructor
@AllArgsConstructor
@TableName("tb_user")
public class User {
    private Long id;
    private String userName;
    private String password;
    private String name;
    private Integer age;
    private String email;
}

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再次运行：

[main] [cn.itcast.mp.simple.mapper.UserMapper.selectList]-[DEBUG] ==> Preparing:
SELECT id,user_name,password,name,age,email FROM tb_user
[main] [cn.itcast.mp.simple.mapper.UserMapper.selectList]-[DEBUG] ==> Parameters:
[main] [cn.itcast.mp.simple.mapper.UserMapper.selectList]-[DEBUG] <== Total: 5
User(id=1, userName=zhangsan, password=123456, name=张三, age=18, email=test1@itcast.cn)
User(id=2, userName=lisi, password=123456, name=李四, age=20, email=test2@itcast.cn)
User(id=3, userName=wangwu, password=123456, name=王五, age=28, email=test3@itcast.cn)
User(id=4, userName=zhaoliu, password=123456, name=赵六, age=21, email=test4@itcast.cn)
User(id=5, userName=sunqi, password=123456, name=孙七, age=24, email=test5@itcast.cn)

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简单说明：

由于使用了MybatisSqlSessionFactoryBuilder进行了构建，继承的BaseMapper中的方法就载入到了 SqlSession中，所以就可以直接使用相关的方法；

上次更新: 2024/03/29, 08:56:31

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