Mybatis 接口方式对数据的增删改查 一对一关联查询

Posted 2020-09-12 赵天成123

数据库中有两个表 student 和studentInfo 

 

student表中的字段和数据

 

studentInfo表中的字段

 

ok数据库说完了,开始建立一个项目,对数据库中的数据进行操作吧

新建java项目,将mybatis的jar包和oracle数据库的访问包导入

 

建立几个需要用的包 entities, dao,util , test建立映射文件(.xml)和db.properties文件

db.properties:

 

 

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">
<!-- mybatis配置的根标签 -->
<configuration>
    <properties resource="db.properties"></properties>
    <!--自动扫描实体类 -->
    <typeAliases>
        <package name="com.maya.entities" />
    </typeAliases>

    <!--default等于那个就执行那个 -->
    <environments default="test">
        <environment id="test">
            <transactionManager type="JDBC"></transactionManager>
            <dataSource type="POOLED">
                <property name="driver" value="${driver}" />
                <property name="url" value="${jdbc}" />
                <property name="username" value="${user}" />
                <property name="password" value="${password}" />
            </dataSource>
        </environment>
    </environments>

<!-- 映射 -->
    <mappers>
        <package name="com.maya.dao" />
    </mappers>
</configuration>

这样,mybatis的配置文件配置完成,接下来写util文件(SqlSessionFactory)

package com.maya.util;

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 SqlSessionUtil {

    private static SqlSessionFactory sessionFactory;
    private static SqlSession session;
    
    public static SqlSession getSqlSession(){
        InputStream input=null;
        try {
            input=Resources.getResourceAsStream("mybatis-config.xml");
            sessionFactory=new SqlSessionFactoryBuilder().build(input);
            session=sessionFactory.openSession();
            input.close();
            
        } catch (Exception e) {
            e.printStackTrace();
        }
        
        return session;
    }
}

接下来写实体类:需要注意的是,如果我们需要查student,需要把studentInfo表中的数据一起查出来的话,需要写出对应的关系;(篇幅原因,get/set和构造函数就不贴进来了)

Student

package com.maya.entities;

public class Student {
    private StudentInfo studentInfo;    //studentInfo的实体类
    private String sname;
    private String ssex;
    private Integer sclass;
    private Integer mark;
}

StudentInfo

package com.maya.entities;

import java.sql.Date;

public class StudentInfo {
    
    private Integer id;
    private Integer sno;
    private String saddress;
    private Date sbirthday;
}

实体类建立完成,接下来写接口,和xml文件

package com.maya.dao;

import java.util.List;

import com.maya.entities.StudentInfo;

public interface StudentInfoMapper {

    //查询所有
    public List<StudentInfo> select();
    
    //根据sno查询
    public StudentInfo selectbysno();
}

<?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.maya.dao.StudentInfoMapper">
  <!-- 查询整个studentInfo表 -->
      <select id="select" resultType="studentInfo">
          select * from studentinfo
      </select>
  </mapper>

建立一个junit测试用例

package com.maya.test;

import static org.junit.Assert.*;
import java.util.List;
import org.apache.ibatis.session.SqlSession;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
import com.maya.dao.StudentInfoMapper;
import com.maya.entities.StudentInfo;
import com.maya.util.SqlSessionUtil;

public class TestJunit {

    private SqlSession session;
    private StudentInfoMapper sim;
    @Before
    public void setUp() throws Exception {
        //获取sqlsession 和StudentInfoMapper
        session=SqlSessionUtil.getSqlSession();
        sim=session.getMapper(StudentInfoMapper.class);
    }

    @After
    public void tearDown() throws Exception {
        session.commit();        //提交
        session.close();        //关闭
    }

    @Test
    public void test() {
        List<StudentInfo> list=sim.select();
        for(StudentInfo info:list){
            System.out.println(info);
        } 
    }
}

执行结果如下

说明我们前面配置的没有问题

建立Student接口和配置文件

package com.maya.dao;

import java.util.List;
import java.util.Map;

import com.maya.entities.Student;

public interface StudentMapper {
    //查询出所有
    public List<Student> select();
    //多条件查询
    public List<Student> select(Map<String,Object> map);
    
}

<?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.maya.dao.StudentMapper">    <!--接口的限定名  -->
    
    <resultMap type="student" id="list">
        <association property="studentInfo" column="sno" select="com.maya.dao.StudentInfoMapper.selectbysno"/>
    </resultMap>
  
  <select id="select" resultMap="list">    <!--返回的值不是单一的表的值时用Map  -->
  select * from student s join studentinfo si on s.sno=si.sno
  </select>
  </mapper>

junit测试:

package com.maya.test;

import static org.junit.Assert.*;
import java.util.List;
import org.apache.ibatis.session.SqlSession;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
import com.maya.dao.StudentInfoMapper;
import com.maya.dao.StudentMapper;
import com.maya.entities.Student;
import com.maya.entities.StudentInfo;
import com.maya.util.SqlSessionUtil;

public class TestJunit {

    private SqlSession session;
    private StudentInfoMapper sim;
    private StudentMapper sdm;
    @Before
    public void setUp() throws Exception {
        //获取sqlsession 和StudentInfoMapper
        session=SqlSessionUtil.getSqlSession();
        sim=session.getMapper(StudentInfoMapper.class);
        sdm=session.getMapper(StudentMapper.class);
    }

    @After
    public void tearDown() throws Exception {
        session.commit();        //提交
        session.close();        //关闭
    }

    @Test
    public void test() {
        List<Student> list=sdm.select();
        for(Student stu:list){
            System.out.println(stu);
        }
    

//        List<StudentInfo> list=sim.select();
//        for(StudentInfo info:list){
//            System.out.println(info);
//        }
//        
        
    }

}

结果如下