MyBatis中一对一表关系查询案例(一)

1 准备两张表employee_basic（员工信息表）,employee_school(员工学历表)


2 在两张表中写入部分测试数据


3 创建pojo实体类

package com.zxf.pojo;

import java.io.Serializable;

public class Employee implements Serializable {
    private String emp_no;
    private String emp_name;
    private String dept_id;
    private String emp_gender;
    private String emp_email;
    //员工基本情况表和员工学历表是一对一的关系，每一个员工有且只有一份学历表
    private EmployeeSchool employeeSchool;

    public String getEmp_no() {
        return emp_no;
    }

    public void setEmp_no(String emp_no) {
        this.emp_no = emp_no;
    }

    public String getEmp_name() {
        return emp_name;
    }

    public void setEmp_name(String emp_name) {
        this.emp_name = emp_name;
    }

    public String getDept_id() {
        return dept_id;
    }

    public void setDept_id(String dept_id) {
        this.dept_id = dept_id;
    }

    public String getEmp_gender() {
        return emp_gender;
    }

    public void setEmp_gender(String emp_gender) {
        this.emp_gender = emp_gender;
    }

    public String getEmp_email() {
        return emp_email;
    }

    public void setEmp_email(String emp_email) {
        this.emp_email = emp_email;
    }

    public EmployeeSchool getEmployeeSchool() {
        return employeeSchool;
    }

    public void setEmployeeSchool(EmployeeSchool employeeSchool) {
        this.employeeSchool = employeeSchool;
    }

}

package com.zxf.pojo;

import java.io.Serializable;

public class EmployeeSchool implements Serializable {
    private String emp_id;
    private String emp_xueli;
    private String emp_major;
    private String by_date;
    private String by_school;

    public String getEmp_id() {
        return emp_id;
    }

    public void setEmp_id(String emp_id) {
        this.emp_id = emp_id;
    }

    public String getEmp_xueli() {
        return emp_xueli;
    }

    public void setEmp_xueli(String emp_xueli) {
        this.emp_xueli = emp_xueli;
    }

    public String getEmp_major() {
        return emp_major;
    }

    public void setEmp_major(String emp_major) {
        this.emp_major = emp_major;
    }

    public String getBy_date() {
        return by_date;
    }

    public void setBy_date(String by_date) {
        this.by_date = by_date;
    }

    public String getBy_school() {
        return by_school;
    }

    public void setBy_school(String by_school) {
        this.by_school = by_school;
    }
}

3 编写Mapper层的数据库操作接口类

package com.zxf.mapper;

import com.zxf.pojo.EmployeeSchool;

public interface EmployeeSchoolMapper {
    public EmployeeSchool selectEmployeeSchoolById(String emp_id);
}

4 编写对应接口的Mybatis的映射配置文件

<?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="com.zxf.mapper.EmployeeMapper">
    <!-- 根据 emp_no 查询 Employee，返回 resultMap -->
      <select id="selectEmployeeById" parameterType="String" resultMap="employeeMap">
          SELECT * FROM employee_basic WHERE emp_no=#{id}
      </select>
    <!-- 映射 Employee 对象的resultMap -->
    <resultMap id="employeeMap" type="Employee">
        <id property="emp_no" column="emp_no"></id>
        <result property="emp_name" column="emp_name"></result>
        <result property="dept_id" column="dept_id"></result>
        <result property="emp_gender" column="emp_gender"></result>
        <result property="emp_email" column="emp_email"></result>
        <!-- 一对一关联映射:association -->
          <association property="employeeSchool" column="emp_no"
                       select="com.zxf.mapper.EmployeeSchoolMapper.selectEmployeeSchoolById"
          javaType="EmployeeSchool"/>

    </resultMap>
</mapper>

<?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.zxf.mapper.EmployeeSchoolMapper">
    <select id="selectEmployeeSchoolById" resultType="EmployeeSchool" parameterType="string">
        SELECT * from employee_school WHERE emp_id=#{emp_id}
    </select>
</mapper>

5 编写Mybatis的核心数据库资源配置文件

<?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>
    <properties resource="jdbc.properties"/>
    <settings>
        <setting name="logImpl" value="LOG4J"/>
    </settings>
    <typeAliases>
        <package name="com.zxf.pojo"/>
    </typeAliases>

    <!-- default引用environment的id,当前所使用的环境 -->
    <environments default="abc">
        <environment id="abc">
            <transactionManager type="JDBC"></transactionManager>
            <dataSource type="POOLED">
                <property name="driver" value="${jdbc.driver}"/>
                <property name="url" value="${jdbc.url}"/>
                <property name="username" value="${jdbc.user}"/>
                <property name="password" value="${jdbc.password}"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper class="com.zxf.mapper.EmployeeSchoolMapper"/>
        <mapper class="com.zxf.mapper.EmployeeMapper"/>
    </mappers>
</configuration>

数据库属性文件

jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://192.168.0.148:3306/test
jdbc.user=root
jdbc.password=abc123

6 编写测试程序

package com.zxf;

import com.zxf.mapper.EmployeeMapper;
import com.zxf.mapper.EmployeeSchoolMapper;
import com.zxf.mapper.TeacherMapper;
import com.zxf.pojo.Employee;
import com.zxf.pojo.EmployeeSchool;
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.After;
import org.junit.Before;
import org.junit.Test;

import java.io.InputStream;

public class Test6 {
    private SqlSessionFactory sqlSessionFactory;
    private SqlSession session;
    //private EmployeeSchoolMapper employeeSchoolMapper;
    private EmployeeMapper employeeMapper;
    private InputStream is;
    @Before  //用于测试方法之前执行。
    public   void init() throws Exception{
        is= Resources.getResourceAsStream("zhangMyBatis.xml");
        sqlSessionFactory = new SqlSessionFactoryBuilder().build(is);
        session=sqlSessionFactory.openSession();
        employeeMapper=session.getMapper(EmployeeMapper.class);
    }
    @After  //用于测试方法之后执行。
    public void destory()throws Exception{
        session.commit();
        session.close();
        is.close();
    }
    /*
    @Test
    public void test1(){
        EmployeeSchool employeeSchool = employeeSchoolMapper.selectEmployeeSchoolById("HW9808");
        System.out.println(employeeSchool.getEmp_xueli()+","+employeeSchool.getBy_school()+","+employeeSchool.getEmp_major());
    }
    */
    @Test
    public void test2(){
        Employee employee = employeeMapper.selectEmployeeById("HW9806");
        System.out.println(employee.getEmp_name()+","+employee.getEmployeeSchool().getBy_school());

    }
}

例如查询员工编号为HW9806的学历和名字