java框架之Mybatis03（一對多）

續 java框架之Mybatis03（一對一）

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數據庫

use Student;
CREATE TABLE grade (
    id INT NOT NULL PRIMARY KEY AUTO_INCREMENT,
    gradeName VARCHAR(20)

)

use student;
CREATE TABLE student (
    sno INT NOT NULL PRIMARY KEY AUTO_INCREMENT,
    sname VARCHAR(12) NOT NULL,
    sage INT NOT NULL,
    addressID INT,
    FOREIGN KEY (addressID)
        REFERENCES address (id),
    gradeID INT,
    FOREIGN KEY (gradeID)
        REFERENCES grade (id)

)

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Model

import java.util.List;

public class Grade {
    private int id;
    private String gradeName;
    private List<Student> students;
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getGradeName() {
        return gradeName;
    }
    public void setGradeName(String gradeName) {
        this.gradeName = gradeName;
    }
    public List<Student> getStudents() {
        return students;
    }
    public void setStudents(List<Student> students) {
        this.students = students;
    }
    @Override
    public String toString() {
        return "Grade [id=" + id + ", gradeName=" + gradeName + ", students=" + students + "]";
    }
}

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import com.imis.model.Grade;

public interface GradeMapper {
    
    public Grade findByID(int id);
}

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映射配置

StudentMapper.xml

<select id="findByGradeId" resultMap="StudentResult" parameterType="Integer">
         select * from student where gradeID=#{gradeID}
     </select>

 

GradeMapper.java

<?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.imis.mappers.GradeMapper">
     
     <resultMap type="Grade" id="GradeResult">
         <result property="id" column="id"/>
         <result property="gradeName" column="gradeName"/>
         <collection property="students" column="id" select="com.imis.mappers.StudentMapper.findByGradeId"></collection>
     </resultMap>
     
     <select id="findByID" parameterType="Integer" resultMap="GradeResult">
         select * from grade where id=#{id}
     </select>

 </mapper>  

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StudentMapper.java

public Student findByGradeId(int gradeID);

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測試

import org.apache.ibatis.session.SqlSession;
import org.apache.log4j.Logger;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

import com.imis.mappers.GradeMapper;
import com.imis.model.Grade;
import com.imis.util.SqlSessionFactoryUtil;

public class GradeTest {
    private static Logger logger=Logger.getLogger(GradeTest.class);
    private SqlSession sqlSession=null;
    private GradeMapper gradeMapper=null;
    @Before
    public void setUp() throws Exception {
        sqlSession=SqlSessionFactoryUtil.openSession();
        gradeMapper=sqlSession.getMapper(GradeMapper.class);
    }

    @After
    public void tearDown() throws Exception {
        sqlSession.close();
    }

    @Test
    public void testFindGradeWithStudent() {
        logger.info("查詢年級（帶學生）");
        System.out.println("1");
        Grade grade=gradeMapper.findByID(2);
        System.out.println("2");
        System.out.println(grade);
    }

}

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查詢學生帶年級，同address