Mybatis一对一，一对多关联查询
classes和teacher为一对一关联
classes和student为一对多关联
classes sql
CREATE TABLE `NewTable` ( `class_id` int(11) NOT NULL AUTO_INCREMENT , `class_name` varchar(255) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL , `class_year` varchar(255) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL , `teacher_id` int(11) NULL DEFAULT NULL , PRIMARY KEY (`class_id`) ) ENGINE=InnoDB DEFAULT CHARACTER SET=utf8 COLLATE=utf8_general_ci AUTO_INCREMENT=2 ROW_FORMAT=COMPACT ;
teacher sql
CREATE TABLE `NewTable` ( `teacher_id` int(11) NOT NULL AUTO_INCREMENT , `teacher_name` varchar(255) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL , `teacher_sex` varchar(255) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL , `teacher_birthday` date NULL DEFAULT NULL , `work_date` int(11) NULL DEFAULT NULL , `professional` varchar(255) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL , PRIMARY KEY (`teacher_id`) ) ENGINE=InnoDB DEFAULT CHARACTER SET=utf8 COLLATE=utf8_general_ci AUTO_INCREMENT=2 ROW_FORMAT=COMPACT ;
student sql
CREATE TABLE `NewTable` ( `student_id` int(11) NOT NULL AUTO_INCREMENT , `student_name` varchar(10) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL , `student_sex` varchar(10) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL , `student_birthday` date NULL DEFAULT NULL , `class_id` int(11) NULL DEFAULT NULL , PRIMARY KEY (`student_id`) ) ENGINE=InnoDB DEFAULT CHARACTER SET=utf8 COLLATE=utf8_general_ci AUTO_INCREMENT=3 ROW_FORMAT=COMPACT ;
classes
package com.mybatis.model;
import java.util.List;
public class classes {
private Integer class_id;
private String class_name;
private String class_year;
private Integer teacher_id;
private teacher teacher;
private List<student> studentList;
public List<student> getStudentList() {
return studentList;
}
public void setStudentList(List<student> studentList) {
this.studentList = studentList;
}
public teacher getTeacher() {
return teacher;
}
public void setTeacher(teacher teacher) {
this.teacher = teacher;
}
public Integer getClass_id() {
return class_id;
}
public void setClass_id(Integer class_id) {
this.class_id = class_id;
}
public String getClass_name() {
return class_name;
}
public void setClass_name(String class_name) {
this.class_name = class_name == null ? null : class_name.trim();
}
public String getClass_year() {
return class_year;
}
public void setClass_year(String class_year) {
this.class_year = class_year == null ? null : class_year.trim();
}
public Integer getTeacher_id() {
return teacher_id;
}
public void setTeacher_id(Integer teacher_id) {
this.teacher_id = teacher_id;
}
}
teacher
package com.mybatis.model;
import java.util.Date;
public class teacher {
private Integer teacher_id;
private String teacher_name;
private String teacher_sex;
private Date teacher_birthday;
private Integer work_date;
private String professional;
public teacher() {
}
public Integer getTeacher_id() {
return teacher_id;
}
public void setTeacher_id(Integer teacher_id) {
this.teacher_id = teacher_id;
}
public String getTeacher_name() {
return teacher_name;
}
public void setTeacher_name(String teacher_name) {
this.teacher_name = teacher_name == null ? null : teacher_name.trim();
}
public String getTeacher_sex() {
return teacher_sex;
}
public void setTeacher_sex(String teacher_sex) {
this.teacher_sex = teacher_sex == null ? null : teacher_sex.trim();
}
public Date getTeacher_birthday() {
return teacher_birthday;
}
public void setTeacher_birthday(Date teacher_birthday) {
this.teacher_birthday = teacher_birthday;
}
public Integer getWork_date() {
return work_date;
}
public void setWork_date(Integer work_date) {
this.work_date = work_date;
}
public String getProfessional() {
return professional;
}
public void setProfessional(String professional) {
this.professional = professional == null ? null : professional.trim();
}
}
注意：teacher类中有一个无参构造，若一对一关联查询时候，被查询类缺少无参构造会报错
student
package com.mybatis.model;
import java.util.Date;
public class student {
private Integer student_id;
private String student_name;
private String student_sex;
private Date student_birthday;
private Integer class_id;
public student() {
super();
}
public Integer getStudent_id() {
return student_id;
}
public void setStudent_id(Integer student_id) {
this.student_id = student_id;
}
public String getStudent_name() {
return student_name;
}
public void setStudent_name(String student_name) {
this.student_name = student_name == null ? null : student_name.trim();
}
public String getStudent_sex() {
return student_sex;
}
public void setStudent_sex(String student_sex) {
this.student_sex = student_sex == null ? null : student_sex.trim();
}
public Date getStudent_birthday() {
return student_birthday;
}
public void setStudent_birthday(Date student_birthday) {
this.student_birthday = student_birthday;
}
public Integer getClass_id() {
return class_id;
}
public void setClass_id(Integer class_id) {
this.class_id = class_id;
}
}
classesMap
package com.mybatis.dao;
import org.springframework.stereotype.Repository;
import com.mybatis.model.classes;
@Repository
public interface classesMapper {
classes getClass(Integer class_id);
}
teacherMap
package com.mybatis.dao;
import org.springframework.stereotype.Repository;
import com.mybatis.model.teacher;
@Repository
public interface teacherMapper {
teacher getTeacher(Integer teacher_id);
}
studentMap
package com.mybatis.dao;
import java.util.List;
import org.springframework.stereotype.Repository;
import com.mybatis.model.student;
@Repository
public interface studentMapper {
List<student>getStudentByClassID();
}
classesMap.xml
<?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.mybatis.dao.classesMapper" >
<resultMap id="ClassesResultMap" type="com.mybatis.model.classes" >
<id column="class_id" property="class_id" jdbcType="INTEGER" />
<result column="class_name" property="class_name" jdbcType="VARCHAR" />
<result column="class_year" property="class_year" jdbcType="VARCHAR" />
<result column="teacher_id" property="teacher_id" jdbcType="INTEGER" />
<association property="teacher" column="teacher_id" select="com.mybatis.dao.teacherMapper.getTeacher" />
<collection property="studentList" column="class_id" javaType="ArrayList" ofType="com.mybatis.model.student" select="com.mybatis.dao.studentMapper.getStudentByClassID"/>
</resultMap>
<select id="getClasses" resultMap="ClassesResultMap" parameterType="java.lang.Integer" >
select *
from classes
where class_id = #{class_id}
</select>
</mapper>
注意：一对一用association,一对多用collection,当中ofType和select指定包名方法
teacherMap.xml
<?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.mybatis.dao.teacherMapper" >
<resultMap id="TeacherResultMap" type="com.mybatis.model.teacher" >
<id column="teacher_id" property="teacher_id" jdbcType="INTEGER" />
<result column="teacher_name" property="teacher_name" jdbcType="VARCHAR" />
<result column="teacher_sex" property="teacher_sex" jdbcType="VARCHAR" />
<result column="teacher_birthday" property="teacher_birthday" jdbcType="DATE" />
<result column="work_date" property="work_date" jdbcType="INTEGER" />
<result column="professional" property="professional" jdbcType="VARCHAR" />
</resultMap>
<select id="getTeacher" resultMap="TeacherResultMap" parameterType="java.lang.Integer" >
select *
from teacher
where teacher_id = #{teacher_id}
</select>
</mapper>
注意 2个xml的resultMap id不要重复，不然可能报错
studentMap.xml
<?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.mybatis.dao.studentMapper" >
<resultMap id="StudentResultMap" type="com.mybatis.model.student" >
<id column="student_id" property="student_id" jdbcType="INTEGER" />
<result column="student_name" property="student_name" jdbcType="VARCHAR" />
<result column="student_sex" property="student_sex" jdbcType="VARCHAR" />
<result column="student_birthday" property="student_birthday" jdbcType="DATE" />
<result column="class_id" property="class_id" jdbcType="INTEGER" />
</resultMap>
<select id="getStudentByClassID" parameterType="int" resultMap="StudentResultMap">
select *
from student
where student.class_id = #{class_id}
</select>
</mapper>
testController
package com.mybatis.controller;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import com.mybatis.model.classes;
import com.mybatis.model.student;
@Controller
public class TestController {
@Autowired
private com.mybatis.dao.classesMapper classesMapper;
@RequestMapping(value = "/nv/test1" ,method=RequestMethod.GET)
public ResponseEntity<?> indexPage() {
classes classes=classesMapper.getClasses(1);
List<student>students=classes.getStudentList();
for (student student : students) {
System.out.println(student.getStudent_name());
}
System.out.println(classes.getClass_name());
System.out.println(classes.getTeacher().getTeacher_name());
System.out.println(classes.getClass_name());
return new ResponseEntity<String>(HttpStatus.OK);
}
}