Mybatis多表操作
1.多表操作概述
多表模型分类
一对一：在任意一方建立外键，关联对方的主键
一对多：在多的一方建立外键，关联一的一方的主键
多对多：借助中间表，中间表至少两个字段，分别关联两张表的主键
2.一对一操作
一对一模型： 人和身份证，一个人只有一个身份证
数据准备
sql数据准备：
CREATE TABLE person(
id INT PRIMARY KEY AUTO_INCREMENT,
NAME VARCHAR(20),
age INT
);
INSERT INTO person VALUES (NULL,'张三',23);
INSERT INTO person VALUES (NULL,'李四',24);
INSERT INTO person VALUES (NULL,'王五',25);
CREATE TABLE card(
id INT PRIMARY KEY AUTO_INCREMENT,
number VARCHAR(30),
pid INT,
CONSTRAINT cp_fk FOREIGN KEY (pid) REFERENCES person(id)
);
INSERT INTO card VALUES (NULL,'12345',1);
INSERT INTO card VALUES (NULL,'23456',2);
INSERT INTO card VALUES (NULL,'34567',3);
bean.Person:
package Mybatis03.bean;
public class Person {
private Integer id; //主键id
private String name; //人的姓名
private Integer age; //人的年龄
public Person() {
}
public Person(Integer id, String name, Integer age) {
this.id = id;
this.name = name;
this.age = age;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
@Override
public String toString() {
return "Person{" +
"id=" + id +
", name='" + name + '\'' +
", age=" + age +
'}';
}
}
bean.Card:
package Mybatis03.bean;
public class Card {
private Integer id; //主键id
private String number; //身份证号
private Person p; //所属人的对象
public Card() {
}
public Card(Integer id, String number, Person p) {
this.id = id;
this.number = number;
this.p = p;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getNumber() {
return number;
}
public void setNumber(String number) {
this.number = number;
}
public Person getP() {
return p;
}
public void setP(Person p) {
this.p = p;
}
@Override
public String toString() {
return "Card{" +
"id=" + id +
", number='" + number + '\'' +
", p=" + p +
'}';
}
}
jdbc.properties:
driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/db1
username=root
password=123456MyBatisConfig.xml:
功能实现
id 属性：唯一标识
type 属性：实体对象类型
column 属性：表中字段名称
property 属性： 实体对象变量名称
property 属性：被包含对象的变量名
javaType 属性：被包含对象的数据类型
新建one_to_one包存放对应映射配置文件
创建接口table01.OneToOneMapper
package table01;
import Mybatis03.bean.Card;
import java.util.List;
public interface OneToOneMapper {
//查询全部
public abstract List selectAll();
}
测试类：
package table01;
import Mybatis03.bean.Card;
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.Test;
import java.io.InputStream;
import java.util.List;
public class Test01 {
@Test
public void selectAll() throws Exception{
//1.加载核心配置文件
InputStream is = Resources.getResourceAsStream("MybatisConfig.xml");
// 2.获取SqlSession工厂对象
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is);
//3.通过工厂对象获取SqlSession
SqlSession sqlSession = sqlSessionFactory.openSession(true);
//4.获取StudentMapper接口的实现类对象
OneToOneMapper mapper = sqlSession.getMapper(OneToOneMapper.class);
//5.调用实现类的方法，接收结果
List list = mapper.selectAll();
//6.处理结果
for(Card c : list){
System.out.println(c);
}
//7.释放资源
sqlSession.close();
is.close();
}
} 3.一对多操作
数据准备
一对多模型： 一对多模型：班级和学生，一个班级可以有多个学生
sql数据准备：
CREATE TABLE classes(
id INT PRIMARY KEY AUTO_INCREMENT,
NAME VARCHAR(20)
);
INSERT INTO classes VALUES (NULL,'一班');
INSERT INTO classes VALUES (NULL,'二班');
CREATE TABLE student(
id INT PRIMARY KEY AUTO_INCREMENT,
NAME VARCHAR(30),
age INT,
cid INT,
CONSTRAINT cs_fk FOREIGN KEY (cid) REFERENCES classes(id)
);
INSERT INTO student VALUES (NULL,'张三',23,1);
INSERT INTO student VALUES (NULL,'李四',24,1);
INSERT INTO student VALUES (NULL,'王五',25,2);
INSERT INTO student VALUES (NULL,'赵六',26,2);
bean.Classes：
package Mybatis03.bean;
import java.util.List;
public class Classes {
private Integer id; //主键id
private String name; //班级名称
private List students; //班级中所有学生对象 一个班级里多个学生
public Classes() {
}
public Classes(Integer id, String name, List students) {
this.id = id;
this.name = name;
this.students = students;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public List getStudents() {
return students;
}
public void setStudents(List students) {
this.students = students;
}
@Override
public String toString() {
return "Classes{" +
"id=" + id +
", name='" + name + '\'' +
", students=" + students +
'}';
}
}
bean.Student：
package Mybatis03.bean;
public class Student {
private Integer id; //主键id
private String name; //学生姓名
private Integer age; //学生年龄
public Student() {
}
public Student(Integer id, String name, Integer age) {
this.id = id;
this.name = name;
this.age = age;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
@Override
public String toString() {
return "Classes{" +
"id=" + id +
", name='" + name + '\'' +
", age=" + age +
'}';
}
}
功能实现
id 属性：唯一标识
type 属性：实体对象类型
column 属性：表中字段名称
property 属性： 实体对象变量名称
property 属性：被包含集合对象的变量名
ofType 属性：集合中保存的对象数据类型
新建one_to_many包存放映射配置文件
配置映射文件：
创建接口：
package Mybatis03.table02;
import Mybatis03.bean.Classes;
import java.util.List;
public interface OneToManyMapper {
//查询全部
public abstract List selectAll();
}
测试类：
package Mybatis03.table02;
import Mybatis03.bean.Classes;
import Mybatis03.bean.Student;
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.Test;
import java.io.InputStream;
import java.util.List;
public class Test01 {
@Test
public void selectAll() throws Exception {
//1.加载核心配置文件
InputStream is = Resources.getResourceAsStream("MybatisConfig.xml");
//2.获取SqlSession工厂对象
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is);
//3.通过工厂对象获取SqlSession
SqlSession sqlSession = sqlSessionFactory.openSession(true);
//4.获取OneToManyMapper接口的实现类对象
OneToManyMapper mapper = sqlSession.getMapper(OneToManyMapper.class);
//5.调用实现类的方法，接收结果
List classes = mapper.selectAll();
//6.处理结果
for(Classes cls : classes){
System.out.println(cls.getId()+","+cls.getName());
List students = cls.getStudents();
for(Student student : students){
System.out.println("\t"+student);
}
}
//7.释放资源
sqlSession.close();
is.close();
}
}
4.多对多操作
数据准备
多对多模型：学生和课程，一个学生可以选择多门课程、一个课程也可以被多个学生所选择
sql数据准备：
CREATE TABLE course(
id INT PRIMARY KEY AUTO_INCREMENT,
NAME VARCHAR(20)
);
INSERT INTO course VALUES (NULL,'语文');
INSERT INTO course VALUES (NULL,'数学');
CREATE TABLE stu_cr(
id INT PRIMARY KEY AUTO_INCREMENT,
sid INT,
cid INT,
CONSTRAINT sc_fk1 FOREIGN KEY (sid) REFERENCES student(id),
CONSTRAINT sc_fk2 FOREIGN KEY (cid) REFERENCES course(id)
);
INSERT INTO stu_cr VALUES (NULL,1,1);
INSERT INTO stu_cr VALUES (NULL,1,2);
INSERT INTO stu_cr VALUES (NULL,2,1);
INSERT INTO stu_cr VALUES (NULL,2,2);
bean.Course：
package Mybatis03.bean;
public class Course {
private Integer id; //主键id
private String name; //课程名称
public Course() {
}
public Course(Integer id, String name) {
this.id = id;
this.name = name;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
@Override
public String toString() {
return "Course{" +
"id=" + id +
", name='" + name + '\'' +
'}';
}
}
修改bean.Student：
package Mybatis03.bean;
import java.util.List;
public class Student {
private Integer id; //主键id
private String name;//学生姓名
private Integer age;//学生年龄
private List courses;//学生所选择的课程集合
public Student() {
}
public Student(Integer id, String name, Integer age, List courses) {
this.id = id;
this.name = name;
this.age = age;
this.courses = courses;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
public List getCourses() {
return courses;
}
public void setCourses(List courses) {
this.courses = courses;
}
@Override
public String toString() {
return "Student{" +
"id=" + id +
", name='" + name + '\'' +
", age=" + age +
", courses=" + courses +
'}';
}
} 功能实现
id 属性：唯一标识
type 属性：实体对象类型
column 属性：表中字段名称
property 属性： 实体对象变量名称
property 属性：被包含集合对象的变量名
ofType 属性：集合中保存的对象数据类型
配置文件：
配置映射文件：
接口：
package Mybatis03.table03;
import Mybatis03.bean.Student;
import java.util.List;
public interface ManyToManyMapper {
//查询全部
public abstract List selectAll();
}
测试类：
package Mybatis03.table03;
import Mybatis03.bean.Course;
import Mybatis03.bean.Student;
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.Test;
import java.io.InputStream;
import java.util.List;
public class Test01 {
@Test
public void selectAll() throws Exception {
//1.加载核心配置文件
InputStream is = Resources.getResourceAsStream("MybatisConfig.xml");
//2.获取SqlSession工厂对象
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is);
//3.通过工厂对象获取SqlSession
SqlSession sqlSession = sqlSessionFactory.openSession(true);
//4.获取ManyToManyMapper接口的实现类对象
ManyToManyMapper mapper = sqlSession.getMapper(ManyToManyMapper.class);
//5.调用实现类的方法，接收结果
List students = mapper.selectAll();
//6.处理结果
for (Student student : students) {
System.out.println(student.getId()+","+student.getName()+","+student.getAge());
List courses = student.getCourses();
for(Course course : courses){
System.out.println("\t"+course);
}
}
//7.释放资源
sqlSession.close();
is.close();
}
}