多表模型：

• 多表模型分類 一對一：在任意一方建立外鍵，關(guān)聯(lián)對方的主鍵。
• 一對多：在多的一方建立外鍵，關(guān)聯(lián)一的一方的主鍵。
• 多對多：借助中間表，中間表至少兩個字段，分別關(guān)聯(lián)兩張表的主鍵。

多表模型一對一操作：

sql語句準備

CREATE TABLE person(id INT PRIMARY KEY AUTO_INCREMENT,NAME VARCHAR(20),age INT ); INSERT INTO person VALUES (NULL,'張三',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);

配置文件

<?xml version="1.0" encoding="UTF-8" ?> <!DOCTYPE mapperPUBLIC "-//mybatis.org//DTD Mapper 3.0//EN""http://mybatis.org/dtd/mybatis-3-mapper.dtd"><mapper namespace="com.duobiao.table.One"> <!-- <resultMap>：配置字段和實體對象屬性的映射關(guān)系標簽。 id 屬性：唯一標識 type 屬性：實體對象類型<id>：配置主鍵映射關(guān)系標簽。 <result>：配置非主鍵映射關(guān)系標簽。column 屬性：表中字段名稱property 屬性： 實體對象變量名稱 <association>：配置被包含對象的映射關(guān)系標簽。property 屬性：被包含對象的變量名javaType 屬性：被包含對象的數(shù)據(jù)類型 --><!--配置字段和實體對象屬性的映射關(guān)系--><resultMap id="oneToOne" type="card"><id column="cid" property="id" /><result column="number" property="number" /><association property="p" javaType="person"><id column="pid" property="id" /><result column="name" property="name" /><result column="age" property="age" /></association></resultMap><select id="selectAll" resultMap="oneToOne">SELECT c.id cid,number,pid,NAME,age FROM card c,person p WHERE c.pid=p.id</select> </mapper>

核心配置文件

<!--起別名--><typeAliases><package name="com.duobiao.bean"/></typeAliases> <!-- mappers引入映射配置文件 --><mappers><!-- mapper 引入指定的映射配置文件 resource屬性指定映射配置文件的名稱 --><mapper resource="OneToOneMapper.xml"/></mappers>

bean包

public class Person {private Integer id;private String name;private Integer age; }public class Card {// 主鍵idprivate Integer id;// 身份證號private String number;// 所屬人對象private Person p; }

接口：

public interface OneToOneMapper {// 查詢?nèi)?/span>List<Card> selectAll(); }

測試類

@Testpublic void selectAll() throws Exception{//1.加載核心配置文件InputStream is = Resources.getResourceAsStream("MyBatisConfig.xml");//2.獲取SqlSession工廠對象SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is);//3.通過工廠對象獲取SqlSession對象SqlSession sqlSession = sqlSessionFactory.openSession(true);//4.獲取OneToOneMapper接口的實現(xiàn)類對象OneToOneMapper mapper = sqlSession.getMapper(OneToOneMapper.class);//5.調(diào)用實現(xiàn)類的方法，接收結(jié)果List<Card> list = mapper.selectAll();//6.處理結(jié)果for (Card c : list) {System.out.println(c);}//7.釋放資源sqlSession.close();is.close();}

一對多：

sql數(shù)據(jù)：

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,'張三',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,'趙六',26,2);

bean：

public class Student {private Integer id;private String name;private Integer age; }public class Classes {// 主鍵idprivate Integer id;// 班級名private String name;// 班級中所有的學生private List<Student> students; }

配置文件：

<?xml version="1.0" encoding="UTF-8" ?> <!DOCTYPE mapperPUBLIC "-//mybatis.org//DTD Mapper 3.0//EN""http://mybatis.org/dtd/mybatis-3-mapper.dtd"><mapper namespace="com.table.OneToManyMapper"><resultMap id="oneToMany" type="classes"><id column="cid" property="id"/><result column="cname" property="name"/><!--collection：配置被包含的集合對象映射關(guān)系property：被包含對象的變量名ofType：被包含對象的實際數(shù)據(jù)類型--><collection property="students" ofType="student"><id column="sid" property="id"/><result column="sname" property="name"/><result column="sage" property="age"/></collection></resultMap><select id="selectAll" resultMap="oneToMany">SELECT c.id cid,c.name cname,s.id sid,s.name sname,s.age sage FROM classes c,student s WHERE c.id=s.cid</select> </mapper>

測試：

@Testpublic void selectAll() throws Exception{//1.加載核心配置文件InputStream is = Resources.getResourceAsStream("MyBatisConfig.xml");//2.獲取SqlSession工廠對象SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is);//3.通過工廠對象獲取SqlSession對象SqlSession sqlSession = sqlSessionFactory.openSession(true);//4.獲取OneToManyMapper接口的實現(xiàn)類對象OneToManyMapper mapper = sqlSession.getMapper(OneToManyMapper.class);//5.調(diào)用實現(xiàn)類的方法，接收結(jié)果List<Classes> classes = mapper.selectAll();//6.處理結(jié)果for (Classes cls : classes) {System.out.println(cls.getId() + "," + cls.getName());List<Student> students = cls.getStudents();for (Student student : students) {System.out.println("\t" + student);}}//7.釋放資源sqlSession.close();is.close();}

多對多：

sql語句：

CREATE TABLE course(id INT PRIMARY KEY AUTO_INCREMENT,NAME VARCHAR(20) ); INSERT INTO course VALUES (NULL,'語文'); INSERT INTO course VALUES (NULL,'數(shù)學');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);

配置文件：

<?xml version="1.0" encoding="UTF-8" ?> <!DOCTYPE mapperPUBLIC "-//mybatis.org//DTD Mapper 3.0//EN""http://mybatis.org/dtd/mybatis-3-mapper.dtd"><mapper namespace="com.tableManyToManyMapper"><resultMap id="manyToMany" type="student"><id column="sid" property="id"/><result column="sname" property="name"/><result column="sage" property="age"/><collection property="courses" ofType="course"><id column="cid" property="id"/><result column="cname" property="name"/></collection></resultMap><select id="selectAll" resultMap="manyToMany">SELECT sc.sid,s.name sname,s.age sage,sc.cid,c.name cname FROM student s,course c,stu_cr sc WHERE sc.sid=s.id AND sc.cid=c.id</select> </mapper>

測試：

@Testpublic void selectAll() throws Exception{//1.加載核心配置文件InputStream is = Resources.getResourceAsStream("MyBatisConfig.xml");//2.獲取SqlSession工廠對象SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is);//3.通過工廠對象獲取SqlSession對象SqlSession sqlSession = sqlSessionFactory.openSession(true);//4.獲取ManyToManyMapper接口的實現(xiàn)類對象ManyToManyMapper mapper = sqlSession.getMapper(ManyToManyMapper.class);//5.調(diào)用實現(xiàn)類的方法，接收結(jié)果List<Student> students = mapper.selectAll();//6.處理結(jié)果for (Student student : students) {System.out.println(student.getId() + "," + student.getName() + "," + student.getAge());List<Course> courses = student.getCourses();for (Course cours : courses) {System.out.println("\t" + cours);}}//7.釋放資源sqlSession.close();is.close();}

標簽解釋：

<resultMap>：配置字段和對象屬性的映射關(guān)系標簽。id 屬性：唯一標識type 屬性：實體對象類型<id>：配置主鍵映射關(guān)系標簽。<result>：配置非主鍵映射關(guān)系標簽。column 屬性：表中字段名稱property 屬性： 實體對象變量名稱<association>：配置被包含對象的映射關(guān)系標簽。property 屬性：被包含對象的變量名javaType 屬性：被包含對象的數(shù)據(jù)類型<collection>：配置被包含集合對象的映射關(guān)系標簽。property 屬性：被包含集合對象的變量名ofType 屬性：集合中保存的對象數(shù)據(jù)類型

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