hibernate MTM 联合主键

Posted 2020-10-20 理想的诱惑

//适用于表里没有其他列，只有主键
//Course.java实体类
package com.tao.pojo;

import java.util.HashSet;
import java.util.Set;

public class Course {
    private int id;
    private String name;
    private Set<Student> stu=new HashSet<Student>();
    
    public Course() {
        super();
    }
    public Course(int id, String name) {
        super();
        this.id = id;
        this.name = name;
    }
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Set<Student> getStu() {
        return stu;
    }
    public void setStu(Set<Student> stu) {
        this.stu = stu;
    }
    @Override
    public String toString() {
        return "Course [id=" + id + ", name=" + name + "]";
    }
    

}

//Student.java实体类

package com.tao.pojo;

import java.util.HashSet;
import java.util.Set;

public class Student {
    private int id;
    private String name;
    private String gender;
    private Set<Course> cou=new HashSet<Course>();
    
    public Student() {
        super();
    }
    public Student(int id, String name, String gender) {
        super();
        this.id = id;
        this.name = name;
        this.gender = gender;
    }
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getGender() {
        return gender;
    }
    public void setGender(String gender) {
        this.gender = gender;
    }
    public Set<Course> getCou() {
        return cou;
    }
    public void setCou(Set<Course> cou) {
        this.cou = cou;
    }
    @Override
    public String toString() {
        return "Student [id=" + id + ", name=" + name + ", gender=" + gender + "]";
    }
    

}


//配置文件
//course.hbm.xml文件名 
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
    "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
    "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping>

    <class name="com.tao.pojo.Course" table="course">
        <id name="id">
        <!-- 自动增长 -->
            <generator class="native"></generator>
        </id>
        <property name="name"/>
        <!-- name：实体来中的属性名 （Clazz的名称） clazz：属性类型（clazz的类型是Clazz）-->
        <!-- column：外键列名称 -->
        <!--stu是实体类中set集合的名，sc是表名 ， cid是Course在sc表中的外键， -->
        <set name="stu" table="sc">
            <key column="cid"></key>
            <!--set集合当中所存放的对象类型 Student类  sid是Student在sc表中的外键  -->
            <many-to-many class="com.tao.pojo.Student" column="sid"></many-to-many>
        </set>
    </class>

</hibernate-mapping>


//student.hbm.xml
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
    "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
    "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping>

    <class name="com.tao.pojo.Student" table="student">
        <id name="id">
        <!-- 自动增长 -->
            <generator class="native"></generator>
        </id>
        <!--普通列  -->
        <property name="name"/>
        <property name="gender"/>
        <!-- set集合的配置   sid是Student在sc表中的列名-->
        <set name="cou" table="sc">
        <!-- Student 自己的键 -->
            <key column="sid"></key>
            <!--set的数据库类型    cid是Course在sc表中的外键 -->
            <!--Course的键  -->
            <many-to-many class="com.tao.pojo.Course" column="cid"></many-to-many>
        </set>
    </class>

</hibernate-mapping>


//映射文件hibernate.cfg.xml

<?xml version=‘1.0‘ encoding=‘utf-8‘?>
<!DOCTYPE hibernate-configuration PUBLIC
        "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
        "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
    <session-factory>
    <!-- 自动生成表，数据库得手动创建 -->
        <property name="connection.driver_class">com.mysql.jdbc.Driver</property>
        <property name="connection.url">jdbc:mysql://localhost:3306/test0105_MTM</property>
        <property name="connection.username">root</property>
        <property name="connection.password">root</property>
        <property name="show_sql">true</property>
        <property name="format_sql">true</property>
        <!-- 自动创建或更新表（没有就创建，有就更新 ）-->
        <property name="hbm2ddl.auto">update</property>
        <!--数据库方言（ 如果外键没有生成就把数据库方言设置一下   ） -->
        <!-- org.hibernate.dialect.MySQL5InnoDBDialect   是 mysql数据库方言的类名  在java文件里巧 MySQL5 选MySQL5InnoDBDialect  -->
        <!-- 如果执行完了没报错，外键还是没有，就把表删了，再执行一次 -->
        
        <property name="hibernate.dialect">org.hibernate.dialect.MySQL5InnoDBDialect</property>
        <!--配置映射文件  -->
        <mapping resource="com/tao/pojo/course.hbm.xml"/>
        <mapping resource="com/tao/pojo/student.hbm.xml"/>
    </session-factory>

</hibernate-configuration>


//测试类
//TestJUnit.java
package com.tao.test;


import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

import com.tao.pojo.Course;
import com.tao.pojo.Student;

public class TestJUnit {
    SessionFactory factory ;
    Session session ;
    @Before
    public void test001() {
        Configuration configure = new Configuration().configure();
        factory= configure.buildSessionFactory();
        session= factory.openSession();
        session.beginTransaction();
    }
    @After
    public void test002() {
        session.getTransaction().commit();
        session.close();
        factory.close();
    }
    @Test
    public void TestStudent() {

    }
    
}
测试的时候测试类里不用写内容,这里用TestStudent()测试