hibernate--多对多单向（双向）关联

电玩女神 2024-02-18 14:51 32阅读 0赞

Teacher和Student来说明：

\------------------------------------------------------------

Annotation注解：

teacher->student

Teacher.java:

package com.bean;
    
    import java.util.HashSet;
    import java.util.Set;
    
    import javax.persistence.Entity;
    import javax.persistence.GeneratedValue;
    import javax.persistence.Id;
    import javax.persistence.JoinColumn;
    import javax.persistence.JoinColumns;
    import javax.persistence.JoinTable;
    import javax.persistence.ManyToMany;
    
    @Entity
    public class Teacher {
    	private int id;
    	private String name;
    	private Set<Student> students = new HashSet<Student>();
    
    	@ManyToMany
    	@JoinTable(name="t_s",
                  joinColumns=@JoinColumn(name="TeacherID"),
                  inverseJoinColumns=@JoinColumn(name="stuendID")
    			)
    	public Set<Student> getStudents() {
    		return students;
    	}
    
    	public void setStudents(Set<Student> students) {
    		this.students = students;
    	}
    
    	@Id
    	@GeneratedValue
    	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;
    	}
    
    }

Student.java:

package com.bean;
    
    import javax.persistence.Entity;
    import javax.persistence.GeneratedValue;
    import javax.persistence.Id;
    
    @Entity
    public class Student {
    	private int id;
    	private String name;
    
    	@Id
    	@GeneratedValue
    	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;
    	}
    
    }

cfg.xml配置文件：

<?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>
         <property name="connection.driver_class">com.mysql.jdbc.Driver</property>    
         <property name="connection.url">jdbc:mysql://localhost:3306/user</property>     
         <property name="connection.username">root</property>   
         <property name="connection.password">root</property>
         
         <property name="dialect">org.hibernate.dialect.MySQLDialect</property>
         <property name="show_sql">true</property>
         
         <property name="hbm2ddl.auto">update</property>
         <property name="show_sql">true</property>
         <property name="format_sql">true</property>  
         
         <property name="current_session_context_class">thread</property>
           <mapping class="com.bean.Student"/>
         <mapping class="com.bean.Teacher"/>  
       </session-factory>
    </hibernate-configuration>

XML配置:

Student.hbm.xml:

<?xml version="1.0" encoding="UTF-8"?>
    <!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.bean.Student" table = "student" >
    
         <id name = "id" column="id">
           <generator class="native"/>
         </id>
         <property name="name" />
      </class>
    </hibernate-mapping>

Teacher.hbm.xml:

<?xml version="1.0" encoding="UTF-8"?>
    <!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.bean.Teacher" table = "teacher" >
    
         <id name = "id" column="id">
           <generator class="native"/>
         </id>
         <property name="name" />
         <set name="students" table="t_s">
           <key column="teacher_Id"></key>
           <many-to-many class="com.bean.Student" column="student_Id"/>
         </set>
      </class>
    </hibernate-mapping>

cfg.xml中修改映射配置

\------------------------------------------------------------------------------------------

多对多双向关联：

1、xml配置：  
Student.hbm.xml中添加配置即可：

2、Annotation配置：

在Student.java中添加：

@ManyToMany(mappedBy="students")
    	public Set<Teacher> getTeachers() {
    		return teachers;
    	}
    
    	public void setTeachers(Set<Teacher> teachers) {
    		this.teachers = teachers;
    	}