Hibernate多对多双向关联的配置

Hibernate的双向多对多关联有两种配置方法:那我们就来看看两种方案是如何配置的。

一、创建以各自类为类型的集合来关联

1.首先我们要在两个实体类(雇员<Emploee>、工程<Project>)中各自给对方添加一个对方的集合

1.1 雇员实体类

package cn.manytomany.one;

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

public class Emploee {
    //雇员id
    private Integer empId;
    //工程
    private String empName;
    //工程的集合
    private Set<Project> projects=new HashSet<Project>();
   
    public Set<Project> getProjects() {
        return projects;
    }
    public void setProjects(Set<Project> projects) {
        this.projects = projects;
    }
    public Integer getEmpId() {
        return empId;
    }
    public void setEmpId(Integer empId) {
        this.empId = empId;
    }
    public String getEmpName() {
        return empName;
    }
    public void setEmpName(String empName) {
        this.empName = empName;
    }
}

1.2 工程实体类

package cn.manytomany.one;

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

public class Project {
    private Integer proId;
    private String proName;
    private Set<Emploee> emploees=new HashSet<Emploee>();
   
    public Set<Emploee> getEmploees() {
        return emploees;
    }
    public void setEmploees(Set<Emploee> emploees) {
        this.emploees = emploees;
    }
    public Integer getProId() {
        return proId;
    }
    public void setProId(Integer proId) {
        this.proId = proId;
    }
    public String getProName() {
        return proName;
    }
    public void setProName(String proName) {
        this.proName = proName;
    }
   
}

2.有了实体类之后呢,我们就能通过实体的属性和数据库的表字段配置映射关系。

2.1 emploees.hbm.xml

<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping package="cn.manytomany.one">
    <class table="Emploee">
        <id>
        <generator>
        <param>SQU_NUM</param>
        </generator>
        </id>
        <property></property>
        <set table="PROEMP">
        <key column="RPROID"></key>
        <many-to-many column="REMPID">
        </many-to-many>
        </set>
    </class>
</hibernate-mapping>

2.2  projects.hbm.xml

<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping package="cn.manytomany.one">
    <class table="PROJECT">
        <id>
        <generator>
        <param>SQU_NUM</param>
        </generator>
        </id>
        <property></property>
       
        <set table="PROEMP" cascade="save-update">
        <key column="REMPID"></key>
        <many-to-many column="RPROID">
        </many-to-many>
        </set>
    </class>
</hibernate-mapping>

2.3 另外还有一个最重要的大配置来引用两个小配置

<?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>