Hibernate的级联查询和添加的分析

 昨天有同学问我，级联添加怎么做，我写过级联查询，但是级联添加，怎么做呢？怎么配置呢？昨天晚上就写了试试，然后分享给大家。拿学生表和系别表来说。先看数据库配置   

首先是学生表studdent

学生表的depid是作为student的外键，主键是id,
 

下面是系别表department

这个没什么好说的。

新建工程，然后进行两个表的hibernate的映射

package org.lyy.entity;

/**
 * Student entity. @author MyEclipse Persistence Tools
 */

public class Student implements java.io.Serializable {

	// Fields

	private Integer id;
	private Department department;//这里要添加系别表的对象
	private String stunumber;
	private String stupwd;
	private String stuname;
	private int  depid;
	
	// Constructors

	public int getDepid() {
		return depid;
	}

	public void setDepid(int depid) {
		this.depid = depid;
	}

	/** default constructor */
	public Student() {
	}

	/** minimal constructor */
	public Student(Department department) {
		this.department = department;
	}

	/** full constructor */
	public Student(Department department, String stunumber, String stupwd,
			String stuname) {
		this.department = department;
		this.stunumber = stunumber;
		this.stupwd = stupwd;
		this.stuname = stuname;
	}

	// Property accessors

	public Integer getId() {
		return this.id;
	}

	public void setId(Integer id) {
		this.id = id;
	}

	public Department getDepartment() {
		return this.department;
	}

	public void setDepartment(Department department) {
		this.department = department;
	}

	public String getStunumber() {
		return this.stunumber;
	}

	public void setStunumber(String stunumber) {
		this.stunumber = stunumber;
	}

	public String getStupwd() {
		return this.stupwd;
	}

	public void setStupwd(String stupwd) {
		this.stupwd = stupwd;
	}

	public String getStuname() {
		return this.stuname;
	}

	public void setStuname(String stuname) {
		this.stuname = stuname;
	}

	public Student(String stunumber, String stupwd, String stuname,
			Department department) {
		super();
		this.id=id;
		this.stunumber = stunumber;
		this.stupwd = stupwd;
		this.stuname = stuname;
		this.department=department;
	}

}

package org.lyy.entity;

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

/**
 * Department entity. @author MyEclipse Persistence Tools
 */

public class Department implements java.io.Serializable {

	// Fields

	private Integer id;
	private String bm;
	private String mc;
	private String tell;
	private String leader;
	private Set students = new HashSet(0);

	// Constructors

	/** default constructor */
	public Department() {
	}

	/** full constructor */
	public Department(String bm, String mc, String tell, String leader,
			Set students) {
		this.bm = bm;
		this.mc = mc;
		this.tell = tell;
		this.leader = leader;
		this.students = students;
	}

	// Property accessors

	public Integer getId() {
		return this.id;
	}

	public void setId(Integer id) {
		this.id = id;
	}

	public String getBm() {
		return this.bm;
	}

	public void setBm(String bm) {
		this.bm = bm;
	}

	public String getMc() {
		return this.mc;
	}

	public void setMc(String mc) {
		this.mc = mc;
	}

	public String getTell() {
		return this.tell;
	}

	public void setTell(String tell) {
		this.tell = tell;
	}

	public String getLeader() {
		return this.leader;
	}

	public void setLeader(String leader) {
		this.leader = leader;
	}

	public Set getStudents() {
		return this.students;
	}

	public void setStudents(Set students) {
		this.students = students;
	}

}

看student.hbm.xml里的 配置会多出这样一句

而department.hbm.xml中会出现这样

下面进行级联查询，直接调用这个方法， 查询student，就可以查到系院信息

public List<Student> getAllStudentList(){
		List<Student> list = null;
		Session session = HibernateSessionFactory.getSession();
		Query q = session.createQuery("from Student");
		list = q.list();
		session.close();
		return list;
<strong><span style="font-size:18px;">		}</span></strong>

或者直接建立个测试类进行测试一下

public class TestDepartmentStudent {
	public static void main(String[] args) {
		Session session = HibernateSessionFactory.getSession();
		session.beginTransaction();
		List<Student> list = session.createQuery("from Student").list();
		for(Student stu:list){
			System.out.println(" 学号："+stu.getStunumber()+" ，姓名："+stu.getStuname()+
					"： ， 系院编码： "+stu.getDepartment().getBm()+"： ， 系院名称： "+stu.getDepartment().getMc());
		}
		session.close();
	}
}

既然能查询，那么如何添加呢？

其实都一样，映射的时候得到系院对象，实现级联查询，那添加的时候，就能用系院对象，设置系院信息，那么这样就好办了

public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		String stunumber=request.getParameter("stunumber");
		String stupwd=request.getParameter("stupwd");
		String stuname=request.getParameter("stuname");
		String depid=request.getParameter("depid");
		
		Department  department=new Department();//得到系院对象
		department.setId( Integer.parseInt(depid));//这里用set赋值系院信息
		Student student=new Student(stunumber, stupwd, stuname, department);
		
		StudentDao stuDao=new StudentDao();
		stuDao.addStudent(student);
		response.sendRedirect("StudentListServlet");
	}

传参的时候，把department对象作为student的一个参数，然后出入一个student对象过去，进行存储

，（这里也可以设置department对象的其他属性）

	public void addStudent(Student student){
		Session session = HibernateSessionFactory.getSession();
		Transaction tran = session.beginTransaction();
		session.save(student);
		tran.commit();
		session.close();
		}

那么我们就实现了这种级联添加

此文仅供参考，若有错，望请大家批评指正。