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 {// Fieldsprivate 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;// Constructorspublic 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 accessorspublic 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 {// Fieldsprivate 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 accessorspublic 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。