第二次调用同一个方法时session关闭

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package com.util;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
import org.hibernate.cfg.Configuration;
import org.hibernate.service.ServiceRegistry;

public class HibernateConnection2 {
	private  static  SessionFactory sessionfactory=null;
	private  static  Transaction ctx=null;
    static{
    	 Configuration config=new Configuration().configure();
    	 ServiceRegistry sr=new StandardServiceRegistryBuilder().applySettings(config.getProperties()).build();
    	 sessionfactory=config.buildSessionFactory(sr);
     }
	public Session getsession(){
    	return sessionfactory.getCurrentSession();
    }

	public void gettransaction(){
			
			ctx=this.getsession().beginTransaction();	
    }
  	public void commitTransaction()
  	{
  		
  		try
  		{   
  			ctx.commit();
  		}
  		catch (Exception e)
  		{
  			if(ctx!=null)
  			{
  				ctx.rollback();
  			}
  		}
  	}
}

这是四大接口

package com.dao;

import java.util.List;

import org.hibernate.Session;

import com.entity.Dept1;
import com.util.HibernateConnection2;

public class Deptdao extends HibernateConnection2 {
	 private Session session=getsession();
//	 public Session set(){
//	 System.out.println("safdasfasfd");
//	 session=getsession();
//	 return session;
//	 }
	public List<Dept1> getall() {
		this.gettransaction();
		@SuppressWarnings("unchecked")
		List<Dept1> list =session.createQuery("from Dept1 order by pid").list();
		this.commitTransaction();
		return list;
	}

	public void update(Dept1 dept) {
		this.gettransaction();
		this.getsession().update(dept);
		commitTransaction();
	
	}

	public Dept1 getone(int pid) {
		this.gettransaction();
		Dept1 dept = (Dept1) this.getsession().get(Dept1.class, pid);
		commitTransaction();		
		return dept;
	}

	public void delete(int pid) {
		this.gettransaction();
		this.getsession().delete(this.getsession().get(Dept1.class, pid));
		commitTransaction();
	}

	public void add(Dept1 dept) {
		this.gettransaction();
		this.getsession().save(dept);
		commitTransaction();
	}
}

这是dao层

package com.action;

import java.util.ArrayList;
import java.util.List;

import com.entity.Dept1;
import com.imple.DeptImple;
import com.service.Deptservice;

public class DeptAction {
	private List<Dept1> list = new ArrayList<Dept1>();
	private int pid;
	private Dept1 dept=new Dept1();
	private Deptservice action = new DeptImple();

	public Dept1 getDept() {
		return dept;
	}

	public void setDept(Dept1 dept) {
		this.dept = dept;
	}

	public List<Dept1> getList() {
		return list;
	}

	public void setList(List<Dept1> list) {
		this.list = list;
	}

	public int getPid() {
		return pid;
	}
	public void setPid(int pid) {
		this.pid = pid;
	}
    public String all(){
    	this.list=action.getall();
    	return "all";
    }
    public List<Dept1> getall(){
    	this.list=action.getall();
    	return list;
    }
    
    
    public String add(){
    	action.add(dept);
    	return this.all();
    }
    public String one(){
    	this.dept=action.getone(pid);
    	return "one";
    }
    public String delete(){
    	this.action.delete(pid);
    	return this.all();
    }
    public String update(){
    	this.action.update(dept);
    	return this.all();
    }
 
}

比如说当我第一次进全查询后，再点击删除调用action中delete方法，执行完后再返回到全查询getall方法就会出现

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在dao里面调用注释的那个方法，又不会出问题。这是为什么？

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大神们，别沉呀