Hibernate中多种方式解除延迟加载

问题引发：因为dao使用load（），默认延迟加载的，当在biz关闭session之后，UI层无法获取对象的非id属性值

解决方案：

1.变成get，即时加载

2.用Hibernate.isInitialized(obj)被初始化

3.类级别的lazy属性设为true

4.用final修饰类，因为用final修饰的类不允许有子类。而我们所说的内存中保存的代理对象其实就是该类的子类。此方法从根本上解决了延迟加载

5.在事务提交之前，先调用一下该类的非id属性

package cn.happy.entity;

public class Users {
    private Integer id;
    private String name;
    private String password;
    private String telephone;
    private String userName;
    private String isAdmin;
    

    public Integer getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public String getTelephone() {
        return telephone;
    }

    public void setTelephone(String telephone) {
        this.telephone = telephone;
    }

    public String getUserName() {
        return userName;
    }

    public void setUserName(String userName) {
        this.userName = userName;
    }

    public String getIsAdmin() {
        return isAdmin;
    }

    public void setIsAdmin(String isAdmin) {
        this.isAdmin = isAdmin;
    }

}

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
        "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">


    <hibernate-mapping package="cn.happy.entity">

        <class name="Users" table="USERS" lazy="false">
            <id name="id" column="ID">
                <generator class="native" />
            </id>
            <property name="name" type="string" column="NAME" />
            <property name="password" />
            <property name="telephone" />
            <property name="userName" />
            <property name="isAdmin" />
        </class>

</hibernate-mapping>

package cn.happy.dao;

import java.io.Serializable;

import cn.happy.until.HibernateUtil;

public class UsersDao {
   //添加用户记录
    public Serializable save(Object object){
        return HibernateUtil.currentSession().save(object);
    } 
    //检索oid
    public Object get(Class clazz, Serializable id){
        return HibernateUtil.currentSession().load(clazz, id);
    }
    
    //修改用户记录
    public void update(Object object){
        HibernateUtil.currentSession().update(object);
    }
    
}

package cn.happy.biz;

import java.io.Serializable;

import org.hibernate.Hibernate;
import org.hibernate.Transaction;

import cn.happy.dao.UsersDao;
import cn.happy.until.HibernateUtil;

public class UsersBiz {
    UsersDao user=new UsersDao();
    //添加用户记录
    public Serializable save(Object object){
        Transaction tx=HibernateUtil.currentSession().beginTransaction();
        Serializable result=user.save(object);
        tx.commit();
        return result;
    } 
    //检索oid
    public Object get(Class clazz, Serializable id){
        Transaction tx = HibernateUtil.currentSession().beginTransaction();
        Object obj=user.get(clazz, id);
//        if(!Hibernate.isInitialized(obj)){
//            Hibernate.initialize(obj);
//        }
        tx.commit();
        HibernateUtil.closeSession();
        return obj;
    }
    
    //修改用户记录
    public void update(Object object){
        Transaction tx=HibernateUtil.currentSession().beginTransaction();
        user.update(object);
        tx.commit();
    }
}

package cn.happy.ui;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;

import cn.happy.biz.UsersBiz;
import cn.happy.entity.Users;
import cn.happy.until.HibernateUtil;

public class Test {
  public static void main(String[] args) {
      get();
}
  //添加
  public static void add(){
      Users user=new Users();
      user.setName("回青");
      user.setIsAdmin("yes");
      user.setPassword("123456");
      user.setTelephone("18265808945");
      user.setUserName("户梦艳");
      UsersBiz usersBiz=new UsersBiz();
      usersBiz.save(user);
      System.out.println("ok");
      
  }
 //修改
  public static void modify(){
      Session session = HibernateUtil.currentSession();
      Transaction transaction = session.beginTransaction();
      Users user = (Users)session.get(Users.class, 6);
      user.setName("岁月静好");
      session.update(user);
      transaction.commit();
      HibernateUtil.closeSession();
  }
  
  //
  public static void get(){
      UsersBiz ub=new UsersBiz();
      Users user = (Users)ub.get(Users.class, 6);
      System.out.println(user.getName());
  }
}

 6.用openSessionInView模式

Open Session In View模式的主要思想：在用户的每一次请求过程始终保持 一个Session对象打开着

 

过滤器：过滤用的。过滤请求和响应。双向过滤

实现步骤：

Until包

package cn.happy.until;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;

public class HibernateUtil {
     private static final ThreadLocal sessionTL=new ThreadLocal();
     private static Configuration configuration;
     private final static SessionFactory sessionFactory;
     static{
        configuration=new Configuration().configure();
        sessionFactory=configuration.buildSessionFactory(); 
     }
     public static Session currentSession(){
            Session session=(Session)sessionTL.get();
            //如果session为null，则打开一个新的session
            if(session==null){
                session=sessionFactory.openSession();
                sessionTL.set(session);
            }
            return session;
        }
     public static void closeSession(){
         Session session=(Session)sessionTL.get();
         sessionTL.set(null);
         session.close();
     }
}

package cn.happy.entity;

public class Users {
    private Integer id;
    private String name;
    private String password;
    private String telephone;
    private String userName;
    private String isAdmin;
    

    public Integer getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public String getTelephone() {
        return telephone;
    }

    public void setTelephone(String telephone) {
        this.telephone = telephone;
    }

    public String getUserName() {
        return userName;
    }

    public void setUserName(String userName) {
        this.userName = userName;
    }

    public String getIsAdmin() {
        return isAdmin;
    }

    public void setIsAdmin(String isAdmin) {
        this.isAdmin = isAdmin;
    }

}

entity包

package cn.happy.entity;

public class Users {
    private Integer id;
    private String name;
    private String password;
    private String telephone;
    private String userName;
    private String isAdmin;
    

    public Integer getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public String getTelephone() {
        return telephone;
    }

    public void setTelephone(String telephone) {
        this.telephone = telephone;
    }

    public String getUserName() {
        return userName;
    }

    public void setUserName(String userName) {
        this.userName = userName;
    }

    public String getIsAdmin() {
        return isAdmin;
    }

    public void setIsAdmin(String isAdmin) {
        this.isAdmin = isAdmin;
    }

}

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
        "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">


    <hibernate-mapping package="cn.happy.entity">

        <class name="Users" table="USERS">
            <id name="id" column="ID">
                <generator class="native" />
            </id>
            <property name="name" type="string" column="NAME" />
            <property name="password" />
            <property name="telephone" />
            <property name="userName" />
            <property name="isAdmin" />
        </class>

</hibernate-mapping>

Dao包

package cn.happy.dao;

import java.io.Serializable;

import cn.happy.until.HibernateUtil;

public class UsersDao {
   //添加用户记录
    public Serializable save(Object object){
        return HibernateUtil.currentSession().save(object);
    } 
    //检索oid
    public Object get(Class clazz, Serializable id){
        return HibernateUtil.currentSession().load(clazz, id);
    }
    
    //修改用户记录
    public void update(Object object){
        HibernateUtil.currentSession().update(object);
    }
    
}

Biz包

package cn.happy.biz;

import java.io.Serializable;

import org.hibernate.Hibernate;
import org.hibernate.Transaction;

import cn.happy.dao.UsersDao;
import cn.happy.until.HibernateUtil;

public class UsersBiz {
    UsersDao user=new UsersDao();
    //添加用户记录
    public Serializable save(Object object){
        Transaction tx=HibernateUtil.currentSession().beginTransaction();
        Serializable result=user.save(object);
        tx.commit();
        return result;
    } 
    //检索oid
    public Object get(Class clazz, Serializable id){
        //Transaction tx = HibernateUtil.currentSession().beginTransaction();
        Object obj=user.get(clazz, id);
//        if(!Hibernate.isInitialized(obj)){
//            Hibernate.initialize(obj);
//        }
        //tx.commit();
        //HibernateUtil.closeSession();
        return obj;
    }
    
    //修改用户记录
    public void update(Object object){
        Transaction tx=HibernateUtil.currentSession().beginTransaction();
        user.update(object);
        tx.commit();
    }
}

Filter包

package cn.happy.filter;

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.Transaction;

import cn.happy.until.HibernateUtil;

public class OpenSessionInViewFilter implements Filter {

    
    public void doFilter(ServletRequest request, ServletResponse response,
            FilterChain chain) throws IOException, ServletException {
        request.setCharacterEncoding("utf-8");
        Session session=null;
        Transaction tx=null;
        try {
            session=HibernateUtil.currentSession();
            System.out.println("filter	"+session.hashCode());
            tx=session.beginTransaction();
            //执行请求处理链   双向过滤
            chain.doFilter(request, response);
            //返回响应  提交事务
            tx.commit();
        } catch (HibernateException e) {
            e.printStackTrace();
            tx.rollback();
        }finally{
            HibernateUtil.closeSession();
        }
        
    }

    public void init(FilterConfig arg0) throws ServletException {
        // TODO Auto-generated method stub
        
    }
    public void destroy() {
        // TODO Auto-generated method stub
        
    }


}

 配置文件

从网址访问即可达到过滤器的作用