dwr+hibernate+spring 延迟加载解决方案!

最新推荐文章于 2025-09-06 09:33:29 发布

原创最新推荐文章于 2025-09-06 09:33:29 发布 · 507 阅读

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文章标签：

#hibernate #dwr #spring #frameworks #constructor #string

本文介绍了解决DWR懒加载Hibernate集合属性时出现的LazyInitializationException异常的四种方法，并通过实例展示了如何配置。

假如一个User对象包含frameWorks对象两者关系是1-N，那么dwr将加载一个对象所有的属性!

就会出现如下错误提示：

org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: com.best.model.User.frameWorks, no session or session was closed

现在我所了解的解决此方案有以下几种：

1、在User.xml关联frameWorks配置文件中将lazy设置为false lazy="false"

2、在dwr.xml文件将converter="bean" 修改为converter="hibernate3"

3、在dwr.xml文件将 "convert" 下添加 "param" 指定需要加载的属性名称

4、在web.xml文件添加 openSessionInViewFilter

第一种方法明显的不好，如果设置了lazy=false后不在灵活！

第二种方法设置converter="hibernate3"后，在js中将无法获取model的关联属性了，调用后也是空值

第三种方法将convert中添加param这样做也算一种比较好的解决方案，但必须在配置文件中写死，如果以后还需要调用关联的方法须在一次在配置一个名字不相同的同一个model

第四种个人认为是最好的解决办法,request打开session,response关闭session,虽然据说openSessionInViewFilter有各种各样的毛病，本人到现在也还未出现过比较严重的问题！

举个例子把：

model

User.java

package com.best.model; import java.util.HashSet; import java.util.Set; /** * User generated by MyEclipse Persistence Tools */ public class User implements java.io.Serializable { // Fields /** * */ private static final long serialVersionUID = -9128928098708867798L; private Integer id; private String name; private String passWord; private Set frameWorks = new HashSet(0); // Constructors /** default constructor */ public User() { } /** minimal constructor */ public User(String name, String passWord) { this.name = name; this.passWord = passWord; } /** full constructor */ public User(String name, String passWord, Set frameWorks) { this.name = name; this.passWord = passWord; this.frameWorks = frameWorks; } // Property accessors public Integer getId() { return this.id; } public void setId(Integer id) { this.id = id; } public String getName() { return this.name; } public void setName(String name) { this.name = name; } public String getPassWord() { return this.passWord; } public void setPassWord(String passWord) { this.passWord = passWord; } public Set getFrameWorks() { return this.frameWorks; } public void setFrameWorks(Set frameWorks) { this.frameWorks = frameWorks; } }

FrameWork.java

package com.best.model; /** * FrameWork generated by MyEclipse Persistence Tools */ public class FrameWork implements java.io.Serializable { // Fields /** * */ private static final long serialVersionUID = 7380074080674478604L; private Integer id; private User user; private String name; // Constructors /** default constructor */ public FrameWork() { } /** full constructor */ public FrameWork(User user, String name) { this.user = user; this.name = name; } // Property accessors public Integer getId() { return this.id; } public void setId(Integer id) { this.id = id; } public User getUser() { return this.user; } public void setUser(User user) { this.user = user; } public String getName() { return this.name; } public void setName(String name) { this.name = name; } }

Dwr

UserAjax.java

package com.best.dwr; import com.best.model.User; import com.best.service.UserService; public class UserAjax { private UserService userService; public UserService getUserService() { return userService; } public void setUserService(UserService userService) { this.userService = userService; } public User getUser(){ return userService.findUserById(1); } }

service层我直接忽略也就是读取dao层得数据方法

jsp

test.jsp

<%@ page language="java" pageEncoding="gbk"%> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <title>My JSP 'test.jsp' starting page</title> <mce:script type='text/javascript' src="/800bestDemo/dwr/interface/userAjax.js" mce_src="800bestDemo/dwr/interface/userAjax.js"></mce:script> <mce:script type='text/javascript' src="/800bestDemo/dwr/engine.js" mce_src="800bestDemo/dwr/engine.js"></mce:script> <mce:script type='text/javascript' src="/800bestDemo/dwr/util.js" mce_src="800bestDemo/dwr/util.js"></mce:script> <mce:script type="text/javascript"></mce:script> </head> <body> </body> </html>

dwr.xml

<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE dwr PUBLIC "-//GetAhead Limited//DTD Direct Web Remoting 2.0//EN" "http://www.getahead.ltd.uk/dwr/dwr20.dtd"> <dwr> <allow> <create javascript="userAjax" creator="spring"> <param name="beanName" value="userAjax"></param> </create> <convert match="com.best.model.User" converter="bean" javascript="user"/> <convert match="com.best.model.FrameWork" converter="bean" javascript="framework"/> </allow> </dwr>

web.xml

<?xml version="1.0" encoding="UTF-8"?> <web-app version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">  <context-param> <param-name>contextConfigLocation</param-name> <param-value>classpath:spring_*.xml</param-value> </context-param> <listener> <listener-class> org.springframework.web.context.ContextLoaderListener </listener-class> </listener>  <filter> <filter-name>hibernateFilter</filter-name> <filter-class> org.springframework.orm.hibernate3.support.OpenSessionInViewFilter </filter-class> </filter>  <filter-mapping> <filter-name>hibernateFilter</filter-name> <url-pattern>*.action</url-pattern> </filter-mapping>  <filter-mapping> <filter-name>hibernateFilter</filter-name> <url-pattern>/dwr/*</url-pattern> </filter-mapping>  <filter> <filter-name>struts2</filter-name> <filter-class> org.apache.struts2.dispatcher.FilterDispatcher </filter-class> </filter> <filter-mapping> <filter-name>struts2</filter-name> <url-pattern>/*</url-pattern> </filter-mapping>  <servlet> <servlet-name>dwr-invoker</servlet-name> <servlet-class> org.directwebremoting.servlet.DwrServlet </servlet-class> <init-param> <param-name>debug</param-name> <param-value>true</param-value> </init-param> </servlet> <servlet-mapping> <servlet-name>dwr-invoker</servlet-name> <url-pattern>/dwr/*</url-pattern> </servlet-mapping> </web-app>

过滤dwr请求只需要添加/dwr/*就可以解决问题