spring_SSH整合之_OpenSessionInView

雨点打透心脏的1/2处 2022-06-15 09:14 153阅读 0赞

HibernateTemplate中的load和get都可以取回一个对象，难道是方法重复吗？绝对不可能，那它们到底有那些区别呢？

一、load有加载延时，需要设置lazy属性，我没有配置lazy的时候，报错，加上了lazy="false"属性时，用load才没有报错

二、当记录不存在时，load产生异常，get返回null

三、load方法可以返回实体的代理类，get方法则返回真是的实体类  
四、load方法可以充分利用[hibernate][]的内部缓存和二级缓存中的现有数据

而get方法仅仅在内部缓存中进行数据查找，如果没有发现数据則将越过二级缓存，直接调用SQL查询[数据库][Link 1]。  
五、也许别人把数据库中的数据修改了，load如何在缓存中找到了数据，则不会再访问数据库，而get则会返回最新数据。

在使用load这个方法时要配置openSessionInView延长Session关闭时间
    在Web.xml文件中配置filter的openSessionInView关闭Session,告诉spring等jsp执行完了再关闭Session。
    必须放到Struts2的filter前面
    
    
    <filter>
    	<filter-name>openSessionInView</filter-name>
    	<filter-class>org.springframework.orm.hibernate3.support.OpenSessionInViewFilter</filter-class>
    </filter>
    
    <filter-mapping>
    	<filter-name>openSessionInView</filter-name>
    	<url-pattern>/*</url-pattern>
    </filter-mapping>

<?xml version="1.0" encoding="UTF-8"?>
    <web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee"
    	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    	xsi:schemaLocation="http://java.sun.com/xml/ns/javaee 
    	http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
    
    	
    	<context-param>
    		<param-name>contextConfigLocation</param-name>
    		
    		<param-value>classpath:beans.xml</param-value>
    	</context-param>
    	<listener>
    		<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
    	</listener>
    
    	
    	<filter>
    		<filter-name>openSessionInView</filter-name>
    		<filter-class>org.springframework.orm.hibernate3.support.OpenSessionInViewFilter</filter-class>
    	</filter>
    
    	<filter-mapping>
    		<filter-name>openSessionInView</filter-name>
    		<url-pattern>/*</url-pattern>
    	</filter-mapping>
    
    	
    	<filter>
    		<filter-name>struts2</filter-name>
    		<filter-class>org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter</filter-class>
    	</filter>
    
    	<filter-mapping>
    		<filter-name>struts2</filter-name>
    		<url-pattern>/*</url-pattern>
    	</filter-mapping>
    
    	
    	<welcome-file-list>
    		<welcome-file>index.jsp</welcome-file>
    	</welcome-file-list>
    </web-app>

<?xml version="1.0" encoding="UTF-8" ?>
    <!DOCTYPE struts PUBLIC
    	"-//Apache Software Foundation//DTD Struts Configuration 2.3//EN"
    	"http://struts.apache.org/dtds/struts-2.3.dtd">
    
    <struts>
    	
    	<constant name="struts.i18n.encoding" value="UTF-8" />
    	
    	<constant name="struts.objectFactory.spring.autoWire" value="type" />
    	
    	<constant name="struts.dewMode" value="true" />
    
    	<package name="registration" namespace="/bjsxt" extends="struts-default">
    		<action name="user_*" class="com.bjsxt.registration.action.UserAction"
    			method="{1}">
    			<result name="SUCCESS">/registSuccess.jsp</result>
    			<result name="FAIL">/registFail.jsp</result>
    			
    			
    			<result name="LIST">/userlist.jsp</result>
    			<result name="LOAD">/user.jsp</result>
    		</action>
    	</package>
    
    </struts>

package com.bjsxt.registration.action;
    
    import java.util.List;
    
    import com.bjsxt.registration.model.User;
    import com.bjsxt.registration.service.UserManager;
    import com.bjsxt.registration.vo.UserRegisterInfo;
    import com.opensymphony.xwork2.ActionSupport;
    import com.opensymphony.xwork2.ModelDriven;
    
    public class UserAction extends ActionSupport implements
    		ModelDriven<UserRegisterInfo> {
    	private UserRegisterInfo info;
    	private UserManager userManager;
    	private List<User> users;
    	private User user;
    
    	public User getUser() {
    		return user;
    	}
    
    	public void setUser(User user) {
    		this.user = user;
    	}
    
    	public UserRegisterInfo getInfo() {
    		return info;
    	}
    
    	public void setInfo(UserRegisterInfo info) {
    		this.info = info;
    	}
    
    	public UserManager getUserManager() {
    		return userManager;
    	}
    
    	public void setUserManager(UserManager userManager) {
    		this.userManager = userManager;
    	}
    
    	public List<User> getUsers() {
    		return users;
    	}
    
    	public void setUsers(List<User> users) {
    		this.users = users;
    	}
    
    	@Override
    	public String execute() throws Exception {
    		User user = new User();
    		user.setUsername(info.getUsername());
    		user.setPassword(info.getPassword());
    		if (userManager.exists(user)) {
    			return "FAIL";
    		}
    		userManager.add(user);
    		return "SUCCESS";
    	}
    
    	public UserRegisterInfo getModel() {
    		return info;
    	}
    
    	public String list() {
    		this.users = this.userManager.getUsers();
    		return "LIST";
    	}
    
    	public String load() {
    		this.user = this.userManager.loadById(info.getId());
    		return "LOAD";
    	}
    }

<%@ page language="java" import="java.util.*" pageEncoding="GB18030"%>
    <%@ taglib uri="/struts-tags" prefix="s"%>
    
    <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
    <html>
    <head>
    
    <title>load列表</title>
    
    <meta http-equiv="pragma" content="no-cache">
    <meta http-equiv="cache-control" content="no-cache">
    <meta http-equiv="expires" content="0">
    </head>
    
    <body>
    	<a href="bjsxt/user_list.action">用户列表</a>
    	<br />
    	<s:property value="user.username" />
    	<s:debug></s:debug>
    </body>
    </html>

package com.bjsxt.registration.action;
    
    import java.util.List;
    
    import org.springframework.context.ApplicationContext;
    
    import com.bjsxt.registration.model.User;
    import com.bjsxt.registration.service.UserManager;
    import com.bjsxt.registration.vo.UserRegisterInfo;
    import com.opensymphony.xwork2.ActionContext;
    import com.opensymphony.xwork2.ActionSupport;
    import com.opensymphony.xwork2.ModelDriven;
    
    public class UserAction extends ActionSupport implements
    		ModelDriven
       
         {
    	private UserRegisterInfo info;
    	private UserManager userManager;
    	private List
        
          users;
    
    	public UserRegisterInfo getInfo() {
    		return info;
    	}
    
    	public void setInfo(UserRegisterInfo info) {
    		this.info = info;
    	}
    
    	public UserManager getUserManager() {
    		return userManager;
    	}
    
    	public void setUserManager(UserManager userManager) {
    		this.userManager = userManager;
    	}
    
    	public List
         
           getUsers() {
    		return users;
    	}
    
    	public void setUsers(List
          
            users) {
    		this.users = users;
    	}
    
    	@Override
    	public String execute() throws Exception {
    		User user = new User();
    		user.setUsername(info.getUsername());
    		user.setPassword(info.getPassword());
    		if (userManager.exists(user)) {
    			return "FAIL";
    		}
    		userManager.add(user);
    		return "SUCCESS";
    	}
    
    	public UserRegisterInfo getModel() {
    		return info;
    	}
    
    	public String list() {
    		this.users = this.userManager.getUsers();
    		return "LIST";
    	}
    }
    
           
    
    
    
            
             
             
             
             
             
             
             
              
              
               /registSuccess.jsp
               
              
               /registFail.jsp
               
               
               
              
               /userlist.jsp
               
              
             
           
    <%@ page language="java" import="java.util.*" pageEncoding="GB18030"%>
    <%@ taglib uri="/struts-tags" prefix="s"%>
    
    
    
    
    
    
           用户列表
    
    
           
        
    
           
        
    
           
        
    
    
    
    	
            
           
           
        
         
          
           用户名 
           密码

[hibernate]: http://lib.csdn.net/base/javaee
[Link 1]: http://lib.csdn.net/base/mysql