访问Web元素

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Struts

Web Servlet Apache Struts IOC

访问Web元素可以有四种方法，下面依次列出

user_login_success.jsp

<%@ page language="java" contentType="text/html; charset=utf-8"

pageEncoding="utf-8"%>

<%@taglib uri="/struts-tags" prefix="s"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

<html>

<head>

<title>success</title>

String path = request.getContextPath();

String basePath = request.getScheme() + "://"

+ request.getServerName() + ":" + request.getServerPort()

+ path + "/";

</head>

<body>

Login success.

<s:property value="#request.r1" />

<%=request.getAttribute("r1")%>

<s:property value="#session.s1" />

<%=session.getAttribute("s1")%>

<s:property value="#application.a1" />

<%=application.getAttribute("a1")%>

<s:debug></s:debug>

</body>

</html>

第一种方法：
LoginAction1.java

package com.bebig.struts2.user.action;

import java.util.Map;

import com.opensymphony.xwork2.ActionContext;

import com.opensymphony.xwork2.ActionSupport;

public class LoginAction1 extends ActionSupport {

//取得Map类型的request、session、application

private Map request;

private Map session;

private Map application;

public LoginAction1() {

request = (Map) ActionContext.getContext().get("request");

session = ActionContext.getContext().getSession();

application = ActionContext.getContext().getApplication();

}

public String execute()

{

request.put("r1", "r1");

session.put("s1", "s1");

application.put("a1", "a1");

return SUCCESS;

}

第二种方法：
LoginAction2.java

package com.bebig.struts2.user.action;

import java.util.Map;

import org.apache.struts2.interceptor.ApplicationAware;

import org.apache.struts2.interceptor.RequestAware;

import org.apache.struts2.interceptor.SessionAware;

import com.opensymphony.xwork2.ActionSupport;

public class LoginAction2 extends ActionSupport implements RequestAware,

SessionAware, ApplicationAware {

//三个对象被容器注入

private Map<String, Object> request;

private Map<String, Object> session;

private Map<String, Object> application;

public String execute() {

request.put("r1", "r1");

session.put("s1", "s1");

application.put("a1", "a1");

return SUCCESS;

}

@Override

public void setRequest(Map<String, Object> request) {

this.request = request;

}

@Override

public void setSession(Map<String, Object> session) {

this.session = session;

}

@Override

public void setApplication(Map<String, Object> application) {

this.application = application;

}

第三种方法：
LoginAction3.java

package com.bebig.struts2.user.action;

import javax.servlet.ServletContext;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpSession;

import org.apache.struts2.ServletActionContext;

import com.opensymphony.xwork2.ActionSupport;

public class LoginAction3 extends ActionSupport {

private HttpServletRequest request;

private HttpSession session;

private ServletContext application;

public LoginAction3() {

request = ServletActionContext.getRequest();

session = request.getSession();

application = session.getServletContext();

}

public String execute()

{

request.setAttribute("r1", "r1");

session.setAttribute("s1", "s1");

application.setAttribute("a1", "a1");

return SUCCESS;

}

第四种方法：
LoginAction4.java

package com.bebig.struts2.user.action;

import javax.servlet.ServletContext;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpSession;

import org.apache.struts2.interceptor.ServletRequestAware;

import com.opensymphony.xwork2.ActionSupport;

public class LoginAction4 extends ActionSupport implements ServletRequestAware {

private HttpServletRequest request;

private HttpSession session;

private ServletContext application;

public String execute() {

request.setAttribute("r1", "r1");

session.setAttribute("s1", "s1");

application.setAttribute("a1", "a1");

return SUCCESS;

}

@Override

public void setServletRequest(HttpServletRequest request) {

this.request = request;

session = request.getSession();

application = session.getServletContext();

}

总结：
第一种方法依赖于Struts2容器，取得相关对象数据；
第二种方法，依赖注入DI（dependency injection），控制反转IoC（Inverse of control），对象数据被容器注入；
第三种方法，依赖于容器取得相关对象数据；
第四种方法，依赖注入一个对象的数据后，再通过这个对象获取到其它对象数据。
推荐使用第二种方法。
另：取得Map类型request,session,application，真实类型HttpServletRequest,HttpSession,ServletContext的引用：

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Struts2中的模块包含 | struts2 / 接收用户输入参数的三种机制

2011-03-05 11:21
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