使用Struts2開發都快1個月了，感覺雖然使用它實現了項目的功能，但很多新的東西都沒有應用進來，
前一段時間項目催的太緊，所以決定最近系統的對Struts2學習一下，也記錄一下學習的過程。
很多細節的例子請參考struts的demo.這里主要介紹一些概念及流程.
另外推薦一個好的strtus2 blog:
blogjava.net/max 1.先看一下官方網站對Struts2的定義(struts2.org)：
Apache Struts 2 was originally known as WebWork 2.
After working independently for several years, the WebWork and Struts communities joined forces to create Struts2.
This new version of Struts is simpler to use and closer to how Struts was always meant to be.
2.
Introduction
(1) 基于MVC2模式(關于MVC＆MVC2，就不羅嗦了)
（2）主要從從
WebWork and XWork 演變過來
Struts is an Open-Source Web Application Framework that simplifies the creation of a Java Web Application.
It is based on the Model-View-Controller 2 (MVC 2) Architecture which was originally found in a language called SmallTalk.
The recent version of Struts is Struts 2.0 and it has borrowed most of the concepts in terms of architecture and functionality
from two frameworks namely WebWork and XWork.
3.Struts2 MVC2 Architecture
(1)
Controller 作為Model＆View的mediator.當Client請求過來時，Controller截獲請求，再轉發給合適的Action處理.
(2)
Model 代表application data以及控制數據的businness logic,當Controller轉發請求給Action后，Action調用Model
處理business logci,application data的狀態被改變,Action控制權交給Controller，由Controller決定顯示在Client端
的View.
(3)View代表顯示在客戶端的數據表現,可以是JSP、Velocity、Freemaker、XSLT.
4.Struts2 的處理流程
(1) Client發送請求給Web application.Web Server 尋找該app對應的配置文件web.xml并加載相關Boot-strap Component. 在Struts2中是Servlet Filter(而在s1中是Action Servlet). (2) servlet Filter 從配置文件(struts.xml)中匹配請求的動作,即xxx.action (3) Controller 先將request請求交給 Interceptor stack 處理，接著在傳給相關Action. (4) 請求被傳給Action后，基于請求的動作，Action執行合適的業務邏輯處理. (5) Action執行完畢，返回結果 (6) Controller根據Action返回的結果選擇具體的View顯示在客戶端. 4.1 加載Filter Servlet
當客戶端請求一個Struts2的web application時，web server將查找關于application的配置文件web.xml
<filter>
<filter-name>Struts2FilterServlet</filter-name>
<filter-class>
org.apache.struts.action2.dispatcher.FilterDispatcher
</filter-class>
</filter>
<filter-mapping>
<filter-name>Struts2FilterServlet</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
4.2 攔截器處理請求
Interceptors 提供pre-processing ＆ post-processing，request在到達framework之前，首先被傳給一系列的攔截器.
可以自定義攔截器并更改配置文件，如下
import com.opensymphony.xwork2.interceptor.*;
class AuthenticationInterceptor implements Interceptor{
public void init(){}
public void destroy(){}
public String intercept(ActionInvocation invocation) throws Exception{
// Get the value of user credentials from the Request and Validate it.
}
}
更改struts.xml
<struts>
<interceptors>
<interceptor name = "authentication"
class = "myinterceptors.AuthenticationInterceptor">
</interceptor>
<interceptors>
</struts>
4.3 執行Action(詳細請參考struts2的例子)
import java.servlet.http.*;
import org.apache.struts.*;
class MyAction extends Action{
public ActionForward execute(ActionMapping mapping, ActionForm form,
HttpServletRequest request, HttpServletResponse response)
throws java.lang.Exception {
// Do some business logic here.
}
}
配置文件定義如下
<struts>
<action name = "Registration" class = "hello.RegistrationAction">
<action name = "Login" class = "hello.LoginAction">
<action name = "Logout" class = "hello.LogoutAction">
</struts>
4.4 返回結果
package myactions;
public class MyAction{
public String execute(){
if (createOperation()){
return "create";
}else if (deleteOperation()){
return "delete";
}else if( readOperation()){
return "read";
}else if (writeOperation()){
return "write";
}
return "error";
}
}
strtus.xml配置:
<struts>
<action name = "MyAction" class = "myactions.MyAction">
<result name = "create">/myApp/create.jsp</result>
<result name = "delete">/myApp/delete.jsp</result>
<result name = "read">/myApp/read.jsp</result>
<result name = "write">/myApp/write.jsp</result>
</action>
</struts>