1. 編寫一個簡單的Action

public class UserAction {
    private String name;
    public String execute(){
        System.out.println("執行execute方法...");//加斷點
        System.out.println("name========"+name);
        return "success";
    }
    public String getName() {
        return name;
    }
    public void
 
 setName(String name) {
        this.name = name;
    }
}

2. 啟動Tomcat伺服器除錯執行

3. 檢視程式碼執行順序

4. 開啟Dispather的serviceAction方法

  public void serviceAction(HttpServletRequest request, HttpServletResponse response, ActionMapping mapping)
            throws ServletException {
        //在下面一行程式碼加斷點再次除錯執行
 

        Map<String, Object> extraContext = createContextMap(request, response, mapping);
        .....
   在該行按F5鍵進入如下程式碼
       public Map<String,Object> createContextMap(request, response,mapping) {
        Map requestMap = new RequestMap(request);
        從以下注釋可以看出引數request獲取引數的方式，存在Map
 
中
        // parameters map wrapping the http parameters.  ActionMapping parameters are now handled and applied separately
        HttpParameters params = HttpParameters.create(request.getParameterMap()).build();
在build方法按F3可以看到如下程式碼
public HttpParameters build() {
...
   for (Map.Entry<String, Object> entry : requestParameterMap.entrySet()) {
     String name = entry.getKey();
     Object value = entry.getValue();
     parameters.put(name, new Parameter.Request(name, value));
    }
    return new HttpParameters(parameters);
}
可以看出把請求引數的Map包裝成HttpParameters
最後建立一個map
Map<String,Object> extraContext = createContextMap(requestMap, params, session, application, request, response);
....
return extraContext;

5. 檢視具體引數位置

public void serviceAction(request, response, mapping)
            throws ServletException {
//加斷點除錯
        Map<String, Object> extraContext = createContextMap(request, response, mapping);
 // If there was a previous value stack, ....
ValueStack stack = .....;   
檢視extraContext 變數中的資料如下圖所示，可以看到呼叫Action時傳入的引數:http://localhost:8080/strutsdemo/userAction?name=admin      

這就是Struts2獲取請求引數的過程。