[STRUTS2] Accessing Request,session and Application objects (GO)

How to access the Servlet API decoupling

Structs2 httpservletrequest,httpsession, and ServletContext were encapsulated, three map objects were constructed to replace these three objects, in action, Use the Httpservletrequest,httpsession,servletcontext Map object directly to save and read data.

To get these three map objects, you can use the Com.opensymphony.xwork2.ActionContext class.

Actioncontext is the context in which the action executes, and the set of objects needed to execute the action, including Parameters,request,session,application,locale, is saved in Actioncontext.

The Actioncontext class does not provide a method like Getrequest () to obtain a map object that encapsulates HttpServletRequest. To request a Map object, you need to pass the parameter "request" with the Get () method

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1. public object get (object key)
3. Public Map getsession ()
5. Public Map getapplication ()

Action:

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1. Actioncontext context = Actioncontext.getcontext ();
2. Map request= (map) context.get ("request");
3. Map session = Context.getsession ();
4. MAP application = Context.getapplication ();
6. Request.put ("greeting", " Hello request");
7. Session.put ("user", user);
9. Integer count = (integer) application.get ("counter");
12. Application.put ("counter", count);

Jsp:

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1. <h3>${sessionscope.user.username},${requestscope.greeting}. </h3><br />
2. ${applicationscope.counter}

There is also a way to pass data using the Request object, which can be saved to actioncontext directly using the put () method of the Actioncontext class

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1. Actioncontext.getcontext (). Put ("greeting","Hello");

Then, in the results page, remove the Greeting property from the Request object

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1. $ (requestscope.greeting) or <%=request.getattribute ("greeting")%>

The data stored in the Actioncontext can be obtained from the request object, The secret lies in the Org.apache.struts2.dispatcher.StrutsRequestWrapper class in Struct2, which is the HttpServletRequest wrapper class, which overrides the GetAttribute () method, in which the object is requested to find the attribute, and if not, it is looked up from the actioncontext. This is why the data saved in Actioncontext can be obtained from the request object.

In addition to Actioncontext to get request,session and application objects this way, the action class can implement certain interfaces, allowing Structs2 to inject a request to the action instance at run time. The Session,application object. The corresponding three interfaces and their methods:

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1. Org.apache.struts2.interceptor.RequestAware
2. Org.apache.struts2.interceptor.SessionAware
3. Org.apache.struts2.interceptor.ApplicationAware

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2. Public class Loginaction implements action,requestaware,sessionaware,applicationaware{
4. private MAP request;
6. Private MAP session;
8. Private MAP Application;
12. // ......
16. @override
18. Public void Setrequest (Map request) {
20. This.request=request;
22. }
24. @override
26. Public void Setsession (Map session) {
28. This.session=session;
30. }
32. @override
34. Public void Setapplication (Map application) {
36. This.application=application;
38. }
42. }

How access is coupled to the Servlet API

To get the HttpServletRequest and ServletContext objects directly, you can use the Org.apache.struts2.ServletActionContext class, where two static methods are defined

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1. Public static Httpserlvetrequest getrequest ()
3. Public static HttpServletResponse GetResponse ()
5. Pubolic static ServletContext getservletcontext ()

The HttpSession object can be obtained through the HttpServletRequest object.

You can also call the Get () method of the Actioncontext object to pass Servletactioncontext.http_request and servletactioncontext.servlet_ The context key value to get the HttpServletRequest and ServletContext objects, as follows:

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1. Actioncontext.getcontext (). get (Servletactioncontext.http_request);
2. Actioncontext.getcontext (). get (Servletactioncontext.http_response);
3. Actioncontext.getcontext (). get (Servletactioncontext.servlet_context);

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1. Httpservletresquest request = Servletactioncontext.getrequest ();
2. HttpSession session = Request.getsession ();
3. ServletContext context = Servletactioncontext.getservletcontext ();
4. Saving data in Application
5. Integer count = (integer) context.getattribute ("counter");

In addition to using Servletactioncontext to get HttpServletRequest objects and ServletContext objects this way, The action class can also implement the Servletrequestaware and Servletcontextaware interfaces, which are injected by Struts2 into the action instance httpservletrequest and ServletContext objects

The Serveletrequestaware interface and the Servletcontextaware interface are not in the same package, The former is in the Org.apache.structs2.interceptor package, the latter in the Org.apache.struts2.util package.

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2. Public class Loginaction implements action,servletrequestaware,servletcontextaware{
4. private HttpServletRequest request;
6. Private ServletContext context;
10. //......
14. @override
16. Public void Setservletrequest (...) {  
18. //...
20. }
24. @override
26. Public void Setservletcontext (...) {  
28. //...
30. }
32. }

[STRUTS2] Accessing Request,session and Application objects (GO)