I have two action classes
public class TokenAction extends Action {
private ActionForward getToken(ActionMapping actionMapping, ActionForm actionForm, HttpServletRequest request,
HttpServletResponse response) throws IOException {
String token = generateToken();
response.setContentType("text/plain");
response.getWriter().print(token);
return null;
}
and
public class ActionTwo extends Action{
private ActionForward doSomething(ActionMapping actionMapping, ActionForm actionForm, HttpServletRequest request,
HttpServletResponse response) {
token = ???
return actionMapping.findForward("page");
}
}
How can I get in ActionTwo from TokenAction?
Basically, in Java there are multiple ways to pass objects across contexts, the most popular being likely:
through static variables (not recommended)
through shared parameter maps
through a controller object
In your case, since the parameters passed to the methods seem to have a lifetime that encompasses both calls (although it's hard to say without the specifics), you should probably store them in the parameters (HttpServletResponse isn't very useful for that purpose, but the ActionMapping and ActionForm likely are). If your Actions are created in the context of some controller, you could use the controller to pass the parameter instead.
Related
I have a question with Spring MVC RequestMapping annotation. need your help.
I have created one IPSLcontroller and i want that IPSLcontroller to handle all request url.i have created two method in this controller.
1)handleLogoutRequest :- this method should invoke on below url.
2)handleRequest :- this method should invoke on all request url otherthan logout.
http://localhost:9086/webapp/login
or
http://localhost:9086/webapp/add
or
http://localhost:9086/webapp/remove
here is my sample code. but it's not working as expected.
#Controller
public class IPSLController {
#RequestMapping(value={"/logout/*"},method = RequestMethod.POST)
protected void handleLogoutRequest(HttpServletRequest request,
HttpServletResponse response) throws Exception {
System.out
.println("........................IPSLController logout request.......................................");
}
#RequestMapping(method = RequestMethod.POST,value={"/*"})
protected void handleRequest(HttpServletRequest request,
HttpServletResponse response) throws Exception {
System.out
.println("........................IPSLController all request Post.......................................");
}
}
You should use a general Prefix for every controller you use, so you can differ between them better. Also you don´t need any "/" for calls like this.
#Controller
#RequestMapping("ispl")
public class IPSLController {
#RequestMapping(value={"logout"},method = RequestMethod.POST)
protected void handleLogoutRequest(HttpServletRequest request,
HttpServletResponse response) throws Exception {
System.out
.println("........................IPSLController logout request.......................................");
}
#RequestMapping(method = RequestMethod.POST,value={"hello"})
protected void handleRequest(HttpServletRequest request,
HttpServletResponse response) throws Exception {
System.out
.println("........................IPSLController all request Post.......................................");
}
}
If you now want to call them over a ServletRequest or with a restService or something similar you should declare them like this
#GET
#Path("ispl/logout")
public void Method (HttpServletResponse ...)
Well it is working the way it should. You have a mapping for /* and for /logout/*. So when you post to /logout it invokes the method for /*. I suspect that if you post to /logout/something it would invoke your logout handler.
If you want it to work, you cannot have a wildcard mapping for the second method. At least use /something/* so that spring can make a correct decision on mappings.
What is the purpose of wrapping an HttpServletRequest using an HttpServletRequestWrapper ? What benefits do we gain from doing this ?
HttpServletRequest is an interface for a HTTP specific servlet request. Typically you get instances of this interface in servlet filters or servlets.
Sometimes you want to adjust the original request at some point. With a HttpServletRequestWrapper you can wrap the original request and overwrite some methods so that it behaves slightly different.
Example:
You have a bunch of servlets and JSPs which expect some request parameters in a certain format. E.g. dates in format yyyy-MM-dd.
Now it is required to support the dates also in a different format, like dd.MM.yyyy with the same functionality. Assuming there is no central string to date function (it's an inherited legacy application), you have to find all places in the servlets and JSPs.
As an alternative you can implement a servlet filter. You map the filter so that all requests to your servlets and JSPs will go through this filter.
The filter's purpose is to check the date parameters' format and reformat them to the old format if necessary. The servlets and JSPs get the date fields always in the expected old format. No need to change them.
This is the skeleton of your filter:
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException {
HttpServletRequest adjustedRequest = adjustParamDates((HttpServletRequest) request);
chain.doFilter(adjustedRequest, response);
}
We take the original request and in method adjustParamDates() we manipulate the request and pass it down the filter chain.
Now, how would we implement adjustParamDates()?
private HttpServletRequest adjustParamDates(HttpServletRequest req) {
// ???
}
We need a new instance of interface HttpServletRequest which behaves exactly like the original instance req. But the four methods getParameter(), getParameterMap(), getParameterNames(), getParameterValues() shouldn't work on the original parameters but on the adjusted parameter set. All other methods of interface HttpServletRequest should behave like the original methods.
So we can do something like that. We create an instance of HttpServletRequest and implement all methods. Most method implementations are very simple by calling the corresponding method of the original request instance:
private HttpServletRequest adjustParamDates(final HttpServletRequest req) {
final Map<String, String[]> adjustedParams = reformatDates(req.getParameterMap());
return new HttpServletRequest() {
public boolean authenticate(HttpServletResponse response) {
return req.authenticate(response);
}
public String changeSessionId() {
return req.changeSessionId();
}
public String getContextPath() {
return req.getContextPath();
}
// Implement >50 other wrapper methods
// ...
// Now the methods with different behaviour:
public String getParameter(String name) {
return adjustedParams.get(name) == null ? null : adjustedParams.get(name)[0];
}
public Map<String, String[]> getParameterMap() {
return adjustedParams;
}
public Enumeration<String> getParameterNames() {
return Collections.enumeration(adjustedParams.keySet());
}
public String[] getParameterValues(String name) {
return adjustedParams.get(name);
}
});
}
There are more than 50 methods to implement. Most of them are only wrapper implementations to the original request. We need only four custom implementations. But we have to write down all these methods.
So here comes the class HttpServletRequestWrapper into account. This is a default wrapper implementation which takes the original request instance and implements all methods of interface HttpServletRequest as simple wrapper methods calling the corresponding method of the original request, just as we did above.
By subclassing HttpServletRequestWrapper we only have to overwrite the four param methods with custom behaviour.
private HttpServletRequest adjustParamDates(final HttpServletRequest req) {
final Map<String, String[]> adjustedParams = reformatDates(req.getParameterMap());
return new HttpServletRequestWrapper(req) {
public String getParameter(String name) {
return adjustedParams.get(name) == null ? null : adjustedParams.get(name)[0];
}
public Map<String, String[]> getParameterMap() {
return adjustedParams;
}
public Enumeration<String> getParameterNames() {
return Collections.enumeration(adjustedParams.keySet());
}
public String[] getParameterValues(String name) {
return adjustedParams.get(name);
}
});
}
I have a MultiActionController with an action that I would only like to be reachable if the POST method is used.
public class MyController extends MultiActionController {
public ModelAndView myAction(final HttpServletRequest request, final HttpServletResponse response) throws Exception {
// I don't want to hit this code unless POST was used
}
}
Is there a way to achieve this through annotations or am I stuck checking request.getMethod() ?
Use:
#RequestMapping(value={"action1","action2","action3"},
method = RequestMethod.POST)
I'm using HandlerInterceptor to trigger all the events/actions happens in my applications and save it to audit table. In table I'm saving the information like servername, session, parameters etc..
So using HandlerInterceptor how can I read all those parameters values and the pathvariable values what I'm passing in my controller.
Here is my code :
public class AuditInterceptor implements HandlerInterceptor {
#Override
public boolean preHandle(HttpServletRequest request,
HttpServletResponse response, Object handler) throws Exception {
LOG.debug("URL path"+request.getRequestURI());
return true;
}
#Override
public void postHandle(HttpServletRequest request,
HttpServletResponse response, Object handler,
ModelAndView modelAndView) throws Exception {
LOG.debug("URL PATH :"+request.getRequestURI());
}
}
My controller class enter code here::
public class ABCDController {
#RequestMapping(value="categories",method=RequestMethod.GET)
#ResponseBody
public List<Category> getCategoryList(#RequestParam String divisions){
return service.getCategoryList(divisions);
}
}
So how can I read the parameter name and values using HandlerInterceptor's HttpServletRequest request object.
The Servlet API provides a way to read the Request Parameters. For example,
ServletRequest.getParameterMap() returns a map of key-values of the request parameters.
However, for Path variables and values, I don't know if Spring MVC offers a simplified way of doing it, but using Servlet API again, you can read the URI using HttpServletRequest.getRequestURI(). You'll have to have your own logic to split it up into appropriate Path parameters.
You should be able to get the variables and its values as a map using the following,
public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) {
final Map<String, String> variableValueMap = (Map<String, String>) request
.getAttribute(HandlerMapping.URI_TEMPLATE_VARIABLES_ATTRIBUTE);
variableValueMap.forEach((k,v)->System.out.println("Key:"+k+"->"+"Value : "+v));
return true;
}
i want to ask you about mvc. How it works. So, this is simple example(I don't use any frameworks)
in Controller(Servlet):
protected void doGet(HttpServletRequest request,
HttpServletResponse response) throws ServletException, IOException {
processRequest(request, response);
}
protected void doPost(HttpServletRequest request,
HttpServletResponse response) throws ServletException, IOException {
processRequest(request, response);
}
private void processRequest(HttpServletRequest request,
HttpServletResponse response) throws ServletException, IOException {
String page = null;
AbstractCommand action;
action = ActionFactory.getAction(request);// get command from factory
page = action.execute(request, response);
RequestDispatcher dispatcher = getServletContext()
.getRequestDispatcher(page);
dispatcher.forward(request, response);
}
for action we create a common interface(Strategy pattern):
public interface AbstractAction {
public String execute(HttpServletRequest request, HttpServletResponse response);
}
Simple Action(Example):
public class HelloAction implements AbstractAction {
#Override
public String execute(HttpServletRequest request,
HttpServletResponse response) {
//....(some actions to modify request)
String page = "/main.jsp";
return page;
}
}
And now, our factory:
public class ActionFactory {
private enum Actions{
HELLO;
}
public static AbstractAction getAction(HttpServletRequest request){
String action = request.getParameter("action");//take parameter from jsp
Actions actionEnum = Actions.valueOf(action.toUpperCase());
switch (actionEnum) {
case HELLO:
return new HelloAction();
}
}
}
We came to the place where I am in confused. Servlet is initialized only once, and only one for all requests. Just forwards requests to the actions where we modify request or response. But, we create NEW instance of the class for every request. Here can occur memory overflow!? Or not?
Can we make these actions static(static method, one for all request)? If two requests come at the same time what will happen to them?
What do you think about this, please share your experience.
P.S. sorry for bad english.
How about Singleton pattern to get the instance of the Action class ?
Just add some abstact getInstance() method in AbstractAction.
Make every implementation provide its own instance.
In every implementation class, use Singleton pattern so that only one instance exists.
Make sure no action class stores any data related to a specific request.
As i understood the jsp, the whole thing is stateless, if u access the servlet by http request, the servlet will be created in a new instance.
After leaving the servlet by .forward(), it will be released by garbage collection.
2,3,...,n requests = 2,3,...,n servlets.
by forwarding to a jsp, the only way to access the servlet from jsp is a new http request = new servlet. ( will move to the doPost method)