Behind the scenes struts will use a requestdispatcher, where the target servletjsp receives the same. What is the difference between requestdispatchers forward. Facing problem with filter and requestdispatcher servlets. B in formbeans section, you can map your actionform subclass to a name. It is used to include the content of another resource also. Requestdispatcher the requestdispacher interface provides the facility of dispatching the request to another resource like html, servlet or jsp. Actionservlet treats all requests made to your struts application and delegates the heavy lifting stuff of handling the request to a requestprocessor object. The forward method of requestdispatcher will forward the servletrequest and servletresponse that it is passed to the path that was specified in getrequestdispatcherstring path. The requestprocessor class takes each request and breaks its processing down into several small tasks. C in globalforwards section you can map a page on your webapp to a name. The controller is responsible for intercepting and translating user input into actions to be performed by the model. Using the request dispatcher function, an attribute msg is sent from process. What is the use of requestprocessor, if we are having actionservlet in struts answer sk niloufer by default struts framework provides applicationcontroller design pattern in the form of requestprocessor whereas actionservlet is a replacement of frontcontroller design pattern implementation.
It forwards the request from one servlet to another resource such as. You might also want to look at the related tutorials. Moduleconfig uses digesters to create java representation of struts. The requestprocessor class is the actual place where the request processing takes place in a struts controller environment. Sep 09, 2006 but in current version of struts, they have replaced requestprocessor with requestdispatcher. In other words, this method allows serverside to include the response of destination program to source program. When the request object first reaches the actionservlet class then it invokes the process method of the underlying requestprocessor class. In fact, the struts controller retains its thread until the action is done with its processing and then it the controller decides which view jsp to forward to. The following are top voted examples for showing how to use org. Servletrequest has its own path elements and parameters adjusted to match the path of the target resource. Out of the following options 1,2,4,5 matches the process that gets carried by actionservlet and requestprocessor. If matching then it will take the type attribute value and load that class. Here servletresponse object are passed as the argument of include method.
To dispatch the request from servlet or jsp to web resource using requestdispatcher we need to perform following steps. Requestprocessor contains the processing logic that the actionservlet performs as it receives each servlet request from the container. We have covered requestdispatcher s forward and include methods. Another difference between the two is that path of the getrequestdispatchestring path of the servletrequest interface cannot extend outside the current servlet context whereas getrequestdispatcherstring path of the servletcontext can use the getcontextstring uripath method to obtain requestdispatcher for resources in foreign contexts. Requestdispatcher include method comes to the rescue. Dec 07, 2014 java requestdispatcher in servlet example instance of java requestdispatcher in servlet instanceofjava this is the java programming blog on oops concepts, servlets jsp freshers and 1, 2,3 years expirieance java interview questions on java with explanation for interview examination. You have to do two things to implement custom request processor in struts. This method of requestdispatcher interface includes the content of web resource servlets, jsp and html file in the response. The requestprocessor class is the actual place where the request processing takes place in a struts controller environment when the request object first reaches the actionservlet class then it invokes the process method of the underlying requestprocessor class this process method then looks into the strutsconfig. It recieves the request from the client and makes decision where to send the request for further processing based on the.
There are two methods defined in the requestdispatcher interface. The servletresponse object has its path elements, and parameters remain unchanged from the callers. The requestdispatcher interface allows you to do a server side forwardinclude whereas sendredirect does a client side redirect. This class does not provide an implementation of the execute method as the normal action class does. Mar 28, 2015 you have to do two things to implement custom request processor in struts. This interface is intended to wrap servlets, but a servlet container can create requestdispatcher objects to wrap any type of resource. Java differecne between requestprocessor and requestdispatcher. Requestprocessor checks whether any tag is available in struts config.
This process method then looks into the strutsconfig. Apr 08, 2008 requestdispatcher object, difference between include and forward method. Struts tutorial code examples struts flowhow struts works. Our focus here is on requestdispatcher requestdispatcher interface from javax. Nullpointerexception with requestdispatcher 800345 jul 8, 2008 11. The servlet container creates the requestdispatcher object, which is used as a wrapper around a server resource located at a particular path or given by a. An actionforward represents a destination to which the controller, requestprocessor, might be directed to perform a requestdispatcher. Requestprocessor contains the processing logic that the struts controller servlet performs as it receives each servlet request from the container. Sendredirect will search the content between the servers. The controller is responsible for selecting the next view based on user input and the outcome of model operations. Requestprocessor checks whether any tag is available in strutsconfig. These examples are extracted from open source projects.
You can also think of a requestdispatcher object as a wrapper for the resource located at a given path that is supplied as an argument to the getrequestdispatcher. Load actionservlet using loadonstartup and do the following tasks. A resource can be another servlet, or an html file, or a jsp file, etc. Struts flow start with actionservlet then call to process method of requestprocessor. The requestdispatcher object has two methods, include and forward. This process method then looks into the struts config. What is the use of requestprocessor, if we are having actionservlet in struts answer sk niloufer by default struts framework provides applicationcontroller design pattern in the form of requestprocessor whereas actionservlet is a replacement of frontcontroller design. Which of the following is performed by actionservlet and. The actionservlet and requestdispatcher are main players in the struts framework. If actioninclude is appended as a url parameter, we see that the requestdispatcher object includes the contents of index. Includes the content of a resource servlet, jsp page, html file in the response. Struts does not use requestdispatcher to forward control to actions.
It comes with two methods include and forward where requestdispatcher can be used. It provides an interface through which the servlets can collaborate with each other. Struts uses the requestprocessor class to perform the processing for all requests received by the actionservlet. This is what javadoc says about requestdispatcher include. A requestdispatcher object can forward a clients request to a resource or include the resource itself in the response back to the client. Requestdispatcher object, difference between include and forward method. Client requests for a servlet say, servleta on the server. Requestdispatcher is an interface, implementation of which defines an object which can dispatch request to any resources. The requestprocessor basically identifies the action from the request through the moduleconfig helper create an actionmapping based on the. This can be done by using requestdispatcher interface. What is the request processor in struts and how it. This approach lets you customize the way each individual part of the request is. Behind the scenes struts will use a requestdispatcher, where the target servlet jsp receives the same requestresponse objects as the original servletjsp. What is the use of requestprocessor, if we are having.
The requestdispatcher interface defines an object that receives the request from client and dispatches it to the resource such as servlet, jsp, html file. Continued from page 1 if the testservlet which is mapped to test is hit with no parameters, we see the following. Interview questions struts interview questions question. As you can see, the request dispatcher results are appended to the previous output results generated by testservlet. What is the request processor in struts and how it works. The servlet container creates the requestdispatcher object, which is used as a wrapper around a server resource located at a particular path or given by a particular name.
Nullpointerexception with requestdispatcher oracle community. In essence, this method enables programmatic serverside includes. In this tutorial, we have covered the java requestdispatcher. What is the difference between requestprocessor and. Any struts web application contain the actionservlet configuration in web. Java requestdispatcher dispatching requests in java web. For a requestdispatcher obtained via getrequestdispatcher, the. Returns a requestdispatcher object that acts as a wrapper for the resource located at the given path.
The included servlet cannot change the response status code or set headers. This interface can also be used to include the content of another resource also. All interceptors are classes, which implements interceptor interface, so we must override all methods in the interceptor interface. The requestdispatcher interface provides the facility of dispatching the request to another resource it may be html, servlet or jsp. The response will not be sent back to the client and the web container for example, tomcat internally redirects the request to the other jspservlet. You can customize the request processing behavior by subclassing this class and overriding the methods whose behavior you are interested in changing. The requestdispatcher class enables your servlet to call another servlet from inside another servlet. Let us see a practical example of requestdispatcher include method. Dec 11, 20 requestdispatcher include method comes to the rescue. Actionservlet which intercept the request and calls requestprocessors process method for further processing requestprocessor read xml file, find the appropriate handler and handles request.
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