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