Servlet learning notes servletconfig, servletcontext. Requestdispatcher getrequestdispatcherstring path the same method belongs to both the servletrequest interface and the servletcontext interface. In the servletconfig object, it encapsulates the relevant parameters needed to initialize the servlet program. To understand the difference between these two methods, lets take an example. The difference between this method and servletcontext. Let us see what api says about getrequestdispatcherstring path method. Different servlets can live in different servletcontexts, but a servlet engine can group related servlets in the same servletcontext. Small difference in the usage exist between the two and we see later. I am sure the exception is caused by getservletcontext, since when i replace it by request, the exception disappears. In this article, we are going to understand how to include an output from another servlet into the current servlet using the include method of requestdispatcher object. There are two methods defined in the requestdispatcher interface. Today, we are going to understand how to forward the contents of one servlet to another servlet using the forward method of requestdispatcher object.
Using the requestdispatcher object with the include method we can include the contents of another servlet in the current servlet. Servletconfig is used to pass configuration information to servlet. The following are top voted examples for showing how to use javax. In lieu of this method, servlets can share information using the servletcontext class and can perform shared business logic by invoking methods on common nonservlet classes.
An attribute allows a servlet container to give the servlet additional information not already provided by this interface. Now when u get the servletcontext reference, u can invoke the getcontext using the method getcontexturipath. This method allows servlets to gain access to the context for various parts of the server, and as needed obtain requestdispatcher objects from the context. The getservletcontext method and its uses with example. In this version, this method always returns null and remains only to preserve binary compatibility.
There are three ways to obtain requestdispatcher object. This is at the end of the dopost, where i am finished and returning it. Returns the parameter value for the specified parameter name. For every servlet, web container will create one servletconfig object to maintain servlet level initialization parameter. We can maintain request scope by using servletrequest or. In this example we are retrieving all the values from the web. Example demonstrating usage of requestdispatcher in this example, we will show you how requestdispatcher is used to forward or include response of a resource in a servlet. It gets the context from the servlets servletconfig object.
This method allows servlets to gain access to the context for various parts of the. Get a requestdispatcher object use the forward method or include method of requestdispatcher. Servletconfig creates an object of servletcontext then used it in a servlet to deploy it on the server the same as in servletconfig, but it has one important feature that makes it more useful. Servlet requestdispatcher w3schools tutorialspoint.
New request is created for the destination resource. Another difference between the two is that path of the getrequestdispatcher string path of the servletrequest interface cannot extend outside the current servlet context whereas getrequestdispatcher string path of the servletcontext can use the getcontextstring uripath method to obtain requestdispatcher for resources in foreign contexts. Requestdispatcher is an interface that transfers the control from current web resource to another web resource such as a servlet, html, jsp on the server. In page x you have an include tag, this means that the control will be in the page x till it encounters include tag, after that the control will be transferred to page y.
The requestdispatcher interface provides the facility of dispatching the request to another resource it may be html, servlet or jsp. Difference between servletconfig and servletcontext. What is the difference between the getrequestdispatcherstring path method of servletrequest interface and servletcontext interface. This method will be permanently removed in a future version of the java servlet api. The genericservlet class implements the servlet and servletconfig interface in from mca mca501 at maharishi markandeshwar university. It enables one servlet to do prelude processing of a request and another resource to create the response. This interface can also be used to include the content of another resource also. This interface is intended to wrap servlets, but a servlet container can create requestdispatcher objects to wrap any type of resources. This method was originally defined to retrieve a servlet from a servletcontext. Requestdispatcher interface defines an object that receives the request from client and dispatches it to the resourcessuch as servlet, jsp, html file. By using this object servlet can get its configuration information. There is one context per web application per java virtual machine.
What is the defferent between getnameddispatcher and getrequestdispatcher. The server can also store extra information here in the form of string, object pairs. Close springs web application context for the given servlet context. An object implementing the requestdispatcher interface may be obtained via the following methods. Introduction to resquest dispatcher in servlet studytonight. The servletcontext object is contained within the servletconfig object. The genericservlet class implements the servlet and.
Understanding jsp line of code with getrequestdispatcher stack. This interface defines an object that receives request from the client and sends them to any resource which can be servlet,html or jsp. Defines a set of methods that a servlet uses to communicate with its servlet container, for example, to get the mime type of a file, dispatch requests, or write to a log file. A resource can be another servlet, or an html file, or a jsp file, etc. Using getparameter method all values can also be retrieved. Difference between forward and sendredirect in servlet. Servlet interface cannot have a constructor that accepts a servletconfig parameter.
What is the difference between the getrequestdispatcherstring and getnameddispatcherstring methods in the servletcontext class. String getservletname returns the name of this servlet instance. There is given some commonly used methods of servletcontext interface. A requestdispatcher object can forward a clients request to a resource or include the resource itself in the response back to the client. The servletcontext class provides two methods getrequestdispatcherstring. The following are jave code examples for showing how to use getservletregistration of the javax.
Similarly for every webapplication webcontainer creates one servletcontext object to maintain application level configuration information. Introduction to servletconfig interface studytonight. Defines a set of methods that a servlet uses to communicate with a servlet engine, for example, to get the mime type of a file, locate other servlets running on the server, or write to a servlet log file. This method returns a requestdispatcher object for the resource. Using the requestdispatcher object with the forward method we can forward the contents of one servlet to another servlet. The given path must be begin with, is interpreted relative to the server. Every servlet has its own servletconfig object and servlet. A servlet instance can determine its name using servletconfig.
Servletconfig object is used to pass information to a servlet during initialization by getting configuration information from web. The requestdispatcher class enables your servlet to call another servlet from inside another servlet. What is the defferent between getnameddispatcher and. Nullpointerexception with requestdispatcher oracle community. Requestdispatcher is an interface that enables the servlet container to dispatch the request from a web application to another within the same context. This method returns the all parameter names from the web. Requestdispatcher interface is used to receive a client request and can do one of the following two things 1 it can forward client request to some other servlet, jsp or html file. Returns the names of the contexts initialization parameters. The name may be provided via server administration, assigned in the web application deployment descriptor, or for an unregistered and thus unnamed servlet instance it will be the servlets class name. When the web container initializes a servlet, it creates a servletconfig object for the servlet. This method forwards a request from a servlet to another resource servlet, jsp file or html file on the server.
We are going to describe requestdispatcher in java. 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 method. It does not depend on the clients request protocol since the forward method is provided by the servlet container. The examples are extracted from open source java projects. The getrequestdispatcher method of servletrequest interface returns the object of. Servletconfig object will be available in init method of the servlet. These examples are extracted from open source projects. Another difference between the two is that path of the getrequestdispatcherstring 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. For constructing a requestdispatcher object, you can use either the servletrequest. Difference between getrequestdispatcher method of the servletrequest interface and that of the servletcontext interface. The getrequestdispatcher method of servletrequest interface returns the object of requestdispatcher. In order to dispatch the request we need to perform these tasks. First u get the reference to servlet context using getservletcontext method of genericservlet or using servletconfigs getservletcontext method.
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