Chapter Interservlet Communication Servlets running together in the same server have several ways to communicate with each other. There are three major . I have a Websocket servlet and a Rest servlet. I want to inform the websocket servlet about changes in order to write these “events” via websocket to a server. hi iam new to interservlet iam familiar with servlet only i am planning to write interservlet

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There are three major reasons to use interservlet communication:.

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The server may–but isn’t required to–load the named servlet and execute its init method if it isn’t already loaded.

The server cannot intervene and make sure your call happens when the servlet is not interacting with another client. You have characters left. Intreservlet back to the ChatServlet from the previous chapter.

interservlet communication (Servlets forum at Coderanch)

Sign up or log in Sign up using Google. The saveState method threw an exception: Get unlimited access to videos, live online training, learning paths, books, tutorials, and more.

I could only find the forward and include approach. There are three major reasons to use interservlet communication:. Checking out the currently loaded servlets import java. There’s nothing too surprising in this servlet.

Because otherwise it would have to cast each Servlet object to some class or interface that includes a saveState method, and the code for each servlet would have to be modified to extend or implement that class or interface.

Sign up using Facebook. Casting the Servlet object returned by getServlet or getServlets to its specific subclass can, in some situations, throw a ClassCastException. With Safari, you learn the way you learn best.

This servlet has no saveState method. The enumeration always includes the calling servlet itself. The most common, situation involves two or more servlets sharing state information. The server maintains one servlet instance per name, so getServlet “file” returns a different ckmmunication instance than getServlet “com.


This method was introduced in Version 2. Interservlet communication Ask Question. Think back to the ChatServlet from the previous chapter. Post as a guest Name.

What you could do is create a third component, let’s call it EventManager for the time being, and have the Rest servlet signal changes to the EventManager. One servlet can use another’s abilities to perform a task. Email Required, but never shown.

The name returned can be a registered name such as “file” or a class name such as “com. Direct servlet manipulation involves one servlet accessing the loaded servlets on its server and optionally performing some task on one or more of them.

Of course, in this case, the servlet must be changed to declare that it implements the interface. Indeed, forward and include are meant to be used when processing a request. By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service.

For example, the following code sometimes works as expected and sometimes throws an exception:.

Interservlet Communication – Java Servlet Programming [Book]

Generally there’s one servlet context per server, but for security or convenience, a server may decide to partition its servlets into separate contexts. Then it prints three items of information about the servlet: Most Popular jGuru Stories. Reflection also avoids the ClassCastException problem noted earlier.

The same type mismatch can occur if the class performing the cast that is, the servlet containing the above code is reloaded.

This method is deprecated in the Servlet API 2. You can also get all of the servlets using getServlets:. Start Free Trial No credit card required. As the name says it, it is communication between servlets. And then calling the function on the returned Servlet object.


Java Servlet Programming by Jason Hunter

For example, a set of servlets managing an online store could share the store’s product inventory count. This can be done by obtaining a handle to the desired servlet through the ServletContext Object by passing it the servlet name this object can return any servlets running in the server. The next example demonstrates another use for these methods. If there’s a problem, it reports the problem. These servlets should be running in the same server. The servlet performing the cast can remain in the servlets directory because its ClassLoader can find MyServlet using the primordial class loader.

The specified name can be the servlet’s registered name such as “file” or its class name such as “com. Example uses these methods to display information about the currently loaded servlets, as shown in Figure The websocket, on the other hand, could be notified by the EventManager that new data are available and then get that new data in order to write it back to the client. Post Your Answer Discard By clicking “Post Your Answer”, you acknowledge that you have read our updated terms of serviceprivacy policy and cookie policyand that your continued use of the website is subject to these policies.

Because its new ClassLoader won’t find MyServlet using the primordial class loader and will load its own copy of MyServlet. QuinStreet does not include all companies or all types of products available in the marketplace.

Session tracking see Chapter 7, “Session Tracking” is a special case of servlet collaboration.