servlets

How to use a Servlet Filter to change/rewrite an incoming URL?

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Implement javax.servlet.Filter. In doFilter() method, cast the incoming ServletRequest to HttpServletRequest. Use HttpServletRequest#getRequestURI() to grab the path. Use straightforward java.lang.String methods like substring(), split(), concat() and so on to extract the part of interest and compose the new path. Use either ServletRequest#getRequestDispatcher() and then RequestDispatcher#forward() to forward the request/response to the new URL (server-side redirect, … Read more

Why do cookie values with whitespace arrive at the client side with quotes?

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When you set a cookie value with one of the following values as mentioned in Cookie#setValue(), With Version 0 cookies, values should not contain white space, brackets, parentheses, equals signs, commas, double quotes, slashes, question marks, at signs, colons, and semicolons. Empty values may not behave the same way on all browsers. then the average … Read more

Where do I get servlet-api.jar from?

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Make sure that you’re using the same Servlet API specification that your Web container supports. Refer to this chart if you’re using Tomcat: http://tomcat.apache.org/whichversion.html The Web container that you use will definitely have the API jars you require. Tomcat 6 for example has it in apache-tomcat-6.0.26/lib/servlet-api.jar

Using special auto start servlet to initialize on startup and share application data

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None of both is the better approach. Servlets are intended to listen on HTTP events (HTTP requests), not on deployment events (startup/shutdown). CDI/EJB unavailable? Use ServletContextListener @WebListener public class Config implements ServletContextListener { public void contextInitialized(ServletContextEvent event) { // Do stuff during webapp’s startup. } public void contextDestroyed(ServletContextEvent event) { // Do stuff during webapp’s … Read more

How to solve this java.lang.NoClassDefFoundError: org/apache/commons/io/output/DeferredFileOutputStream?

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The particular exception message is telling you that the mentioned class is missing in the classpath. As the org.apache.commons.io package name hints, the mentioned class is part of the http://commons.apache.org/io project. And indeed, Commons FileUpload has Commons IO as a dependency. You need to download and drop commons-io.jar in the /WEB-INF/lib as well. See also: … Read more

Why Servlets are not thread Safe? [duplicate]

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I need to know why the servlets are not thread safe ? Servlet instances are inherently not thread safe because of the multi threaded nature of the Java programming language in general. The Java Virtual Machine supports executing the same code by multiple threads. This is a great performance benefit on machines which have multiple … Read more

ServletContainerInitializer vs ServletContextListener

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The ServletContainerInitializer implementation is intented to be bundled in a JAR file which is in turn been dropped in /WEB-INF/lib of the webapp. The JAR file itself should have a /META-INF/services/javax.servlet.ServletContainerInitializer file containing the FQN of the ServletContainerInitializer implementation in the JAR. Please note that this file should thus not be placed in the webapp … Read more

How do delete a HTTP response header?

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You can’t delete headers afterwards by the standard Servlet API. Your best bet is to just prevent the header from being set. You can do this by creating a Filter which replaces the ServletResponse with a custom HttpServletResponseWrapper implementation which skips the setHeader()‘s job whenever the header name is Content-Disposition. Basically: @Override public void doFilter(ServletRequest … Read more

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