- doGet() processes HEAD requests in the absence of a doHead() method
- Not the service() method but the methods that are called by the service method are better candidates for overriding
- HttpServlet supports GET, POST, DELETE, OPTIONS, and TRACE requests
- Retrieve a single value for a form parameter named “username”: String u = request.getParameter(“username”);, String u = request.getParameterValues(“username”)[0];
- java.util.Enumeration getHeaderNames() – retrieves the complete collection of request headers
- set the content type of a servlet response:
response.setContentType(“text/html”);
response.setHeader(“Content-Type”, “text/html”);
response.addHeader(“Content-Type”, “text/html”); - Servlet.destroy(): Servlets release resources: When called, the servlet container may not route other requests to that instance of the servlet: Servlet.destroy() may never be called
- The destroy() method, called by the web container when the servlet (or the web application) is being shutdown. This is a very good place to put the code to close related socket connection
- no guarantee on when the finalize() method will be called by the JVM
- The init() method is called by the web container before any HTTP requests are processed by the servlet. This is a good place to open a socket connection
- web.xml, JAR files, Class files, the deployment descriptor – are expected to be placed under WEB-INF directory
- A welcome file: used when a user requests a directory
- welcome files may be used at any directory level
- the default servlet is used to handle requests for specific files that exist in the webapp
- By default, the web container sends a 404 error back if the requested file does not exist
- Define a mime-mapping:pdfapplication/pdf
- WAR files are created using the jar command.
- A web application may be packaged into a WAR file for deployment, but it is not required.
- The files within the WEB-INF directory and the files within the META-INF directory of a WAR file must not be directly served as content by the container in response to a Web client’s request.
- A webapp can only have one web.xml file and all configuration must exist in that one file even if the Java class files exist in some other package
- String boundObjectName = getServletContext().getInitParameter(“com.example.BoundObj”);:returns a String if an initializathttp://www.justetc.net/knowledge/editArticlesNext.phphttp://www.justetc.net/knowledge/editArticlesNext.phpion parameter of that name exists in web.xml
- session.removeAttribute(“app.util.DataSource”);: removes a session attribute
- Servlet context listeners are notified when the context is ready to process requests and when it is about to be shut down
- HttpSession.setAttribute(String attributeName,Object value): method stores an object
From: http://sitestree.com/?p=4929
Categories:Java Short Notes
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Post Data:2008-09-09 09:45:43
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