Advance java session 6
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The document discusses annotations in Servlets 3.0. It introduces annotations as an easier way to develop servlets, filters, and listeners compared to traditional deployment descriptors. Key annotations include @WebServlet, @ServletFilter, and @WebServletContextListener. While annotations can be used with deployment descriptors, annotations take precedence unless metadata-complete is set to true.
Advance java session 6
- 2. Agenda • Ease of Development • Annotation Support
- 3. Annotation in Servlets 3.0 specification • The new specification focuses on - Ease of development - Plugability and extensibility - Asynchronous Support - Security Enhancements
- 4. Ease of Development • Annotation based declarative-style programming • Use @WebServlet for developing Servlet • Use @ServletFilter for developing Filter • Use @WebServletContextListener for creating ServletContext Listener
- 5. Annotation v/s Deployment Descriptor • Interesting note: - Deployment descriptor can be used along with annotation - Deployment descriptor takes precedence over annotation - Metadata-complete is a new attribute which contains either true or false • True means deployment tool will ignore any servlet annotation • False means container must scan all the files for annotation along with the deployment descriptor
- 6. Annotation v/s Deployment Descriptor • @WebServlet(name="mytest", urlPatterns={"/myurl"}, initParams={ @InitParam(name="n1", value="v1"), @InitParam(name="n2", value="v2") }) public class TestServlet extends javax.servlet.http.HttpServlet { .... }
- 7. Annotation v/s Deployment Descriptor • web.xml <init-param> <param-name>n1</param-name> <param-value>v1</param-value> </init-param> <init-param> <param-name>n2</param-name> <param-value>v2</param-value> </init-param>
- 8. Servlet Context Listener Annotation • @WebServletContextListener public class TestServletContextListener implements javax.servlet.ServletContextListener { .... public void contextInitialized(ServletContextEvent sce) { .... } public void contextDestroyed(ServletContextEvent sce) { .... } }
- 9. Servlet Filter Annotation • @ServletFilter(urlPatterns={"/myurl"}. initParams={ @InitParam(name="mesg", value="my filter") }) public class TestFilter implements javax.servlet.Filter { .... public void init(FilterConfig filterConfig) throws ServletException { .... } public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException { .... } public void destroy() { .... } }
- 10. Summary • Annotation support is available only from JDK 1.5 or above • Annotation can be used along with tradition approach. • Annotation makes development easier