Annotations in Servlets

1. Annotations in Servlet

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