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The Annotations Servlet Sample Application

This is a simple Servlet application that uses annotations for servlets, filters, and content listeners.

Description

Servlet

The servlet reads the initial parameter, a request attribute and a context attribute and provides the result.

@WebServlet(name="mytest",
            urlPatterns={"/"},
            initParams={ @WebInitParam(name="message",value="my servlet") } )
public class TestServlet extends HttpServlet {
    public void init(ServletConfig config) throws ServletException {
        // read the context attribute
        ...
    }
    public void service(HttpServletRequest req, HttpServletResponse res) throws IOException, ServletException {
    } 
}

@javax.servlet.annotation.WebServlet is an annotation that specifies metadata for a servlet. In this case, it specifies the URL pattern and an initialization parameter. You need to extend javax.servlet.http.HttpServlet.

Filter

The filter reads the initial parameter and sets a request attribute.

@WebFilter(urlPatterns={"/"}, 
           initParams={ @WebInitParam(name="mesg", value="my filter") })
public class TestFilter implements Filter {
    public void init(FilterConfig filterConfig) throws ServletException {
        ...
    }
    public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) 
	                     throws IOException, ServletException {
        ...
    }
    public void destroy() {
        ...
    }
}

@javax.servlet.annotation.WebFilter is an annotation that specifies meta-data for a filter. In this case, it specifies the URL pattern and an initialization parameter. You need to extend javax.servlet.Filter.

ContextListener

The context listener sets a context attribute in the contextInitialized() method.

@javax.servlet.annotation.WebListener
public class TestServletContextListener implements ServletContextListener {
    public void contextInitialized(ServletContextEvent sce) {
        ...
    }
    public void contextDestroyed(ServletContextEvent sce) {
        ...
    }
}

@javax.servlet.annotaton.WebListener indicates that a class is a context listener.

Deployment Descriptor

By using annotations, the deployment descriptor is no longer required.

GlassFish Server Specific Deployment Configuration

There is no need to define any GlassFish Server deployment descriptor (sun-web.xml) for this sample.

Key Features

• Specifying metadata for a servlet using annotations.
• Specifying the URL pattern and initialization parameters using annotations instead of declaring them in the deployment descriptor.

Building, Deploying, and Running the Application

Follow these instructions for building, deploying, and running this sample application:

1. Set up your build environment and configure the application server with which the build system has to work by following the common build instructions.
2. app_dir is the sample application base directory: samples_install_dir/servlet/annotation-war.
3. Change directory to app_dir.

4. Build and deploy the sample application using the mvn target:

   Use the command below to run this sample using the Cargo framework:

   app_dir> mvn clean verify cargo:run

   You can point Cargo to an already installed and running Glassfish server:

   app_dir> mvn clean verify cargo:run -Dglassfish.home=$<glassfish_dir> (e.g. ../glassfish4)

   You can also build, deploy the sample application without Cargo:

   app_dir> mvn install

   app_dir> asadmin deploy ./target/<app_name>.war

5. Run the sample as follows:
   • Use the browser to access
     http://<javaee.server.name>:<javaee.server.port>/annotation-war
     
     The expected message in the browser is the following:
     Hello, my servlet, my filter, my listener.
6. Use the glassfish command line to undeploy the application.

   app_dir> asadmin undeploy <app_name>

7. Use the target clean to remove the temporary directories like /target.

   app_dir> mvn clean

Building, Deploying, and Running the Application in NetBeans IDE

Perform the following steps to build, deploy, and run the application using NetBeans IDE:

1. Refer to the common build instructions for setting up NetBeans IDE and Java EE 7 SDK.
2. In the NetBeans IDE, choose File → Open Project (Ctrl-Shift-O), navigate to the samples_install_dir/servlet/ directory, select annotation-war, and click Open Project.
3. In the Projects tab, right click annotation-war and select Run to build, deploy, and run the project.

Troubleshooting

If you have problems when running the application, refer the troubleshooting document.

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