Version: 9.4.19.v20190610 |

Using Annotations with Jetty Embedded
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## Using Annotations with Jetty Embedded

### Setting up the Classpath

You will need to place the following Jetty jar files onto the classpath of your application. You can obtain them from the Jetty distribution, or the Maven repository:

    jetty-plus.jar
    jetty-annotations.jar

You will also need the asm jar, which you can obtain from this link.

### Example

Here’s an example application that sets up a Jetty server, performs some setup to ensure that annotations are scanned, and then deploys a webapp that uses annotations. This example also uses the @Resource annotation which involves JNDI, so we would also add the necessary JNDI jars to the classpath. The example also adds in the configuration classes that are responsible for JNDI (see line 19).

The code is as follows:

    import org.eclipse.jetty.security.HashLoginService;
    import org.eclipse.jetty.server.Server;
    import org.eclipse.jetty.webapp.WebAppContext;

    /**
     * ServerWithAnnotations
     *
     *
     */
    public class ServerWithAnnotations
    {
        public static final void main(String args[]) throws Exception
        {
            //Create the server
            Server server = new Server(8080);

            //Enable parsing of jndi-related parts of web.xml and jetty-env.xml
            org.eclipse.jetty.webapp.Configuration.ClassList classlist = org.eclipse.jetty.webapp.Configuration.ClassList.setServerDefault(server);
            classlist.addAfter("org.eclipse.jetty.webapp.FragmentConfiguration", "org.eclipse.jetty.plus.webapp.EnvConfiguration", "org.eclipse.jetty.plus.webapp.PlusConfiguration");
            classlist.addBefore("org.eclipse.jetty.webapp.JettyWebXmlConfiguration", "org.eclipse.jetty.annotations.AnnotationConfiguration");

            //Create a WebApp
            WebAppContext webapp = new WebAppContext();
            webapp.setContextPath("/");
            webapp.setWar("../../tests/test-webapps/test-servlet-spec/test-spec-webapp/target/test-spec-webapp-9.0.4-SNAPSHOT.war");
            server.setHandler(webapp);

            //Register new transaction manager in JNDI
            //At runtime, the webapp accesses this as java:comp/UserTransaction
            org.eclipse.jetty.plus.jndi.Transaction transactionMgr = new org.eclipse.jetty.plus.jndi.Transaction(new com.acme.MockUserTransaction());

            //Define an env entry with webapp scope.
            org.eclipse.jetty.plus.jndi.EnvEntry maxAmount = new org.eclipse.jetty.plus.jndi.EnvEntry (webapp, "maxAmount", new Double(100), true);

            // Register a  mock DataSource scoped to the webapp
            org.eclipse.jetty.plus.jndi.Resource mydatasource = new org.eclipse.jetty.plus.jndi.Resource(webapp, "jdbc/mydatasource", new com.acme.MockDataSource());

            // Configure a LoginService
            HashLoginService loginService = new HashLoginService();
            loginService.setName("Test Realm");
            loginService.setConfig("src/test/resources/realm.properties");
            server.addBean(loginService);

            server.start();
            server.join();
        }

    }

On line 19 the configuration classes responsible for setting up JNDI and `java:comp/env` are added.

On line 20 we add in the configuration class that ensures annotations are inspected.

On lines 30, 33 and 37 JNDI resources that we will be able to reference with @Resource annotations are configured.

With the setup above, a servlet that uses annotations and Jetty will honour the annotations when the webapp is deployed can be created:

    import javax.annotation.security.DeclareRoles;
    import javax.annotation.security.RunAs;
    import javax.servlet.ServletConfig;
    import javax.servlet.ServletException;
    import javax.servlet.ServletOutputStream;
    import javax.servlet.annotation.WebInitParam;
    import javax.servlet.annotation.WebServlet;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import javax.sql.DataSource;
    import javax.transaction.UserTransaction;

    /**
     * AnnotationTest
     *
     * Use servlet 3.0 annotations from within Jetty.
     *
     * Also uses servlet 2.5 resource injection and lifecycle callbacks
     */

    @RunAs("special")
    @WebServlet(urlPatterns = {"/","/test/*"}, name="AnnotationTest", initParams={@WebInitParam(name="fromAnnotation", value="xyz")})
    @DeclareRoles({"user","client"})
    public class AnnotationTest extends HttpServlet
    {
        private DataSource myDS;

        @Resource(mappedName="UserTransaction")
        private UserTransaction myUserTransaction;

        @Resource(mappedName="maxAmount")
        private Double maxAmount;

        @Resource(mappedName="jdbc/mydatasource")
        public void setMyDatasource(DataSource ds)
        {
            myDS=ds;
        }

        @PostConstruct
        private void myPostConstructMethod ()
        {
            System.err.println("PostConstruct called");
        }

        @PreDestroy
        private void myPreDestroyMethod()
        {
            System.err.println("PreDestroy called");
        }

        public void init(ServletConfig config) throws ServletException
        {
            super.init(config);
        }

        public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
        {
            doGet(request, response);
        }

        public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
        {
            try
            {
                response.setContentType("text/html");
                ServletOutputStream out = response.getOutputStream();
                out.println("<html>");
                out.println("<body>");
                out.println("<h1>Results</h1>");
                out.println(myDS.toString());
                out.println("<br/>");
                out.println(maxAmount.toString());
                out.println("</body>");
                out.println("</html>");
                out.flush();
            }
            catch (Exception e)
            {
                throw new ServletException(e);
            }
        }
    }

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