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Using Maven
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Using Maven

Using Embedded Jetty with Maven
Developing a Standard WebApp with Jetty and Maven

Apache Maven is a software project management and comprehension tool. Based on the concept of a project object model (POM), Maven can manage a project's build, reporting and documentation from a central piece of information.

It is an ideal tool to build a web application project, and such projects can use the jetty-maven-plugin to easily run the web application and save time in development. You can also use Maven to build, test and run a project which embeds Jetty.

First we'll have a look at a very simple HelloWorld java application that embeds Jetty, then a simple webapp which makes use of the jetty-maven-plugin to speed up the development cycle.

Using Embedded Jetty with Maven

To understand the basic operations of building and running against Jetty, first review

Maven uses convention over configuration, so it is best to use the project structure Maven recommends. You can use archetypes to quickly setup Maven projects, but we will set up the structure manually for this simple tutorial example:

> mkdir JettyMavenHelloWorld
> cd JettyMavenHelloWorld
> mkdir -p src/main/java/org/example

Creating the HelloWorld Class

Use an editor to create the file src/main/java/org/example/HelloWorld.java with the following contents:

package org.example;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.ServletException;
import java.io.IOException;
import org.eclipse.jetty.server.Server;
import org.eclipse.jetty.server.Request;
import org.eclipse.jetty.server.handler.AbstractHandler;

public class HelloWorld extends AbstractHandler
{
    public void handle(String target,
                       Request baseRequest,
                       HttpServletRequest request,
                       HttpServletResponse response) 
        throws IOException, ServletException
    {
        response.setContentType("text/html;charset=utf-8");
        response.setStatus(HttpServletResponse.SC_OK);
        baseRequest.setHandled(true);
        response.getWriter().println("<h1>Hello World</h1>");
    }

    public static void main(String[] args) throws Exception
    {
        Server server = new Server(8080);
        server.setHandler(new HelloWorld());
 
        server.start();
        server.join();
    }
}

Creating the POM Descriptor

The pom.xml file declares the project name and its dependencies. Use an editor to create the file pom.xml with the following contents:

<project xmlns="http://maven.apache.org/POM/4.0.0" 
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">

  <modelVersion>4.0.0</modelVersion>
  <groupId>org.example</groupId>
  <artifactId>hello-world</artifactId>
  <version>0.1-SNAPSHOT</version>
  <packaging>jar</packaging>
  <name>Jetty HelloWorld</name>

  <properties>
    <jettyVersion>9.0.0</jettyVersion>
  </properties>

  <dependencies>
    <dependency>
      <groupId>org.eclipse.jetty</groupId>
      <artifactId>jetty-server</artifactId>
      <version>${jettyVersion}</version>
    </dependency>
  </dependencies>

  <build>
    <plugins>
      <plugin>
        <groupId>org.codehaus.mojo</groupId>
        <artifactId>exec-maven-plugin</artifactId>
        <version>1.1</version>
        <executions>
          <execution><goals><goal>java</goal></goals></execution>
        </executions>
        <configuration>
          <mainClass>org.example.HelloWorld</mainClass>
        </configuration>
      </plugin>
    </plugins>
  </build>
</project>

Building and Running Embedded HelloWorld

You can now compile and execute the HelloWorld class by using these commands:

> mvn clean compile exec:java

You can point your browser to http://localhost:8080 to see the hello world page. You can observe what Maven is doing for you behind the scenes by using the mvn dependency:tree command, which reveals the transitive dependency resolved and downloaded as:

> mvn dependency:tree
[INFO] Scanning for projects...
[INFO] Searching repository for plugin with prefix: 'dependency'.
[INFO] ------------------------------------------------------------------------
[INFO] Building Jetty HelloWorld
[INFO]    task-segment: [dependency:tree]
[INFO] ------------------------------------------------------------------------
[INFO] [dependency:tree {execution: default-cli}]
[INFO] org.example:hello-world:jar:0.1-SNAPSHOT
[INFO] \- org.eclipse.jetty:jetty-server:jar:9.0.0:compile
[INFO]    +- org.eclipse.jetty:javax.servlet:jar:3.0.0.v201112011016:compile
[INFO]    +- org.eclipse.jetty:jetty-continuation:jar:9.0.0:compile
[INFO]    \- org.eclipse.jetty:jetty-http:jar:9.0.0:compile
[INFO]       \- org.eclipse.jetty:jetty-io:jar:9.0.0:compile
[INFO]          \- org.eclipse.jetty:jetty-util:jar:9.0.0:compile
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESSFUL
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 4 seconds
[INFO] Finished at: Thu Jan 24 16:19:08 EST 2013
[INFO] Final Memory: 11M/68M
[INFO] ------------------------------------------------------------------------

Developing a Standard WebApp with Jetty and Maven

The previous section demonstrated how to use Maven with an application that embeds Jetty. Now we will examine instead how to develop a standard webapp with Maven and Jetty. First create the Maven structure (you can use the maven webapp archetype instead if you prefer):

> mkdir JettyMavenHelloWarApp
> cd JettyMavenHelloWebApp
> mkdir -p src/main/java/org/example
> mkdir -p src/main/webapp/WEB-INF

Creating a Servlet

Use an editor to create the file src/main/java/org/example/HelloServlet.java with the following contents:

package org.example;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class HelloServlet extends HttpServlet
{
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
    {
        response.setContentType("text/html");
        response.setStatus(HttpServletResponse.SC_OK);
        response.getWriter().println("<h1>Hello Servlet</h1>");
        response.getWriter().println("session=" + request.getSession(true).getId());
    }
}

You need to declare this servlet in the deployment descriptor, so edit the file src/main/webapp/WEB-INF/web.xml and add the following contents:

<?xml version="1.0" encoding="ISO-8859-1"?>
<web-app 
   xmlns="http://java.sun.com/xml/ns/javaee" 
   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
   xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
   metadata-complete="false"
   version="3.0">

  <servlet>
    <servlet-name>Hello</servlet-name>
    <servlet-class>org.example.HelloServlet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>Hello</servlet-name>
    <url-pattern>/hello/*</url-pattern>
  </servlet-mapping>

</web-app>

Creating the POM Descriptor

The pom.xml file declares the project name and its dependencies. Use an editor to create the file pom.xml with the following contents, noting particularly the declaration of the jetty-maven-plugin:

<project xmlns="http://maven.apache.org/POM/4.0.0" 
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">

  <modelVersion>4.0.0</modelVersion>
  <groupId>org.example</groupId>
  <artifactId>hello-world</artifactId>
  <version>0.1-SNAPSHOT</version>
  <packaging>war</packaging>
  <name>Jetty HelloWorld WebApp</name>

  <properties>
    <jettyVersion>9.0.0</jettyVersion>
  </properties>

  <dependencies>
    <dependency>
      <groupId>org.eclipse.jetty.orbit</groupId>
      <artifactId>javax.servlet</artifactId>
      <version>3.0.0.v201112011016</version>
      <scope>provided</scope>
    </dependency>
  </dependencies>

  <build>
    <plugins>
      <plugin>
        <groupId>org.eclipse.jetty</groupId>
        <artifactId>jetty-maven-plugin</artifactId>
        <version>${jettyVersion}</version>
      </plugin>
    </plugins>
  </build>

</project>

Building and Running the Web Application

Now you can both build and run the web application without needing to assemble it into a war by using the jetty-maven-plugin via the command:

> mvn jetty:run

You can see the static and dynamic content at http://localhost:8080/hello

There are a great deal of configuration options available for the jetty-maven-plugin to help you build and run your webapp. The full reference is at Configuring the Jetty Maven Plugin.

Building a WAR file

You can create a Web Application Archive (WAR) file from the project with the command:

> mvn package

The resulting war file is in the target directory and may be deployed on any standard servlet server, including Jetty.

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