Version: 9.3.29.v20201019 |

Chapter 23. Maven and Jetty
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## Chapter 23. Maven and Jetty

This chapter explains how to use Jetty with Maven and the Jetty Maven plugin.

## Using 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.

> ### Note

> Use of Maven and the jetty-maven-plugin is not required. Using Maven for Jetty implementations is a popular choice, but users encouraged to manage their projects in whatever way suits their needs. Other popular tools include Ant and Gradle.

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:

- Embedding with Jetty
- Jetty HelloWorld example

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` in the `JettyMavenHelloWorld` directory 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>
          <!-- Adapt this to a version found on
               http://central.maven.org/maven2/org/eclipse/jetty/jetty-maven-plugin/
            -->
          <jettyVersion>9.3.9.v20160517</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]
    [INFO] ------------------------------------------------------------------------
    [INFO] Building Jetty HelloWorld 0.1-SNAPSHOT
    [INFO] ------------------------------------------------------------------------
    [INFO]
    [INFO] --- maven-dependency-plugin:2.8:tree (default-cli) @ hello-world ---
    ...
    [INFO] org.example:hello-world:jar:0.1-SNAPSHOT
    [INFO] \- org.eclipse.jetty:jetty-server:jar:9.3.9.v20160517:compile
    [INFO]    +- javax.servlet:javax.servlet-api:jar:3.1.0:compile
    [INFO]    +- org.eclipse.jetty:jetty-http:jar:9.3.9.v20160517:compile
    [INFO]    |  \- org.eclipse.jetty:jetty-util:jar:9.3.9.v20160517:compile
    [INFO]    \- org.eclipse.jetty:jetty-io:jar:9.3.9.v20160517:compile
    [INFO] ------------------------------------------------------------------------
    [INFO] BUILD SUCCESS
    [INFO] ------------------------------------------------------------------------
    [INFO] Total time: 4.145 s
    [INFO] Finished at: 2016-08-01T13:46:42-04:00
    [INFO] Final Memory: 15M/209M
    [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 create the file `src/main/webapp/WEB-INF/web.xml` and add the following contents:

    <?xml version="1.0" encoding="UTF-8"?>
    <web-app
       xmlns="http://xmlns.jcp.org/xml/ns/javaee"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
       metadata-complete="false"
       version="3.1">

      <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 in the `JettyMavenHelloWarApp` directory, 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>9.3.29.v20201019</jettyVersion>
      </properties>

      <dependencies>
        <dependency>
          <groupId>javax.servlet</groupId>
          <artifactId>javax.servlet-api</artifactId>
          <version>3.1.0</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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