Simple Gradle Web Application

Gradle easily supports Java web applications through the “war” and “jetty” plugins. This tutorial will show you how to quickly make a simple Java Servlet web application.

Our basic project structure will be:

basic-web
  src
    main
      java
        com
          codetutr
            HelloWorldServlet.java
      webapp
        WEB-INF
          web.xml

First, create a folder called basic-web, and then let’s create the Gradle build file inside the folder:

build.gradle
apply plugin: 'java' 
apply plugin: 'war' 
apply plugin: 'jetty' 
apply plugin: 'eclipse-wtp'

repositories {
  mavenCentral()
}

dependencies {
  providedCompile 'javax.servlet:servlet-api:2.5'
  runtime 'javax.servlet:jstl:1.1.2'
}

The eclipse-wtp plugin allows us to import the project into Eclipse as a Dynamic Web Project to be run from Eclipse if desired. The war plugin extends the java plugin and adds support for packaging the WAR file. The jetty plugin adds tasks to support running our Gradle project in an embedded Jetty instance from our build-file. Notice that we are including the servlet-api as a “providedCompile” dependency. This means we do not want it to be packaged in the WAR, because it will be included in the application server in which it will run.

Now, let’s create the web.xml descriptor file in src/main/webapp/WEB-INF

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" 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_2_5.xsd">

  <servlet>
    <display-name>HelloWorldServlet</display-name>
    <servlet-name>HelloWorldServlet</servlet-name>
    <servlet-class>com.codetutr.HelloWorldServlet</servlet-class>
  </servlet>

  <servlet-mapping>
    <servlet-name>HelloWorldServlet</servlet-name>
    <url-pattern>/</url-pattern>
  </servlet-mapping>

</web-app>

We set up a simple servlet backed by com.codetutr.HelloWorldServlet and mapped to “/”.

Finally, let’s create the servlet in src/main/java package com.codetutr:

HelloWorldServlet.java

package com.codetutr;

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 HelloWorldServlet extends HttpServlet {

    private static final long serialVersionUID = 1L;

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp)  
            throws ServletException, IOException {
        resp.getOutputStream().write("Hello World.".getBytes());
    }
}

That’s all. We can now launch the jetty server and see our web application in action:

$ gradle jettyRunWar
:compileJava UP-TO-DATE
:processResources UP-TO-DATE
:classes UP-TO-DATE
:war
:jettyRunWar

Now go to http://localhost:8080/basic-web to access your servlet. You should see “Hello, World.” on the screen.

Full source: basic-web.zip
Unpack the archive. Open command prompt at unarchived root. Type gradle jettyRunWar. Go to http://localhost:8080/basic-web.

Tagged with: , , ,
Posted in Gradle, Java
  • sermyro

    How to stop jetty?

    I got the following:

    “gradle jettyStop
    :jettyStop FAILED

    FAILURE: Build failed with an exception.

    * What went wrong:
    Execution failed for task ‘:jettyStop’.
    > Please specify a valid port”

    Thanks

  • Himanshu Singh

    -> Now go to http://localhost:8080/basic-web
    Incorrectly the above hyperlink points to http://localhost:8080/web-basic
    Just after finishing the tutorial and clicked the link given in your tutorial and realized that.

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