Using the Google Plugin for Eclipse

It's easy to use the Eclipse development environment to develop your Java App Engine application, just as you can to develop any other servlet-based web application. With the Google Plugin for Eclipse, it's even easier. The plugin lets you create, test, and upload App Engine applications from within Eclipse. You can also import an App Engine application packaged as a Maven project, and let Eclipse use Maven to manage dependencies and builds. (For more information, see Using Apache Maven.)

The Google Plugin for Eclipse also makes it easy to develop applications using Google Web Toolkit (GWT), to run on App Engine or in any other environment.

This article describes how to install the Google Plugin for Eclipse, create or import a new App Engine project, and debug it using the development server running within Eclipse. The article also describes how to use the plugin to upload your project to App Engine.

For more information about the plugin, including how to use it for Google Web Toolkit projects, see the Google Plugin for Eclipse documentation.

Getting Eclipse

The Eclipse IDE is available in several packages. The "Eclipse IDE for Java EE Developers" package includes all of the components you will need for web application development.

In addition to the Google Plugin for Eclipse, we recommend the Eclipse Web Tools Platform (WTP) plugins for web development. Among other things, WTP provides editing modes for JSP and HTML files.

Installing the Google Plugin for Eclipse

To use the plugin you must be running Java version 7 and a recent version of Eclipse. You can install the Google Plugin for Eclipse using the software update feature of Eclipse. Be sure to use the plugin that corresponds to your version of Eclipse. Follow the installation instructions provided at the links below or, if you are familiar with installing Eclipse plugins, you can simply paste the appropriate plugin link directly into Eclipse.

If you are looking for older versions of the plugin, click here.

If you are having trouble installing from the update sites (due to firewall issues, for instance), please see this FAQ entry.

As an alternative to installing from the update site, you can install the Google Plugin for Eclipse by downloading and installing an archive of the update site.

Creating a project

To create a new App Engine project:

1. Select the File menu > New > Web Application Project . If you do not see this menu option, select the Window menu > Reset Perspective..., click OK, then try the File menu again. Alternatively, click the Google button in the Eclipse toolbar and select New Web Application Project.

2. The "Create a Web Application Project" wizard opens. For "Project name," enter a name for your project, such as Guestbook for the project described in the Getting Started Guide. For "Package," enter an appropriate package name, such as guestbook.

3. If you're not using Google Web Toolkit, uncheck "Use Google Web Toolkit." Verify that "Use Google App Engine" is checked.

4. If you installed the App Engine SDK using Software Update, the plugin is already configured to use the SDKs that were installed. If you would like to use a separate installation of the App Engine SDK, click Configure SDKs..., and follow the prompts to add a configuration with your SDK's appengine-java-sdk/ directory.

5. Click Finish to create the project.

The wizard creates a directory structure for the project, including a src/ directory for Java source files, and a war/ directory for compiled classes and other files for the application, libraries, configuration files, static files such as images and CSS, and other data files. The wizard also creates a servlet source file and two configuration files. The complete directory structure looks like this:

Guestbook/
  src/
    guestbook/
      server/
        GuestbookServlet.java
    META-INF/
      jdoconfig.xml
    log4j.properties
    logging.properties
  war/
    WEB-INF/
      lib/
        ...App Engine JARs...
      appengine-web.xml
      web.xml
    index.html

The war/ directory uses the WAR standard layout for bundling web applications. (WAR archive files are not yet supported by the SDK.) The Eclipse plugin uses this directory for running the development server, and for deploying the app to App Engine.

When Eclipse builds your project, it creates a directory named classes/ in war/WEB-INF/, and puts compiled class files here. Eclipse also copies non-source files found in src/ to war/WEB-INF/classes/, including META-INF/ and the log4j.properties and logging.properties files. The final contents of the war/ directory make up your application for testing and deployment.

For details about the new project that the plugin creates, see the Getting Started Guide.

Importing a Maven project

An existing App Engine project that has been packaged as a Maven project can be imported as an Eclipse project. The directory at the root of the Maven project must have a pom.xml file. The <plugins> element in the pom.xml file must include a <plugin> element for appengine-maven-plugin.

To import the existing App Engine project:

1. Select the File menu > Import > Maven > Existing Maven Projects.

2. Click Next.

3. Specify the root directory of the Maven project, which is the directory containing the pom.xml file. You can either type the path into the Root Directory text field or click the Browse button and use a file-selection dialog.

4. Click Finish.

Running the project

The App Engine SDK includes a web server for testing your application in a simulated environment. The Google Plugin for Eclipse adds new items to the Run menu for starting this server. The items added, and the details for using them, depend on whether you are using a Maven project:

• If your project is not a Maven project, you can run your application in the web server inside the Eclipse debugger by selecting the Run menu, Debug As > Web Application.

• If your project is a Maven project, you can run your application in the web server inside the Eclipse debugger by selecting the Run menu, Debug As

  1 Debug on Server. You will then be taken to a page where you will be asked to select a server. The first time you run the application, you should use the Manually define a new server option:

  

  Feel free to change the server name if you like, but accept the remaining defaults and click Finish. On subsequent runs of the application, you should use the Choose an existing server option, make sure the server you defined for this application is highlighted, and click Finish:

  

Eclipse builds the project, switches to the Debug perspective, and the server starts. If the server starts successfully, the server displays several messages, including a message similar to the following, in the Console:

The server is running at http://localhost:8888/

If you want to customize how the server is started, you can create a new Run/Debug configuration. For a non-Maven project, create a configuration of the type "Web Application." For a Maven project, create a configuration of the type "Maven Build" by cloning and modifying the "DevAppServer" configuration.

To test the new application that the plugin created, start the server as above, then visit the following URL in your browser (using a URL path appropriate to your application):

http://localhost:8888/guestbook

With Eclipse, you can leave the server running in the debugger while you make changes to source code, JSPs, static files and appengine-web.xml. When you save changes to source code, Eclipse compiles the class automatically, then attempts to insert it into the running web server dynamically. In most cases, you can simply reload the page in your browser to test the new version of the code. Changes to JSPs, static files and appengine-web.xml are recognized by the development server automatically, and also take effect without restarting the server. If you change web.xml or other configuration files, you must stop and start the server for the changes to take effect.

To stop the server, make sure the Debug panel is selected, then click the Terminate button:

Uploading to Google App Engine

Before you upload your app for the first time, you must register an application ID with App Engine using the Admin Console. Register an application ID, then edit the appengine-web.xml file and change the <application>...</application> element to contain the new ID.

To begin deployment of your application:

• For a non-Maven application, click the Google button in the Eclipse toolbar, and select Deploy to App Engine. Eclipse might prompt you for your administrator account username (your email address) and password. Enter your account information and click the Upload button to complete the upload.

• For a Maven application, select the Run menu, Run As > 5 Maven build.... On the Edit Configuration panel that pops up, enter appengine:update in the Goals field and click Run.

Eclipse gets the application ID and version information from the appengine-web.xml file, and uploads the contents of the war/ directory.

Test your application on App Engine by visiting its URL:

http://<your_app_id>.appspot.com/guestbook

Running the command line tools

Some features of the App Engine Java SDK tools are only available by running the tools directly from the command line. If you have installed the SDK using Eclipse, you can run these tools from the Eclipse plugin installation directory.

The SDK is located in your Eclipse installation directory, under plugins/com.google.appengine.eclipse.sdkbundle_<VERSION>/, where <VERSION> is a version identifier for the SDK. In this directory is the appengine-java-sdk/bin/ subdirectory containing the tools.

For more information on the features available exclusively from the command line, see Uploading and Managing.

Errors launching Eclipse

You can encounter JVM version issues that prevent Eclipse from starting. This can be caused by a configuration error in the eclipse.ini file: the JVM (Java Virtual Machine) needs to be specified in eclipse.ini for Eclipse to run properly. Doing this ensures that Eclipse will use the correct JVM and insulates you from changes that can alter the "default" JVM on your system.

To fix this:

1. Locate the eclipse.ini file. Note: On a Mac OS X system, you can find eclipse.ini file right-clicking (or Ctrl+click) on the Eclipse executable in Finder, choose Show Package Contents, and then locate eclipse.ini in the MacOS folder under Contents, for example, ../Eclipse/Contents/MacOS.

2. Close Eclipse (in Mac OS X, press ⌘-Q). Make sure all Eclipse processes are closed in the activity monitor.

3. Open the eclipse.ini file, and locate the --vmargs line.

4. Enter the following two lines above the --vmargs line:

   -vm /Library/Java/JavaVirtualMachines/jdk[VersionNumber].jdk/Contents/Home/jre

   replacing [VersionNumber] with the current version of Java

5. Make sure the following is true about the -vm line:

   1. The format of the -vm option must be exactly as shown.
   2. The -vm option and its value (the path to the JVM executable) must be on separate lines.
   3. The -vm option must occur before the --vmargs option, since everything after --vmargs is passed directly to the JVM.
   4. For a 32-bit Eclipse executable (eclipse.exe on Windows), you must use a 32-bit JVM; for a 64-bit Eclipse executable, you must use a 64-bit JVM. (32-bit Eclipse will not work with a 64-bit JVM.)

6. Save and close the file, then launch Eclipse.

Except as otherwise noted, the content of this page is licensed under the Creative Commons Attribution 3.0 License, and code samples are licensed under the Apache 2.0 License. For details, see our Site Policies.