Category: GWT

Categories
GWT Java Maven

HTMLUnit and GWT

After developing on an other aspect of a project, I realized later that all my GWT testcases didn’t work anymore. I got the following strange Exception:

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java.lang.NoSuchFieldError: FIREFOX_17
	at com.google.gwt.junit.RunStyleHtmlUnit.<clinit>(RunStyleHtmlUnit.java:200)
	at java.lang.Class.forName0(Native Method)
	at java.lang.Class.forName(Class.java:264)
	at com.google.gwt.junit.JUnitShell.createRunStyle(JUnitShell.java:1181)
	at com.google.gwt.junit.JUnitShell.doStartup(JUnitShell.java:942)
	at com.google.gwt.dev.DevModeBase.startUp(DevModeBase.java:982)
	at com.google.gwt.junit.JUnitShell.getUnitTestShell(JUnitShell.java:698)
	at com.google.gwt.junit.JUnitShell.runTest(JUnitShell.java:672)
	at com.google.gwt.junit.client.GWTTestCase.runTest(GWTTestCase.java:421)
	at junit.framework.TestCase.runBare(TestCase.java:141)
	at junit.framework.TestResult$1.protect(TestResult.java:122)
	at junit.framework.TestResult.runProtected(TestResult.java:142)
	at junit.framework.TestResult.run(TestResult.java:125)
	at junit.framework.TestCase.run(TestCase.java:129)
	at com.google.gwt.junit.client.GWTTestCase.run(GWTTestCase.java:247)
	at junit.framework.TestSuite.runTest(TestSuite.java:255)
	at junit.framework.TestSuite.run(TestSuite.java:250)
	at org.junit.internal.runners.JUnit38ClassRunner.run(JUnit38ClassRunner.java:84)
	at org.junit.runner.JUnitCore.run(JUnitCore.java:160)
	at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:69)
	at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:234)
	at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:74)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at com.intellij.rt.execution.application.AppMain.main(AppMain.java:144)
</clinit>

The exception also occurred via Maven and not only in IntelliJ, so I knew it has something to do with my Maven-Project.

After checking the dependencies of my project with mvn dependency:tree, I found a new transitive dependency of a new added dependency. Because I didn’t need the htmlunit-part of this component I excluded the htmlunit-dependency with the following directive in my pom.xml:

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<dependencies>
....
    <dependency>
        <groupdid>my.dependency
        <artifactid>mydependency
        <exclusions>
            <exclusion>
                <groupid>net.sourceforge.htmlunit</groupid>
                <artifactid>htmlunit</artifactid>
            </exclusion>
        </exclusions>
    </artifactid></groupdid></dependency>
....
</dependencies>

A deeper analysis of the problem shows, that the transitive dependency was too new, because the field FIREFOX_17 is not available any more, but the newer one like FIREFOX_38.

Categories
GWT Java Javascript Maven

GWT-Hidden-Feature: code coverage

In July 2012 a until now rarely documented feature was added to GWT (related Git-Commit). It’s code coverage on the client side.

How it works

You can activate it via the System-Property “gwt.coverage”. The property-value must contain either all named Java source files separated by comma, or it must point to a text file containing all Java source files; one per line. Now the GWT compiler will instrument the corresponding JavaScript which is based on the named Java source files. Additionally the compiler registers an onUnLoad-Event, which stores the code coverage into LocalStorage of the browser.

Maven-Example

I have a simple GWT-Project which is build via Maven. In the main source (src/main/java/org/jajax/gwt/test/client/MyEntryPoint.java) I have the following file:

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package org.jajax.gwt.test.client;
 
import com.google.gwt.core.client.EntryPoint;
import com.google.gwt.user.client.Window;
 
public class MyEntryPoint implements EntryPoint {
 
   @Override
   public void onModuleLoad() {
       Window.alert("Hello world");
   }
}

Additionally I created a Textfile (target/gwt-coverage-sources.txt) with the following content:

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org/jajax/gwt/test/client/MyEntryPoint.java

Now only the configuration of GWT is missing. You have to add the Parameter gwt.coverage=target/gwt-coverage-sources.txt.

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<plugin>
    <groupid>org.codehaus.mojo</groupid>
    <artifactid>gwt-maven-plugin</artifactid>
    <version>2.7.0</version>
    <configuration>
        <extrajvmargs>-Dgwt.coverage=target/gwt-coverage-sources.txt</extrajvmargs>
    </configuration>
</plugin>

Now if you run you application, you can access the code coverage via JavaScript

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localStorge.getItem("gwt_coverage");

You will get a JSON with the following content:

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{"org/jajax/gwt/test/client/MyEntryPoint.java":{"6":1,"10":1}}

The inner object has for every line as key a value of 0 for a missing coverage or 1 for covered code.

Conclusion

This feature is very interesting, because the alternatives are very rare. The old option to use Emma / Jacoco is not functional anymore with the current versions of Java (1.8), GWT (2.7.0 / 2.8.0-SNAPSHOT), etc. So this feature seems to be a good alternative. Unfortunately there is no tool to extract the code coverage of Unit-Tests or Integration-Tests, but I will release a Tool, which connects the GWT code coverage with Jacoco Reports. So stay tuned!

Categories
GWT Polymer/Webcomponents

Resources for Quickstart with GWT and Polymer

Today I would like to give some resources for a quick start in development with GWT and Polymer components. Polymer components are an implementation of basic components with the Webcomponents technology.

  1. The first point is an overview of the Polymer components in GWT. So you have an overview what is possible. You can click through the show case of the gwt-polymer-elements library.
  2. The second point is the official documentation from the GWT-Project. This is a good start to see how you will consume webcomponents with GWT.
  3. As described there you will use the gwt-polymer-elements library from vaadin. This library provides standard polymer (paper and iron elements and some vaadin elements) ready for use with GWT. Currently the Version 1.2.3.0 is the latest release and you will need to use the 2.8.0-SNAPSHOT version of the GWT project.

With these resources and the provided demos you will be able to start your development and play a little bit with the technologies. In the next days I will write some more Howtos about concerning points. If you have some problems with the setup, feel free to write a comment.