DDevelopment & Design

Modular Web Application using Eclipse Snaps

Few days ago, new milestone 3.0.0.M03 of Eclipse Virgo was released. Final release of this well prepared OSGi-based application Server getting closer so I decided to take a look at how to use it to write simple modular web application.

What does it mean a modular web application in OSGi environment? I imagine that this application should:

1) Change their look after installation of some extensions.

2) Also we should be able to write new request handlers for our application or modify flow control of existed.

First idea which occurred to me how to resolve first mentioned problem is to use fragment bundles mechanism. Fragment bundles give opportunity to create bundles with resources and classes which will be accessible from host bundle classloader. A key use case of its was “providing translation files for different locales“. So we can do few fragments with jsp files which should be able to include in index servlet page. Also we can provide some configuration files with class names of new request handlers which could be created using java reflection.

But fragment bundles have some disadvantages. How we can read in specification: “The new content of the updated fragment must not be allowed to attach to the host bundles until the Framework is restarted or the host bundle is refreshed“. This mean that we cannot do installation of extention without refreshing host bundle. Also new jsps must be compiled as a part of host application’s jsps so it is second reason why host bundle should be restarted. The last thing is that fragment bundles can’t have Bundle Activator which is also useful in many cases.

Eclipse Virgo gives component which resolves this problems – Virgo Snaps. It is easy in use extension which helps create modular web application framework. Sources are available here

After build of project and copy artifacts to virgo:

cd build-snaps

ant jar

cd ..

cp org.eclipse.virgo.snaps.api/target/artifacts/org.eclipse.virgo.snaps.api.jar ${virgo.home}/repository/usr/

cp org.eclipse.virgo.snaps.core/target/artifacts/org.eclipse.virgo.snaps.core.jar ${virgo.home}/repository/usr/

… and restart of server, we are ready to use snaps.

In samples dir there is example menu-bar showing idea of Snaps. In host bundle – animal.menu.bar we can see in top.jsp usage of taglib snaps:

  • “> ${snap.properties[‘link.text’]}

 

 

It is simple way to iterate through snaps associated with this host. Only thing which we must to do is to add this snippet to MANIFEST.MF:

Snap-Host: animal.menu.bar;version="[1.0, 2.0)"

Snap-ContextPath: /cat

In first line we are manifesting that this snap will be used as a part of host animal.menu.bar. In the second that all servlets will be deployed in this subcontext of context of host.

In this example also were used properties from file snap.properties which are available in session as attribute properties of snap.

After install host bundle at url: http://localhost:8080/animal-menu-bar we can see page without menu items. After installation of new items are become available.

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DDevelopment & Design

Spock, Java and Maven

Few months ago I've came across Groovy - powerful language for JVM platform which combines the power of Java with abilities typical for scripting languages (dynamic typing, metaprogramming).

Together with Groovy I've discovered spock framework (https://code.google.com/p/spock/) - specification framework for Groovy (of course you can test Java classes too!). But spock is not only test/specification framework - it also contains powerful mocking tools.

Even though spock is dedicated for Groovy there is no problem with using it for Java classes tests. In this post I'm going to describe how to configure Maven project to build and run spock specifications together with traditional JUnit tests.


Firstly, we need to prepare pom.xml and add necessary dependencies and plugins.

Two obligatory libraries are:
<dependency>
    <groupid>org.spockframework</groupId>
    <artifactid>spock-core</artifactId>
    <version>0.7-groovy-2.0</version>
    <scope>test</scope>
</dependency>
<dependency>
    <groupid>org.codehaus.groovy</groupId>
    <artifactid>groovy-all</artifactId>
    <version>${groovy.version}</version>
    <scope>test</scope>
</dependency>
Where groovy.version is property defined in pom.xml for more convenient use and easy version change, just like this: 
<properties>
    <gmaven-plugin.version>1.4</gmaven-plugin.version>
    <groovy.version>2.1.5</groovy.version>
</properties>

I've added property for gmaven-plugin version for the same reason ;)

Besides these two dependencies, we can use few additional ones providing extra functionality:
  • cglib - for class mocking
  • objenesis - enables mocking classes without default constructor
To add them to the project put these lines in <dependencies> section of pom.xml:
<dependency>
    <groupid>cglib</groupId>
    <artifactid>cglib-nodep</artifactId>
    <version>3.0</version>
    <scope>test</scope>
</dependency>
<dependency>
    <groupid>org.objenesis</groupId>
    <artifactid>objenesis</artifactId>
    <version>1.3</version>
    <scope>test</scope>
</dependency>

And that's all for dependencies section. Now we will focus on plugins necessary to compile Groovy classes. We need to add gmaven-plugin with gmaven-runtime-2.0 dependency in plugins section:
<plugin>
    <groupid>org.codehaus.gmaven</groupId>
    <artifactid>gmaven-plugin</artifactId>
    <version>${gmaven-plugin.version}</version>
    <configuration>
        <providerselection>2.0</providerSelection>
    </configuration>
    <executions>
        <execution>
            <goals>
                <goal>compile</goal>
                <goal>testCompile</goal>
            </goals>
        </execution>
    </executions>
    <dependencies>
        <dependency>
            <groupid>org.codehaus.gmaven.runtime</groupId>
            <artifactid>gmaven-runtime-2.0</artifactId>
            <version>${gmaven-plugin.version}</version>
            <exclusions>
                <exclusion>
                    <groupid>org.codehaus.groovy</groupId>
                    <artifactid>groovy-all</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
        <dependency>
            <groupid>org.codehaus.groovy</groupId>
            <artifactid>groovy-all</artifactId>
            <version>${groovy.version}</version>
        </dependency>
    </dependencies>
</plugin>

With these configuration we can use spock and write our first specifications. But there is one issue: default settings for maven-surefire plugin demand that test classes must end with "..Test" postfix, which is ok when we want to use such naming scheme for our spock tests. But if we want to name them like CommentSpec.groovy or whatever with "..Spec" ending (what in my opinion is much more readable) we need to make little change in surefire plugin configuration:
<plugin>
    <groupid>org.apache.maven.plugins</groupId>
    <artifactid>maven-surefire-plugin</artifactId>
    <version>2.15</version>
    <configuration>
        <includes>
            <include>**/*Test.java</include>
            <include>**/*Spec.java</include>
        </includes>
    </configuration>
</plugin>

As you can see there is a little trick ;) We add include directive for standard Java JUnit test ending with "..Test" postfix, but there is also an entry for spock test ending with "..Spec". And there is a trick: we must write "**/*Spec.java", not "**/*Spec.groovy", otherwise Maven will not run spock tests (which is strange and I've spent some time to figure out why Maven can't run my specs).

Little update: instead of "*.java" postfix for both types of tests we can write "*.class" what is in my opinion more readable and clean:
<include>**/*Test.class</include>
<include>**/*Spec.class</include>
(thanks to Tomek Pęksa for pointing this out!)

With such configuration, we can write either traditional JUnit test and put them in src/test/java directory or groovy spock specifications and place them in src/test/groovy. And both will work together just fine :) In one of my next posts I'll write something about using spock and its mocking abilities in practice, so stay in tune.

DDevelopment & Design

Grails with Spock unit test + IntelliJ IDEA = No thread-bound request found

During my work with Grails project using Spock test in IntelliJ IDEA I've encountered this error:

java.lang.IllegalStateException: No thread-bound request found: Are you referring to request attributes outside of an actual web request, or processing a request outside of the originally receiving thread? If you are actually operating within a web request and still receive this message, your code is probably running outside of DispatcherServlet/DispatcherPortlet: In this case, use RequestContextListener or RequestContextFilter to expose the current request.
 at org.springframework.web.context.request.RequestContextHolder.currentRequestAttributes(RequestContextHolder.java:131)
 at org.codehaus.groovy.grails.plugins.web.api.CommonWebApi.currentRequestAttributes(CommonWebApi.java:205)
 at org.codehaus.groovy.grails.plugins.web.api.CommonWebApi.getParams(CommonWebApi.java:65)
... // and few more lines of stacktrace ;)

It occurred when I tried to debug one of test from IDEA level. What is interesting, this error does not happen when I'm running all test using grails test-app for instance.

So what was the issue? With little of reading and tip from Tomek Kalkosiński (http://refaktor.blogspot.com/) it turned out that our test was missing @TestFor annotation and adding it solved all problems.

This annotation, according to Grails docs (link), indicates Spock what class is being tested and implicitly creates field with given type in test class. It is somehow strange as problematic test had explicitly and "manually" created field with proper controller type. Maybe there is a problem with mocking servlet requests?