Weaving production classes with AspectJ aspects in Maven for tests execution only

Question

I have a project with Maven build and need to add some basic performance tracing to methods. I decided to use AspectJ for this. Main requirement is to weave tracing aspect into production classes but only for unit tests execution phase .

I was able to configure weaving in Maven however after execution of tests same production classes with aspect applied go to packaged war.

The case looks like pretty common nevertheless I wasn't able to find solution for it in web.

Answer 1

You can put your aspects in the test directory and set the weaveMainSourceFolder flag to true in the test-compile configuration

<plugin>
    <groupId>org.codehaus.mojo</groupId>
    <artifactId>aspectj-maven-plugin</artifactId>
    <version>1.4</version>
    <configuration>
        <showWeaveInfo>true</showWeaveInfo>
        <source>1.7</source>
        <target>1.7</target>
    </configuration>
        <executions>
            <execution>
                <id>test-compile</id>
                <configuration>
                    <weaveMainSourceFolder>true</weaveMainSourceFolder>
                </configuration>
                <goals>
                    <goal>test-compile</goal>
                </goals>
            </execution>
        </executions>
    <dependencies>
        <dependency>
            <groupId>org.aspectj</groupId>
            <artifactId>aspectjrt</artifactId>
            <version>${aspectj.version}</version>
        </dependency>
        <dependency>
            <groupId>org.aspectj</groupId>
            <artifactId>aspectjtools</artifactId>
            <version>${aspectj.version}</version>
        </dependency>
    </dependencies>
</plugin>

See http://mojo.codehaus.org/aspectj-maven-plugin/test-compile-mojo.html

Answer 2

I solved this with load-time weaving. That way the weaving happens when your unit-tests are run (via a command line argument when running unit-tests), but your aspects are not woven into the published artifacts.

For example, I wanted to fake out the system clock in my unit-tests, but obviously not mess with it in the live code. Here's my aspect class:

@Aspect
public class TweakSystemAspects {
    private static long timeOffsetMillis = 0;

    public static void advanceTime(int amount, TimeUnit unit) {
        timeOffsetMillis += unit.toMillis(amount);
    }

    @Around("call (long System.currentTimeMillis())")
    public long aroundSystemTime(ProceedingJoinPoint joinPoint) throws Throwable {
        return ((Long) joinPoint.proceed()) + timeOffsetMillis;
    }
}

Obviously, this is used in unit-tests by calling the TweakSystemAspects.advanceTime() mehtod to fake the passage of time in the system. To accomplish the load time weaving, I just had to make an aop.xml file that defined my aspects (and that weaving should happen in all classes):

<aspectj>
    <aspects>
        <aspect name="com.mypackage.TweakSystemAspects"/>
    </aspects>
    <weaver options="-nowarn -Xlint:ignore"/>
    <!-- During testing this was useful, but I didn't want all that output normally. -->
    <!--<weaver options="-verbose -showWeaveInfo"/>-->
</aspectj>

Finally, I made changes in my pom file to declare the AspectJ runtime dependency and tell surefire to do run-time weaving.

<project ...>
    ...
    <properties>
        ...
        <version.aspectj>1.8.10</version.aspectj>
    <properties>

    <dependencies>
        ...
        <dependency>
            <groupId>org.aspectj</groupId>
            <artifactId>aspectjrt</artifactId>
            <version>${version.aspectj}</version>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            ...
            <plugin>
                <artifactId>maven-surefire-plugin</artifactId>
                <configuration>
                    <!-- For Load Time Weaving of our AspectJ helper code -->
                    <argLine>-javaagent:${settings.localRepository}/org/aspectj/aspectjweaver/${version.aspectj}/aspectjweaver-${version.aspectj}.jar</argLine>
                    ...
                </configuration>
            </plugin>
        </plugins>
    </build>
    ...
</project>

Answer 3

I would do that in a dedicated module, use the Maven Dependency Plugin to unpack the artifact "under test" during the generate-test-sources phase, then weave the classes and finally run the tests.

---

Let me try to illustrate what I mean. Let's imagine the following project structure:

.
|-- pom.xml
`-- some-module    // this is the module that we want to weave 
    |-- pom.xml    // but only for testing purpose
    `-- ...

So my suggestion is to do something like this:

.
|-- pom.xml
|-- some-module      
|   |-- pom.xml      
|   `-- ...
`-- test-module    // we're going to weave the classes here because we don't want
    |-- pom.xml    // the tracing aspect to be packaged in the "production" jar
    `-- ...

The idea is to have an additional "test-module" where we would unpack the artifact that we want to test so that we can weave its classes without affecting the "real" production jar.

To do so, declare a dependency on the module under test and use dependency:unpack to unpack the classes into target/classes before invoking the AspectJ plugin to weave the "main" classes.

Answer 4

Based on the sample provided in AspectJ compiler Maven Plugin - Usage something like the following should work:

<project>
    ...
    <build>
        <plugins>
            ...
            <plugin>
                <groupId>org.codehaus.mojo</groupId>
                <artifactId>aspectj-maven-plugin</artifactId>
                <executions>
                    <execution>
                        <goals>
                            <goal>test-compile</goal>
                        </goals>
                    </execution>
               </executions>
           </plugin>
           ...
       </plugins>
   <build>
   ...
</project>