2

I am trying get the AspectJ weaving working in a simple Maven project, and not sure where it is going wrong : when I run the code using "mvn exec:java", I dont see expected output.

I am sure the code is working, because I tried the same in STS, where it works fine. I just wanted to get the AspectJ working in a Maven project.

Any hints to how to debug this kind of issues will be much appreciated.

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>

<groupId>com.aop</groupId>
<artifactId>aop1</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>

<name>aop1</name>
<url>http://maven.apache.org</url>

<properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
</properties>

<dependencies>
    <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>3.8.1</version>
        <scope>test</scope>
    </dependency>
    <dependency>
        <groupId>org.aspectj</groupId>
        <artifactId>aspectjrt</artifactId>
        <version>1.7.3</version> <!-- specify your version -->
    </dependency>
</dependencies>

<build>
    <pluginManagement>
        <plugins>
            <plugin>
                <groupId>org.codehaus.mojo</groupId>
                <artifactId>aspectj-maven-plugin</artifactId>
                <executions>
                    <execution>
                        <goals>
                            <goal>compile</goal>
                        </goals>
                        <configuration>
                            <source>1.7</source>
                            <target>1.7</target>
                        </configuration>
                    </execution>
                </executions>
                <configuration>
                    <outxml>true</outxml>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.codehaus.mojo</groupId>
                <artifactId>exec-maven-plugin</artifactId>
                <version>1.1</version>
                <configuration>
                    <mainClass>com.aop.aop1.App</mainClass>
                </configuration>
            </plugin>
        </plugins>
    </pluginManagement>
</build>

Aspect file in same folder as code : 

    package com.aop.aop1;


public aspect aspect {

    pointcut secureAccess()
        : execution(* *.foo(..));

    before() : secureAccess() {
        System.out.println("BEHOLD the power of AOP !!!");
    }
}

Java file : 

package com.aop.aop1;
public class App 
{
    public static void main( String[] args )
    {
        System.out.println( "Hello World!" );
        foo();
    }
    public static void foo() {
        System.out.println(" IN FOO.");
    }
}
Ajeet Ganga
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1 Answers1

16

There are several problems with your configuration:

  • The aspect should be named Aspect with a capital "A" instead of aspect which is a reserved keyword.
  • The POM is missing a closing </project> tag.
  • The POM has a <pluginManagement> section, but no separate <plugins> section, i.e. you provide defaults for your plugins, but do not actually declare that you want to use them. So either you use a stand-alone <plugins> section without <pluginManagement> or you redeclare the plugins in an additional <plugins> section.
  • The aspectj-maven-plugin needs a <version>. You forgot to specify one.
  • The aspectj-maven-plugin also needs a <complianceLevel> configuration.
  • You use compile-time weaving, so you do not need the <outxml> setting. It is only needed for load-time weaving.
  • The aspectjrt dependency needs at least version 1.7.4 in order to be compatible with the version used in aspectj-maven-plugin 1.6 by default in order to compile your sources.

In addition to that, I recommend to use newer versions of Maven plugins and dependencies such as JUnit and exec-maven-plugin if you do not have any compelling reasons to use older ones. I also recommend to use the latest AspectJ version 1.8.2 and also specify to use that one internally in aspectj-maven-plugin.

Working pom.xml with minimal changes:

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.aop</groupId>
    <artifactId>aop1</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

    <name>aop1</name>
    <url>http://maven.apache.org</url>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>

    <dependencies>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>3.8.1</version>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.aspectj</groupId>
            <artifactId>aspectjrt</artifactId>
            <version>1.7.4</version>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.codehaus.mojo</groupId>
                <artifactId>aspectj-maven-plugin</artifactId>
                <version>1.6</version>
                <configuration>
                    <complianceLevel>1.7</complianceLevel>
                </configuration>
                <executions>
                    <execution>
                        <goals>
                            <goal>compile</goal>
                        </goals>
                        <configuration>
                            <source>1.7</source>
                            <target>1.7</target>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
            <plugin>
                <groupId>org.codehaus.mojo</groupId>
                <artifactId>exec-maven-plugin</artifactId>
                <version>1.1</version>
                <configuration>
                    <mainClass>com.aop.aop1.App</mainClass>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

Working pom.xml with recommended changes:

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.aop</groupId>
    <artifactId>aop1</artifactId>
    <version>0.0.1-SNAPSHOT</version>

    <name>AOP Sample</name>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <aspectj.version>1.8.2</aspectj.version>
        <java.source-target.version>1.7</java.source-target.version>
    </properties>

    <build>
        <plugins>
            <plugin>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.1</version>
                <configuration>
                    <source>${java.source-target.version}</source>
                    <target>${java.source-target.version}</target>
                    <!-- IMPORTANT -->
                    <useIncrementalCompilation>false</useIncrementalCompilation>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.codehaus.mojo</groupId>
                <artifactId>aspectj-maven-plugin</artifactId>
                <version>1.6</version>
                <configuration>
                    <showWeaveInfo>true</showWeaveInfo>
                    <source>${java.source-target.version}</source>
                    <target>${java.source-target.version}</target>
                    <Xlint>ignore</Xlint>
                    <complianceLevel>${java.source-target.version}</complianceLevel>
                    <encoding>UTF-8</encoding>
                    <verbose>true</verbose>
                </configuration>
                <executions>
                    <execution>
                        <!-- IMPORTANT -->
                        <phase>process-sources</phase>
                        <goals>
                            <goal>compile</goal>
                            <goal>test-compile</goal>
                        </goals>
                    </execution>
                </executions>
                <dependencies>
                    <dependency>
                        <groupId>org.aspectj</groupId>
                        <artifactId>aspectjtools</artifactId>
                        <version>${aspectj.version}</version>
                    </dependency>
                </dependencies>
            </plugin>
            <plugin>
                <groupId>org.codehaus.mojo</groupId>
                <artifactId>exec-maven-plugin</artifactId>
                <version>1.3</version>
                <configuration>
                    <mainClass>com.aop.aop1.App</mainClass>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.dstovall</groupId>
                <artifactId>onejar-maven-plugin</artifactId>
                <version>1.4.4</version>
                <executions>
                    <execution>
                        <configuration>
                            <onejarVersion>0.96</onejarVersion>
                            <mainClass>com.aop.aop1.App</mainClass>
                            <attachToBuild>true</attachToBuild>
                        </configuration>
                        <goals>
                            <goal>one-jar</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>

    <pluginRepositories>
        <pluginRepository>
            <id>OneJAR googlecode.com</id>
            <url>http://onejar-maven-plugin.googlecode.com/svn/mavenrepo</url>
        </pluginRepository>
    </pluginRepositories>

    <dependencies>
        <dependency>
            <groupId>org.aspectj</groupId>
            <artifactId>aspectjrt</artifactId>
            <version>${aspectj.version}</version>
            <!--<scope>runtime</scope>-->
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.11</version>
            <scope>test</scope>
        </dependency>
    </dependencies>
</project>

BTW, the onejar-maven-plugin is just a goodie which I like to use in order to build a stand-alone uber JAR (a.k.a. fat JAR) containing everything you need to run the software, i.e. your classes/aspects plus the AspectJ runtime. You can just run the program with

java -jar aop1-0.0.1-SNAPSHOT.one-jar.jar

The output should be similar to mvn exec:java just without the Maven stuff:

Hello World!
BEHOLD the power of AOP !!!
IN FOO.
kriegaex
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  • Thank you so much. Not having some of the closing brackets was due to SO somehow trimming my paste. I had done a ^A^C^V here. :) Es hat sehr geholfen. Danke Schon. :) – Ajeet Ganga Aug 25 '14 at 07:16
  • Could you comment on the `useIncrementalCompilation` configuration? This was the only piece missing for me, and I do not understand the implications. – C-Otto Sep 04 '15 at 14:10
  • Yes, I can: The Maven Compiler Plugin has actually a bug because it inverts the meaning of "use incremental compilation". Setting it to false activates it, setting it to true deactivates it. Really strange indeed and obviously nobody wants to fix it even though there is a ticket for it. – kriegaex Sep 04 '15 at 14:53
  • This is a fantastic answer. @kriegaex Thanks for taking the time to go through and explaining the details. kudos mate. – Edward J Beckett Jan 28 '16 at 03:17