AspectJ: How to weave an aspect library into a Java project

Question

I build small library (Java and Maven) - using AspectJ. Library must be independent. Library deliver Aspects and Annotations. Function of library is - \"call advice when exe

Answer 1

According to the AspectJ Maven documentation, chapter "using aspect libraries", you need to

• add the aspect library as a regular ,
• also add the same dependency (without because it is already assigned in step 1) in the plugin section as an .

Here is a concrete example:

Aspect library POM, marker annotation and sample aspect:

    4.0.0

    de.scrum-master.stackoverflow
    aspectj-lib
    0.0.1-SNAPSHOT

    AspectJ Library

    
        UTF-8
        1.8
        1.8.7
    

    
        
            
                
                    org.apache.maven.plugins
                    maven-compiler-plugin
                    3.3
                    
                        ${java.source-target.version}
                        ${java.source-target.version}
                        
                        false
                    
                
                
                    org.codehaus.mojo
                    aspectj-maven-plugin
                    1.7
                    
                        
                        ${java.source-target.version}
                        ${java.source-target.version}
                        ignore
                        ${java.source-target.version}
                        ${project.build.sourceEncoding}
                        
                        
                    
                    
                        
                            
                            process-sources
                            
                                compile
                                test-compile
                            
                        
                    
                    
                        
                            org.aspectj
                            aspectjtools
                            ${aspectj.version}
                        
                    
                
            
        
        
            
                org.codehaus.mojo
                aspectj-maven-plugin
            
            
        
    

    
        
            
                org.aspectj
                aspectjrt
                ${aspectj.version}
                runtime
            
        
    

    
        
            org.aspectj
            aspectjrt
        
    

    
        Scrum-Master.de - Agile Project Management
        http://scrum-master.de
    

package de.scrum_master.aspect;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface Marker {}

package de.scrum_master.aspect;

public aspect MyAspect {
    before() : execution(* *(..)) && @annotation(Marker) {
        System.out.println(thisJoinPoint);
    }
}

Now run mvn clean install on the aspect library project so as to install the dependency into your local Maven repo.

Java application POM and sample application:

By the way, in the POM I have also added two optional plugins:

• One-JAR plugin packages your application with all dependencies (e.g. aspect library and AspectJ runtime) into one artifact, here target/java-app-0.0.1-SNAPSHOT.one-jar.jar. You can just run your application via java -jar target/java-app-0.0.1-SNAPSHOT.one-jar.jar.
• Exec Maven plugin is useful if you easily want to test your application from the command line via mvn clean install exec:java.

These two are only for convenience, you do not need them if you dislike them.

    4.0.0

    de.scrum-master.stackoverflow
    java-app
    0.0.1-SNAPSHOT

    Java Application

    
        UTF-8
        1.8
        1.8.7
        de.scrum_master.app.Application
    

    
        
            
                
                    org.apache.maven.plugins
                    maven-compiler-plugin
                    3.3
                    
                        ${java.source-target.version}
                        ${java.source-target.version}
                        
                        false
                    
                
                
                    org.codehaus.mojo
                    aspectj-maven-plugin
                    1.7
                    
                        
                        ${java.source-target.version}
                        ${java.source-target.version}
                        ignore
                        ${java.source-target.version}
                        ${project.build.sourceEncoding}
                        
                        
                        
                            
                                de.scrum-master.stackoverflow
                                aspectj-lib
                            
                        
                    
                    
                        
                            
                            process-sources
                            
                                compile
                                test-compile
                            
                        
                    
                    
                        
                            org.aspectj
                            aspectjtools
                            ${aspectj.version}
                        
                    
                
                
                    org.codehaus.mojo
                    exec-maven-plugin
                    1.4.0
                    
                        ${main-class}
                    
                
                
                    org.dstovall
                    onejar-maven-plugin
                    1.4.4
                    
                        
                            
                                one-jar
                            
                        
                    
                    
                        0.96
                        ${main-class}
                        true
                    
                
            
        
        
            
                org.codehaus.mojo
                aspectj-maven-plugin
            
            
            
                org.codehaus.mojo
                exec-maven-plugin
                
                    ${main-class}
                
            
            
                org.dstovall
                onejar-maven-plugin
                
                    ${main-class}
                
            
        
    

    
        
            OneJAR googlecode.com
            http://onejar-maven-plugin.googlecode.com/svn/mavenrepo
        
    

    
        
            
                org.aspectj
                aspectjrt
                ${aspectj.version}
                runtime
            
            
                de.scrum-master.stackoverflow
                aspectj-lib
                0.0.1-SNAPSHOT
            
        
    

    
        
            org.aspectj
            aspectjrt
        
            
                de.scrum-master.stackoverflow
                aspectj-lib
            
    

    
        Scrum-Master.de - Agile Project Management
        http://scrum-master.de
    

This little driver application demonstrates that you can now annotate methods with @Marker, in this case only foo and zot, but not bar:

package de.scrum_master.app;

import de.scrum_master.aspect.Marker;

public class Application {
    @Marker
    public static void foo() {}

    public static void bar() {}

    @Marker
    public static void zot() {}

    public static void main(String[] args) {
        foo();
        bar();
        zot();
    }
}

Console log:

java -jar target/java-app-0.0.1-SNAPSHOT.one-jar.jar

execution(void de.scrum_master.app.Application.foo())
execution(void de.scrum_master.app.Application.zot())