AspectJ: How to weave an aspect library into a Java project
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 executed a method with specific annotation". All is ok when I use everything in one module, but problem appers when i separate library and project with classes which advice must be applied. I create simple schema.
Library B - my library (aspects and annotations)
Project A - project with buisness methods which adivce must be applied
Is any posibility to do this?
Solution
According to the AspectJ Maven documentation, chapter "using aspect libraries", you need to
- add the aspect library as a regular
<dependency>, - also add the same dependency (without
<version>because it is already assigned in step 1) in the plugin<configuration><aspectLibraries>section as an<aspectLibrary>.
Here is a concrete example:
Aspect library POM, marker annotation and sample aspect:
<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>de.scrum-master.stackoverflow</groupId>
<artifactId>aspectj-lib</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>AspectJ Library</name>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<java.source-target.version>1.8</java.source-target.version>
<aspectj.version>1.8.7</aspectj.version>
</properties>
<build>
<pluginManagement>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.3</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>1.7</version>
<configuration>
<!--<showWeaveInfo>true</showWeaveInfo> -->
<source>${java.source-target.version}</source>
<target>${java.source-target.version}</target>
<Xlint>ignore</Xlint>
<complianceLevel>${java.source-target.version}</complianceLevel>
<encoding>${project.build.sourceEncoding}</encoding>
<!--<verbose>true</verbose> -->
<!--<warn>constructorName,packageDefaultMethod,deprecation,maskedCatchBlocks,unusedLocals,unusedArguments,unusedImport</warn> -->
</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>${aspectj.version}</version>
</dependency>
</dependencies>
</plugin>
</plugins>
</pluginManagement>
<plugins>
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>aspectj-maven-plugin</artifactId>
</plugin>
<!--
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
</plugin>
-->
</plugins>
</build>
<dependencyManagement>
<dependencies>
<dependency>
<groupId>org.aspectj</groupId>
<artifactId>aspectjrt</artifactId>
<version>${aspectj.version}</version>
<scope>runtime</scope>
</dependency>
</dependencies>
</dependencyManagement>
<dependencies>
<dependency>
<groupId>org.aspectj</groupId>
<artifactId>aspectjrt</artifactId>
</dependency>
</dependencies>
<organization>
<name>Scrum-Master.de - Agile Project Management</name>
<url>http://scrum-master.de</url>
</organization>
</project>
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 viajava -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.
<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>de.scrum-master.stackoverflow</groupId>
<artifactId>java-app</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>Java Application</name>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<java.source-target.version>1.8</java.source-target.version>
<aspectj.version>1.8.7</aspectj.version>
<main-class>de.scrum_master.app.Application</main-class>
</properties>
<build>
<pluginManagement>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.3</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>1.7</version>
<configuration>
<!--<showWeaveInfo>true</showWeaveInfo> -->
<source>${java.source-target.version}</source>
<target>${java.source-target.version}</target>
<Xlint>ignore</Xlint>
<complianceLevel>${java.source-target.version}</complianceLevel>
<encoding>${project.build.sourceEncoding}</encoding>
<!--<verbose>true</verbose> -->
<!--<warn>constructorName,packageDefaultMethod,deprecation,maskedCatchBlocks,unusedLocals,unusedArguments,unusedImport</warn> -->
<aspectLibraries>
<aspectLibrary>
<groupId>de.scrum-master.stackoverflow</groupId>
<artifactId>aspectj-lib</artifactId>
</aspectLibrary>
</aspectLibraries>
</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>${aspectj.version}</version>
</dependency>
</dependencies>
</plugin>
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>exec-maven-plugin</artifactId>
<version>1.4.0</version>
<configuration>
<mainClass>${main-class}</mainClass>
</configuration>
</plugin>
<plugin>
<groupId>org.dstovall</groupId>
<artifactId>onejar-maven-plugin</artifactId>
<version>1.4.4</version>
<executions>
<execution>
<goals>
<goal>one-jar</goal>
</goals>
</execution>
</executions>
<configuration>
<onejarVersion>0.96</onejarVersion>
<mainClass>${main-class}</mainClass>
<attachToBuild>true</attachToBuild>
</configuration>
</plugin>
</plugins>
</pluginManagement>
<plugins>
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>aspectj-maven-plugin</artifactId>
</plugin>
<!--
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
</plugin>
-->
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>exec-maven-plugin</artifactId>
<configuration>
<mainClass>${main-class}</mainClass>
</configuration>
</plugin>
<plugin>
<groupId>org.dstovall</groupId>
<artifactId>onejar-maven-plugin</artifactId>
<configuration>
<mainClass>${main-class}</mainClass>
</configuration>
</plugin>
</plugins>
</build>
<pluginRepositories>
<pluginRepository>
<id>OneJAR googlecode.com</id>
<url>http://onejar-maven-plugin.googlecode.com/svn/mavenrepo</url>
</pluginRepository>
</pluginRepositories>
<dependencyManagement>
<dependencies>
<dependency>
<groupId>org.aspectj</groupId>
<artifactId>aspectjrt</artifactId>
<version>${aspectj.version}</version>
<scope>runtime</scope>
</dependency>
<dependency>
<groupId>de.scrum-master.stackoverflow</groupId>
<artifactId>aspectj-lib</artifactId>
<version>0.0.1-SNAPSHOT</version>
</dependency>
</dependencies>
</dependencyManagement>
<dependencies>
<dependency>
<groupId>org.aspectj</groupId>
<artifactId>aspectjrt</artifactId>
</dependency>
<dependency>
<groupId>de.scrum-master.stackoverflow</groupId>
<artifactId>aspectj-lib</artifactId>
</dependency>
</dependencies>
<organization>
<name>Scrum-Master.de - Agile Project Management</name>
<url>http://scrum-master.de</url>
</organization>
</project>
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())
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