maven | edwin's journey

Setting Up Custom Maven Repository with a Relative Folder

Leave a Comment / Java, Programming / By edwin

There are times where we want to build our application while pointing our library to a specific custom folder, which is having a relative folder location to current project Java folder.

For example, i have a Java project and a Libs folder with structure like below

libs/
+--- org
|   +--- postgresql
|   |   +--- postgresql
|   |   |   +--- random.version
|   |   |   |   +--- postgresql-random.version.jar

java_project/
+--- pom.xml
+--- src
|   +--- main
|   |   +--- java

We can build our java_project by refering to libs folder by using this configuration on our pom.xml

    <repositories>
        <repository>
            <id>local-repo</id>
            <name>Local Repository</name>
            <url>file://${project.basedir}/../libs</url>
        </repository>
    </repositories>

And refer it

	<dependency>
		<groupId>org.postgresql</groupId>
		<artifactId>postgresql</artifactId>
		<version>random.version</version>
	</dependency>

Running maven build command will display the complete build log where library is coming from our relative folder location,

$ mvn clean package

.......

Downloading from local-repo: file:///source/java_project/../libs/org/postgresql/postgresql/random.version/postgresql-random.version.jar
[WARNING] Could not validate integrity of download from file:///source/java_project/../libs/org/postgresql/postgresql/random.version/postgresql-random.version.jar: Checksum validation failed, no checksums available
[WARNING] Checksum validation failed, no checksums available from local-repo for file:///source/java_project/../libs/org/postgresql/postgresql/random.version/postgresql-random.version.jar
Downloaded from local-repo: file:///source/java_project/../libs/org/postgresql/postgresql/random.version/postgresql-random.version.jar (1.0 MB at 7.0 MB/s)

Using Settings.xml to handle Multiple Mirrors in Maven

Leave a Comment / Java, Programming / By edwin

The goal of having an internal artifactory is to host library for maven, so everytime we do java build, we dont need to pull the whole libraries from internet. Usally we have something like Nexus or JFrog for this.

But the thing is, sometimes we already have a working application that is running well when pulling libraries from online before, and now we need to change it into pointing into our artifact repository without have to change the maven’s pom.xml configuration.

for example, we have some pom.xml file which is pointing to a specific online repository like the sample below,

<?xml version="1.0" encoding="UTF-8"?>
<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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>2.7.4</version>
		<relativePath /> 
	</parent>
	<groupId>com.something</groupId>
	<artifactId>some-java-app</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<name>some-java-app</name>
	<description>some java app</description>
	<properties>
		<java.version>17</java.version>
		<tomcat.version>9.0.68</tomcat.version>
	</properties>
	<repositories>
		<repository>
			<id>splunk-releases</id>
			<name>Splunk Releases</name>
			<url>https://splunk.jfrog.io/splunk/ext-releases-local</url>
		</repository>
		<repository>
			<id>spring-releases</id>
			<name>Spring Releases</name>
			<url>https://repo.spring.io/libs-release</url>
		</repository>
	</repositories>
	...
</project>

We can see that application is connecting to multiple maven repositories, such as Splunk JFrog and Spring Repository, other than the default Maven Central.

For this approach, we can create a custom settings.xml and implement a multiple mirror approach for handling to this problem. The result is looks like below xml,

<?xml version="1.0" encoding="UTF-8"?>
<settings xmlns="http://maven.apache.org/SETTINGS/1.0.0"
          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
          xsi:schemaLocation="http://maven.apache.org/SETTINGS/1.0.0 http://maven.apache.org/xsd/settings-1.0.0.xsd">
    <servers>
        <server>
            <id>default</id>
            <username>username</username>
            <password>password</password>
        </server>
        <server>
            <id>splunk-releases</id>
            <username>username</username>
            <password>password</password>
        </server>
		<server>
            <id>spring-releases</id>
            <username>username</username>
            <password>password</password>
        </server>
    </servers>

    <mirrors>
        <mirror>
            <id>default</id>
            <name>Default Repository</name>
            <url>https://my-artifact-repository/default/maven2/</url>
            <mirrorOf>*, !splunk-releases, !spring-releases</mirrorOf>
        </mirror>
        <mirror>
            <id>splunk-releases</id>
            <name>Splunk Local Repository</name>
            <url>https://my-artifact-repository/splunk/maven2/</url>
            <mirrorOf>splunk-releases</mirrorOf>
        </mirror>
		<mirror>
            <id>spring-releases</id>
            <name>Spring Local Repository</name>
            <url>https://my-artifact-repository/spring/maven2/</url>
            <mirrorOf>spring-releases</mirrorOf>
        </mirror>
    </mirrors>
</settings>

As we can see on above, we have multiple mirror of repositories with each pointing to different local artifact repository endpoints. We can run maven build with having this configuration as parameter.

$ mvn clean package -s settings.xml

[Netbeans] Error NoClassDefFoundError when Building Java Project using Maven

Leave a Comment / Java, Programming / By edwin

I got this error when trying to build my maven project on Netbeans,

java.lang.NoClassDefFoundError: org/apache/commons/lang/StringUtils

Here is my complete stacktrace,

Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/commons/lang/StringUtils
	at org.apache.maven.wagon.providers.file.FileWagon.resolveDestinationPath(FileWagon.java:206)
	at org.apache.maven.wagon.providers.file.FileWagon.resourceExists(FileWagon.java:265)
	at org.sonatype.aether.connector.wagon.WagonRepositoryConnector$GetTask.run(WagonRepositoryConnector.java:577)
	at org.sonatype.aether.util.concurrency.RunnableErrorForwarder$1.run(RunnableErrorForwarder.java:60)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
	at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.ClassNotFoundException: org.apache.commons.lang.StringUtils
	at org.codehaus.plexus.classworlds.strategy.SelfFirstStrategy.loadClass(SelfFirstStrategy.java:50)
	at org.codehaus.plexus.classworlds.realm.ClassRealm.loadClass(ClassRealm.java:244)
	at org.codehaus.plexus.classworlds.realm.ClassRealm.loadClass(ClassRealm.java:230)
	... 7 more

Looks like it happen because my maven doesnt have a StringUtils class, from apache-commons-lang library. Adding commons-lang-2.6.jar to my Netbeans maven folder (E:\Program\NetBeans 8.2\java\maven\lib\ext) solves this issue.

Building A Runnable Maven JavaSE Desktop Application And Including Its Jar Dependencies

Leave a Comment / Java, Programming / By edwin

Usually it’s very easy to create a runnable jar using Netbean’s ant plugin, but on this project im trying to utilize maven. One painfull thing is somehow maven is unable to build create a runnable jar file which included its jar dependencies.

After several minutes googling, i’ve found a very good solution. Here is the content of my pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<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.edw</groupId>
    <artifactId>Edw</artifactId>
    <version>1.0</version>
    <packaging>jar</packaging>
    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.source>1.7</maven.compiler.source>
        <maven.compiler.target>1.7</maven.compiler.target>
    </properties>
    
    <dependencies>
        <dependency>
            <groupId>commons-io</groupId>
            <artifactId>commons-io</artifactId>
            <version>2.4</version>
        </dependency>        
    </dependencies>
    
    <build>
        <plugins>
            <plugin>
                <artifactId>maven-dependency-plugin</artifactId>
                <executions>
                    <execution>
                        <phase>process-sources</phase>
                        <goals>
                            <goal>copy-dependencies</goal>
                        </goals>
                        <configuration>
                            <outputDirectory>${targetdirectory}</outputDirectory>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-jar-plugin</artifactId>
                <configuration>
                    <archive>
                        <manifest>
                            <addClasspath>true</addClasspath>                            
                            <classpathPrefix>lib/</classpathPrefix>                            
                            <mainClass>com.edw.Main</mainClass>
                        </manifest>
                    </archive>
                </configuration>
            </plugin>
            <plugin>
                <artifactId>maven-assembly-plugin</artifactId>
                <version>2.4</version>
                <configuration>
                    <descriptors>
                        <descriptor>src/main/assembly/customAssembly.xml</descriptor>
                    </descriptors>
                </configuration>
                <executions>
                    <execution>
                        <id>make-assembly</id> 
                        <phase>package</phase> 
                        <goals>
                            <goal>single</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>
</project>

And dont forget, adding an xml file, customAssembly.xml which located on src/main/assembly/ folder

<assembly xmlns="http://maven.apache.org/plugins/maven-assembly-plugin/assembly/1.1.2" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
          xsi:schemaLocation="http://maven.apache.org/plugins/maven-assembly-plugin/assembly/1.1.2 http://maven.apache.org/xsd/assembly-1.1.2.xsd">
    <id>bin</id>
    <formats>
        <format>zip</format>
    </formats>
    <fileSets>
        <fileSet>
            <directory>${project.build.directory}</directory>
            <outputDirectory>/</outputDirectory>
            <includes>
                <include>*.jar</include>
            </includes>
        </fileSet>
        <fileSet>
            <directory>${project.build.directory}/dependency</directory>
            <outputDirectory>lib</outputDirectory>
        </fileSet>
    </fileSets>
</assembly>

Just build your application from Netbeans, and you will find a zip file on your Netbeans’ target folder, which consist of a runnable jar file and a lib folder containing your jar dependencies. 😉