Add classpath in manifest using Gradle

StackOverflow https://stackoverflow.com/questions/22659463

Question

I would like my Gradle build script to add the complete Classpath to the manifest file contained in JAR file created after the build.

Example:

Manifest-Version: 1.0
Class-Path: MyProject.jar SomeLibrary.jar AnotherLib.jar

My build script already add some information to the manifest this way:

jar {
    manifest {
        attributes("Implementation-Title": project.name,
            "Implementation-Version": version,
            "Main-Class": mainClassName,
    }
}

How do I get the list of dependencies to add to the manifest?

This page of Java tutorials describes more in detail how and why adding classpath to the manifest: Adding Classes to the JAR File's Classpath

Was it helpful?

Solution

Found a solution on Gradle's forum:

jar {
  manifest {
    attributes(
      "Class-Path": configurations.compile.collect { it.getName() }.join(' '))
  }
}

Source: Manifest with Classpath in Jar Task for Subprojects

OTHER TIPS

In the latest versions of gradle, compile and runtime becomes deprecated. Instead, use runtimeClasspath as follows:

'Class-Path': configurations.runtimeClasspath.files.collect { it.getName() }.join(' ')

EDIT:

Note that if you are using Kotlin DSL, you can configure the manifest as follows:

configure<JavaPluginConvention> {
    sourceCompatibility = JavaVersion.VERSION_1_8
    targetCompatibility = JavaVersion.VERSION_1_8
    manifest {
        attributes(
                "Manifest-Version" to "1.0",
                "Main-Class" to "io.fouad.AppLauncher")
    }
}


tasks.withType(Jar::class) {
    manifest {
        attributes["Manifest-Version"] = "1.0"
        attributes["Main-Class"] = "io.fouad.AppLauncher"
    }
}

Place this at the end of the buid.gradle file. Change the com.example.Main to your own Main class.

jar {
    doFirst {
        manifest {
            if (!configurations.compile.isEmpty()) {
                attributes(
                        'Class-Path': configurations.compile.collect{it.toURI().toString()}.join(' '),
                        'Main-Class': 'com.example.Main')
            }
        }
    }
}

The top answers helped me a lot. Here is what worked for me:

jar {
    manifest {
        attributes "Main-Class": "your.package.classWithMain"
        attributes "Class-Path": configurations.compile.collect { it.absolutePath }.join(" ")
    }
}

So, instead of name, I had to use absolutePath. This may or may not work for you. Some suggest using runtime instead of compile. I used compile because, I have a compile section in dependencies in my build.gradle. So, the jar step picks up dependencies from there. The best thing to do is pick up something that you think will work, do a gradle build, then find the JAR file and expand it to find the META-INF/MANIFEST.MF file. You should be able to see all the directories separated by spaces. If not, you should try something different. Autocomplete feature of your IDE should be helpful in seeing what all methods or fields are available under configurations/compile etc. All this can be done easily in IntelliJ.

Oh.. and if you want to see where the library JARs are physically located on your disk, right click on your project->open module settings->Libraries and then click on any library.

Here is another solution for Kotlin DSL (build.gradle.kts).
When running your app, the library files are supposed to be in libs/ subdirectory of the app.

tasks.jar {
    manifest.attributes["Main-Class"] = "com.example.MyMainClass"
    manifest.attributes["Class-Path"] = configurations
        .runtimeClasspath
        .get()
        .joinToString(separator = " ") { file ->
            "libs/${file.name}"
        }
}

I know this is likely trivial for the groovy people here, but in my case, I wanted to change the location of the Class-Path in the manifest file depending on whether I was going to run in the production environment or local environment. I did this by making my build.gradle's jar section look like this:

jar {
  from configurations.runtime
  manifest {
    attributes ('Main-Class': 'com.me.Main',
                'Class-Path': configurations.runtime.files.collect { jarDir+"/$it.name" }.join(' ')
               )
  }
}

In this case, the argument to gradle build is passed like so:

$ gradle build -PjarDir="/opt/silly/path/"

Looks like gradle has evolved. This is another answer that looks similar to others, but there is a key difference: if you use a new keyword implementation in the dependencies, none of the other answers will work and you'll get an empty class path

dependencies {
    // ensure the keyword here matches what 
    // you have in the jar->manifest->attributes
    // that is "implementation"
    implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-core:1.3.3'
    // ...
}

// by default, implementation cannot be referenced, 
// this allows us to use it below
project.configurations.implementation.setCanBeResolved(true)

jar{
    manifest {
        attributes(
                "Main-Class": "app.Program",                
                "Class-Path":  configurations.implementation.collect { it.name }.join(' ')              
        )
    }
    dependsOn ('dependencies')
}

If your project has external library dependencies, you could copy the jars to a folder and add the classpath entries in the manifest.

 def dependsDir = "${buildDir}/libs/dependencies/"
    task copyDependencies(type: Copy) {
    from configurations.compile
    into "${dependsDir}"
   }
task createJar(dependsOn: copyDependencies, type: Jar) {
  
    manifest {
        attributes('Main-Class': 'com.example.gradle.App',
                'Class-Path': configurations.compile.collect { 'dependencies/' + it.getName() }.join(' ')
        )
    }
    with jar
}

More details can be read here

I managed to create a custom Jar file with its own manifest file like so:

task createJar(type : Jar) {
    manifest {
        attributes(
            'Manifest-Version': "1.0",
            'Main-Class': "org.springframework.boot.loader.JarLauncher",
            'Start-Class': "com.my.app.AppApplication",
            'Spring-Boot-Version': "2.2.4.RELEASE",
            'Spring-Boot-Classes': "BOOT-INF/classes/",
            'Spring-Boot-Lib': "BOOT-INF/lib/"
        )
    }
    def originDir = file("${buildDir}/unpacked")
    def destinationFile = "${buildDir}/repackaged/${project.name}-${version}"
    entryCompression ZipEntryCompression.STORED // no compression in case there are files in BOOT-INF/lib
    archiveName destinationFile
    from originDir
    archiveFile
}

I had a similar yet not identical problem. I was publishing my lib jar L into Artifactory, and later fetching it as a dependency of module M, but the transitive dependencies, the ones which L need for compile and runtime, did not arrive with it. It took me sometime to realize that my jar was published into Artifactory with an empty pom file, hence gradle was not able to know which are L's transitive dependencies to be fetched. The missing piece was an instruction, in the L's build.gradle, to publish the pom. As often with gradle, the connection between the name of the instruction, and its meaning, is completely:

apply plugin: 'maven'

uploadArchives {
    repositories {
        mavenDeployer {
            repository(url: "file://localhost/tmp/myRepo/")
        }
    }
}

Source: uploading_to_maven_repositories

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