Gradle jlink plugin fails during createMergedModule with "the service implementation does not have a default constructor"

Question

I'm using Gradle (4.10.3, but I've tried most versions up through 5.4.1) with JDK 12.0.1 and the org.beryx.jlink plugin (2.10.4), but am running into this error every time I attempt to create the jlink image:

-> Task :createMergedModule

Cannot derive uses clause from service loader invocation in: com/fasterxml/jackson/databind/ObjectMapper$2.run().

Cannot derive uses clause from service loader invocation in: com/fasterxml/jackson/databind/ObjectMapper.secureGetServiceLoader().

Cannot derive uses clause from service loader invocation in: org/apache/commons/compress/utils/ServiceLoaderIterator.().

C:\Users\MyName\IdeaProjects\myapp\build\jlinkbase\tmpjars\myapp.merged.module\module-info.java:393: error: the service implementation does not have a default constructor: XBeansXPath provides org.apache.xmlbeans.impl.store.PathDelegate.SelectPathInterface with org.apache.xmlbeans.impl.xpath.saxon.XBeansXPath;

C:\Users\MyName\IdeaProjects\myapp\build\jlinkbase\tmpjars\myapp.merged.module\module-info.java:394: error: the service implementation does not have a default constructor: XBeansXQuery provides org.apache.xmlbeans.impl.store.QueryDelegate.QueryInterface with org.apache.xmlbeans.impl.xquery.saxon.XBeansXQuery; 2 errors

-> Task :createMergedModule FAILED

When I click through to the lines throwing the errors in the merged module-info.java, it points to these two:

provides org.apache.xmlbeans.impl.store.PathDelegate.SelectPathInterface with org.apache.xmlbeans.impl.xpath.saxon.XBeansXPath;
provides org.apache.xmlbeans.impl.store.QueryDelegate.QueryInterface with org.apache.xmlbeans.impl.xquery.saxon.XBeansXQuery;

My build.gradle file looks like this:

plugins {
    id 'application'
    id 'idea'
    id 'java'
    id 'org.openjfx.javafxplugin' version '0.0.7'
    id 'org.beryx.jlink' version '2.10.4'
}

repositories {
    mavenCentral()
}

dependencies {
    compile 'org.apache.commons:commons-csv:1.6'
    compile 'org.apache.poi:poi-ooxml:4.1.0'
    compile 'com.fasterxml.jackson.core:jackson-core:2.9.9'
    compile 'com.fasterxml.jackson.core:jackson-annotations:2.9.9'
    compile 'com.fasterxml.jackson.core:jackson-databind:2.9.9'
    testCompile 'org.junit.jupiter:junit-jupiter-api:5.5.0-M1'
    testRuntime 'org.junit.jupiter:junit-jupiter-engine:5.5.0-M1'
}

// ### Application plugin settings
application {
    mainClassName = "$moduleName/path.to.myapp"
}

// ### Idea plugin settings
idea {
    module {
        outputDir = file("out/production/classes")
    }
}

// ### Java plugin settings
sourceCompatibility = JavaVersion.VERSION_11

compileJava {
    options.compilerArgs << "-Xlint:unchecked" << "-Xlint:deprecation"
}

test {
    useJUnitPlatform()
    testLogging {
        events 'PASSED', 'FAILED', 'SKIPPED'
    }
}

// ### JavaFX plugin settings
javafx {
    version = "12.0.1"
    modules = ['javafx.controls', 'javafx.fxml']
}

// ### jlink plugin settings
jlink {
    options = ['--strip-debug', '--compress', '2', '--no-header-files', '--no-man-pages']
    launcher {
        name = 'myapp'
    }
}

Any ideas on how I can address this?

Answer 1

The following possible solution is based just on your build file, without knowing about your module-info or the project's code, so it might not work.

It is also based on this issue at the jlink plugin's repository.

First, let me explain how this plugin works: since the (JDK) jlink tool doesn't allow non-modular dependencies, the plugin will try to collect all of them and create on the fly a module, that can be added to the module-path. This module is named $yourModuleName.mergedModule.

Now I'm adding your dependencies to a simple JavaFX project. When I run ./gradlew jlink I get the same errors you have posted. If you check the errors:

myapp\build\jlinkbase\tmpjars\myapp.merged.module\module-info.java:394: error

This shows that the created module is named myapp.merged.module, and that it has a module-info descriptor. If you open it you will see all the exports (the module will export every package of the dependencies by default), the requires and the provides:

open module myapp.merged.module {
    exports com.fasterxml.jackson.annotation;
    exports com.fasterxml.jackson.core;
    exports com.fasterxml.jackson.core.async;
    ...
    exports schemaorg_apache_xmlbeans.system.sXMLTOOLS;
    requires java.xml.crypto;
    requires java.logging;
    requires java.sql;
    requires java.xml;
    requires java.desktop;
    requires java.security.jgss;
    requires jdk.javadoc;
    uses java.nio.file.spi.FileSystemProvider;
    provides com.fasterxml.jackson.core.JsonFactory with com.fasterxml.jackson.core.JsonFactory;
    provides com.fasterxml.jackson.core.ObjectCodec with com.fasterxml.jackson.databind.ObjectMapper;
    provides org.apache.xmlbeans.impl.store.QueryDelegate.QueryInterface with org.apache.xmlbeans.impl.xquery.saxon.XBeansXQuery;
    provides org.apache.xmlbeans.impl.store.PathDelegate.SelectPathInterface with org.apache.xmlbeans.impl.xpath.saxon.XBeansXPath;
}

So now the question is: should you add some more requirements to your own module? The answer is explained here: that will increase unnecessary your project's size. A better way is to use the mergedModule script block:

The mergedModule block allows you to configure the module descriptor of the merged module

And:

the module descriptor is created using the algorithm implemented by the suggestMergedModuleInfo task.

If you run ./gradlew suggestMergedModuleInfo you will basically get the same contents for the merged module descriptor as above.

A possible solution is to start just adding some requires to the merged module descriptor, and try again.

I started with:

jlink {

    mergedModule {
        requires "java.xml"
    }

    options = ['--strip-debug', '--compress', '2', '--no-header-files', '--no-man-pages']
    launcher {
        name = 'myapp'
    }
}

and I could run ./gradlew jlink successfully.

If you check the merged module descriptor now, it will look like:

open module myapp.merged.module {
    requires java.xml;

    exports com.fasterxml.jackson.annotation;
    exports com.fasterxml.jackson.core;
    exports com.fasterxml.jackson.core.async;
    ...
    exports schemaorg_apache_xmlbeans.system.sXMLTOOLS;
}

containing only the explicit requires, all the exports, but without provides, so the errors will be gone.

Since I don't have your code, I can't say if this will work for you, but it did for me with the same dependencies.