I have a project that I build FatJar from. Recently I have included additional dependencies from geotools. What I quickly discovered is that due to the geotools architecture I need to merge the META-INF/services, which I do using the mergeServiceFiles() in my shadowJar task. However, even with the mergeServiceFiles I still get an error:
WARNING: Can't load a service for category "Operation". Cause is "ServiceConfigurationError: org.geotools.api.coverage.processing.Operation: Provider org.geotools.coverage.processing.operation.ShadedRelief could not be instantiated".

Both, org.geotools.api.coverage.processing.Operation and the org.geotools.coverage.processing.operation.ShadedRelief are present in my dependencies (gt-api and gt-coverage) and are also included in the services.

Also, after inspecting the generated FatJar I can see that classes org.geotools.api.coverage.processing.Operation and org.geotools.coverage.processing.operation.ShadedRelief are present in the jar and org.geotools.api.coverage.processing.Operation is present in the META-INF/services and it does contain org.geotools.coverage.processing.operation.ShadedRelief.

My Gradle settings is in line with the GeoTools for creating FatJars FAQ instruction – I am using Gradle’s shadowJar plugin with the mergeServiceFiles task which is equivalent of the Maven’s shadow plugin with the ServicesResourceTransformer:

plugins {
    id("com.gradleup.shadow") version "8.3.0"
    java
}

group = "test.it"
version = "0.0.1"

application {
    mainClass.set("test.it.ApplicationKt")
}

repositories {
    maven { url = uri("https://repo.osgeo.org/repository/release/") }
    mavenCentral()
}

dependencies {
    implementation("org.geotools:gt-coverage:31.2")
    implementation("org.geotools:gt-main:31.2")
    implementation("org.geotools:gt-api:31.2")
    implementation("org.geotools:gt-geotiff:31.2")
    implementation("org.geotools:gt-tile-client:31.2")
    implementation("org.geotools.xsd:gt-xsd-kml:31.2")
    implementation("org.geotools:gt-epsg-hsql:31.2")
    implementation("org.osgeo:proj4j:0.1.0")

}

tasks {
    shadowJar {
        mergeServiceFiles()
        isZip64 = true
        archiveFileName.set("${project.name}-${project.version}.jar")
        manifest {
            attributes["Main-Class"] = "test.it.ApplicationKt"
            //fix for the imageio vendor!=null error
            ///questions/7051603/jai-vendorname-null/18495658#18495658
            attributes["Specification-Title"] = "Java Advanced Imaging Image I/O Tools"
            attributes["Specification-Version"] = version
            attributes["Specification-Vendor"] = "Sun Microsystems, Inc."
            attributes["Implementation-Title"] = "com.sun.media.imageio"
            attributes["Implementation-Version"] = version
            attributes["Implementation-Vendor"] = "Sun Microsystems, Inc."
        }
    }
}

I tried (with no luck):

• using all versions of geo-tools from 20.0 to 31.2
• using JAVA 11, 17 and 21 for both, gradle and running the actual JAR
• updating Gradle to the most recent version 8.10

It works fine when run with the -classpath including locations of the gt-api and gt-coverage jars.

UPADATE 12/09/2024

A temporary solution – adding exclude("META-INF/services/org.geotools.api.coverage.processing.*") to the shadowJar task helps. This resolves the issue for that particular missing Class throwing the error.