[JAVA] Output relative path in .classpath file generated by gradle eclipse

Overview

Since I am trying to build an environment of docker + eclipse + eclim + vim at hand, I tried to rewrite the file path in the .classpath file written by gradle eclipse from an absolute path to a relative path.

Preparation

$ mkdir javajava/ && cd javajava/

Create a file for using gradle from docker container.

Dockerfile:

FROM openjdk:8
WORKDIR /usr/local/app
ENV M2_HOME=/apache-maven-3.5.4/
ENV PATH=$PATH:/apache-maven-3.5.4/bin/:/gradle-4.8.1/bin/
RUN cd / && \
    wget http://ftp.jaist.ac.jp/pub/apache/maven/maven-3/3.5.4/binaries/apache-maven-3.5.4-bin.tar.gz && \
    tar xzvf apache-maven-3.5.4-bin.tar.gz && \
    rm apache-maven-3.5.4-bin.tar.gz
RUN cd / && \
    wget https://downloads.gradle.org/distributions/gradle-4.8.1-bin.zip && \
    unzip gradle-4.8.1-bin.zip && \
    rm gradle-4.8.1-bin.zip

docker-compose.yml:


version: "3"
services:
  java8:
    build: .
    volumes:
      - .:/usr/local/app
      - .m2/:/root/.m2/
      - .gradle/:/root/.gradle/

I mount ./.gradle on the host side to /root/.gradle/ on the container side and cache it on the host side as well, so when I refer to this project from another eclimd container , I want the path in .classpath to be a relative path.

So, if you create the above file, you can execute the following for the time being.

$ docker-compose run --rm java8 gradle tasks 

Bad pattern

First, create a suitable build script and write .classpath with gradle eclipse.

build.gradle:

apply plugin: 'eclipse'
apply plugin: 'java-library'

repositories {
    mavenCentral()
}

dependencies {
    compile group: 'log4j', name: 'log4j', version: '1.2.17'
}
$ docker-compose run --rm java8 gradle eclipse
(Abbreviation)
$ cat .classpath 
<?xml version="1.0" encoding="UTF-8"?>
<classpath>
        <classpathentry kind="output" path="bin/default"/>
        <classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/JavaSE-1.8/"/>
        <classpathentry sourcepath="/root/.gradle/caches/modules-2/files-2.1/log4j/log4j/1.2.17/677abe279b68c5e7490d6d50c6951376238d7d3e/log4j-1.2.17-sources.jar" kind="lib" path="/root/.gradle/caches/modules-2/files-2.1/log4j/log4j/1.2.17/5af35056b4d257e4b64b9e8069c0746e8b08629f/log4j-1.2.17.jar">
                <attributes>
                        <attribute name="gradle_used_by_scope" value="main,test"/>
                </attributes>
        </classpathentry>
</classpath>

As mentioned above, the path is /root/.gradle, and it is a setting that can not be used anywhere else.

Export .classpath as a relative path

Here, add the following to build.gradle.

import java.util.regex.Pattern
import org.gradle.plugins.ide.eclipse.model.Library
import org.gradle.plugins.ide.eclipse.model.internal.FileReferenceFactory

eclipse {
    classpath {
        file {
            whenMerged { classpath ->
                classpath.getEntries().each {
                    if (it instanceof Library) {
                        def path = it.getPath()
                        def sourcePath = it.getSourcePath()
                        def pattern = Pattern.compile(gradle.gradleUserHomeDir.absolutePath)
                        it.setPath(path.replaceFirst(pattern, ".gradle"))
                        if(sourcePath) {
                            def newSourcePath = sourcePath.path.replaceFirst(pattern, ".gradle")
                            def fileReference = new FileReferenceFactory().fromPath(newSourcePath)
                            it.setSourcePath(fileReference)
                        }
                    }
                }
            }
        }
    }
}

Try re-running gradle eclipse.

$ docker-compose run --rm java8 gradle eclipse                                                                        (Abbreviation)
$ cat .classpath 
<?xml version="1.0" encoding="UTF-8"?>
<classpath>
        <classpathentry kind="output" path="bin/default"/>
        <classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/JavaSE-1.8/"/>
        <classpathentry sourcepath=".gradle/caches/modules-2/files-2.1/log4j/log4j/1.2.17/677abe279b68c5e7490d6d50c6951376238d7d3e/log4j-1.2.17-sources.jar" kind="lib" path=".gradle/caches/modules-2/files-2.1/log4j/log4j/1.2.17/5af35056b4d257e4b64b9e8069c0746e8b08629f/log4j-1.2.17.jar">
                <attributes>
                        <attribute name="gradle_used_by_scope" value="main,test"/>
                </attributes>
        </classpathentry>
</classpath>

It was root / .gradle, but now it's .gradle, so it feels like it can be used outside the java8 container.

Reference material

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