Gradleのスクリプトから、Eclipse Maven Project吐くためのタスクをプラグイン化 based on https://gist.github.com/ritalin/5394398

build.gradle

apply plugin: SyncPomPlugin

class SyncPomPlugin implements Plugin<Project> {
    void apply(Project project) {
        project.task('to-pom', type: ToPomTask).dependsOn('eclipse')
    }
}

class ToPomTask extends DefaultTask {
    def ToPomTask() {
        project.eclipse {
            project {
                natures = [
                    'org.eclipse.jdt.core.javanature',
                    'org.eclipse.m2e.core.maven2Nature'
                ]
                
                buildCommand 'org.eclipse.m2e.core.maven2Builder'
            }
            
            classpath {
                containers = [
                    'org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/JavaSE-1.7',
                    'org.eclipse.m2e.MAVEN2_CLASSPATH_CONTAINER'
                ]

                file {
                    whenMerged { classpath ->
                        classpath.configure classpath.entries.grep { entry ->
                            !(entry instanceof org.gradle.plugins.ide.eclipse.model.Library)
                        }
                    }
                }
            }
        }
    }
    
    @TaskAction
    def 'to-pom'() {
        def dir = "${project.projectDir.absolutePath}".replaceAll('[\\\\]', '/')
        
        def parser = new XmlSlurper(false, false)
        def doc = parser.parse(new File("${dir}/pom.xml.default"))
        
        def repos = doc.repositories.repository
            .collect { repo ->
                repo.url.toString()
            }
            .toSet()
        
        def celtralRepo = project.repositories.mavenCentral().getUrl().toString()
        def reposDiff = project.repositories.grep {
            def url = it.getUrl().toString()
            (url != celtralRepo) && (! repos.contains(url))
        }
        
        reposDiff.each { r ->
            def repoUrl = r.getUrl().toString()
            def repoId = r.getUrl().getHost()
            
            doc.repositories.appendNode {
                repository {
                    'id' repoId
                    'name ' repoId
                    'url' repoUrl
                }
            }
        }
        
        def deps = doc.dependencies.dependency
            .collect {
                new Tuple(it.groupId.toString(), it.artifactId.toString(), it.version.toString())
            }
            .toSet()
        
        def depsDiff = project.configurations.compile.dependencies
            .grep {
                ! deps.contains(new Tuple(it.getGroup(), it.getName(), it.getVersion()))
            }
        
        depsDiff.each { d ->
            doc.dependencies.appendNode {
                dependency {
                    'groupId' d.getGroup()
                    'artifactId' d.getName()
                    'version ' d.getVersion()
                }
            }
        }
        
        def output = new File("${dir}/pom.xml");
        def xml = groovy.xml.XmlUtil.serialize(new groovy.xml.StreamingMarkupBuilder().bind {
            mkp.yield doc
        })
        output.write(xml)
    }
}