build.gradle

def jvmRunFlags = '''
-Xmx700m
- ...
'''.split().toList()

def jvmTestFlags = '''
-Dlocally=true
-ea
- ...
'''.split().toList()

...

apply plugin: 'idea'

def IDEA_MODULE_NAME = 'mymodule'
def IDEA_ARTIFACT_NAME = 'myproject'

def IDEA_BUILD_DIR = 'build_ide'
def IDEA_BUILD_APP_DIR = IDEA_BUILD_DIR + '/exploded-app'
def GAE_DATASTORE_DIR = IDEA_BUILD_DIR + '/local_db.bin'

// make sure build dir exists
new File(IDEA_BUILD_DIR).mkdirs()

idea {
    // see 'http://www.gradle.org/docs/current/dsl/org.gradle.plugins.ide.idea.model.IdeaModule.html'
    module {
        name = IDEA_MODULE_NAME

        outputDir = file(IDEA_BUILD_DIR)
        testOutputDir = file(IDEA_BUILD_DIR)
        excludeDirs += file(IDEA_BUILD_APP_DIR)

        downloadSources = true
        downloadJavadoc = false

        iml.withXml { xmlFile ->
            // setup 'Web' and 'App Engine' facets
            def facetManager = xmlFile.asNode().component.find { it.@name == 'FacetManager' } as Node
            if (facetManager) {
                Node webFacet = facetManager.facet.find { it.@type == 'web' }
                if (webFacet)
                    facetManager.remove(webFacet)
            } else {
                facetManager = xmlFile.asNode().appendNode('component', [name: 'FacetManager']);
            }

            def builder = new NodeBuilder()
            def webFacet = builder.facet(type: "web", name: 'Web') {
                configuration {
                    descriptors {
                        deploymentDescriptor(name: 'web.xml', url: 'file://$MODULE_DIR$/web/WEB-INF/web.xml')
                    }
                    webroots {
                        root(url: 'file://$MODULE_DIR$/web', relative: '/')
                    }
                    sourceRoots {
                        root(url: 'file://$MODULE_DIR$/src/main/resources')
                        root(url: 'file://$MODULE_DIR$/src/main/java')
                    }
                }
                facet(type: 'google-app-engine', name: 'Google App Engine') {
                    configuration {
                        'sdk-home-path'(GAE_SDK_DIR)
                    }
                }
            }
            facetManager.append webFacet
        }
    }

    project {
        ipr.withXml { xmlFile ->
            // enable 'Annotation Processors'
            xmlFile.asNode().component.find { it.@name == 'CompilerConfiguration' }['annotationProcessing'][0].replaceNode {
                annotationProcessing {
                    profile(default: true, name: 'Default', useClasspath: 'true', enabled: true)
                }
            }

            // setup Git root
            xmlFile.asNode().component.find { it.@name == 'VcsDirectoryMappings' }.replaceNode {
                component(name: 'VcsDirectoryMappings') {
                    mapping(directory: "",  vcs: "")
                    mapping(directory: "\$PROJECT_DIR\$", vcs: 'Git')
                }
            }

            // setup compiler output directory
            xmlFile.asNode().component.find { it.@name == 'ProjectRootManager' }['output'][0].replaceNode {
                output(url: "file://\$PROJECT_DIR\$/$IDEA_BUILD_DIR/out")
            }

            // setup artifact configuration
            def artifactManager = xmlFile.asNode().component.find { it.@name == 'ArtifactManager' } as Node
            if (artifactManager) {
                Node artifact = artifactManager.artifact.find { it.@type == 'exploded-war' }
                if (artifact)
                    artifactManager.remove(artifact)
            } else {
                artifactManager = xmlFile.asNode().appendNode('component', [name: 'ArtifactManager']);
            }

            def artifact = new NodeBuilder().artifact(type: 'exploded-war', 'build-on-make': "true", name: "$IDEA_ARTIFACT_NAME") {
                'output-path'("\$PROJECT_DIR\$/$IDEA_BUILD_APP_DIR")

                root(id: 'root') {
                    element(id: 'directory', name: 'WEB-INF') {
                        element(id: 'directory', name: 'classes') {
                            element(id: 'module-output', name: IDEA_MODULE_NAME)
                        }
                        element(id: 'directory', name: 'lib') {
                            this.project.configurations.runtime.each {
                                element(id: 'file-copy', path: it)
                            }
                        }
                    }
                    element(id: 'javaee-facet-resources', facet: "$IDEA_MODULE_NAME/web/Web")
                }
            }
            artifactManager.append artifact
        }
    }

    workspace {
        iws.withXml { xmlFile ->
            def runManager = xmlFile.asNode().component.find { it.@name == 'RunManager' }

            // setup JUnit's default run configuration
            def junitDefaults = runManager.configuration.find { it.@default == 'true' && it.@type == 'JUnit' }
            junitDefaults.option.find { it.@name == 'VM_PARAMETERS' }.replaceNode {
                option(name: 'VM_PARAMETERS', value: jvmTestFlags.join(" "))
            }
            junitDefaults.module.replaceNode {
                module(name: IDEA_MODULE_NAME)
            }

            // setup App Engine's default run configuration
            def gaeDefaults = runManager.configuration.find { it.@default == 'true' && it.@type == 'GoogleAppEngineDevServer' }
            if (!gaeDefaults) {
                def builder = new NodeBuilder()
                gaeDefaults = builder.configuration(default: 'true', factoryName: 'Local', type: 'GoogleAppEngineDevServer') {
                    option(name: 'OPEN_IN_BROWSER', value: 'false')
                    option(name: 'SHOW_DIALOG_ON_UPDATE', value: 'false')
                }
                runManager.append gaeDefaults
            }

            def gaeJvmArgs = gaeDefaults.option.find { it.@name == 'COMMON_VM_ARGUMENTS' }
            if (gaeJvmArgs)
                gaeDefaults.remove(gaeJvmArgs)
            def jvmArgs = jvmRunFlags.join(" ") + " -Ddatastore.backing_store=\$PROJECT_DIR\$/$GAE_DATASTORE_DIR"
            gaeDefaults.append new NodeBuilder().option(name: 'COMMON_VM_ARGUMENTS', value: jvmArgs)

            def gaeServerSettings = gaeDefaults.'server-settings'
            if (gaeServerSettings)
                gaeDefaults.remove(gaeServerSettings)
            gaeDefaults.append new NodeBuilder().'server-settings' {
                option(name: "artifact", value: IDEA_ARTIFACT_NAME)
            }
        }
    }
}