Merge pull request #131 from sap-contributions/jvm-version-from-maven

Extract JVM version from Maven MANIFEST.MF entries

build.go

@@ -55,7 +55,11 @@ func (b Build) Build(context libcnb.BuildContext) (libcnb.BuildResult, error) {
 	cl := NewCertificateLoader()
 	cl.Logger = b.Logger.BodyWriter()
 
-	v, _ := cr.Resolve("BP_JVM_VERSION")
+	jvmVersion := JVMVersion{Logger: b.Logger}
+	v, err := jvmVersion.GetJVMVersion(context.Application.Path, cr)
+	if err != nil {
+		return libcnb.BuildResult{}, fmt.Errorf("unable to determine jvm version\n%w", err)
+	}
 
 	jreSkipped := false
 	if t, _ := cr.Resolve("BP_JVM_TYPE"); strings.ToLower(t) == "jdk" {

init_test.go

@@ -41,5 +41,6 @@ func TestUnit(t *testing.T) {
 	suite("Manifest", testManifest)
 	suite("MavenJARListing", testMavenJARListing)
 	suite("Versions", testVersions)
+	suite("JVMVersions", testJVMVersion)
 	suite.Run(t)
 }

jvm_version.go

@@ -0,0 +1,55 @@
+package libjvm
+
+import (
+	"strings"
+
+	"github.com/heroku/color"
+	"github.com/paketo-buildpacks/libpak"
+	"github.com/paketo-buildpacks/libpak/bard"
+)
+
+type JVMVersion struct {
+	Logger bard.Logger
+}
+
+func (jvmVersion JVMVersion) GetJVMVersion(appPath string, cr libpak.ConfigurationResolver) (string, error) {
+	version, explicit := cr.Resolve("BP_JVM_VERSION")
+
+	if !explicit {
+		manifest, err := NewManifest(appPath)
+		if err != nil {
+			return version, err
+		}
+
+		javaVersion := ""
+
+		buildJdkSpecVersion, ok := manifest.Get("Build-Jdk-Spec")
+		if ok {
+			javaVersion = buildJdkSpecVersion
+		}
+
+		buildJdkVersion, ok := manifest.Get("Build-Jdk")
+		if ok {
+			javaVersion = buildJdkVersion
+		}
+
+		if len(javaVersion) > 0 {
+			javaVersionFromMaven := extractMajorVersion(javaVersion)
+			f := color.New(color.Faint)
+			jvmVersion.Logger.Body(f.Sprintf("Using Java version %s extracted from METADATA.MF", javaVersionFromMaven))
+			return javaVersionFromMaven, nil
+		}
+	}
+
+	return version, nil
+}
+
+func extractMajorVersion(version string) string {
+	versionParts := strings.Split(version, ".")
+
+	if versionParts[0] == "1" {
+		return versionParts[1]
+	}
+
+	return versionParts[0]
+}

jvm_version_test.go

@@ -0,0 +1,150 @@
+/*
+ * Copyright 2018-2020 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package libjvm_test
+
+import (
+	"github.com/paketo-buildpacks/libpak"
+	"github.com/paketo-buildpacks/libpak/bard"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/buildpacks/libcnb"
+	. "github.com/onsi/gomega"
+	"github.com/sclevine/spec"
+
+	"github.com/paketo-buildpacks/libjvm"
+)
+
+func testJVMVersion(t *testing.T, context spec.G, it spec.S) {
+	var (
+		Expect    = NewWithT(t).Expect
+		appPath   string
+		logger    bard.Logger
+		buildpack libcnb.Buildpack
+	)
+
+	it.Before(func() {
+		buildpack = libcnb.Buildpack{
+			Metadata: map[string]interface{}{
+				"configurations": []map[string]interface{}{
+					{
+						"name":    "BP_JVM_VERSION",
+						"default": "1.1.1",
+					},
+				},
+			},
+		}
+		logger = bard.NewLogger(ioutil.Discard)
+	})
+
+	it("detecting JVM version from default", func() {
+		jvmVersion := libjvm.JVMVersion{Logger: logger}
+
+		cr, err := libpak.NewConfigurationResolver(buildpack, &logger)
+		Expect(err).ToNot(HaveOccurred())
+		version, err := jvmVersion.GetJVMVersion(appPath, cr)
+		Expect(err).ToNot(HaveOccurred())
+		Expect(version).To(Equal("1.1.1"))
+	})
+
+	context("detecting JVM version", func() {
+		it.Before(func() {
+			Expect(os.Setenv("BP_JVM_VERSION", "17")).To(Succeed())
+		})
+
+		it.After(func() {
+			Expect(os.Unsetenv("BP_JVM_VERSION")).To(Succeed())
+		})
+
+		it("from environment variable", func() {
+			jvmVersion := libjvm.JVMVersion{Logger: logger}
+
+			cr, err := libpak.NewConfigurationResolver(buildpack, &logger)
+			Expect(err).ToNot(HaveOccurred())
+			version, err := jvmVersion.GetJVMVersion(appPath, cr)
+			Expect(err).ToNot(HaveOccurred())
+			Expect(version).To(Equal("17"))
+		})
+	})
+
+	context("detecting JVM version", func() {
+		it.Before(func() {
+			temp, err := prepareAppWithEntry("Build-Jdk: 1.8")
+			Expect(err).ToNot(HaveOccurred())
+			appPath = temp
+		})
+
+		it.After(func() {
+			os.RemoveAll(appPath)
+		})
+
+		it("from manifest via Build-Jdk-Spec", func() {
+			jvmVersion := libjvm.JVMVersion{Logger: logger}
+
+			cr, err := libpak.NewConfigurationResolver(buildpack, &logger)
+			Expect(err).ToNot(HaveOccurred())
+			version, err := jvmVersion.GetJVMVersion(appPath, cr)
+			Expect(err).ToNot(HaveOccurred())
+			Expect(version).To(Equal("8"))
+		})
+	})
+
+	context("detecting JVM version", func() {
+		it.Before(func() {
+			Expect(os.Setenv("BP_JVM_VERSION", "17")).To(Succeed())
+			temp, err := prepareAppWithEntry("Build-Jdk: 1.8")
+			Expect(err).ToNot(HaveOccurred())
+			appPath = temp
+		})
+
+		it.After(func() {
+			Expect(os.Unsetenv("BP_JVM_VERSION")).To(Succeed())
+			os.RemoveAll(appPath)
+		})
+
+		it("prefers environment variable over manifest", func() {
+			jvmVersion := libjvm.JVMVersion{Logger: logger}
+
+			cr, err := libpak.NewConfigurationResolver(buildpack, &logger)
+			Expect(err).ToNot(HaveOccurred())
+			version, err := jvmVersion.GetJVMVersion(appPath, cr)
+			Expect(err).ToNot(HaveOccurred())
+			Expect(version).To(Equal("17"))
+		})
+	})
+
+}
+
+func prepareAppWithEntry(entry string) (string, error) {
+	temp, err := ioutil.TempDir("", "jre-app")
+	if err != nil {
+		return "", err
+	}
+	err = os.Mkdir(filepath.Join(temp, "META-INF"), 0744)
+	if err != nil {
+		return "", err
+	}
+	manifest := filepath.Join(temp, "META-INF", "MANIFEST.MF")
+	manifestContent := []byte(entry)
+	err = ioutil.WriteFile(manifest, manifestContent, 0644)
+	if err != nil {
+		return "", err
+	}
+	return temp, nil
+}