[go-migration] Prevent compatibility issues with existing apps due to JRE relocation

src/java/jres/graalvm.go

@@ -215,5 +215,5 @@ func (g *GraalVMJRE) findJavaHome() (string, error) {
 // writeProfileDScript creates a profile.d script that exports JAVA_HOME, JRE_HOME, and PATH at runtime
 // Delegates to the shared helper function in jre.go
 func (g *GraalVMJRE) writeProfileDScript() error {
-	return WriteJavaHomeProfileD(g.ctx, g.jreDir, g.javaHome)
+	return WriteJavaHomeProfileD(g.ctx, g.jreDir, g.javaHome, g.Name())
 }

src/java/jres/ibm.go

@@ -219,5 +219,5 @@ func (i *IBMJRE) findJavaHome() (string, error) {
 
 // writeProfileDScript creates the profile.d script for setting JAVA_HOME, JRE_HOME, and PATH at runtime
 func (i *IBMJRE) writeProfileDScript() error {
-	return WriteJavaHomeProfileD(i.ctx, i.jreDir, i.javaHome)
+	return WriteJavaHomeProfileD(i.ctx, i.jreDir, i.javaHome, i.Name())
 }

src/java/jres/jre.go

@@ -374,9 +374,10 @@ func WriteJavaOptsWithPriority(ctx *common.Context, priority int, name string, o
 //  1. Exports JAVA_HOME using $DEPS_DIR runtime variable
 //  2. Exports JRE_HOME (same as JAVA_HOME)
 //  3. Prepends $JAVA_HOME/bin to PATH
+//  4. Create symlink with old ruby based jre path to JAVA_HOME. See https://github.com/cloudfoundry/java-buildpack/issues/1151
 //
 // It also sets these environment variables during staging for use by frameworks.
-func WriteJavaHomeProfileD(ctx *common.Context, jreDir, javaHome string) error {
+func WriteJavaHomeProfileD(ctx *common.Context, jreDir, javaHome, jreName string) error {
 	// Compute relative path from jreDir to javaHome
 	relPath, err := filepath.Rel(jreDir, javaHome)
 	if err != nil {
@@ -396,12 +397,38 @@ func WriteJavaHomeProfileD(ctx *common.Context, jreDir, javaHome string) error {
 		javaHomePath = fmt.Sprintf("$DEPS_DIR/%s/jre/%s", depsIdx, relPath)
 	}
 
+	var jreFolder string
+	switch jreName {
+	case "OpenJDK":
+		jreFolder = "open_jdk_jre"
+	case "SapMachine":
+		jreFolder = "sap_machine_jre"
+	case "Oracle JRE":
+		jreFolder = "oracle_jre"
+	case "Zing JRE":
+		jreFolder = "zing_jre"
+	case "Zulu":
+		jreFolder = "zulu_jre"
+	case "GraalVM":
+		jreFolder = "graal_vm_jre"
+	case "IBM JRE":
+		jreFolder = "ibm_jre"
+	default:
+		jreFolder = "open_jdk_jre"
+	}
+
 	// Create the profile.d script content with JAVA_HOME, JRE_HOME, and PATH
 	// Following the pattern from reference buildpacks (Ruby, Python, Go)
+	// Symlink to JAVA_HOME is added following the old ruby based buidpack jre path due to possible compatibility issues
+	// because ruby based bp apps relied on hardcoded paths to jre home. Thus providing the same path giving them possibility
+	// to migrate without breaking them when migrating to the go-based version.
+	// For more info check https://github.com/cloudfoundry/java-buildpack/issues/1151
 	envContent := fmt.Sprintf(`export JAVA_HOME=%s
 export JRE_HOME=%s
 export PATH=$JAVA_HOME/bin:$PATH
-`, javaHomePath, javaHomePath)
+mkdir -p /home/vcap/app/.java-buildpack
+ln -sf $JAVA_HOME /home/vcap/app/.java-buildpack/%s
+`, javaHomePath, javaHomePath, jreFolder)
 
 	// Write the profile.d script using libbuildpack API
 	if err := ctx.Stager.WriteProfileD("java.sh", envContent); err != nil {

src/java/jres/openjdk.go

@@ -250,5 +250,5 @@ func (o *OpenJDKJRE) findJavaHome() (string, error) {
 // writeProfileDScript creates a profile.d script that exports JAVA_HOME, JRE_HOME, and PATH at runtime
 // Delegates to the shared helper function in jre.go
 func (o *OpenJDKJRE) writeProfileDScript() error {
-	return WriteJavaHomeProfileD(o.ctx, o.jreDir, o.javaHome)
+	return WriteJavaHomeProfileD(o.ctx, o.jreDir, o.javaHome, o.Name())
 }

src/java/jres/oracle.go

@@ -208,5 +208,5 @@ func (o *OracleJRE) findJavaHome() (string, error) {
 
 // writeProfileDScript creates the profile.d script for setting JAVA_HOME, JRE_HOME, and PATH at runtime
 func (o *OracleJRE) writeProfileDScript() error {
-	return WriteJavaHomeProfileD(o.ctx, o.jreDir, o.javaHome)
+	return WriteJavaHomeProfileD(o.ctx, o.jreDir, o.javaHome, o.Name())
 }

src/java/jres/sapmachine.go

@@ -215,5 +215,5 @@ func (s *SapMachineJRE) findJavaHome() (string, error) {
 // writeProfileDScript creates a profile.d script that exports JAVA_HOME, JRE_HOME, and PATH at runtime
 // Delegates to the shared helper function in jre.go
 func (s *SapMachineJRE) writeProfileDScript() error {
-	return WriteJavaHomeProfileD(s.ctx, s.jreDir, s.javaHome)
+	return WriteJavaHomeProfileD(s.ctx, s.jreDir, s.javaHome, s.Name())
 }

src/java/jres/zulu.go

@@ -215,5 +215,5 @@ func (z *ZuluJRE) findJavaHome() (string, error) {
 // writeProfileDScript creates a profile.d script that exports JAVA_HOME, JRE_HOME, and PATH at runtime
 // Delegates to the shared helper function in jre.go
 func (z *ZuluJRE) writeProfileDScript() error {
-	return WriteJavaHomeProfileD(z.ctx, z.jreDir, z.javaHome)
+	return WriteJavaHomeProfileD(z.ctx, z.jreDir, z.javaHome, z.Name())
 }