Issue 1255 server port sb fix

src/java/containers/spring_boot.go

@@ -233,6 +233,16 @@ func (s *SpringBootContainer) Finalize() error {
 		return fmt.Errorf("failed to write JAVA_OPTS: %w", err)
 	}
 
+	// Ensure the app binds to CF's assigned port, overriding any server.port set in
+	// application.yml or other Spring config. Without this, apps with a hardcoded
+	// server.port will either bind to the wrong port (health check fails) or crash
+	// with java.net.BindException: Permission denied for privileged ports (< 1024).
+	// Uses WriteProfileD (not WriteEnvFile) so that $PORT is shell-expanded at runtime.
+	// Mirrors Ruby buildpack: lib/java_buildpack/container/spring_boot.rb release()
+	if err := s.context.Stager.WriteProfileD("spring_boot_server_port.sh", "export SERVER_PORT=$PORT\n"); err != nil {
+		return fmt.Errorf("failed to write SERVER_PORT profile.d script: %w", err)
+	}
+
 	return nil
 }
 

src/java/containers/spring_boot_cli.go

@@ -107,15 +107,13 @@ func (s *SpringBootCLIContainer) Finalize() error {
 	s.context.Log.BeginStep("Finalizing Spring Boot CLI")
 
 	// Set environment variables for Spring Boot CLI
-	envVars := map[string]string{
-		"JAVA_OPTS":   "$JAVA_OPTS",
-		"SERVER_PORT": "$PORT",
+	if err := s.context.Stager.WriteEnvFile("JAVA_OPTS", "$JAVA_OPTS"); err != nil {
+		s.context.Log.Warning("Failed to set JAVA_OPTS: %s", err.Error())
 	}
 
-	for key, value := range envVars {
-		if err := s.context.Stager.WriteEnvFile(key, value); err != nil {
-			s.context.Log.Warning("Failed to set %s: %s", key, err.Error())
-		}
+	// Use WriteProfileD so $PORT is shell-expanded at runtime (WriteEnvFile writes plain text, no expansion).
+	if err := s.context.Stager.WriteProfileD("spring_boot_cli_server_port.sh", "export SERVER_PORT=$PORT\n"); err != nil {
+		return fmt.Errorf("failed to write SERVER_PORT profile.d script: %w", err)
 	}
 
 	return nil

src/java/containers/spring_boot_cli_test.go

@@ -0,0 +1,82 @@
+package containers_test
+
+import (
+	"fmt"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strings"
+
+	"github.com/cloudfoundry/java-buildpack/src/java/common"
+	"github.com/cloudfoundry/java-buildpack/src/java/containers"
+	"github.com/cloudfoundry/libbuildpack"
+	. "github.com/onsi/ginkgo/v2"
+	. "github.com/onsi/gomega"
+)
+
+var _ = Describe("Spring Boot CLI Container", func() {
+	var (
+		ctx       *common.Context
+		container *containers.SpringBootCLIContainer
+		buildDir  string
+		depsDir   string
+		cacheDir  string
+	)
+
+	BeforeEach(func() {
+		var err error
+		buildDir, err = os.MkdirTemp("", "build")
+		Expect(err).NotTo(HaveOccurred())
+
+		depsDir, err = os.MkdirTemp("", "deps")
+		Expect(err).NotTo(HaveOccurred())
+
+		cacheDir, err = os.MkdirTemp("", "cache")
+		Expect(err).NotTo(HaveOccurred())
+
+		err = os.MkdirAll(filepath.Join(depsDir, "0"), 0755)
+		Expect(err).NotTo(HaveOccurred())
+
+		logger := libbuildpack.NewLogger(os.Stdout)
+		manifest := &libbuildpack.Manifest{}
+		installer := &libbuildpack.Installer{}
+		stager := libbuildpack.NewStager([]string{buildDir, cacheDir, depsDir, "0"}, logger, manifest)
+		command := &libbuildpack.Command{}
+
+		ctx = &common.Context{
+			Stager:    stager,
+			Manifest:  manifest,
+			Installer: installer,
+			Log:       logger,
+			Command:   command,
+		}
+
+		container = containers.NewSpringBootCLIContainer(ctx)
+	})
+
+	AfterEach(func() {
+		os.RemoveAll(buildDir)
+		os.RemoveAll(depsDir)
+		os.RemoveAll(cacheDir)
+	})
+
+	Describe("Finalize", func() {
+		It("writes a profile.d script that exports SERVER_PORT=$PORT so the variable is shell-expanded at runtime", func() {
+			err := container.Finalize()
+			Expect(err).NotTo(HaveOccurred())
+
+			profileScript := filepath.Join(depsDir, "0", "profile.d", "spring_boot_cli_server_port.sh")
+			data, err := os.ReadFile(profileScript)
+			Expect(err).NotTo(HaveOccurred())
+			Expect(string(data)).To(Equal("export SERVER_PORT=$PORT\n"))
+
+			// Verify $PORT is actually shell-expanded at runtime (not left as literal "$PORT").
+			// Simulates what CF's launcher does: source the profile.d script with PORT set in env.
+			cmd := exec.Command("bash", "-c", fmt.Sprintf("PORT=8080 . %s && echo $SERVER_PORT", profileScript))
+			out, bashErr := cmd.Output()
+			Expect(bashErr).NotTo(HaveOccurred())
+			Expect(strings.TrimSpace(string(out))).To(Equal("8080"),
+				"SERVER_PORT should be the expanded value of $PORT, not the literal string \"$PORT\"")
+		})
+	})
+})

src/java/containers/spring_boot_test.go

@@ -1,8 +1,11 @@
 package containers_test
 
 import (
+	"fmt"
 	"os"
+	"os/exec"
 	"path/filepath"
+	"strings"
 
 	"github.com/cloudfoundry/java-buildpack/src/java/common"
 	"github.com/cloudfoundry/java-buildpack/src/java/containers"
@@ -169,5 +172,23 @@ var _ = Describe("Spring Boot Container", func() {
 			err := container.Finalize()
 			Expect(err).NotTo(HaveOccurred())
 		})
+
+		It("writes a profile.d script that exports SERVER_PORT=$PORT so the variable is shell-expanded at runtime", func() {
+			err := container.Finalize()
+			Expect(err).NotTo(HaveOccurred())
+
+			profileScript := filepath.Join(depsDir, "0", "profile.d", "spring_boot_server_port.sh")
+			data, err := os.ReadFile(profileScript)
+			Expect(err).NotTo(HaveOccurred())
+			Expect(string(data)).To(Equal("export SERVER_PORT=$PORT\n"))
+
+			// Verify $PORT is actually shell-expanded at runtime (not left as literal "$PORT").
+			// Simulates what CF's launcher does: source the profile.d script with PORT set in env.
+			cmd := exec.Command("bash", "-c", fmt.Sprintf("PORT=8080 . %s && echo $SERVER_PORT", profileScript))
+			out, bashErr := cmd.Output()
+			Expect(bashErr).NotTo(HaveOccurred())
+			Expect(strings.TrimSpace(string(out))).To(Equal("8080"),
+				"SERVER_PORT should be the expanded value of $PORT, not the literal string \"$PORT\"")
+		})
 	})
 })