Merge pull request #330 from tjuchniewicz/feature/dd-java-agent-link

Add dd-java-agent.jar as symlink

README.md

@@ -10,7 +10,7 @@ This buildpack will participate if all the following conditions are met
 
 The buildpack will do the following for Java applications:
 
-* Contributes the Datadog Java agent to a layer and configures `$JAVA_TOOL_OPTIONS` or `$BP_NATIVE_IMAGE_BUILD_ARGUMENTS` to use it
+* Contributes the Datadog Java agent to a layer: `dd-java-agent-<version>.jar` and `dd-java-agent.jar` (as symlink) and configures `$JAVA_TOOL_OPTIONS` or `$BP_NATIVE_IMAGE_BUILD_ARGUMENTS` to use it.
 
 The buildpack will do the following for Node.js applications:
 

datadog/java_agent.go

@@ -42,6 +42,9 @@ func (j JavaAgent) Contribute(layer libcnb.Layer) (libcnb.Layer, error) {
 		if err := sherpa.CopyFile(artifact, file); err != nil {
 			return libcnb.Layer{}, fmt.Errorf("unable to copy artifact to %s\n%w", file, err)
 		}
+		if err := os.Symlink(file, filepath.Join(layer.Path, "dd-java-agent.jar")); err != nil {
+			return libcnb.Layer{}, fmt.Errorf("unable to create symlink to %s\n%w", file, err)
+		}
 
 		if j.NativeImage {
 			layer.BuildEnvironment.Appendf("BP_NATIVE_IMAGE_BUILD_ARGUMENTS", " ", "-J-javaagent:%s", file)

datadog/java_agent_test.go

@@ -18,6 +18,7 @@ import (
 	. "github.com/onsi/gomega"
 	"github.com/paketo-buildpacks/libpak"
 	"github.com/paketo-buildpacks/libpak/bard"
+	"github.com/paketo-buildpacks/libpak/sherpa"
 	"github.com/sclevine/spec"
 
 	"github.com/paketo-buildpacks/datadog/datadog"
@@ -63,6 +64,7 @@ func testJavaAgent(t *testing.T, context spec.G, it spec.S) {
 
 		Expect(layer.Launch).To(BeTrue())
 		Expect(filepath.Join(layer.Path, "stub-datadog-agent.jar")).To(BeARegularFile())
+		Expect(sherpa.SymlinkExists(filepath.Join(layer.Path, "dd-java-agent.jar"))).To(BeTrue())
 		Expect(layer.LaunchEnvironment["BPI_DATADOG_AGENT_PATH.default"]).To(Equal(filepath.Join(layer.Path, "stub-datadog-agent.jar")))
 	})
 }