feat: Add configuration for Java buildpack

The detect now checks for func.yaml OR they explicitly
defined an environment variable for the function class or
the default function name.

Signed-off-by: Andrew Su <[email protected]>

buildpacks/java/README.md

@@ -4,20 +4,29 @@ The Java Function Buildpack is a Cloud Native Buildpack that provides a Spring B
 
 ## Behaviour
 This buildpack will participate if any of the following conditions are met:
-* A file with the name `func.yaml` is detected
+* A buildpack configuration variable `BP_FUNCTION` is explicitly set.
+* A file with the name `func.yaml` is detected.
 
 The buildpack will do the following if detection passed:
 * Request for a JRE to be installed
-* Contributes the Spring Boot application to a layer marked `launch` with the layer's path prepended to `$CLASSPATH`
+* Contributes the function invoker to a layer marked `launch` with the layer's path prepended to `$CLASSPATH`
 * Contributes environment variables defined in `func.yaml` to the `launch` layer
+* Contributes environment variables to configure the invoker if any configuration variables are defined. (Overrides anything from `func.yaml`)
+
+## Configuration
+
+| Environment Variable | Description |
+|----------------------|-------------|
+| `$BP_FUNCTION` | Configure the function to load. If the function lives in the default package: `<class>`. If the function lives in their own package: `<package>.<class>`. Defaults to `functions.Handler` |
+| `$BP_DEFAULT_FUNCTION` | Configure the default function. By specifying this property, a function with the name can be accessed via the `/` path. Defaults to empty. |
 
 ## Getting started
 To get started you'll need to create a directory where your function will be defined.
 
 From within this directory we require a few files to properly detect this as a Java function:
-* `func.yaml`: We use this to configure the runtime environment variables. See the [Knative Func CLI docs](https://github.com/knative-sandbox/kn-plugin-func/blob/main/docs/guides/func_yaml.md) for more details.
+* `func.yaml` (optional): We use this to configure the runtime environment variables. See the [Knative Func CLI docs](https://github.com/knative-sandbox/kn-plugin-func/blob/main/docs/guides/func_yaml.md) for more details.
 * `pom.xml` or `build.gradle`: These are used by the other Java buildpacks to compile your function.
-* Java package in folder `src/main/java/functions`: This is the default location your function will be detected. If you do choose to use another package to store your functions, you will need to [set a new search location](#TODO).
+* Java package in folder `src/main/java/functions`: This is the default location your function will be detected. If you do choose to use another package to store your functions, you will need to define where your function is located with the `BP_FUNCTION` configuration for the buildpack.
 
 ## Compiling Your Function
 To compile your function with the buildpack, we've provided a builder which has all the pre-requisites ready to go.

buildpacks/java/buildpack.toml

@@ -13,6 +13,18 @@ api = "0.6"
   include-files = ["README.md", "bin/build", "bin/detect", "bin/main", "buildpack.toml", "VERSION"]
   pre-package = "./build.sh"
 
+  [[metadata.configurations]]
+    build = true
+    default = "functions.Handler"
+    description = "The function to run. It must be in the format of <package>.<class>, if it is in the default package then just <class>"
+    name = "BP_FUNCTION"
+
+  [[metadata.configurations]]
+    build = true
+    default = ""
+    description = "The default function name. In the event there are multiple functions. Specifying the name of the function will make it accessible through the root path '/'"
+    name = "BP_DEFAULT_FUNCTION"
+
   [[metadata.dependencies]]
     id      = "invoker"
     name    = "Java Invoker"

buildpacks/java/java/build.go

@@ -22,7 +22,7 @@ func (b Build) Build(context libcnb.BuildContext) (libcnb.BuildResult, error) {
 	b.Logger.Title(context.Buildpack)
 	result := libcnb.NewBuildResult()
 
-	_, err := libpak.NewConfigurationResolver(context.Buildpack, &b.Logger)
+	cr, err := libpak.NewConfigurationResolver(context.Buildpack, &b.Logger)
 	if err != nil {
 		return libcnb.BuildResult{}, fmt.Errorf("unable to create configuration resolver\n%w", err)
 	}
@@ -47,6 +47,11 @@ func (b Build) Build(context libcnb.BuildContext) (libcnb.BuildResult, error) {
 	if !ok {
 		return result, nil
 	}
+	if e.Metadata["has_func_yaml"] == true {
+		envs := NewFuncYamlEnvs(context.Application.Path)
+		envs.Logger = b.Logger
+		result.Layers = append(result.Layers, envs)
+	}
 
 	dep, err := dr.Resolve("invoker", "")
 	if err != nil {
@@ -71,10 +76,10 @@ func (b Build) Build(context libcnb.BuildContext) (libcnb.BuildResult, error) {
 		result.BOM.Entries = append(result.BOM.Entries, be)
 	}
 
-	f := NewFunction(e, context.Application.Path)
-	if err != nil {
-		return libcnb.BuildResult{}, fmt.Errorf("unable to create function\n%w", err)
-	}
+	funcDef, _ := cr.Resolve("BP_FUNCTION")
+	defaultDef, _ := cr.Resolve("BP_DEFAULT_FUNCTION")
+
+	f := NewFunction(funcDef, defaultDef, context.Application.Path)
 	f.Logger = b.Logger
 	result.Layers = append(result.Layers, f)
 

buildpacks/java/java/detect.go

@@ -9,6 +9,7 @@ import (
 	"path/filepath"
 
 	"github.com/buildpacks/libcnb"
+	"github.com/paketo-buildpacks/libpak"
 	"github.com/paketo-buildpacks/libpak/bard"
 	knfn "knative.dev/kn-plugin-func"
 )
@@ -17,22 +18,45 @@ type Detect struct {
 	Logger bard.Logger
 }
 
-func (d Detect) Detect(context libcnb.DetectContext) (libcnb.DetectResult, error) {
-	result := libcnb.DetectResult{}
+func (d Detect) checkConfigs(cr libpak.ConfigurationResolver) bool {
+	if _, defined := cr.Resolve("BP_FUNCTION"); defined {
+		return true
+	}
+
+	if _, defined := cr.Resolve("BP_DEFAULT_FUNCTION"); defined {
+		return true
+	}
+
+	return false
+}
 
-	configFile := filepath.Join(context.Application.Path, knfn.ConfigFile)
+func (d Detect) checkFuncYaml(appPath string) bool {
+	configFile := filepath.Join(appPath, knfn.ConfigFile)
 	_, err := os.Stat(configFile)
 	if err != nil {
-		d.logf(fmt.Sprintf("unable to find file '%s'", configFile))
-		return result, nil
+		d.Logger.Bodyf("unable to find file '%s'", configFile)
+		return false
 	}
 
-	f, err := knfn.NewFunction(context.Application.Path)
+	return true
+}
+
+func (d Detect) Detect(context libcnb.DetectContext) (libcnb.DetectResult, error) {
+	result := libcnb.DetectResult{}
+
+	appPath := context.Application.Path
+	funcYamlPass := d.checkFuncYaml(appPath)
+
+	cr, err := libpak.NewConfigurationResolver(context.Buildpack, &d.Logger)
 	if err != nil {
-		return result, fmt.Errorf("parsing function config: %v", err)
+		return result, fmt.Errorf("unable to create configuration resolver: %v", err)
 	}
 
-	envs := envsToMap(f.Envs)
+	configPass := d.checkConfigs(cr)
+	if err != nil {
+		d.Logger.Bodyf("unable to check buildpack configurations: %v", err)
+		return result, nil
+	}
 
 	result.Plans = append(result.Plans, libcnb.BuildPlan{
 		Provides: []libcnb.BuildPlanProvide{
@@ -44,8 +68,8 @@ func (d Detect) Detect(context libcnb.DetectContext) (libcnb.DetectResult, error
 			{
 				Name: "java-function",
 				Metadata: map[string]interface{}{
-					"launch": true,
-					"envs":   envs,
+					"launch":        true,
+					"has_func_yaml": funcYamlPass,
 				},
 			},
 			{
@@ -60,25 +84,6 @@ func (d Detect) Detect(context libcnb.DetectContext) (libcnb.DetectResult, error
 		},
 	})
 
-	result.Pass = true
+	result.Pass = funcYamlPass || configPass
 	return result, nil
 }
-
-func (d Detect) logf(format string, args ...interface{}) {
-	d.Logger.Infof(format, args...)
-}
-
-func envsToMap(envs knfn.Envs) map[string]string {
-	result := map[string]string{}
-
-	for _, e := range envs {
-		key := *e.Name
-		val := ""
-		if e.Value != nil {
-			val = *e.Value
-		}
-		result[key] = val
-	}
-
-	return result
-}

buildpacks/java/java/func_yaml_envs.go

@@ -0,0 +1,81 @@
+// Copyright 2021-2022 VMware, Inc.
+// SPDX-License-Identifier: BSD-2-Clause
+
+package java
+
+import (
+	"os"
+	"path/filepath"
+
+	"github.com/buildpacks/libcnb"
+	"github.com/paketo-buildpacks/libpak"
+	"github.com/paketo-buildpacks/libpak/bard"
+	knfn "knative.dev/kn-plugin-func"
+)
+
+type FuncYamlEnvs struct {
+	LayerContributor libpak.LayerContributor
+	Logger           bard.Logger
+
+	Envs map[string]string
+}
+
+func NewFuncYamlEnvs(applicationPath string) FuncYamlEnvs {
+	envs := getFuncYamlEnvs(applicationPath)
+	return FuncYamlEnvs{
+		LayerContributor: libpak.NewLayerContributor(
+			"func-yaml-envs",
+			envs,
+			libcnb.LayerTypes{
+				Launch: true,
+			},
+		),
+		Envs: envs,
+	}
+}
+
+func (f FuncYamlEnvs) Contribute(layer libcnb.Layer) (libcnb.Layer, error) {
+	f.LayerContributor.Logger = f.Logger
+	return f.LayerContributor.Contribute(layer, func() (libcnb.Layer, error) {
+		for k, v := range f.Envs {
+			layer.LaunchEnvironment.Default(k, v)
+		}
+		return layer, nil
+	})
+}
+
+func (f FuncYamlEnvs) Name() string {
+	return f.LayerContributor.Name
+}
+
+func getFuncYamlEnvs(applicationPath string) map[string]string {
+	envs := map[string]string{}
+
+	configFile := filepath.Join(applicationPath, knfn.ConfigFile)
+	_, err := os.Stat(configFile)
+	if err != nil {
+		return envs
+	}
+
+	f, err := knfn.NewFunction(applicationPath)
+	if err != nil {
+		return envs
+	}
+
+	return envsToMap(f.Envs)
+}
+
+func envsToMap(envs knfn.Envs) map[string]string {
+	result := map[string]string{}
+
+	for _, e := range envs {
+		key := *e.Name
+		val := ""
+		if e.Value != nil {
+			val = *e.Value
+		}
+		result[key] = val
+	}
+
+	return result
+}

buildpacks/java/java/function.go

@@ -4,8 +4,6 @@
 package java
 
 import (
-	"strings"
-
 	"github.com/buildpacks/libcnb"
 	"github.com/paketo-buildpacks/libpak"
 	"github.com/paketo-buildpacks/libpak/bard"
@@ -16,42 +14,36 @@ type Function struct {
 	Logger           bard.Logger
 
 	ApplicationPath string
-	Handler         string
-	Envs            map[string]interface{}
+	Function        string
+	DefaultFunction string
 }
 
-func NewFunction(plan libcnb.BuildpackPlanEntry, applicationPath string) Function {
-	envs := plan.Metadata["envs"].(map[string]interface{})
-
+func NewFunction(function string, defaultFunc string, applicationPath string) Function {
 	return Function{
 		ApplicationPath: applicationPath,
 		LayerContributor: libpak.NewLayerContributor(
-			plan.Name,
-			envs,
+			"java-function",
+			map[string]string{
+				"function": function,
+			},
 			libcnb.LayerTypes{
 				Launch: true,
 			},
 		),
-		Envs: envs,
+		Function:        function,
+		DefaultFunction: defaultFunc,
 	}
 }
 
 func (f Function) Contribute(layer libcnb.Layer) (libcnb.Layer, error) {
 	f.LayerContributor.Logger = f.Logger
 
 	return f.LayerContributor.Contribute(layer, func() (libcnb.Layer, error) {
-		if len(f.Handler) > 0 {
-			if strings.ContainsAny(f.Handler, ".") {
-				layer.LaunchEnvironment.Default("SPRING_CLOUD_FUNCTION_FUNCTION_CLASS", f.Handler)
-			} else {
-				layer.LaunchEnvironment.Default("SPRING_CLOUD_FUNCTION_DEFINITION", f.Handler)
-			}
-		}
-
 		layer.LaunchEnvironment.Default("SPRING_CLOUD_FUNCTION_LOCATION", f.ApplicationPath)
+		layer.LaunchEnvironment.Default("SPRING_CLOUD_FUNCTION_FUNCTION_CLASS", f.Function) // Function lives here
 
-		for k, v := range f.Envs {
-			layer.LaunchEnvironment.Default(k, v)
+		if len(f.DefaultFunction) > 0 {
+			layer.LaunchEnvironment.Default("SPRING_CLOUD_FUNCTION_DEFINITION", f.DefaultFunction)
 		}
 
 		return layer, nil

invokers/java/src/main/java/com/vmware/functions/JavaFunctionInvokerApplication.java

@@ -8,8 +8,6 @@
 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.SpringBootApplication;
 
-import java.util.function.Function;
-
 @SpringBootApplication
 public class JavaFunctionInvokerApplication {
 	public static void main(String[] args) {

invokers/java/src/main/resources/application.properties

@@ -1 +1,2 @@
-spring.cloud.function.location:/workspace
+spring.cloud.function.location:/workspace
+spring.cloud.function.scan.enabled:false

samples/java/cloudevents/txt-to-pdf-maven/Makefile

@@ -5,7 +5,7 @@ FUNCTION_IMAGE ?= us.gcr.io/daisy-284300/functions/demo:txttopdfjava
 FUNCTION := out/image
 $(FUNCTION):
 	@mkdir -p $(@D)
-	pack build $(FUNCTION_IMAGE) --path ./spring-java-fn/ --builder ghcr.io/vmware-tanzu/function-buildpacks-for-knative/functions-builder:0.0.10
+	pack build $(FUNCTION_IMAGE) --path ./spring-java-fn/ --builder ghcr.io/vmware-tanzu/function-buildpacks-for-knative/functions-builder:0.0.10 --env BP_FUNCTION=com.example.demo.DemoApplication --env BP_DEFAULT_FUNCTION=func
 	printf $(FUNCTION_IMAGE) > $@
 
 build: $(FUNCTION)

samples/java/cloudevents/txt-to-pdf-maven/README.md

@@ -106,7 +106,7 @@ If you encounter any Knative errors while re-deploying the app, be sure to delet
     ```
 
 ## Legacy Deployment YAML
-
+```
 apiVersion: v1
 kind: Secret
 metadata:

samples/java/http/request-response-gradle/README.md

@@ -1,3 +1,7 @@
 # request-response
 
-This is a sample function for how to create and send HTTP requests via our Java HTTP function.
+This is a sample function for how to create and send HTTP requests via our Java HTTP function.
+
+# Building
+
+To build this sample, use the latest buildpack and build with `--env BP_FUNCTION=com.vmware.functions.Handler` set on the `pack` cli command.

samples/java/http/request-response-maven/README.md

@@ -1,3 +1,7 @@
 # request-response
 
-This is a sample function for how to create and send HTTP requests via our Java HTTP function.
+This is a sample function for how to create and send HTTP requests via our Java HTTP function.
+
+# Building
+
+To build this sample, use the latest buildpack and build with `--env BP_FUNCTION=com.vmware.functions.Handler` set on the `pack` cli command.

samples/java/http/request-response-maven/src/main/java/com/vmware/functions/Handler.java

@@ -39,4 +39,11 @@ public Function<String, String> hello() {
 			}
 		};
 	}
+
+	@Bean
+	public Function<String, String> bye() {
+		return in -> {
+			return "bye";
+		};
+	}
 }