feature: v0.5.0: Spring Cloud Function Support

README.md

@@ -144,6 +144,26 @@ class Router(
     )
 }
 ```
+### Serverless components - Spring Cloud Function support
+
+If you want to deploy your application on a serverless platform such as AWS Lambda or Azure Functions you can easily do that with the Spring Cloud Function support.
+
+Just add the dependency `implementation("org.springframework.cloud:spring-cloud-function-context")` to your build.gradle.kts.
+
+Create a @ViewComponent that implements the functional interface `Supplier<ViewContext>`. Instead of the render() function we will now override the get method of the Supplier interface.
+
+If you start your application the component should be automatically rendered on http://localhost:8080
+```kotlin
+@ViewComponent
+class HomeViewComponent(
+    private val exampleService: ExampleService,
+) : Supplier<ViewContext> {
+    override fun get() = ViewContext(
+        "helloWorld" toProperty exampleService.getHelloWorld(),
+        "coffee" toProperty exampleService.getCoffee()
+    )
+}
+```
 
 ### Local Development
 
@@ -347,6 +367,38 @@ public class Router {
 }
 ```
 
+### Serverless components - Spring Cloud Function support
+
+If you want to deploy your application on a serverless platform such as AWS Lambda or Azure Functions you can easily do that with the Spring Cloud Function support. 
+
+Just add the dependency `implementation("org.springframework.cloud:spring-cloud-function-context")` to your build.gradle.kts.
+
+Create a @ViewComponent that implements the functional interface `Supplier<ViewContext>`. Instead of the render() function we will now override the get method of the Supplier interface.
+
+If you start your application the component should be automatically rendered on http://localhost:8080
+
+
+```java
+// HomeViewComponent.java
+@ViewComponent
+public class HomeViewComponent implements Supplier<ViewContext> {
+    private final ExampleService exampleService;
+
+    public HomeViewComponent(ExampleService exampleService) {
+        this.exampleService = exampleService;
+    }
+
+    @Override
+    public ViewContext get() {
+        return new ViewContext(
+                ViewProperty.of("helloWorld", "Hello World"),
+                ViewProperty.of("coffee", exampleService.getCoffee()),
+                ViewProperty.of("office", exampleService.getOfficeHours())
+        );
+    }
+}
+```
+
 ### Local Development
 
 To enable live reload of the components on each save without rebuilding the application add this configuration:

build.gradle.kts

@@ -22,6 +22,7 @@ dependencies {
 	implementation("org.springframework.boot:spring-boot-starter-web")
 	implementation("org.springframework.boot:spring-boot-starter-aop")
 	implementation("org.springframework.boot:spring-boot-devtools")
+	implementation("io.projectreactor:reactor-core")
 	implementation("com.fasterxml.jackson.module:jackson-module-kotlin")
 	implementation("org.jetbrains.kotlin:kotlin-reflect")
 	implementation("org.jetbrains.kotlin:kotlin-stdlib-jdk8")

src/main/kotlin/de/tschuehly/thymeleafviewcomponent/ViewComponent.kt

@@ -3,6 +3,7 @@ package de.tschuehly.thymeleafviewcomponent
 import org.aspectj.lang.ProceedingJoinPoint
 import org.aspectj.lang.annotation.Around
 import org.aspectj.lang.annotation.Aspect
+import org.aspectj.lang.annotation.Pointcut
 import org.springframework.stereotype.Component
 
 
@@ -14,7 +15,17 @@ annotation class ViewComponent
 @Aspect
 @Component
 class ViewComponentAspect {
-    @Around("execution(* render(..)) && @within(de.tschuehly.thymeleafviewcomponent.ViewComponent)")
+    @Pointcut("@within(de.tschuehly.thymeleafviewcomponent.ViewComponent)")
+    fun isViewComponent(){
+        //
+    }
+
+    @Pointcut("execution(* render(..)) || execution(* get(..))")
+    fun isRenderOrGetMethod(){
+        //
+    }
+
+    @Around("isViewComponent() && isRenderOrGetMethod()")
     fun renderInject(joinPoint: ProceedingJoinPoint): ViewContext {
 
         val returnValue = joinPoint.proceed()

src/main/kotlin/de/tschuehly/thymeleafviewcomponent/ViewComponentMvcConfigurer.kt

@@ -6,10 +6,11 @@ import org.springframework.web.servlet.config.annotation.WebMvcConfigurer
 
 @Component
 class ViewComponentMvcConfigurer(
-    private val viewContextContainerMethodReturnValueHandler: ViewContextContainerMethodReturnValueHandler
+    private val viewContextContainerMethodReturnValueHandler: ViewContextContainerMethodReturnValueHandler,
 ) : WebMvcConfigurer {
 
     override fun addReturnValueHandlers(handlers: MutableList<HandlerMethodReturnValueHandler>) {
+        handlers.add(ViewContextAsyncHandlerMethodReturnValueHandler())
         handlers.add(viewContextContainerMethodReturnValueHandler)
         handlers.add(ViewContextMethodReturnValueHandler())
         super.addReturnValueHandlers(handlers)

src/main/kotlin/de/tschuehly/thymeleafviewcomponent/ViewComponentProcessor.kt

@@ -60,7 +60,13 @@ class ViewComponentProcessor(dialectPrefix: String) :
         val viewContext = try {
             expression.execute(webContext) as ViewContext
         } catch (e: TemplateProcessingException) {
-            throw ViewComponentProcessingException(e.message, e.cause)
+            try{
+                val supplierExpression = parser.parseExpression(webContext,expressionString.replace(".render(",".get("))
+                supplierExpression.execute(webContext) as ViewContext
+            }catch (e: TemplateProcessingException){
+                throw ViewComponentProcessingException(e.message, e.cause)
+            }
+
         }
         val engine = appCtx.getBean(SpringTemplateEngine::class.java)
 

src/main/kotlin/de/tschuehly/thymeleafviewcomponent/ViewContextAsyncHandlerMethodReturnValueHandler.kt

@@ -0,0 +1,40 @@
+package de.tschuehly.thymeleafviewcomponent
+
+import org.springframework.core.MethodParameter
+import org.springframework.http.ResponseEntity
+import org.springframework.web.context.request.NativeWebRequest
+import org.springframework.web.method.support.AsyncHandlerMethodReturnValueHandler
+import org.springframework.web.method.support.ModelAndViewContainer
+import reactor.core.publisher.Mono
+
+class ViewContextAsyncHandlerMethodReturnValueHandler() : AsyncHandlerMethodReturnValueHandler {
+    override fun supportsReturnType(returnType: MethodParameter): Boolean {
+        return Mono::class.java.isAssignableFrom(returnType.parameterType)
+    }
+
+    override fun handleReturnValue(
+        returnValue: Any?,
+        returnType: MethodParameter,
+        mavContainer: ModelAndViewContainer,
+        webRequest: NativeWebRequest
+    ) {
+        if(returnValue == null){
+            throw Exception("Return Value is null")
+        }
+        val mono= returnValue.takeIf {
+            (Mono::class.java.isAssignableFrom(it.javaClass))
+        } as Mono<*>
+        val responseEntity = mono.block()?.takeIf {
+            ResponseEntity::class.java.isAssignableFrom(it.javaClass)
+        } as ResponseEntity<*>
+        val viewContext = responseEntity.body?.takeIf {
+            ViewContext::class.java.isAssignableFrom(it.javaClass)
+        } as ViewContext
+        mavContainer.view = viewContext.componentTemplate
+        mavContainer.addAllAttributes(viewContext.contextAttributes.toMap())
+    }
+
+    override fun isAsyncReturnValue(returnValue: Any?, returnType: MethodParameter): Boolean {
+        return returnValue != null && supportsReturnType(returnType)
+    }
+}

src/main/kotlin/de/tschuehly/thymeleafviewcomponent/ViewContextMethodReturnValueHandler.kt

@@ -18,7 +18,9 @@ class ViewContextMethodReturnValueHandler : HandlerMethodReturnValueHandler {
         mavContainer: ModelAndViewContainer,
         webRequest: NativeWebRequest
     ) {
-        val viewContext = returnValue as ViewContext
+        val viewContext = returnValue?.takeIf {
+            (ViewContext::class.java.isAssignableFrom(it.javaClass))
+        } as ViewContext
         mavContainer.view = viewContext.componentTemplate
         mavContainer.addAllAttributes(viewContext.contextAttributes.toMap())
     }