added LambdaCompilingFunction

spring-cloud-function-core/src/main/java/org/springframework/cloud/function/support/LambdaCompilingFunction.java

@@ -0,0 +1,66 @@
+/*
+ * Copyright 2017 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.cloud.function.support;
+
+import java.io.InputStreamReader;
+import java.util.function.Function;
+
+import org.springframework.beans.factory.BeanNameAware;
+import org.springframework.beans.factory.InitializingBean;
+import org.springframework.cloud.function.compiler.CompiledFunctionFactory;
+import org.springframework.cloud.function.compiler.FunctionCompiler;
+import org.springframework.core.io.Resource;
+import org.springframework.util.Assert;
+import org.springframework.util.FileCopyUtils;
+
+/**
+ * @author Mark Fisher
+ */
+public class LambdaCompilingFunction<T, R> implements Function<T, R>, InitializingBean, BeanNameAware {
+
+	private final Resource resource;
+
+	private final FunctionCompiler<T, R> compiler;
+
+	private String beanName;
+
+	private Function<T, R> compiledFunction;
+
+	public LambdaCompilingFunction(Resource resource, FunctionCompiler<T, R> compiler) {
+		Assert.notNull(resource, "Resource must not be null");
+		Assert.notNull(compiler, "FunctionCompiler must not be null");
+		this.resource = resource;
+		this.compiler = compiler;
+	}
+
+	@Override
+	public void setBeanName(String beanName) {
+		this.beanName = beanName;
+	}
+
+	@Override
+	public void afterPropertiesSet() throws Exception {
+		String lambda = FileCopyUtils.copyToString(new InputStreamReader(this.resource.getInputStream()));
+		CompiledFunctionFactory<Function<T, R>> factory = this.compiler.compile(this.beanName, lambda);
+		this.compiledFunction = factory.getResult();
+	}
+
+	@Override
+	public R apply(T input) {
+		return this.compiledFunction.apply(input);
+	}
+}