Support filterFunction and spelFunction composition

function/filter-function/README.adoc

@@ -14,11 +14,11 @@ Once injected, you can use the `apply` method of the `Function` to invoke it and
 
 ## Configuration Options
 
-The filter function makes uses of link:../spel-function/README.adoc[SpEL function].
+All configuration properties are prefixed with `filter.function`.
 
-For more information on the various options available, please see link:../spel-function/src/main/java/org/springframework/cloud/fn/spel/SpelFunctionProperties.java[SpelFunctionProperties.java]
+For more information on the various options available, please see link:src/main/java/org/springframework/cloud/fn/filter/FilterFunctionProperties.java[FilterFunctionProperties.java]
 
-## Tests
+## Examples
 
 See this link:src/test/java/org/springframework/cloud/fn/filter/FilterFunctionApplicationTests.java[test suite] for examples of how this function is used.
 

function/filter-function/pom.xml

@@ -17,8 +17,12 @@
     <dependencies>
         <dependency>
             <groupId>org.springframework.cloud.fn</groupId>
-            <artifactId>spel-function</artifactId>
-            <version>1.0.0-SNAPSHOT</version>
+            <artifactId>payload-converter-function</artifactId>
+            <version>${project.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-integration</artifactId>
         </dependency>
         <dependency>
             <groupId>org.springframework.boot</groupId>

function/filter-function/src/main/java/org/springframework/cloud/fn/filter/FilterFunctionConfiguration.java

@@ -19,25 +19,36 @@ package org.springframework.cloud.fn.filter;
 import java.util.Optional;
 import java.util.function.Function;
 
-import org.springframework.beans.factory.annotation.Qualifier;
-import org.springframework.cloud.fn.spel.SpelFunctionConfiguration;
+import org.springframework.boot.context.properties.EnableConfigurationProperties;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
-import org.springframework.context.annotation.Import;
+import org.springframework.expression.spel.standard.SpelExpressionParser;
+import org.springframework.integration.transformer.ExpressionEvaluatingTransformer;
 import org.springframework.messaging.Message;
 
+/**
+ * @author Artem Bilan
+ * @author David Turanski
+ */
 @Configuration
-@Import(SpelFunctionConfiguration.class)
+@EnableConfigurationProperties(FilterFunctionProperties.class)
 public class FilterFunctionConfiguration {
 
 	@Bean
 	public Function<Message<?>, Message<?>> filterFunction(
-			@Qualifier("spelFunction") Function<Message<?>, Message<?>> spelFunction) {
+			ExpressionEvaluatingTransformer filterExpressionEvaluatingTransformer) {
 
-		return message ->
-				Optional.of(message)
-						.filter(m -> (Boolean) spelFunction.apply(m).getPayload())
-						.orElse(null);
+		return message -> Optional.of(message)
+				.filter(m -> (Boolean) filterExpressionEvaluatingTransformer.transform(m).getPayload())
+				.orElse(null);
+	}
+
+	@Bean
+	public ExpressionEvaluatingTransformer filterExpressionEvaluatingTransformer(
+			FilterFunctionProperties filterFunctionProperties) {
+
+		return new ExpressionEvaluatingTransformer(new SpelExpressionParser()
+				.parseExpression(filterFunctionProperties.getExpression()));
 	}
 
 }

function/filter-function/src/main/java/org/springframework/cloud/fn/filter/FilterFunctionProperties.java

@@ -0,0 +1,47 @@
+/*
+ * Copyright 2020-2020 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
+ *
+ *      https://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.fn.filter;
+
+import org.springframework.boot.context.properties.ConfigurationProperties;
+import org.springframework.expression.Expression;
+import org.springframework.expression.spel.standard.SpelExpressionParser;
+
+/**
+ * Configuration properties for the SpEL function.
+ *
+ * @author Gary Russell
+ * @author Artem Bilan
+ */
+@ConfigurationProperties("filter.function")
+public class FilterFunctionProperties {
+
+	private static final Expression DEFAULT_EXPRESSION = new SpelExpressionParser().parseExpression("payload");
+
+	/**
+	 * A SpEL expression to apply.
+	 */
+	private String expression = DEFAULT_EXPRESSION.getExpressionString();
+
+	public String getExpression() {
+		return this.expression;
+	}
+
+	public void setExpression(String expression) {
+		this.expression = expression;
+	}
+
+}

function/filter-function/src/test/java/org/springframework/cloud/fn/filter/FilterFunctionApplicationTests.java

@@ -30,7 +30,7 @@ import org.springframework.test.annotation.DirtiesContext;
 
 import static org.assertj.core.api.Assertions.assertThat;
 
-@SpringBootTest(properties = "spel.function.expression=payload.length() > 5")
+@SpringBootTest(properties = "filter.function.expression=payload.length() > 5")
 @DirtiesContext
 public class FilterFunctionApplicationTests {