Initial Commit

Migrating the existing structure from the following location:
https://github.com/spring-cloud-stream-app-starters/stream-applications/tree/restructuring

functions/function/filter-function/.gitignore

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+/target/
+!.mvn/wrapper/maven-wrapper.jar
+
+### STS ###
+.apt_generated
+.classpath
+.factorypath
+.project
+.settings
+.springBeans
+.sts4-cache
+
+### IntelliJ IDEA ###
+.idea
+*.iws
+*.iml
+*.ipr
+
+### NetBeans ###
+/nbproject/private/
+/nbbuild/
+/dist/
+/nbdist/
+/.nb-gradle/
+/build/
+
+### VS Code ###
+.vscode/

functions/function/filter-function/pom.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+		 xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+	<modelVersion>4.0.0</modelVersion>
+	<artifactId>filter-function</artifactId>
+	<version>1.0.0.BUILD-SNAPSHOT</version>
+	<name>filter-function</name>
+	<description>Spring Native Function for applying filter SpEL expressions</description>
+
+	<parent>
+		<groupId>org.springframework.cloud.fn</groupId>
+		<artifactId>spring-functions-parent</artifactId>
+		<version>1.0.0.BUILD-SNAPSHOT</version>
+		<relativePath>../../spring-functions-parent</relativePath>
+	</parent>
+
+	<dependencies>
+		<dependency>
+			<groupId>org.springframework.cloud.fn</groupId>
+			<artifactId>spel-function</artifactId>
+			<version>1.0.0.BUILD-SNAPSHOT</version>
+		</dependency>
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter-test</artifactId>
+			<scope>test</scope>
+			<exclusions>
+				<exclusion>
+					<groupId>org.junit.vintage</groupId>
+					<artifactId>junit-vintage-engine</artifactId>
+				</exclusion>
+			</exclusions>
+		</dependency>
+	</dependencies>
+
+</project>

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

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+/*
+ * Copyright (c) 2020 Pivotal Software Inc, All Rights Reserved.
+ *
+ * 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 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.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.Import;
+import org.springframework.messaging.Message;
+
+@Configuration
+@Import(SpelFunctionConfiguration.class)
+public class FilterFunctionConfiguration {
+
+	@Bean
+	public Function<Message<?>, Message<?>> filterFunction(
+			@Qualifier("spelFunction") Function<Message<?>, Message<?>> spelFunction) {
+
+		return message ->
+				Optional.of(message)
+						.filter(m -> (Boolean) spelFunction.apply(m).getPayload())
+						.orElse(null);
+	}
+
+}

functions/function/filter-function/src/main/resources/application.properties

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+spel.function.expression=true

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

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+/*
+ * Copyright (c) 2011-2020 Pivotal Software Inc, All Rights Reserved.
+ *
+ * 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 static org.assertj.core.api.Assertions.assertThat;
+
+import java.util.function.Function;
+
+import org.junit.jupiter.api.Test;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.beans.factory.annotation.Qualifier;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.messaging.Message;
+import org.springframework.messaging.support.GenericMessage;
+import org.springframework.test.annotation.DirtiesContext;
+
+@SpringBootTest(properties = "spel.function.expression=payload.length() > 5")
+@DirtiesContext
+public class FilterFunctionApplicationTests {
+
+	@Autowired
+	@Qualifier("filterFunction")
+	Function<Message<?>, Message<?>> filter;
+
+	@Test
+	public void testFilter() {
+		Message<?> filtered = this.filter.apply(new GenericMessage<>("hello"));
+		assertThat(filtered).isNull();
+		filtered = this.filter.apply(new GenericMessage<>("hello world"));
+		assertThat(filtered).isNotNull()
+				.extracting(Message::getPayload)
+				.isEqualTo("hello world");
+	}
+
+	@SpringBootApplication
+	static class TestApplication {}
+}