Github user mattyb149 commented on a diff in the pull request:
https://github.com/apache/nifi/pull/271#discussion_r56446675
--- Diff:
nifi-nar-bundles/nifi-spring-bundle/nifi-spring-processors/src/main/java/org/apache/nifi/spring/SpringContextProcessor.java
---
@@ -0,0 +1,392 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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.apache.nifi.spring;
+
+import java.io.File;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Map.Entry;
+import java.util.Set;
+import java.util.concurrent.TimeUnit;
+
+import org.apache.nifi.annotation.behavior.TriggerWhenEmpty;
+import org.apache.nifi.annotation.documentation.CapabilityDescription;
+import org.apache.nifi.annotation.documentation.Tags;
+import org.apache.nifi.annotation.lifecycle.OnScheduled;
+import org.apache.nifi.annotation.lifecycle.OnStopped;
+import org.apache.nifi.components.PropertyDescriptor;
+import org.apache.nifi.components.ValidationContext;
+import org.apache.nifi.components.ValidationResult;
+import org.apache.nifi.components.Validator;
+import org.apache.nifi.flowfile.FlowFile;
+import org.apache.nifi.processor.AbstractProcessor;
+import org.apache.nifi.processor.ProcessContext;
+import org.apache.nifi.processor.ProcessSession;
+import org.apache.nifi.processor.Processor;
+import org.apache.nifi.processor.Relationship;
+import org.apache.nifi.processor.exception.ProcessException;
+import org.apache.nifi.processor.io.InputStreamCallback;
+import org.apache.nifi.processor.io.OutputStreamCallback;
+import org.apache.nifi.processor.util.StandardValidators;
+import org.apache.nifi.spring.SpringDataExchanger.SpringResponse;
+import org.apache.nifi.stream.io.StreamUtils;
+import org.apache.nifi.util.FormatUtils;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.messaging.Message;
+import org.springframework.messaging.MessageChannel;
+import org.springframework.messaging.PollableChannel;
+
+/**
+ * Implementation of {@link Processor} capable of sending and receiving
data
+ * from application defined in Spring Application context. It does so via
+ * predefined in/out {@link MessageChannel}s (see spring-messaging module
of
+ * Spring). Once such channels are defined user is free to implement the
rest of
+ * the application any way they wish (e.g., custom code and/or using
frameworks
+ * such as Spring Integration or Camel).
+ * <p>
+ * The requirement and expectations for channel types are:
+ * <ul>
+ * <li>Input channel must be of type {@link MessageChannel} and named
"fromNiFi"
+ * (see {@link SpringNiFiConstants#FROM_NIFI})</li>
+ * <li>Output channel must be of type {@link PollableChannel} and named
"toNiFi"
+ * (see {@link SpringNiFiConstants#TO_NIFI})</li>
+ * </ul>
+ * </p>
+ * Below is the example of sample configuration:
+ *
+ * <pre>
+ * <?xml version="1.0" encoding="UTF-8"?>
+ * <beans xmlns="http://www.springframework.org/schema/beans";
+ * xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance";
+ * xmlns:int="http://www.springframework.org/schema/integration";
+ * xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
+ * http://www.springframework.org/schema/integration
http://www.springframework.org/schema/integration/spring-integration-4.2.xsd">
+ *
+ * <int:channel id="fromNiFi"/>
+ *
+ * . . . . .
+ *
+ * <int:channel id="toNiFi">
+ * <int:queue/>
+ * </int:channel>
+ *
+ * </beans>
+ * </pre>
+ * <p>
+ * Defining {@link MessageChannel} is optional. That's why this processor
+ * supports 3 modes of interaction with Spring Application Context:
+ * <ul>
+ * <li>Headless â no channels are defined therefore nothing is sent to or
+ * received from such Application Contexts (i.e., some monitoring
app).</li>
+ * <li>One way (NiFi -> Spring or Spring -> NiFi) - depends on
existence
+ * of one of "fromNiFi" or "toNiFi" channel in the Spring Application
Context.
+ * </li>
+ * <li>Bi-directional (NiFi -> Spring -> Nifi or Spring -> NiFi
->
+ * Spring) - depends on existence of both "fromNiFi" and "toNiFi" channels
in
+ * the Spring Application Context</li>
+ * </ul>
+ *
+ * </p>
+ * <p>
+ * To create an instance of the ApplicationConetxt this processor requires
user
+ * to provide configuration file path and the path to the resources that
needs
+ * to be added to the classpath of ApplicationContext. This essentially
allows
+ * user to package their Spring Application any way they want as long as
+ * everything it requires is available on the classpath.
+ * </p>
+ * <p>
+ * Data exchange between Spring and NiFi relies on simple mechanism which
is
+ * exposed via {@link SpringDataExchanger}; {@link FlowFile}s's content is
+ * converted to primitive representation that can be easily wrapped in
Spring
+ * {@link Message}. The requirement imposed by this Processor is to
send/receive
+ * {@link Message} with <i>payload</i> of type <i>byte[]</i> and headers
of type
+ * <i>Map<String, Object></i>. This is primarily for simplicity and
type
+ * safety. Converters and Transformers could be used by either side to
change
+ * representation of the content that is being exchanged between NiFi and
+ * Spring.
+ */
+@TriggerWhenEmpty
+@Tags({ "Spring", "Message", "Get", "Put", "Integration" })
+@CapabilityDescription("A Processor that supports sending and receiving
data from application defined in "
+ + "Spring Application Context via predefined in/out
MessageChannels.")
+public class SpringContextProcessor extends AbstractProcessor {
+ private final Logger logger =
LoggerFactory.getLogger(SpringContextProcessor.class);
+
+ public static final PropertyDescriptor CTX_CONFIG_NAME = new
PropertyDescriptor.Builder()
+ .name("Application Context config path")
+ .description("The path to the Spring Application Context
configuration file relative to the classpath")
+ .required(true)
+ .addValidator(StandardValidators.NON_EMPTY_VALIDATOR)
--- End diff --
Sounds like a job for https://issues.apache.org/jira/browse/NIFI-1121
(someday)
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