Github user trkurc commented on a diff in the pull request:
https://github.com/apache/nifi/pull/271#discussion_r56105950
--- Diff:
nifi-nar-bundles/nifi-spring-bundle/nifi-spring-processors/src/main/java/org/apache/nifi/spring/bootstrap/SpringContextDelegate.java
---
@@ -0,0 +1,141 @@
+/*
+ * 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.bootstrap;
+
+import java.io.Closeable;
+import java.io.IOException;
+import java.net.URLClassLoader;
+import java.util.Map;
+
+import org.apache.nifi.spring.SpringDataExchanger;
+import org.apache.nifi.spring.SpringNiFiConstants;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.context.support.ClassPathXmlApplicationContext;
+import org.springframework.messaging.Message;
+import org.springframework.messaging.MessageChannel;
+import org.springframework.messaging.PollableChannel;
+import org.springframework.messaging.support.MessageBuilder;
+
+/**
+ * Scopes instance of itself to a dedicated {@link ClassLoader}, thus
allowing
+ * Spring Application Context and its class path to be modified and
refreshed by
+ * simply re-starting SpringContextProcessor. Also ensures that there are
no
+ * class path collisions between multiple instances of Spring Context
Processor
+ * which are loaded by the same NAR Class Loader.
+ */
+/*
+ * This class is for internal use only and must never be instantiated by
the NAR
+ * Class Loader (hence in a isolated package with nothing referencing it).
It is
+ * loaded by a dedicated CL via byte array that represents it ensuring
that this
+ * class can be loaded multiple times by multiple Class Loaders within a
single
+ * instance of NAR.
+ */
+final class SpringContextDelegate implements Closeable,
SpringDataExchanger {
+
+ private final Logger logger =
LoggerFactory.getLogger(SpringContextDelegate.class);
+
+ private final ClassPathXmlApplicationContext applicationContext;
+
+ private final MessageChannel toSpringChannel;
+
+ private final PollableChannel fromSpringChannel;
+
+ /**
+ *
+ */
+ private SpringContextDelegate(String configName) {
+ ClassLoader orig = Thread.currentThread().getContextClassLoader();
+
Thread.currentThread().setContextClassLoader(this.getClass().getClassLoader());
+ if (logger.isDebugEnabled()) {
+ logger.debug("Using " +
Thread.currentThread().getContextClassLoader()
+ + " as context class loader while loading Spring
Context '" + configName + "'.");
+ }
+ try {
+ this.applicationContext = new
ClassPathXmlApplicationContext(configName);
+ if
(this.applicationContext.containsBean(SpringNiFiConstants.FROM_NIFI)){
+ this.toSpringChannel =
this.applicationContext.getBean(SpringNiFiConstants.FROM_NIFI,
MessageChannel.class);
+ if (logger.isDebugEnabled()) {
+ logger.debug("Spring Application Context defined in '"
+ configName
+ + "' is capable of receiving messages from
NiFi since 'fromNiFi' channel was discovered.");
+ }
+ } else {
+ this.toSpringChannel = null;
+ }
+ if
(this.applicationContext.containsBean(SpringNiFiConstants.TO_NIFI)){
+ this.fromSpringChannel =
this.applicationContext.getBean(SpringNiFiConstants.TO_NIFI,
PollableChannel.class);
+ if (logger.isDebugEnabled()) {
+ logger.debug("Spring Application Context defined in '"
+ configName
+ + "' is capable of sending messages to " +
"NiFi since 'toNiFi' channel was discovered.");
+ }
+ } else {
+ this.fromSpringChannel = null;
+ }
+ if (logger.isInfoEnabled() && this.toSpringChannel == null &&
this.fromSpringChannel == null){
+ logger.info("Spring Application Context is headless since
neither 'fromNiFi' nor 'toNiFi' channels were defined. "
+ + "No data will be exchanged.");
+ }
+ } finally {
+ Thread.currentThread().setContextClassLoader(orig);
+ }
+ }
+
+ /**
+ *
+ */
+ @Override
+ public <T> boolean send(T payload, Map<String, ?> messageHeaders, long
timeout) {
+ if (this.toSpringChannel != null){
+ return
this.toSpringChannel.send(MessageBuilder.withPayload(payload).copyHeaders(messageHeaders).build(),
timeout);
+ }
+ return false;
+ }
+
+ /**
+ *
+ */
+ @SuppressWarnings("unchecked")
+ @Override
+ public <T> SpringResponse<T> receive(long timeout) {
+ if (this.fromSpringChannel != null) {
+ final Message<T> message = (Message<T>)
this.fromSpringChannel.receive(timeout);
+ if (message != null) {
+ if (!(message.getPayload() instanceof byte[]) &&
!(message.getPayload() instanceof String)) {
+ throw new IllegalStateException("Failed while
receiving message from Spring due to the "
+ + "payload type being other then byte[] which
is currently not supported. Please "
--- End diff --
not sure on this one, but should this be "byte[] or String"?
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