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-rw-r--r--utils/src/main/java/org/onap/policy/common/utils/services/OrderedService.java (renamed from utils/src/main/java/org/onap/policy/common/utils/slf4j/LoggerFactoryWrapper.java)36
-rw-r--r--utils/src/main/java/org/onap/policy/common/utils/services/OrderedServiceImpl.java135
2 files changed, 153 insertions, 18 deletions
diff --git a/utils/src/main/java/org/onap/policy/common/utils/slf4j/LoggerFactoryWrapper.java b/utils/src/main/java/org/onap/policy/common/utils/services/OrderedService.java
index 6f800015..c5050c83 100644
--- a/utils/src/main/java/org/onap/policy/common/utils/slf4j/LoggerFactoryWrapper.java
+++ b/utils/src/main/java/org/onap/policy/common/utils/services/OrderedService.java
@@ -1,9 +1,8 @@
/*
* ============LICENSE_START=======================================================
- * ONAP Policy Engine - Common Modules
+ * utils
* ================================================================================
- * Copyright (C) 2019 Samsung Electronics. All rights reserved.
- * Modifications Copyright (C) 2019 AT&T Intellectual Property.
+ * Copyright (C) 2019 AT&T Intellectual Property. 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.
@@ -19,29 +18,30 @@
* ============LICENSE_END=========================================================
*/
-package org.onap.policy.common.utils.slf4j;
-
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
+package org.onap.policy.common.utils.services;
/**
- * Helper class to retrieve particular types of loggers without storing the logger name everywhere in ths code.
+ * This is a base interface that is used to control the order of a list
+ * of services (features) discovered via 'ServiceLoader'. See
+ * 'OrderedServiceImpl' for more details.
*/
-public class LoggerFactoryWrapper {
-
+@FunctionalInterface
+public interface OrderedService {
/**
- * Constructs the object.
+ * Get sequence number.
+ *
+ * @return an integer sequence number, which determines the order of a list
+ * of objects implementing this interface
*/
- private LoggerFactoryWrapper() {
- super();
- }
+ public int getSequenceNumber();
+
/**
- * Get Network Logger.
+ * Get the name.
*
- * @return logger instance
+ * @return the name of the ordered service
*/
- public static Logger getNetworkLogger() {
- return LoggerFactory.getLogger("network");
+ public default String getName() {
+ return this.getClass().getName();
}
}
diff --git a/utils/src/main/java/org/onap/policy/common/utils/services/OrderedServiceImpl.java b/utils/src/main/java/org/onap/policy/common/utils/services/OrderedServiceImpl.java
new file mode 100644
index 00000000..bbd30220
--- /dev/null
+++ b/utils/src/main/java/org/onap/policy/common/utils/services/OrderedServiceImpl.java
@@ -0,0 +1,135 @@
+/*
+ * ============LICENSE_START=======================================================
+ * utils
+ * ================================================================================
+ * Copyright (C) 2019 AT&T Intellectual Property. 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
+ *
+ * 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.
+ * ============LICENSE_END=========================================================
+ */
+
+package org.onap.policy.common.utils.services;
+
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.ServiceLoader;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * This class is a template for building a sorted list of service instances,
+ * which are discovered and created using 'ServiceLoader'.
+ */
+public class OrderedServiceImpl<T extends OrderedService> {
+ // logger
+ private static Logger logger = LoggerFactory.getLogger(OrderedServiceImpl.class);
+
+ // sorted list of instances implementing the service
+ private List<T> implementers = null;
+
+ // 'ServiceLoader' that is used to discover and create the services
+ private ServiceLoader<T> serviceLoader = null;
+
+ // use this to ensure that we only use one unique instance of each class
+ @SuppressWarnings("rawtypes")
+ private static HashMap<Class,OrderedService> classToSingleton = new HashMap<>();
+
+ /**
+ * Constructor - create the 'ServiceLoader' instance.
+ *
+ * @param clazz the class object associated with 'T' (I supposed it could
+ * be a subclass, but I'm not sure this is useful)
+ */
+ public OrderedServiceImpl(Class<T> clazz) {
+ // This constructor wouldn't be needed if 'T.class' was legal
+ serviceLoader = ServiceLoader.load(clazz);
+ }
+
+ /**
+ * Get List of implementers.
+ *
+ * @return the sorted list of services implementing interface 'T' discovered
+ * by 'ServiceLoader'.
+ */
+ public synchronized List<T> getList() {
+ if (implementers == null) {
+ rebuildList();
+ }
+ return implementers;
+ }
+
+ /**
+ * This method is called by 'getList', but could also be called directly if
+ * we were running with a 'ClassLoader' that supported the dynamic addition
+ * of JAR files. In this case, it could be invoked in order to discover any
+ * new services implementing interface 'T'. This is probably a relatively
+ * expensive operation in terms of CPU and elapsed time, so it is best if it
+ * isn't invoked too frequently.
+ *
+ * @return the sorted list of services implementing interface 'T' discovered
+ * by 'ServiceLoader'.
+ */
+ @SuppressWarnings("unchecked")
+ public synchronized List<T> rebuildList() {
+ // build a list of all of the current implementors
+ List<T> tmp = new LinkedList<>();
+ for (T service : serviceLoader) {
+ tmp.add((T)getSingleton(service));
+ }
+
+ // Sort the list according to sequence number, and then alphabetically
+ // according to full class name.
+ Collections.sort(tmp, (o1, o2) -> {
+ int s1 = o1.getSequenceNumber();
+ int s2 = o2.getSequenceNumber();
+ if (s1 < s2) {
+ return -1;
+ } else if (s1 > s2) {
+ return 1;
+ } else {
+ return o1.getClass().getName().compareTo(o2.getClass().getName());
+ }
+ });
+
+ // create an unmodifiable version of this list
+ implementers = Collections.unmodifiableList(tmp);
+ logger.info("***** OrderedServiceImpl implementers:\n {}", implementers);
+ return implementers;
+ }
+
+ /**
+ * If a service implements multiple APIs managed by 'ServiceLoader', a
+ * separate instance is created for each API. This method ensures that
+ * the first instance is used in all of the lists.
+ *
+ * @param service this is the object created by ServiceLoader
+ * @return the object to use in place of 'service'. If 'service' is the first
+ * object of this class created by ServiceLoader, it is returned. If not,
+ * the object of this class that was initially created is returned
+ * instead.
+ */
+ private static synchronized OrderedService getSingleton(OrderedService service) {
+ // see if we already have an instance of this class
+ OrderedService rval = classToSingleton.get(service.getClass());
+ if (rval == null) {
+ // No previous instance of this class exists -- use the supplied
+ // instance, and place it in the table.
+ rval = service;
+ classToSingleton.put(service.getClass(), service);
+ }
+ return rval;
+ }
+}