+package org.opendaylight.controller.config.spi;
+
+import org.opendaylight.controller.config.api.DependencyResolver;
+import org.opendaylight.controller.config.api.ModuleIdentifier;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Base implementation of Module. This implementation contains base logic for Module reconfiguration with associated fields.
+ * @param <M> Type of module implementation. Enables easier implementation for the {@link #isSame} method
+ */
+public abstract class AbstractModule<M extends AbstractModule<M>> implements org.opendaylight.controller.config.spi.Module {
+
+ private static final Logger LOG = LoggerFactory.getLogger(AbstractModule.class);
+
+ private final M oldModule;
+ private final AutoCloseable oldInstance;
+ protected final ModuleIdentifier identifier;
+ private AutoCloseable instance;
+ protected final DependencyResolver dependencyResolver;
+
+ /**
+ * Called when module is configured.
+ *
+ * @param identifier id of current instance.
+ * @param dependencyResolver resolver used in dependency injection and validation.
+ */
+ public AbstractModule(ModuleIdentifier identifier, DependencyResolver dependencyResolver) {
+ this(identifier, dependencyResolver, null, null);
+ }
+
+ /**
+ * Called when module is reconfigured.
+ *
+ * @param identifier id of current instance.
+ * @param dependencyResolver resolver used in dependency injection and validation.
+ * @param oldModule old instance of module that is being reconfigred(replaced) by current instance. The old instance can be examined for reuse.
+ * @param oldInstance old instance wrapped by the old module. This is the resource that is actually being reused if possible or closed otherwise.
+ */
+ public AbstractModule(ModuleIdentifier identifier, DependencyResolver dependencyResolver, M oldModule, AutoCloseable oldInstance) {
+ this.identifier = identifier;
+ this.dependencyResolver = dependencyResolver;
+ this.oldModule = oldModule;
+ this.oldInstance = oldInstance;
+ }
+
+ @Override
+ public ModuleIdentifier getIdentifier() {
+ return identifier;
+ }
+
+ /**
+ *
+ * General algorithm for spawning/closing and reusing wrapped instances.
+ *
+ * @return current instance of wrapped resource either by reusing the old one (if present) or constructing a brand new.
+ */
+ @Override
+ public final AutoCloseable getInstance() {
+ if(instance==null) {
+ if(oldInstance!=null && canReuseInstance(oldModule)) {
+ resolveDependencies();
+ instance = reuseInstance(oldInstance);
+ } else {
+ if(oldInstance!=null) {
+ try {
+ oldInstance.close();
+ } catch(Exception e) {
+ LOG.error("An error occurred while closing old instance {} for module {}", oldInstance, getIdentifier(), e);
+ }
+ }
+ resolveDependencies();
+ instance = createInstance();
+ if (instance == null) {
+ throw new IllegalStateException("Error in createInstance - null is not allowed as return value. Module: " + getIdentifier());
+ }
+ }
+ }
+ return instance;
+ }
+
+ /**
+ * @return Brand new instance of wrapped class in case no previous instance is present or reconfiguration is impossible.
+ */
+ protected abstract AutoCloseable createInstance();
+
+ @Override
+ public final boolean canReuse(Module oldModule) {
+ // Just cast into a specific instance
+ // TODO unify this method with canReuseInstance (required Module interface to be generic which requires quite a lot of changes)
+ return getClass().isInstance(oldModule) ? canReuseInstance((M) oldModule) : false;
+ }
+
+ /**
+ *
+ * Users are welcome to override this method to provide custom logic for advanced reusability detection.
+ *
+ * @param oldModule old instance of a Module
+ * @return true if the old instance is reusable false if a new one should be spawned
+ */
+ protected abstract boolean canReuseInstance(final M oldModule);
+
+ /**
+ * By default the oldInstance is returned since this method is by default called only if the oldModule had the same configuration and dependencies configured.
+ * Users are welcome to override this method to provide custom logic for advanced reusability.
+ *
+ * @param oldInstance old instance of a class wrapped by the module
+ * @return reused instance
+ */
+ protected AutoCloseable reuseInstance(AutoCloseable oldInstance) {
+ // implement if instance reuse should be supported. Override canReuseInstance to change the criteria.
+ return oldInstance;
+ }
+
+ /**
+ * Inject all the dependencies using dependency resolver instance.
+ */
+ protected abstract void resolveDependencies();
+}
Code Review / controller.git / commitdiff