Extension storage based on Java Service Provider (META-INf/services)

demo/app/src/main/java/ro/fortsoft/pf4j/demo/HowdyGreeting.java

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+/*
+ * Copyright 2015 Decebal Suiu
+ *
+ * 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.
+ */
+package ro.fortsoft.pf4j.demo;
+
+import ro.fortsoft.pf4j.demo.api.Greeting;
+
+/**
+ * A Service Implementation (no @Extension) declared via Java Service Provider mechanism (using META-INF/services).
+ *
+ * @author Decebal Suiu
+ */
+public class HowdyGreeting implements Greeting {
+
+    @Override
+    public String getGreeting() {
+        return "Howdy";
+    }
+
+}

demo/app/src/main/resources/META-INF/services/ro.fortsoft.pf4j.demo.api.Greeting

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+ro.fortsoft.pf4j.demo.HowdyGreeting

pf4j/src/main/java/ro/fortsoft/pf4j/AbstractExtensionFinder.java

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+/*
+ * Copyright 2015 Decebal Suiu
+ *
+ * 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.
+ */
+package ro.fortsoft.pf4j;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+
+/**
+ * @author Decebal Suiu
+ */
+public abstract class AbstractExtensionFinder implements ExtensionFinder, PluginStateListener {
+
+    protected static final Logger log = LoggerFactory.getLogger(AbstractExtensionFinder.class);
+
+    protected PluginManager pluginManager;
+    protected volatile Map<String, Set<String>> entries; // cache by pluginId
+
+    public AbstractExtensionFinder(PluginManager pluginManager) {
+        this.pluginManager = pluginManager;
+    }
+
+    public abstract Map<String, Set<String>> readPluginsStorages();
+
+    public abstract Map<String, Set<String>> readClasspathStorages();
+
+    @Override
+	public <T> List<ExtensionWrapper<T>> find(Class<T> type) {
+		log.debug("Finding extensions for extension point '{}'", type.getName());
+        Map<String, Set<String>> entries = getEntries();
+
+        List<ExtensionWrapper<T>> result = new ArrayList<>();
+        for (Map.Entry<String, Set<String>> entry : entries.entrySet()) {
+            String pluginId = entry.getKey();
+
+            if (pluginId != null) {
+                PluginWrapper pluginWrapper = pluginManager.getPlugin(pluginId);
+                if (PluginState.STARTED != pluginWrapper.getPluginState()) {
+                    continue;
+                }
+            }
+
+            for (String className : entry.getValue()) {
+                try {
+                    ClassLoader classLoader;
+                    if (pluginId != null) {
+                        classLoader = pluginManager.getPluginClassLoader(pluginId);
+                    } else {
+                        classLoader = getClass().getClassLoader();
+                    }
+                    log.debug("Loading class '{}' using class loader '{}'", className, classLoader);
+                    Class<?> extensionClass = classLoader.loadClass(className);
+
+                    log.debug("Checking extension type '{}'", className);
+                    if (type.isAssignableFrom(extensionClass)) {
+                        ExtensionDescriptor descriptor = new ExtensionDescriptor();
+                        int ordinal = 0;
+                        if (extensionClass.isAnnotationPresent(Extension.class)) {
+                            ordinal = extensionClass.getAnnotation(Extension.class).ordinal();
+                        }
+                        descriptor.setOrdinal(ordinal);
+                        descriptor.setExtensionClass(extensionClass);
+
+                        ExtensionWrapper extensionWrapper = new ExtensionWrapper<>(descriptor);
+                        extensionWrapper.setExtensionFactory(pluginManager.getExtensionFactory());
+                        result.add(extensionWrapper);
+                        log.debug("Added extension '{}' with ordinal {}", className, ordinal);
+                    } else {
+                        log.debug("'{}' is not an extension for extension point '{}'", className, type.getName());
+                    }
+                } catch (ClassNotFoundException e) {
+                    log.error(e.getMessage(), e);
+                }
+            }
+        }
+
+        if (entries.isEmpty()) {
+        	log.debug("No extensions found for extension point '{}'", type.getName());
+        } else {
+        	log.debug("Found {} extensions for extension point '{}'", result.size(), type.getName());
+        }
+
+        // sort by "ordinal" property
+        Collections.sort(result);
+
+		return result;
+	}
+
+    @Override
+    public Set<String> findClassNames(String pluginId) {
+        return getEntries().get(pluginId);
+    }
+
+    @Override
+	public void pluginStateChanged(PluginStateEvent event) {
+        // TODO optimize (do only for some transitions)
+        // clear cache
+        entries = null;
+    }
+
+    private Map<String, Set<String>> readStorages() {
+        Map<String, Set<String>> result = new LinkedHashMap<>();
+
+        result.putAll(readClasspathStorages());
+        result.putAll(readPluginsStorages());
+
+        return result;
+    }
+
+    private Map<String, Set<String>> getEntries() {
+        if (entries == null) {
+            entries = readStorages();
+        }
+
+        return entries;
+    }
+
+}