Relax Plugin construction (remove dependency on PluginWrapper) (#512)

demo/api/src/main/java/org/pf4j/demo/api/DemoPlugin.java

@@ -0,0 +1,35 @@
+/*
+ * Copyright (C) 2012-present the original author or authors.
+ *
+ * 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 org.pf4j.demo.api;
+
+import org.pf4j.Plugin;
+
+/**
+ * Base {@link Plugin} for all demo plugins.
+ *
+ * @author Decebal Suiu
+ */
+public abstract class DemoPlugin extends Plugin {
+
+    protected final PluginContext context;
+
+    protected DemoPlugin(PluginContext context) {
+        super();
+
+        this.context = context;
+    }
+
+}

demo/api/src/main/java/org/pf4j/demo/api/PluginContext.java

@@ -0,0 +1,39 @@
+/*
+ * Copyright (C) 2012-present the original author or authors.
+ *
+ * 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 org.pf4j.demo.api;
+
+import org.pf4j.RuntimeMode;
+
+/**
+ * An instance of this class is provided to plugins in their constructor.
+ * It's safe for plugins to keep a reference to the instance for later use.
+ * This class facilitates communication with application and plugin manager.
+ *
+ * @author Decebal Suiu
+ */
+public class PluginContext {
+
+    private final RuntimeMode runtimeMode;
+
+    public PluginContext(RuntimeMode runtimeMode) {
+        this.runtimeMode = runtimeMode;
+    }
+
+    public RuntimeMode getRuntimeMode() {
+        return runtimeMode;
+    }
+
+}

demo/app/src/main/java/org/pf4j/demo/Boot.java

@@ -16,7 +16,6 @@
 package org.pf4j.demo;
 
 import org.apache.commons.lang.StringUtils;
-import org.pf4j.DefaultPluginManager;
 import org.pf4j.PluginManager;
 import org.pf4j.PluginWrapper;
 import org.pf4j.demo.api.Greeting;
@@ -40,7 +39,7 @@ public class Boot {
         printLogo();
 
         // create the plugin manager
-        PluginManager pluginManager = createPluginManager();
+        PluginManager pluginManager = new DemoPluginManager();
 
         // load the plugins
         pluginManager.loadPlugins();
@@ -129,23 +128,4 @@ public class Boot {
         log.info(StringUtils.repeat("#", 40));
     }
 
-    private static PluginManager createPluginManager() {
-        return new DefaultPluginManager();
-
-        // use below plugin manager instance if you want to enable ServiceProviderExtensionFinder
-        /*
-        return new DefaultPluginManager() {
-
-            @Override
-            protected ExtensionFinder createExtensionFinder() {
-                DefaultExtensionFinder extensionFinder = (DefaultExtensionFinder) super.createExtensionFinder();
-                extensionFinder.addServiceProviderExtensionFinder(); // to activate "HowdyGreeting" extension
-
-                return extensionFinder;
-            }
-
-        };
-        */
-    }
-
 }

demo/app/src/main/java/org/pf4j/demo/DemoPluginFactory.java

@@ -0,0 +1,40 @@
+/*
+ * Copyright (C) 2012-present the original author or authors.
+ *
+ * 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 org.pf4j.demo;
+
+import org.pf4j.DefaultPluginFactory;
+import org.pf4j.Plugin;
+import org.pf4j.PluginWrapper;
+import org.pf4j.demo.api.PluginContext;
+
+import java.lang.reflect.Constructor;
+
+class DemoPluginFactory extends DefaultPluginFactory {
+
+    @Override
+    protected Plugin createInstance(Class<?> pluginClass, PluginWrapper pluginWrapper) {
+        PluginContext context = new PluginContext(pluginWrapper.getRuntimeMode());
+        try {
+            Constructor<?> constructor = pluginClass.getConstructor(PluginContext.class);
+            return (Plugin) constructor.newInstance(context);
+        } catch (Exception e) {
+            log.error(e.getMessage(), e);
+        }
+
+        return null;
+    }
+
+}

demo/app/src/main/java/org/pf4j/demo/DemoPluginManager.java

@@ -0,0 +1,42 @@
+/*
+ * Copyright (C) 2012-present the original author or authors.
+ *
+ * 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 org.pf4j.demo;
+
+import org.pf4j.DefaultExtensionFinder;
+import org.pf4j.DefaultPluginFactory;
+import org.pf4j.DefaultPluginManager;
+import org.pf4j.ExtensionFinder;
+import org.pf4j.PluginFactory;
+
+class DemoPluginManager extends DefaultPluginManager {
+
+    // Use below code if you want to enable ServiceProviderExtensionFinder
+    /*
+    @Override
+    protected ExtensionFinder createExtensionFinder() {
+        DefaultExtensionFinder extensionFinder = (DefaultExtensionFinder) super.createExtensionFinder();
+        extensionFinder.addServiceProviderExtensionFinder(); // to activate "HowdyGreeting" extension
+
+        return extensionFinder;
+    }
+    */
+
+    @Override
+    protected PluginFactory createPluginFactory() {
+        return new DemoPluginFactory();
+    }
+
+}

demo/plugins/plugin1/src/main/java/org/pf4j/demo/welcome/WelcomePlugin.java

@@ -16,27 +16,26 @@
 package org.pf4j.demo.welcome;
 
 import org.apache.commons.lang.StringUtils;
-
-import org.pf4j.PluginWrapper;
+import org.pf4j.Extension;
 import org.pf4j.RuntimeMode;
+import org.pf4j.demo.api.DemoPlugin;
 import org.pf4j.demo.api.Greeting;
-import org.pf4j.Extension;
-import org.pf4j.Plugin;
+import org.pf4j.demo.api.PluginContext;
 
 /**
  * @author Decebal Suiu
  */
-public class WelcomePlugin extends Plugin {
+public class WelcomePlugin extends DemoPlugin {
 
-    public WelcomePlugin(PluginWrapper wrapper) {
-        super(wrapper);
+    public WelcomePlugin(PluginContext context) {
+        super(context);
     }
 
     @Override
     public void start() {
         log.info("WelcomePlugin.start()");
         // for testing the development mode
-        if (RuntimeMode.DEVELOPMENT.equals(wrapper.getRuntimeMode())) {
+        if (RuntimeMode.DEVELOPMENT.equals(context.getRuntimeMode())) {
             log.info(StringUtils.upperCase("WelcomePlugin"));
         }
     }

demo/plugins/plugin2/src/main/java/org/pf4j/demo/hello/HelloPlugin.java

@@ -16,19 +16,19 @@
 package org.pf4j.demo.hello;
 
 import org.pf4j.Extension;
-import org.pf4j.Plugin;
-import org.pf4j.PluginWrapper;
+import org.pf4j.demo.api.DemoPlugin;
 import org.pf4j.demo.api.Greeting;
+import org.pf4j.demo.api.PluginContext;
 
 /**
  * A very simple plugin.
  *
  * @author Decebal Suiu
  */
-public class HelloPlugin extends Plugin {
+public class HelloPlugin extends DemoPlugin {
 
-    public HelloPlugin(PluginWrapper wrapper) {
-        super(wrapper);
+    public HelloPlugin(PluginContext context) {
+        super(context);
     }
 
     @Override

pf4j/src/main/java/org/pf4j/DefaultPluginFactory.java

@@ -23,18 +23,16 @@ import java.lang.reflect.Modifier;
 
 /**
  * The default implementation for {@link PluginFactory}.
- * It uses {@link Class#newInstance()} method.
+ * It uses {@link Constructor#newInstance(Object...)} method.
  *
  * @author Decebal Suiu
  */
 public class DefaultPluginFactory implements PluginFactory {
 
-    private static final Logger log = LoggerFactory.getLogger(DefaultPluginFactory.class);
+    protected static final Logger log = LoggerFactory.getLogger(DefaultPluginFactory.class);
 
     /**
-     * Creates a plugin instance. If an error occurs than that error is logged and the method returns null.
-     * @param pluginWrapper
-     * @return
+     * Creates a plugin instance. If an error occurs than that error is logged and the method returns {@code null}.
      */
     @Override
     public Plugin create(final PluginWrapper pluginWrapper) {
@@ -58,10 +56,26 @@ public class DefaultPluginFactory implements PluginFactory {
             return null;
         }
 
-        // create the plugin instance
+        return createInstance(pluginClass, pluginWrapper);
+    }
+
+    protected Plugin createInstance(Class<?> pluginClass, PluginWrapper pluginWrapper) {
         try {
             Constructor<?> constructor = pluginClass.getConstructor(PluginWrapper.class);
             return (Plugin) constructor.newInstance(pluginWrapper);
+        } catch (NoSuchMethodException e) {
+            return createUsingNoParametersConstructor(pluginClass);
+       } catch (Exception e) {
+            log.error(e.getMessage(), e);
+        }
+
+        return null;
+    }
+
+    protected Plugin createUsingNoParametersConstructor(Class<?> pluginClass) {
+        try {
+            Constructor<?> constructor = pluginClass.getConstructor();
+            return (Plugin) constructor.newInstance();
         } catch (Exception e) {
             log.error(e.getMessage(), e);
         }

pf4j/src/main/java/org/pf4j/Plugin.java

@@ -33,14 +33,20 @@ public class Plugin {
 
     /**
      * Wrapper of the plugin.
+     * @deprecated Use application custom {@code PluginContext} instead of {@code PluginWrapper}.
+     * See demo for more details.
      */
+    @Deprecated
     protected PluginWrapper wrapper;
 
     /**
      * Constructor to be used by plugin manager for plugin instantiation.
      * Your plugins have to provide constructor with this exact signature to
      * be successfully loaded by manager.
+     * @deprecated Use application custom {@code PluginContext} instead of {@code PluginWrapper}.
+     * See demo for more details.
      */
+    @Deprecated
     public Plugin(final PluginWrapper wrapper) {
         if (wrapper == null) {
             throw new IllegalArgumentException("Wrapper cannot be null");
@@ -49,9 +55,15 @@ public class Plugin {
         this.wrapper = wrapper;
     }
 
+    public Plugin() {
+    }
+
     /**
      * Retrieves the wrapper of this plug-in.
+     * @deprecated Use application custom {@code PluginContext} instead of {@code PluginWrapper}.
+     * See demo for more details.
      */
+    @Deprecated
     public final PluginWrapper getWrapper() {
         return wrapper;
     }

pf4j/src/main/java/org/pf4j/SecurePluginManagerWrapper.java

@@ -10,10 +10,13 @@ import java.util.stream.Collectors;
 
 /**
  * Use this class to wrap the original plugin manager to prevent full access from within plugins.
- * Override AbstractPluginManager.createPluginWrapper to use this class
- * @author Wolfram Haussig
+ * Override AbstractPluginManager.createPluginWrapper to use this class.
+ * @deprecated Use application custom {@code PluginContext} instead of {@code PluginWrapper} to communicate with {@link Plugin}.
+ * See demo for more details.
  *
+ * @author Wolfram Haussig
  */
+@Deprecated()
 public class SecurePluginManagerWrapper implements PluginManager {
 
     private static final String PLUGIN_PREFIX = "Plugin ";
@@ -38,7 +41,7 @@ public class SecurePluginManagerWrapper implements PluginManager {
     /**
      * constructor
      * @param original the original plugin manager
-     * @param currentPlugin the current pluginId
+     * @param currentPluginId the current pluginId
      */
     public SecurePluginManagerWrapper(PluginManager original, String currentPluginId) {
         this.original = original;

pf4j/src/test/java/org/pf4j/DefaultPluginFactoryTest.java

@@ -17,6 +17,7 @@ package org.pf4j;
 
 import org.junit.jupiter.api.Test;
 import org.pf4j.test.AnotherFailTestPlugin;
+import org.pf4j.test.AnotherTestPlugin;
 import org.pf4j.test.FailTestPlugin;
 import org.pf4j.test.TestPlugin;
 
@@ -48,6 +49,22 @@ public class DefaultPluginFactoryTest {
         assertThat(result, instanceOf(TestPlugin.class));
     }
 
+    @Test
+    public void pluginConstructorNoParameters() {
+        PluginDescriptor pluginDescriptor = mock(PluginDescriptor.class);
+        when(pluginDescriptor.getPluginClass()).thenReturn(AnotherTestPlugin.class.getName());
+
+        PluginWrapper pluginWrapper = mock(PluginWrapper.class);
+        when(pluginWrapper.getDescriptor()).thenReturn(pluginDescriptor);
+        when(pluginWrapper.getPluginClassLoader()).thenReturn(getClass().getClassLoader());
+
+        PluginFactory pluginFactory = new DefaultPluginFactory();
+
+        Plugin result = pluginFactory.create(pluginWrapper);
+        assertNotNull(result);
+        assertThat(result, instanceOf(AnotherTestPlugin.class));
+    }
+
     @Test
     public void testCreateFail() {
         PluginDescriptor pluginDescriptor = mock(PluginDescriptor.class);

pf4j/src/test/java/org/pf4j/test/AnotherFailTestPlugin.java

@@ -19,7 +19,7 @@ import org.pf4j.Plugin;
 
 /**
  * A wrong {@link org.pf4j.Plugin}.
- * It's wrong because it doesn't contain a constructor with one parameter ({@link org.pf4j.PluginWrapper} as parameter type).
+ * It's wrong because it calls super constructor with {@code null} for ({@link org.pf4j.PluginWrapper} parameter).
  *
  * @author Mario Franco
  */

pf4j/src/test/java/org/pf4j/test/AnotherTestPlugin.java

@@ -0,0 +1,34 @@
+/*
+ * Copyright (C) 2012-present the original author or authors.
+ *
+ * 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 org.pf4j.test;
+
+import org.pf4j.Plugin;
+
+/**
+ * A simple {@link Plugin}.
+ *
+ * In real applications you don't need to create a plugin like this if you are not interested in lifecycle events.
+ * {@code PF4J} will automatically create a plugin similar to this (empty / dummy) if no class plugin is specified.
+ *
+ * @author Decebal Suiu
+ */
+public class AnotherTestPlugin extends Plugin {
+
+    public AnotherTestPlugin() {
+        super();
+    }
+
+}