Issue GoogleCloudPlatform#231 - Overhauling logging handlers for java…

….util.logging

+ Slf4j is now present, capturing logging events from:
  * commons-logging
  * log4j
  * java.util.logging
  * slf4j-api
+ Slf4j is configured to use java.util.logging as its source
  for output, appending, handlers, and configuration
+ Introducing appengine-java-logging CoreLogging with ability
  to configure user/app logging then system logging in a
  consisten way.

appengine-java-logging/pom.xml

@@ -29,12 +29,46 @@
   <packaging>jar</packaging>
   <description>Support code for writing log files compatible with Google App Engine</description>
 
+  <properties>
+    <slf4j.version>1.7.16</slf4j.version>
+  </properties>
+
   <dependencies>
+    <!-- Logging: API -->
+    <dependency>
+      <groupId>org.slf4j</groupId>
+      <artifactId>slf4j-api</artifactId>
+      <version>${slf4j.version}</version>
+    </dependency>
+    <!-- Logging: Capturing Layers -->
+    <dependency>
+      <groupId>org.slf4j</groupId>
+      <artifactId>jcl-over-slf4j</artifactId>
+      <version>${slf4j.version}</version>
+    </dependency>
+    <dependency>
+      <groupId>org.slf4j</groupId>
+      <artifactId>log4j-over-slf4j</artifactId>
+      <version>${slf4j.version}</version>
+    </dependency>
+    <!-- Logging: Output / Appender Layer -->
+    <dependency>
+      <groupId>org.slf4j</groupId>
+      <artifactId>slf4j-jdk14</artifactId>
+      <version>${slf4j.version}</version>
+    </dependency>
+
     <dependency>
       <groupId>com.google.code.gson</groupId>
       <artifactId>gson</artifactId>
     </dependency>
 
+    <dependency>
+      <groupId>org.hamcrest</groupId>
+      <artifactId>hamcrest-library</artifactId>
+      <scope>test</scope>
+    </dependency>
+
     <dependency>
       <groupId>junit</groupId>
       <artifactId>junit</artifactId>

appengine-java-logging/src/main/java/com/google/apphosting/logging/CoreLogging.java

@@ -0,0 +1,102 @@
+/*
+ * Copyright 2016 Google Inc. 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.
+ */
+
+package com.google.apphosting.logging;
+
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.IOException;
+import java.util.ServiceLoader;
+import java.util.logging.LogManager;
+
+/**
+ * Logging Core behavior.
+ */
+public class CoreLogging {
+  public static final String JAVA_UTIL_LOGGING_CONFIG_PROPERTY = "java.util.logging.config.file";
+
+  /**
+   * Initialize the java.util.logging Environment.
+   * <p>
+   * Order is:
+   * <ol>
+   * <li>Apply App (User) Configuration</li>
+   * <li>Apply System Mandated Configuration</li>
+   * </ol>
+   * </p>
+   *
+   * @param appConfigFile the filename for the (optional) app specific java.util.logging
+   *                      properties file configuration.
+   */
+  public static void init(File appConfigFile) throws IOException {
+    // Use App (User) Configuration specified as a file parameter
+    if (appConfigFile != null && appConfigFile.exists()) {
+      appConfig(appConfigFile);
+    } else {
+      // Use App (User) Configuration specified as a System property
+      String julConfigFile = System.getProperty(JAVA_UTIL_LOGGING_CONFIG_PROPERTY);
+      if (julConfigFile != null) {
+        File configFile = new File(julConfigFile);
+        if (configFile.exists()) {
+          appConfig(configFile);
+        }
+      }
+    }
+
+    // Manually Adjust Configuration to support System Logging Requirements
+    systemConfig();
+  }
+
+  /**
+   * Convenience method for {@link #init(File)}
+   *
+   * @param appConfigFilename the filename of the config file (or null)
+   * @throws IOException if unable to configure the logging
+   */
+  public static void init(String appConfigFilename) throws IOException {
+    File appConfigFile = null;
+    if (appConfigFilename == null) {
+      appConfigFile = new File(appConfigFilename);
+    }
+    init(appConfigFile);
+  }
+
+  private static void appConfig(File configFile) {
+    try (FileInputStream is = new FileInputStream(configFile)) {
+      LogManager logManager = LogManager.getLogManager();
+      logManager.reset();
+      logManager.readConfiguration(is);
+    } catch (SecurityException | IOException e) {
+      System.err.println("Warning: caught exception when reading logging properties: " + configFile
+          .getAbsolutePath());
+      e.printStackTrace(System.err);
+    }
+  }
+
+  /**
+   * Manually Configure the System Level requirements for java.util.logging
+   */
+  private static void systemConfig() throws IOException {
+    // Since System Loggers can arrive from deep within the various compat layers, it
+    // makes sense to use the ServiceLoader to obtain references to specific System loggers
+    // that need to be initialized during this step in the logging initialization.
+
+    ServiceLoader<SystemLogger> serviceLoader = ServiceLoader.load(SystemLogger.class);
+    for (SystemLogger systemLogger : serviceLoader) {
+      systemLogger.configure();
+    }
+  }
+}

appengine-java-logging/src/main/java/com/google/apphosting/logging/SystemLogger.java

@@ -0,0 +1,32 @@
+/*
+ * Copyright 2016 Google Inc. 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.
+ */
+
+package com.google.apphosting.logging;
+
+import java.io.IOException;
+
+/**
+ * Interface for any component wanting to participate in the System Logging level
+ * configuration.
+ */
+public interface SystemLogger {
+  /**
+   * Configure your System Level Logger on this event.
+   *
+   * @throws IOException if unable to configure the System Level Logger
+   */
+  void configure() throws IOException;
+}

appengine-java-logging/src/test/java/com/google/apphosting/logging/CommonsLoggingExample.java

@@ -0,0 +1,37 @@
+/*
+ * Copyright 2016 Google Inc. 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.
+ */
+
+package com.google.apphosting.logging;
+
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+
+import java.util.concurrent.ThreadLocalRandom;
+
+public class CommonsLoggingExample implements Runnable {
+  private static final Log LOG = LogFactory.getLog(CommonsLoggingExample.class);
+
+  @Override
+  public void run() {
+    ThreadLocalRandom rand = ThreadLocalRandom.current();
+    LOG.trace(String.format("A CommonsLogging Trace Event: %d", rand.nextInt()));
+    LOG.debug(String.format("A CommonsLogging Debug Event: %d", rand.nextInt()));
+    LOG.info(String.format("A CommonsLogging Info Event: %d", rand.nextInt()));
+    LOG.warn(String.format("A CommonsLogging Warn Event: %d", rand.nextInt()));
+    LOG.error(String.format("A CommonsLogging Error Event: %d", rand.nextInt()),
+        new RuntimeException("Generic Error"));
+  }
+}

appengine-java-logging/src/test/java/com/google/apphosting/logging/JsonCaptureHandler.java

@@ -0,0 +1,51 @@
+/*
+ * Copyright 2016 Google Inc. 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.
+ */
+
+package com.google.apphosting.logging;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.logging.Handler;
+import java.util.logging.LogRecord;
+
+public class JsonCaptureHandler extends Handler {
+
+  private JsonFormatter formatter;
+  private List<String> events;
+
+  public JsonCaptureHandler() {
+    super();
+    formatter = new JsonFormatter();
+    events = new ArrayList<>();
+  }
+
+  @Override
+  public void publish(LogRecord record) {
+    events.add(formatter.format(record));
+  }
+
+  @Override
+  public void flush() {
+  }
+
+  @Override
+  public void close() throws SecurityException {
+  }
+
+  public List<String> getEvents() {
+    return events;
+  }
+}