Refactored the dynamic module loading mechanism

The dynamic module loader no uses its own class loader which can add
files from multiple directories. It is based on the standard
URLClassLoader. 

The folder from which modules are loaded dynamically is no longer
provided via command line arguments but via a system property. The name
of the property is flux.pluginsdir; it expects an absolute path name.
The default setting for the module directory has been removed. If the
property is not set, no module directory is used.

In addition, a second directory whose contents are loaded dynamically,
is introduced for loading libraries typically provided by the user such
as JDBC drivers or JNDI providers. This directory is configured via the
flux.provideddir property.

The maven config has been changed to place libraries with scope provided
in the provided-libs dir instead of the standard libs dir. These
libraries are not added to the class path.

As first libary, the scope of the slf4j-log4j dependency has been
changed into a provided dependency.

Author: cboehme

pom.xml

@@ -105,7 +105,7 @@
 								used to specify that all needed libraries are found under lib/ directory. -->
 							<classpathPrefix>lib/</classpathPrefix>
 							<!-- Specifies the main class of the application -->
-							<mainClass>org.culturegraph.mf.cmdline.Flux</mainClass>
+							<mainClass>org.culturegraph.mf.runner.Flux</mainClass>
 						</manifest>
 						<manifestEntries>
 							<git-commit>${buildNumber}</git-commit>
@@ -222,22 +222,26 @@
 			<version>2.0.0-SNAPSHOT</version>
 		</dependency>
 
+		<dependency>
+			<groupId>org.slf4j</groupId>
+			<artifactId>slf4j-api</artifactId>
+			<version>1.7.6</version>
+		</dependency>
+
 		<dependency>
 			<groupId>org.slf4j</groupId>
 			<artifactId>slf4j-log4j12</artifactId>
 			<version>1.7.2</version>
-			<scope>runtime</scope>
+			<scope>provided</scope>
 		</dependency>
 
-
 		<dependency>
 			<groupId>junit</groupId>
 			<artifactId>junit</artifactId>
 			<version>4.11</version>
 			<scope>test</scope>
 		</dependency>
 
-	
 	</dependencies>
 
 	<profiles>

src/main/assembly/assembly.xml

@@ -9,15 +9,25 @@
 		<format>zip</format>
 	</formats>
 
-	<!-- Adds dependencies to distribution package under lib directory -->
 	<dependencySets>
+
 		<dependencySet>
 			<useProjectArtifact>false</useProjectArtifact>
 			<outputDirectory>lib</outputDirectory>
 			<unpack>false</unpack>
 			<directoryMode>0755</directoryMode>
 			<fileMode>0644</fileMode>
 		</dependencySet>
+
+		<dependencySet>
+			<scope>provided</scope>
+			<useProjectArtifact>false</useProjectArtifact>
+			<outputDirectory>provided-libs</outputDirectory>
+			<unpack>false</unpack>
+			<directoryMode>0755</directoryMode>
+			<fileMode>0644</fileMode>
+		</dependencySet>
+
 	</dependencySets>
 
 	<fileSets>

src/main/config/java-options.conf

@@ -1,13 +1,15 @@
-# JVM options in this file are passed to the java command. 
-# Environment variables can be specified by prefixing them 
-# with $ (e.g. $VAR). The variable $METAFACTURE_HOME refers 
-# to the folder containing the flux start-up script. 
-# Undefined variables remain in the configuration. 
-
--Xmx512m
--Dlog4j.configuration="file:///$METAFACTURE_HOME/config/log4j.xml"
-
-# Append additional options defined in the 
-# environment (The start-up script ensures 
-# that this variable is always defined):
-$FLUX_JAVA_OPTIONS
+# JVM options in this file are passed to the java command. 
+# Environment variables can be specified by prefixing them 
+# with $ (e.g. $VAR). The variable $METAFACTURE_HOME refers 
+# to the folder containing the flux start-up script. 
+# Undefined variables remain in the configuration. 
+
+-Xmx512m
+-Dlog4j.configuration="file:///$METAFACTURE_HOME/config/log4j.xml"
+-Dflux.pluginsdir="$METAFACTURE_HOME/plugins"
+-Dflux.provideddir="$METAFACTURE_HOME/provided-libs"
+
+# Append additional options defined in the 
+# environment (The start-up script ensures 
+# that this variable is always defined):
+$FLUX_JAVA_OPTIONS

src/main/config/log4j.xml

@@ -9,10 +9,13 @@
 		</layout>
 	</appender>
 
-	
 	<root>
 		<priority value="info" />
 		<appender-ref ref="stdout" />
 	</root>
 
+	 <logger name="org.culturegraph.mf.runner.util.DirectoryClassLoader">
+		<priority value="warning" />
+	</logger>
+
 </log4j:configuration>

src/main/java/org/culturegraph/mf/cmdline/Flux.java

@@ -0,0 +1,106 @@
+/*
+ *  Copyright 2013 Deutsche Nationalbibliothek
+ *
+ *  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.culturegraph.mf.runner;
+
+import java.io.File;
+import java.io.IOException;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+import org.antlr.runtime.RecognitionException;
+import org.culturegraph.mf.flux.FluxCompiler;
+import org.culturegraph.mf.flux.parser.FluxProgramm;
+import org.culturegraph.mf.runner.util.DirectoryClassLoader;
+import org.culturegraph.mf.util.ResourceUtil;
+
+/**
+ * @author Markus Michael Geipel
+ * @author Christoph Böhme
+ *
+ */
+public final class Flux {
+
+	public static final String PLUGINS_DIR_PROPERTY = "flux.pluginsdir";
+	public static final String PROVIDED_DIR_PROPERTY = "flux.provideddir";
+
+	private static final Pattern VAR_PATTERN = Pattern.compile("([^=]*)=(.*)");
+	private static final String SCRIPT_HOME = "FLUX_DIR";
+
+	private Flux() {
+		// No instances allowed
+	}
+
+	public static void main(final String[] args) throws IOException, RecognitionException {
+
+		loadCustomJars();
+
+		if (args.length < (1)) {
+			FluxProgramm.printHelp(System.out);
+			System.exit(2);
+		} else {
+
+			final File fluxFile = new File(args[0]);
+			if (!fluxFile.exists()) {
+				System.err.println("File not found: " + args[0]);
+				System.exit(1);
+				return;
+			}
+
+			// get variable assignments
+			final Map<String, String> vars = new HashMap<String, String>();
+			vars.put(SCRIPT_HOME, fluxFile.getAbsoluteFile().getParent()
+					+ System.getProperty("file.separator"));
+
+			for (int i = 1; i < args.length; ++i) {
+				final Matcher matcher = VAR_PATTERN.matcher(args[i]);
+				if (!matcher.find()) {
+					FluxProgramm.printHelp(System.err);
+					return;
+				}
+				vars.put(matcher.group(1), matcher.group(2));
+			}
+
+			// run parser and builder
+			FluxCompiler.compile(ResourceUtil.getStream(fluxFile), vars).start();
+		}
+	}
+
+	private static void loadCustomJars() {
+		final DirectoryClassLoader dirClassLoader = new DirectoryClassLoader(getClassLoader());
+
+		final String pluginsDir = System.getProperty(PLUGINS_DIR_PROPERTY);
+		if (pluginsDir != null) {
+			dirClassLoader.addDirectory(new File(pluginsDir));
+		}
+		final String providedDir = System.getProperty(PROVIDED_DIR_PROPERTY);
+		if (providedDir != null) {
+			dirClassLoader.addDirectory(new File(providedDir));
+		}
+
+		setClassLoader(dirClassLoader);
+	}
+
+	private static ClassLoader getClassLoader() {
+		return Thread.currentThread().getContextClassLoader();
+	}
+
+	private static void setClassLoader(final ClassLoader classLoader) {
+		Thread.currentThread().setContextClassLoader(classLoader);
+	}
+
+}

src/main/java/org/culturegraph/mf/runner/Flux.java

@@ -13,7 +13,7 @@
  *  See the License for the specific language governing permissions and
  *  limitations under the License.
  */
-package org.culturegraph.mf.cmdline;
+package org.culturegraph.mf.runner;
 
 import java.io.File;
 import java.io.FileOutputStream;