#136 UniversalDecompressor hard-codes configuration file location

- removes the hardcoded string PROPERTIES_PATH from `UniversalDecompressor`
- adds a new constructor to `UniversalDecompressor` taking a Path reference for custom XML file configs
- adds new test class `UniversalDecompressorTest`, previously totally untested
- demonstrates the handling of custom `ar` archive approach via decompressor-ar.xml, as 7z is not present on many platforms by default
- adjusts GZipDecompressor / BZip2Decompressor to check both ways to read an archive: classpath or external (file) location
- resolves #136

dkpro-jwpl-parser/src/main/java/org/dkpro/jwpl/parser/Template.java

@@ -55,8 +55,8 @@ public void setParameters(List<String> parameters)
     }
 
     /**
-     * Returns the Position Span of this Template refering to the ContentElement in which the
-     * Template occures. This is mainly the same like Link.getPos(), but a Template does�n know it�s
+     * Returns the Position Span of this Template referring to the ContentElement in which the
+     * Template occurs. This is mainly the same as {@link Link#getPos()}, but a Template doesn't know it's
      * HomeElement.
      */
     public Span getPos()
@@ -72,14 +72,15 @@ public void setPos(Span pos)
         this.pos = pos;
     }
 
+    @Override
     public String toString()
     {
         StringBuilder result = new StringBuilder();
-        result.append("TE_NAME: \"" + name + "\"");
-        result.append("\nTE_PARAMETERS: " + parameters.size());
+        result.append("TE_NAME: \"").append(name).append("\"");
+        result.append("\nTE_PARAMETERS: ").append(parameters.size());
         for (String parameter : parameters)
-            result.append("\nTE_PARAMETER: \"" + parameter + "\"");
-        result.append("\nTE_POS: " + pos);
+            result.append("\nTE_PARAMETER: \"").append(parameter).append("\"");
+        result.append("\nTE_POS: ").append(pos);
         return result.toString();
     }
 }

dkpro-jwpl-wikimachine/src/main/java/org/dkpro/jwpl/wikimachine/decompression/AbstractDecompressor.java

@@ -0,0 +1,60 @@
+/*
+ * Licensed to the Technische Universität Darmstadt under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The Technische Universität Darmstadt
+ * licenses this file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.
+ *
+ * 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.dkpro.jwpl.wikimachine.decompression;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+
+public abstract class AbstractDecompressor implements IDecompressor {
+
+    /**
+     * Attempts to open an {@link InputStream} to an external or internal resource.
+     * In this context, external resources a referenced via a relative or absolute path, including
+     * the actual file name of that resource.
+     * In case only a plain file name is given and no directory or path elements are contained
+     * in {@code resource}, an attempt is made to detect and load the resource from the classpath.
+     *
+     * @param resource References a resource via a path or by its file name only.
+     *                 If {@code null}, this will result in an {@link IOException}.
+     * @return An open {@link InputStream} or {@code null} if {@code resource} could not be found.
+     * 
+     * @throws IOException Thrown if IO errors occurred.
+     */
+    protected InputStream openStream(String resource) throws IOException
+    {
+        if (resource == null) {
+            throw new IOException("Can't load a 'null' resource!");
+        }
+        final InputStream in;
+        final Path file = Paths.get(resource).toAbsolutePath();
+        if (Files.exists(file)) {
+            in = Files.newInputStream(file);
+        } else {
+            in = getContextClassLoader().getResourceAsStream(resource);
+        }
+        return in;
+    }
+
+    private ClassLoader getContextClassLoader()
+    {
+       return Thread.currentThread().getContextClassLoader();
+    }
+}

dkpro-jwpl-wikimachine/src/main/java/org/dkpro/jwpl/wikimachine/decompression/BZip2Decompressor.java

@@ -18,36 +18,25 @@
 package org.dkpro.jwpl.wikimachine.decompression;
 
 import java.io.BufferedInputStream;
-import java.io.FileInputStream;
 import java.io.IOException;
 import java.io.InputStream;
 
 import org.apache.commons.compress.compressors.bzip2.BZip2CompressorInputStream;
 
 /**
- * BZip2 Decompressor (based on Singleton Design Pattern). Uses getInputStream to set up the archive
- * path and returns the InputStream to read from
+ * BZip2 Decompressor (based on Singleton Design Pattern).
+ * Uses {@link IDecompressor#getInputStream(String)} to set up the archive
+ * path and returns the {@link InputStream} to read from.
+ *
+ * @see IDecompressor
  */
-public class BZip2Decompressor
-    implements IDecompressor
+public final class BZip2Decompressor
+    extends AbstractDecompressor implements IDecompressor
 {
 
     @Override
     public InputStream getInputStream(String fileName) throws IOException
     {
-        InputStream outputStream;
-
-        BufferedInputStream inputStream = new BufferedInputStream(new FileInputStream(fileName));
-        /*
-         * skip 2 first bytes (see the documentation of CBZip2InputStream) e.g. here
-         * http://lucene.apache.org/tika/xref/org/apache/tika/parser /pkg/bzip2
-         * /CBZip2InputStream.html
-         */
-        inputStream.skip(2);
-        outputStream = new BZip2CompressorInputStream(inputStream);
-
-        return outputStream;
-
+        return new BZip2CompressorInputStream(new BufferedInputStream(openStream(fileName)));
     }
-
 }

dkpro-jwpl-wikimachine/src/main/java/org/dkpro/jwpl/wikimachine/decompression/GZipDecompressor.java

@@ -17,23 +17,26 @@
  */
 package org.dkpro.jwpl.wikimachine.decompression;
 
-import java.io.FileInputStream;
+import java.io.BufferedInputStream;
 import java.io.IOException;
 import java.io.InputStream;
 import java.util.zip.GZIPInputStream;
 
 /**
- * GZip Decompressor (based on Singleton Design Pattern). Uses getInputStream to set up the archive
- * path and returns the InputStream to read from
+ * GZip Decompressor (based on Singleton Design Pattern).
+ * Uses {@link IDecompressor#getInputStream(String)} to set up the archive
+ * path and returns the {@link InputStream} to read from.
+ *
+ * @see IDecompressor
  */
-public class GZipDecompressor
-    implements IDecompressor
+public final class GZipDecompressor
+    extends AbstractDecompressor implements IDecompressor
 {
 
     @Override
     public InputStream getInputStream(String fileName) throws IOException
     {
-        return new GZIPInputStream(new FileInputStream(fileName));
+        return new GZIPInputStream(new BufferedInputStream(openStream(fileName)));
     }
 
 }

dkpro-jwpl-wikimachine/src/main/java/org/dkpro/jwpl/wikimachine/decompression/IDecompressor.java

@@ -21,11 +21,23 @@
 import java.io.InputStream;
 
 /**
- * The main interface for all Decompressors, which uses a archive file path and returns a
- * InputStream
+ * Uses a archive file path and returns an {@link InputStream}.
  */
 public interface IDecompressor
 {
 
+    /**
+     * Attempts to open an {@link InputStream} to a compressed archive.
+     * In this context, external archives a referenced via a relative or absolute path, including
+     * the actual file name of that resource.
+     * In case only a plain file name is given and no directory or path elements are contained
+     * in {@code resource}, an attempt is made to detect and load the resource from the classpath.
+     *
+     * @param fileName References an archive via a path or by its file name only.
+     *                 If {@code null}, this will result in an {@link IOException}.
+     * @return An open {@link InputStream} or {@code null} if the archive could not be found.
+     *
+     * @throws IOException Thrown if IO errors occurred.
+     */
     InputStream getInputStream(String fileName) throws IOException;
 }