1 files changed, 165 insertions, 0 deletions
diff --git a/bkucommon/src/main/java/at/gv/egiz/bku/viewer/ValidatorFactory.java b/bkucommon/src/main/java/at/gv/egiz/bku/viewer/ValidatorFactory.java
new file mode 100644
index 00000000..e16a261e
--- /dev/null
+++ b/bkucommon/src/main/java/at/gv/egiz/bku/viewer/ValidatorFactory.java
@@ -0,0 +1,165 @@
+/*
+* Copyright 2008 Federal Chancellery Austria and
+* Graz University of Technology
+*
+* 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 at.gv.egiz.bku.viewer;
+
+import java.io.IOException;
+import java.net.URL;
+import java.util.Collections;
+import java.util.Enumeration;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Properties;
+
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+
+public class ValidatorFactory {
+  
+  /**
+   * Logging facility.
+   */
+  protected static Log log = LogFactory.getLog(ValidatorFactory.class);
+  
+  private static final Class<Validator> VALIDATOR_CLASS = Validator.class;
+  
+  private static final String SERVICE_ID = "META-INF/services/" + VALIDATOR_CLASS.getName();
+
+  /**
+   * Creates a new Validator for the given <code>mimeType</code>.
+   * 
+   * @param mimeType
+   * 
+   * @return
+   * 
+   * @throws IllegalArgumentException
+   *           if no Validator for the <code>mimeType</code> could be found
+   */
+  public static Validator newValidator(String mimeType) throws IllegalArgumentException {
+    
+    ClassLoader classLoader = ValidatorFactory.class.getClassLoader();
+    ValidatorFactory factory = new ValidatorFactory(classLoader);
+    
+    Validator validator = factory.createValidator(mimeType);
+    
+    if (validator == null) {
+      throw new IllegalArgumentException("Validator for '" + mimeType
+          + "' could not be found.");
+    }
+
+    return validator;
+    
+  }
+  
+  private ClassLoader classLoader;
+  
+  /**
+   * Private constructor.
+   * 
+   * @param classLoader must not be <code>null</code>
+   */
+  private ValidatorFactory(ClassLoader classLoader) {
+    
+    if (classLoader == null) {
+      throw new NullPointerException("Argument 'classLoader' must no be null.");
+    }
+    
+    this.classLoader = classLoader;
+    
+  }
+
+  private Validator createValidator(String mimeType) {
+    
+    Iterator<URL> serviceIterator = createServiceIterator();
+    while (serviceIterator.hasNext()) {
+      URL url = serviceIterator.next();
+      
+      Properties properties = new Properties();
+      try {
+        properties.load(url.openStream());
+      } catch (IOException e) {
+        log.error("Failed to load service properties " + url.toExternalForm());
+        continue;
+      }
+      String className = properties.getProperty(mimeType);
+      if (className != null) {
+        try {
+          return createValidatorInstance(className);
+        } catch (Exception e) {
+          continue;
+        }
+      }
+      
+    }
+    
+    return null;
+    
+  }
+  
+  private Validator createValidatorInstance(String className)
+      throws ClassNotFoundException, InstantiationException,
+      IllegalAccessException {
+    
+    try {
+      Class<?> implClass = classLoader.loadClass(className);
+      return (Validator) implClass.newInstance();
+    } catch (ClassNotFoundException e) {
+      log.error("Validator class '" + className + "' not found.", e);
+      throw e;
+    } catch (InstantiationException e) {
+      log.error("Faild to initialize validator class '" + className + "'.", e);
+      throw e;
+    } catch (IllegalAccessException e) {
+      log.error("Faild to initialize validator class '" + className + "'.", e);
+      throw e;
+    } catch (ClassCastException e) {
+      log.error("Class '" + className + "' is not a validator implementation.", e);
+      throw e;
+    }
+    
+  }
+  
+  private Iterator<URL> createServiceIterator() {
+    
+    try {
+      final Enumeration<URL> resources = classLoader.getResources(SERVICE_ID);
+      return new Iterator<URL> () {
+
+        @Override
+        public boolean hasNext() {
+          return resources.hasMoreElements();
+        }
+
+        @Override
+        public URL next() {
+          return resources.nextElement();
+        }
+
+        @Override
+        public void remove() {
+          throw new UnsupportedOperationException();
+        }
+        
+      };
+    } catch (IOException e) {
+      log.error("Failed to enumerate resources " + SERVICE_ID);
+      List<URL> list = Collections.emptyList(); 
+      return list.iterator();
+    }
+    
+  }
+  
+}