allow override of core classes

scm-webapp/src/main/java/sonia/scm/ClassOverrides.java

@@ -0,0 +1,214 @@
+/**
+ * Copyright (c) 2010, Sebastian Sdorra All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ * this list of conditions and the following disclaimer. 2. Redistributions in
+ * binary form must reproduce the above copyright notice, this list of
+ * conditions and the following disclaimer in the documentation and/or other
+ * materials provided with the distribution. 3. Neither the name of SCM-Manager;
+ * nor the names of its contributors may be used to endorse or promote products
+ * derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE FOR
+ * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * http://bitbucket.org/sdorra/scm-manager
+ *
+ */
+
+
+
+package sonia.scm;
+
+//~--- non-JDK imports --------------------------------------------------------
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+//~--- JDK imports ------------------------------------------------------------
+
+import java.io.IOException;
+
+import java.net.URL;
+
+import java.util.ArrayList;
+import java.util.Enumeration;
+import java.util.Iterator;
+import java.util.List;
+
+import javax.xml.bind.JAXBContext;
+import javax.xml.bind.JAXBException;
+import javax.xml.bind.annotation.XmlAccessType;
+import javax.xml.bind.annotation.XmlAccessorType;
+import javax.xml.bind.annotation.XmlElement;
+import javax.xml.bind.annotation.XmlRootElement;
+
+/**
+ *
+ * @author Sebastian Sdorra
+ */
+@XmlRootElement(name = "overrides")
+@XmlAccessorType(XmlAccessType.FIELD)
+public class ClassOverrides implements Iterable<ClassOverride>
+{
+
+  /** Field description */
+  public static final String OVERRIDE_PATH = "META-INF/scm/override.xml";
+
+  /**
+   * the logger for ClassOverrides
+   */
+  private static final Logger logger =
+    LoggerFactory.getLogger(ClassOverrides.class);
+
+  //~--- methods --------------------------------------------------------------
+
+  /**
+   * Method description
+   *
+   *
+   * @return
+   *
+   */
+  public static ClassOverrides findOverrides()
+  {
+    ClassOverrides overrides = new ClassOverrides();
+
+    try
+    {
+      Enumeration<URL> overridesEnm =
+        getClassLoader().getResources(OVERRIDE_PATH);
+      JAXBContext context = JAXBContext.newInstance(ClassOverrides.class);
+
+      while (overridesEnm.hasMoreElements())
+      {
+        URL overrideUrl = overridesEnm.nextElement();
+
+        try
+        {
+          ClassOverrides co =
+            (ClassOverrides) context.createUnmarshaller().unmarshal(
+                overrideUrl);
+        }
+        catch (Exception ex)
+        {
+          logger.error("could not load ".concat(overrideUrl.toExternalForm()),
+                       ex);
+        }
+      }
+    }
+    catch (IOException ex)
+    {
+      logger.error("could not load overrides", ex);
+    }
+    catch (JAXBException ex)
+    {
+      logger.error("could not create jaxb context for ClassOverrides", ex);
+    }
+
+    return overrides;
+  }
+  
+  public <T> Class<T> getOverride(Class<T> clazz){
+    Class<T> implementation = null;
+    for ( ClassOverride co : getOverrides() ){
+      if ( co.getBind().equals(clazz) ){
+        implementation = (Class<T>) co.getTo();
+      }
+    }
+    return implementation;
+  }
+
+  //~--- get methods ----------------------------------------------------------
+
+  /**
+   * Method description
+   *
+   *
+   * @return
+   */
+  private static ClassLoader getClassLoader()
+  {
+    ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
+
+    if (classLoader == null)
+    {
+      classLoader = ClassOverrides.class.getClassLoader();
+    }
+
+    return classLoader;
+  }
+
+  //~--- methods --------------------------------------------------------------
+
+  /**
+   * Method description
+   *
+   *
+   * @param overrides
+   */
+  public void append(ClassOverrides overrides)
+  {
+    getOverrides().addAll(overrides.getOverrides());
+  }
+
+  /**
+   * Method description
+   *
+   *
+   * @return
+   */
+  @Override
+  public Iterator<ClassOverride> iterator()
+  {
+    return getOverrides().iterator();
+  }
+
+  //~--- get methods ----------------------------------------------------------
+
+  /**
+   * Method description
+   *
+   *
+   * @return
+   */
+  public List<ClassOverride> getOverrides()
+  {
+    if (overrides == null)
+    {
+      overrides = new ArrayList<ClassOverride>();
+    }
+
+    return overrides;
+  }
+
+  //~--- set methods ----------------------------------------------------------
+
+  /**
+   * Method description
+   *
+   *
+   * @param overrides
+   */
+  public void setOverrides(List<ClassOverride> overrides)
+  {
+    this.overrides = overrides;
+  }
+
+  //~--- fields ---------------------------------------------------------------
+
+  /** Field description */
+  @XmlElement(name = "override")
+  private List<ClassOverride> overrides;
+}