make PluginLoader dependency of MustacheTemplateEngine optional

scm-webapp/src/main/java/sonia/scm/template/MustacheTemplateEngine.java

@@ -37,27 +37,22 @@ package sonia.scm.template;
 
 import com.github.mustachejava.Mustache;
 import com.github.mustachejava.MustacheException;
-
 import com.google.common.base.Throwables;
 import com.google.common.util.concurrent.ThreadFactoryBuilder;
 import com.google.common.util.concurrent.UncheckedExecutionException;
 import com.google.inject.Inject;
-
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
-
 import sonia.scm.Default;
 import sonia.scm.plugin.PluginLoader;
 
-//~--- JDK imports ------------------------------------------------------------
-
+import javax.servlet.ServletContext;
 import java.io.IOException;
 import java.io.Reader;
-
 import java.util.concurrent.Executors;
 import java.util.concurrent.ThreadFactory;
 
-import javax.servlet.ServletContext;
+//~--- JDK imports ------------------------------------------------------------
 
 /**
  *
@@ -67,6 +62,14 @@ import javax.servlet.ServletContext;
 public class MustacheTemplateEngine implements TemplateEngine
 {
 
+  /**
+   * Used to implement optional injection for the PluginLoader.
+   * @see <a href="https://github.com/google/guice/wiki/FrequentlyAskedQuestions#how-can-i-inject-optional-parameters-into-a-constructor">Optional Injection</a>
+   */
+  static class PluginLoaderHolder {
+    @Inject(optional = true) PluginLoader pluginLoader;
+  }
+
   /** Field description */
   public static final TemplateType TYPE = new TemplateType("mustache",
                                             "Mustache", "mustache");
@@ -87,13 +90,12 @@ public class MustacheTemplateEngine implements TemplateEngine
    *
    *
    * @param context
-   * @param pluginLoader
+   * @param pluginLoaderHolder
    */
   @Inject
-  public MustacheTemplateEngine(@Default ServletContext context,
-    PluginLoader pluginLoader)
+  public MustacheTemplateEngine(@Default ServletContext context, PluginLoaderHolder pluginLoaderHolder)
   {
-    factory = new ServletMustacheFactory(context, pluginLoader);
+    factory = new ServletMustacheFactory(context, createClassLoader(pluginLoaderHolder.pluginLoader));
 
     ThreadFactory threadFactory =
       new ThreadFactoryBuilder().setNameFormat(THREAD_NAME).build();
@@ -101,6 +103,13 @@ public class MustacheTemplateEngine implements TemplateEngine
     factory.setExecutorService(Executors.newCachedThreadPool(threadFactory));
   }
 
+  private ClassLoader createClassLoader(PluginLoader pluginLoader) {
+    if (pluginLoader == null) {
+      return Thread.currentThread().getContextClassLoader();
+    }
+    return pluginLoader.getUberClassLoader();
+  }
+
   //~--- get methods ----------------------------------------------------------
 
   /**
@@ -112,12 +121,9 @@ public class MustacheTemplateEngine implements TemplateEngine
    *
    * @return
    *
-   * @throws IOException
    */
   @Override
-  public Template getTemplate(String templateIdentifier, Reader reader)
-    throws IOException
-  {
+  public Template getTemplate(String templateIdentifier, Reader reader) {
     if (logger.isTraceEnabled())
     {
       logger.trace("try to create mustache template from reader with id {}",

scm-webapp/src/main/java/sonia/scm/template/ServletMustacheFactory.java

@@ -36,22 +36,17 @@ package sonia.scm.template;
 //~--- non-JDK imports --------------------------------------------------------
 
 import com.github.mustachejava.DefaultMustacheFactory;
-
 import com.google.common.base.Charsets;
-
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-import sonia.scm.plugin.PluginLoader;
-
-//~--- JDK imports ------------------------------------------------------------
-
+import javax.servlet.ServletContext;
 import java.io.BufferedReader;
 import java.io.InputStream;
 import java.io.InputStreamReader;
 import java.io.Reader;
 
-import javax.servlet.ServletContext;
+//~--- JDK imports ------------------------------------------------------------
 
 /**
  *
@@ -73,13 +68,12 @@ public class ServletMustacheFactory extends DefaultMustacheFactory
    *
    *
    * @param servletContext
-   * @param pluginLoader
+   * @param classLoader
    */
-  public ServletMustacheFactory(ServletContext servletContext,
-    PluginLoader pluginLoader)
+  public ServletMustacheFactory(ServletContext servletContext, ClassLoader classLoader)
   {
     this.servletContext = servletContext;
-    this.pluginLoader = pluginLoader;
+    this.classLoader = classLoader;
   }
 
   //~--- get methods ----------------------------------------------------------
@@ -116,7 +110,7 @@ public class ServletMustacheFactory extends DefaultMustacheFactory
         resourceName = resourceName.substring(1);
       }
 
-      is = pluginLoader.getUberClassLoader().getResourceAsStream(resourceName);
+      is = classLoader.getResourceAsStream(resourceName);
     }
 
     if (is != null)
@@ -144,9 +138,8 @@ public class ServletMustacheFactory extends DefaultMustacheFactory
 
   //~--- fields ---------------------------------------------------------------
 
-  /** Field description */
-  private final PluginLoader pluginLoader;
-
   /** Field description */
   private ServletContext servletContext;
+
+  private ClassLoader classLoader;
 }