Add localization option for template engines

scm-core/src/main/java/sonia/scm/template/TemplateEngine.java

@@ -37,6 +37,7 @@ package sonia.scm.template;
 
 import java.io.IOException;
 import java.io.Reader;
+import java.util.Locale;
 
 /**
  * The {@link TemplateEngine} searches for {@link Template}s and prepares the
@@ -59,11 +60,42 @@ public interface TemplateEngine
    *
    * @param templatePath path of the template
    *
-   * @return template associated withe the given path or null
+   * @return template associated with the given path or null
    *
    * @throws IOException
    */
-  public Template getTemplate(String templatePath) throws IOException;
+  Template getTemplate(String templatePath) throws IOException;
+
+  /**
+   * Returns the template associated with the given path and the given language
+   * or the default version. To do this, the template path will be extended
+   * with the language. For example `my-template.type` will be extended to
+   * `my-template_en.type`, if the language is {@link Locale#ENGLISH}. If no
+   * dedicated template can be found, the template without the extension will
+   * be used.
+   * <p>The template engine
+   * will search the template in the folder of the web application and in
+   * the classpath. This method will return null,
+   * if no template could be found for the given path.
+   *
+   *
+   * @param templatePath path of the template
+   * @param locale the preferred language
+   *
+   * @return template associated with the given path, extended by the language
+   *   if found, or null
+   *
+   * @throws IOException
+   */
+  default Template getTemplate(String templatePath, Locale locale) throws IOException {
+    String templatePathWithLanguage = extendWithLanguage(templatePath, locale);
+    Template templateForLanguage = getTemplate(templatePathWithLanguage);
+    if (templateForLanguage == null) {
+      return getTemplate(templatePath);
+    } else {
+      return templateForLanguage;
+    }
+  }
 
   /**
    * Creates a template of the given reader. Note some template implementations 
@@ -79,7 +111,7 @@ public interface TemplateEngine
    * 
    * @since 1.22
    */
-  public Template getTemplate(String templateIdentifier, Reader reader)
+  Template getTemplate(String templateIdentifier, Reader reader)
     throws IOException;
 
   /**
@@ -87,5 +119,12 @@ public interface TemplateEngine
    *
    * @return type of template engine
    */
-  public TemplateType getType();
+  TemplateType getType();
+
+  static String extendWithLanguage(String templatePath, Locale locale) {
+    int lastIndexOfDot = templatePath.lastIndexOf('.');
+    String filename = templatePath.substring(0, lastIndexOfDot);
+    String extension = templatePath.substring(lastIndexOfDot);
+    return filename + "_" + locale.getLanguage() + extension;
+  }
 }

scm-webapp/src/test/java/sonia/scm/template/MustacheTemplateEngineTest.java

@@ -97,6 +97,11 @@ public class MustacheTemplateEngineTest extends TemplateEngineTestBase
     return "sonia/scm/template/001.mustache";
   }
 
+  @Override
+  public String getTemplateResourceWithGermanTranslation() {
+    return "sonia/scm/template/loc.mustache";
+  }
+
   /**
    * Method description
    *

scm-webapp/src/test/java/sonia/scm/template/TemplateEngineTestBase.java

@@ -37,6 +37,7 @@ package sonia.scm.template;
 
 import com.google.common.collect.Maps;
 
+import org.assertj.core.api.Assertions;
 import org.junit.Test;
 
 import static org.junit.Assert.*;
@@ -52,6 +53,7 @@ import java.io.StringWriter;
 
 import java.net.URL;
 
+import java.util.Locale;
 import java.util.Map;
 
 import javax.servlet.ServletContext;
@@ -92,6 +94,8 @@ public abstract class TemplateEngineTestBase
    */
   public abstract String getTemplateResource();
 
+  public abstract String getTemplateResourceWithGermanTranslation();
+
   /**
    * Method description
    *
@@ -126,7 +130,7 @@ public abstract class TemplateEngineTestBase
    * @throws IOException
    */
   @Test
-  public void testGetTemlateNotFound() throws IOException
+  public void testGetTemplateNotFound() throws IOException
   {
     ServletContext context = mock(ServletContext.class);
     TemplateEngine engine = createEngine(context);
@@ -151,6 +155,32 @@ public abstract class TemplateEngineTestBase
     assertNotNull(engine.getTemplate(getTemplateResource()));
   }
 
+  @Test
+  public void testGetTemplateFromClasspathWithExistingLocale() throws IOException
+  {
+    ServletContext context = mock(ServletContext.class);
+
+    TemplateEngine engine = createEngine(context);
+
+    Template template = engine.getTemplate(getTemplateResourceWithGermanTranslation(), Locale.GERMAN);
+    StringWriter writer = new StringWriter();
+    template.execute(writer, new Object());
+    Assertions.assertThat(writer.toString()).contains("German");
+  }
+
+  @Test
+  public void testGetTemplateFromClasspathWithNotExistingLocale() throws IOException
+  {
+    ServletContext context = mock(ServletContext.class);
+
+    TemplateEngine engine = createEngine(context);
+
+    Template template = engine.getTemplate(getTemplateResourceWithGermanTranslation(), Locale.CHINESE);
+    StringWriter writer = new StringWriter();
+    template.execute(writer, new Object());
+    Assertions.assertThat(writer.toString()).contains("English");
+  }
+
   /**
    * Method description
    *

scm-webapp/src/test/resources/sonia/scm/template/loc.mustache

@@ -0,0 +1 @@
+English

scm-webapp/src/test/resources/sonia/scm/template/loc_de.mustache

@@ -0,0 +1 @@
+German