Package org.apache.wicket.resource.loader

Source Code of org.apache.wicket.resource.loader.ComponentStringResourceLoader

/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements.  See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF 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.  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 org.apache.wicket.resource.loader;

import java.util.ArrayList;
import java.util.List;
import java.util.Locale;

import org.apache.wicket.Application;
import org.apache.wicket.Component;
import org.apache.wicket.MarkupContainer;
import org.apache.wicket.Page;
import org.apache.wicket.markup.html.WebComponent;
import org.apache.wicket.markup.html.WebMarkupContainer;
import org.apache.wicket.markup.html.WebPage;
import org.apache.wicket.resource.IPropertiesFactory;
import org.apache.wicket.resource.Properties;
import org.apache.wicket.util.resource.locator.ResourceNameIterator;
import org.apache.wicket.util.string.Strings;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;


/**
* This is Wicket's default string resource loader.
* <p>
* The component based string resource loader attempts to find the resource from a bundle that
* corresponds to the supplied component object or one of its parent containers.
* <p>
* The search order for resources is built around the containers that hold the component (if it is
* not a page). Consider a Page that contains a Panel that contains a Label. If we pass the Label as
* the component then resource loading will first look for the resource against the page, then
* against the panel and finally against the label.
* <p>
* The above search order may seem slightly odd at first, but can be explained thus: Team A writes a
* new component X and packages it as a reusable Wicket component along with all required resources.
* Team B then creates a new container component Y that holds a instance of an X. However, Team B
* wishes the text to be different to that which was provided with X so rather than needing to
* change X, they include override values in the resources for Y. Finally, Team C makes use of
* component Y in a page they are writing. Initially they are happy with the text for Y so they do
* not include any override values in the resources for the page. However, after demonstrating to
* the customer, the customer requests the text for Y to be different. Team C need only provide
* override values against their page and thus do not need to change Y.
* <p>
* This implementation is fully aware of both locale and style values when trying to obtain the
* appropriate resources.
* <p>
* In addition to the above search order, each key will be pre-pended with the relative path of the
* current component related to the component that is being searched. E.g. assume a component
* hierarchy like page1.form1.input1 and your are requesting a key named 'Required'. Wicket will
* search the property in the following order:
*
* <pre>
*        page1.properties =&gt; form1.input1.Required
*        page1.properties =&gt; Required
*        form1.properties =&gt; input1.Required
*        form1.properties =&gt; Required
*        input1.properties =&gt; Required
*        myApplication.properties =&gt; page1.form1.input1.Required
*        myApplication.properties =&gt; Required
* </pre>
*
* Note that the latter two property files are only checked if the ClassStringResourceLoader has
* been registered with Application as well, which is the default.
* <p>
* In addition to the above search order, each component that is being searched for a resource also
* includes the resources from any parent classes that it inherits from. For example, PageA extends
* CommonBasePage which in turn extends WebPage. When a resource lookup is requested on PageA, the
* resource bundle for PageA is first checked. If the resource is not found in this bundle then the
* resource bundle for CommonBasePage is checked. This allows designers of base pages and components
* to define default sets of string resources and then developers implementing subclasses to either
* override or extend these in their own resource bundle.
* <p>
* This implementation can be subclassed to implement modified behavior. The new implementation must
* be registered with the Application (ResourceSettings) though.
* <p>
* You may enable log debug messages for this class to fully understand the search order.
*
* @author Chris Turner
* @author Juergen Donnerstag
*/
public class ComponentStringResourceLoader implements IStringResourceLoader
{
  /** Log. */
  private static final Logger log = LoggerFactory.getLogger(ComponentStringResourceLoader.class);

  /**
   * Create and initialize the resource loader.
   */
  public ComponentStringResourceLoader()
  {
  }

  /**
   * Get the string resource for the given combination of class, key, locale and style. The
   * information is obtained from a resource bundle associated with the provided Class (or one of
   * its super classes).
   *
   * @param clazz
   *            The Class to find resources to be loaded
   * @param key
   *            The key to obtain the string for
   * @param locale
   *            The locale identifying the resource set to select the strings from
   * @param style
   *            The (optional) style identifying the resource set to select the strings from (see
   *            {@link org.apache.wicket.Session})
   * @return The string resource value or null if resource not found
   */
  public String loadStringResource(Class clazz, final String key, final Locale locale,
    final String style)
  {
    if (clazz == null)
    {
      return null;
    }

    // Load the properties associated with the path
    IPropertiesFactory propertiesFactory = Application.get()
      .getResourceSettings()
      .getPropertiesFactory();

    while (true)
    {
      // Create the base path
      String path = clazz.getName().replace('.', '/');

      // Iterator over all the combinations
      ResourceNameIterator iter = new ResourceNameIterator(path, style, locale,
        "properties,xml");
      while (iter.hasNext())
      {
        String newPath = (String)iter.next();

        final Properties props = propertiesFactory.load(clazz, newPath);
        if (props != null)
        {
          // Lookup the value
          String value = props.getString(key);
          if (value != null)
          {
            if (log.isDebugEnabled())
            {
              log.debug("Found resource from: " + props + "; key: " + key);
            }

            return value;
          }
        }
      }

      // Didn't find the key yet, continue searching if possible
      if (isStopResourceSearch(clazz))
      {
        break;
      }

      // Move to the next superclass
      clazz = clazz.getSuperclass();

      if (clazz == null)
      {
        // nothing more to search, done
        break;
      }
    }

    // not found
    return null;
  }

  /**
   *
   * @see org.apache.wicket.resource.loader.IStringResourceLoader#loadStringResource(org.apache.wicket.Component,
   *      java.lang.String)
   */
  public String loadStringResource(final Component component, final String key)
  {
    if (component == null)
    {
      return null;
    }

    // The return value
    String string = null;
    Locale locale = component.getLocale();
    String style = component.getStyle();

    // The key prefix is equal to the component path relative to the
    // current component on the top of the stack.
    String prefix = Strings.replaceAll(component.getPageRelativePath(), ":", ".").toString();

    // The reason why we need to create that stack is because we need to
    // walk it downwards starting with Page down to the Component
    List searchStack = getComponentStack(component);

    // Walk the component hierarchy down from page to the component
    for (int i = searchStack.size() - 1; (i >= 0) && (string == null); i--)
    {
      Class clazz = (Class)searchStack.get(i);

      // First, try the fully qualified resource name relative to the
      // component on the path from page down.
      if ((prefix != null) && (prefix.length() > 0))
      {
        string = loadStringResource(clazz, prefix + '.' + key, locale, style);

        if (string == null)
        {
          prefix = Strings.afterFirst(prefix, '.');
        }
      }

      // If not found, than check if a property with the 'key' provided by
      // the user can be found.
      if (string == null)
      {
        string = loadStringResource(clazz, key, locale, style);
      }
    }

    return string;
  }

  /**
   * Traverse the component hierarchy up to the Page and add each component class to the list
   * (stack) returned
   *
   * @param component
   *            The component to evaluate
   * @return The stack of classes
   */
  private List getComponentStack(final Component component)
  {
    // Build the search stack
    final List searchStack = new ArrayList();
    searchStack.add(component.getClass());

    if (!(component instanceof Page))
    {
      // Add all the component on the way to the Page
      MarkupContainer container = component.getParent();
      while (container != null)
      {
        searchStack.add(container.getClass());
        if (container instanceof Page)
        {
          break;
        }

        container = container.getParent();
      }
    }
    return searchStack;
  }

  /**
   * Check the supplied class to see if it is one that we shouldn't bother further searches up the
   * class hierarchy for properties.
   *
   * @param clazz
   *            The class to check
   * @return Whether to stop the search
   */
  protected boolean isStopResourceSearch(final Class clazz)
  {
    if (clazz == null || clazz.equals(Object.class) || clazz.equals(Application.class))
    {
      return true;
    }

    // Stop at all html markup base classes
    if (clazz.equals(WebPage.class) || clazz.equals(WebMarkupContainer.class) ||
      clazz.equals(WebComponent.class))
    {
      return true;
    }

    // Stop at all wicket base classes
    return clazz.equals(Page.class) || clazz.equals(MarkupContainer.class) ||
      clazz.equals(Component.class);
  }
}
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