FreeMarkerControlProxy.java

/*
 * Copyright (c) 2001-2007, Inversoft Inc., All Rights Reserved
 *
 * 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 org.primeframework.mvc.control;

import java.io.IOException;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;

import freemarker.core.Environment;
import freemarker.ext.beans.BeansWrapper;
import freemarker.template.ObjectWrapper;
import freemarker.template.TemplateDirectiveBody;
import freemarker.template.TemplateDirectiveModel;
import freemarker.template.TemplateException;
import freemarker.template.TemplateModel;
import freemarker.template.TemplateModelException;

/**
 * This class is a proxy between FreeMarker and the Prime MVC controls.
 *
 * @author Brian Pontarelli
 */
public class FreeMarkerControlProxy implements TemplateDirectiveModel {
  private final Control control;

  private final ObjectWrapper objectWrapper;

  public FreeMarkerControlProxy(Control control, ObjectWrapper objectWrapper) {
    this.control = control;
    this.objectWrapper = objectWrapper;
  }

  /**
   * Chains to the {@link Control#renderStart(java.io.Writer, java.util.Map, java.util.Map)} method and the {@link
   * Control#renderEnd(java.io.Writer)}
   *
   * @param env      The FreeMarker environment.
   * @param params   The parameters passed to this control in the FTL file.
   * @param loopVars Loop variables (not really used).
   * @param body     The body of the directive.
   */
  public void execute(Environment env, Map params, TemplateModel[] loopVars, TemplateDirectiveBody body)
      throws IOException, TemplateException {
    Map<String, String> dynamicAttributes = makeDynamicAttributes(params);
    Map<String, Object> attributes = makeAttributes(params);

    control.renderStart(env.getOut(), attributes, dynamicAttributes);
    control.renderBody(env.getOut(), new FreeMarkerBodyProxy(body));
    control.renderEnd(env.getOut());
  }

  /**
   * Executes the FreeMarker directive body if it is not null. Sub-classes can overwrite this method to change the body
   * handling.
   *
   * @param env  The environment that can be used to get the writer. This default implementation uses this writer.
   * @param body The body.
   * @throws TemplateException If the body fails to render.
   * @throws IOException If the render can't write to the writer.
   */
  protected void executeBody(Environment env, TemplateDirectiveBody body) throws IOException, TemplateException {
    if (body != null) {
      body.render(env.getOut());
    }
  }

  /**
   * Makes the attributes from the parameters passed to the control by unwrapping the FreeMarker models.
   *
   * @param params The parameters passed to this control in the FTL file.
   * @return The attributes.
   * @throws freemarker.template.TemplateModelException If the unwrapping fails.
   */
  protected Map<String, Object> makeAttributes(Map params) throws TemplateModelException {
    Map<String, Object> attributes = new HashMap<>(params.size());
    for (Object o : params.entrySet()) {
      Map.Entry entry = (Map.Entry) o;
      Object value = entry.getValue();
      if (value != null) {
        attributes.put((String) entry.getKey(), ((BeansWrapper) objectWrapper).unwrap((TemplateModel) value));
      }
    }

    return attributes;
  }

  /**
   * Creates the list of dynamic attributes from the given Map of parameters passed ot the control.
   *
   * @param params The parameters passed to this control in the FTL file.
   * @return The dynamic attributes.
   */
  @SuppressWarnings("unchecked")
  protected Map<String, String> makeDynamicAttributes(Map params) {
    Map<String, String> dynamicAttributes = new HashMap<>();
    for (Iterator<String> i = params.keySet().iterator(); i.hasNext(); ) {
      String key = i.next();
      if (key.startsWith("_")) {
        Object value = params.get(key);
        dynamicAttributes.put(key.substring(1), value.toString());
        i.remove();
      }
    }
    return dynamicAttributes;
  }
}