TrinidadTagSupport

/*
 * 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.myfaces.trinidad.webapp;

import java.util.Enumeration;
import java.util.Hashtable;

import javax.servlet.jsp.JspException;
import javax.servlet.jsp.PageContext;
import javax.servlet.jsp.tagext.IterationTag;
import javax.servlet.jsp.tagext.Tag;

/**
 * This is the Trinidad version of the JSP <code>TagSupport</code> class.
 * The main difference is that this class is <b>NOT</b> implementing the
 * <code>Serializable</code> interface.
 *
 * @author Apache Tomcat team
 */
public class TrinidadTagSupport implements IterationTag
{
  /**
   * Find the instance of a given class type that is closest to a given
   * instance. This method uses the getParent method from the Tag interface.
   * This method is used for coordination among cooperating tags.
   *
   * <p>
   * The current version of the specification only provides one formal way of
   * indicating the observable type of a tag handler: its tag handler
   * implementation class, described in the tag-class subelement of the tag
   * element. This is extended in an informal manner by allowing the tag library
   * author to indicate in the description subelement an observable type. The
   * type should be a subtype of the tag handler implementation class or void.
   * This addititional constraint can be exploited by a specialized container
   * that knows about that specific tag library, as in the case of the JSP
   * standard tag library.
   *
   * <p>
   * When a tag library author provides information on the observable type of a
   * tag handler, client programmatic code should adhere to that constraint.
   * Specifically, the Class passed to findAncestorWithClass should be a subtype
   * of the observable type.
   *
   *
   * @param from
   *          The instance from where to start looking.
   * @param klass
   *          The subclass of Tag or interface to be matched
   * @return the nearest ancestor that implements the interface or is an
   *         instance of the class specified
   */
  public static final Tag findAncestorWithClass(Tag from,
  // TCK signature test fails with generics
      @SuppressWarnings("unchecked") Class klass)
  {
    boolean isInterface = false;

    if (from == null
        || klass == null
        || (!Tag.class.isAssignableFrom(klass) && !(isInterface = klass
            .isInterface())))
    {
      return null;
    }

    for (;;)
    {
      Tag tag = from.getParent();

      if (tag == null)
      {
        return null;
      }

      if ((isInterface && klass.isInstance(tag))
          || klass.isAssignableFrom(tag.getClass()))
        return tag;
      else
        from = tag;
    }
  }

  /**
   * Default constructor, all subclasses are required to define only a public
   * constructor with the same signature, and to call the superclass
   * constructor.
   *
   * This constructor is called by the code generated by the JSP translator.
   */

  public TrinidadTagSupport()
  {
  }

  /**
   * Default processing of the start tag, returning SKIP_BODY.
   *
   * @return SKIP_BODY
   * @throws JspException
   *           if an error occurs while processing this tag
   *
   * @see Tag#doStartTag()
   */

  public int doStartTag() throws JspException
  {
    return SKIP_BODY;
  }

  /**
   * Default processing of the end tag returning EVAL_PAGE.
   *
   * @return EVAL_PAGE
   * @throws JspException
   *           if an error occurs while processing this tag
   *
   * @see Tag#doEndTag()
   */

  public int doEndTag() throws JspException
  {
    return EVAL_PAGE;
  }

  /**
   * Default processing for a body.
   *
   * @return SKIP_BODY
   * @throws JspException
   *           if an error occurs while processing this tag
   *
   * @see IterationTag#doAfterBody()
   */

  public int doAfterBody() throws JspException
  {
    return SKIP_BODY;
  }

  // Actions related to body evaluation

  /**
   * Release state.
   *
   * @see Tag#release()
   */

  public void release()
  {
    parent = null;
    id = null;
    if (values != null)
    {
      values.clear();
    }
    values = null;
  }

  /**
   * Set the nesting tag of this tag.
   *
   * @param t
   *          The parent Tag.
   * @see Tag#setParent(Tag)
   */

  public void setParent(Tag t)
  {
    parent = t;
  }

  /**
   * The Tag instance most closely enclosing this tag instance.
   *
   * @see Tag#getParent()
   *
   * @return the parent tag instance or null
   */

  public Tag getParent()
  {
    return parent;
  }

  /**
   * Set the id attribute for this tag.
   *
   * @param id
   *          The String for the id.
   */

  public void setId(String id)
  {
    this.id = id;
  }

  /**
   * The value of the id attribute of this tag; or null.
   *
   * @return the value of the id attribute, or null
   */

  public String getId()
  {
    return id;
  }

  /**
   * Set the page context.
   *
   * @param pageContext
   *          The PageContext.
   * @see Tag#setPageContext
   */

  public void setPageContext(PageContext pageContext)
  {
    this.pageContext = pageContext;
  }

  /**
   * Associate a value with a String key.
   *
   * @param k
   *          The key String.
   * @param o
   *          The value to associate.
   */

  public void setValue(String k, Object o)
  {
    if (values == null)
    {
      values = new Hashtable<String, Object>();
    }
    values.put(k, o);
  }

  /**
   * Get a the value associated with a key.
   *
   * @param k
   *          The string key.
   * @return The value associated with the key, or null.
   */

  public Object getValue(String k)
  {
    if (values == null)
    {
      return null;
    } else
    {
      return values.get(k);
    }
  }

  /**
   * Remove a value associated with a key.
   *
   * @param k
   *          The string key.
   */

  public void removeValue(String k)
  {
    if (values != null)
    {
      values.remove(k);
    }
  }

  /**
   * Enumerate the keys for the values kept by this tag handler.
   *
   * @return An enumeration of all the keys for the values set, or null or an
   *         empty Enumeration if no values have been set.
   */

  public Enumeration<String> getValues()
  {
    if (values == null)
    {
      return null;
    }
    return values.keys();
  }

  // private fields

  private Tag parent;
  private Hashtable<String, Object> values;
  /**
   * The value of the id attribute of this tag; or null.
   */
  protected String id;

  // protected fields

  /**
   * The PageContext.
   */
  protected PageContext pageContext;
}