defaultlookupvalue.java

这是一个mvc模式

package jsp.tags.dapact.lookup;
/**
 * Title:        Data Aware Processing And Control Tags
 * Description:  Tag library for the processing and controlling the input and output of data.
 * Copyright:    LGPL (http://www.gnu.org/copyleft/lesser.html)
 * Compile Date: @compile_date@
 * @author Allen M Servedio
 * @amp_sign@version @VERSION@
 */

import javax.servlet.jsp.PageContext;
import javax.servlet.jsp.tagext.TagSupport;

/**
 * Default lookup value object - implements Null Object pattern - as in it does not
 * do anything, just returns the values.
 */
public class DefaultLookupValue extends BaseLookupValue
{
  /**
   * Default constructor.
   */
  public DefaultLookupValue()
  {
  }

  /**
   * This function will be called by the tags when they want to store a string object
   * (most common case: storing attributes). As the default, it just returns the value.
   *
   * @param key the key of the value to be saved.
   * @param value the value to be added - this will be overridden by what is returned by
   *   this function.
   * @param tag the tag that will be used to save the value.
   * @param pc the page context associated with the tag that is also a parameter. This
   *   will be used to search parameters and contexts (page, session, request, and servlet).
   *
   * @return the lookedup value.
   */
  public String lookupValue(String key, String value, TagSupport tag, PageContext pc)
  {
    return value;
  }

  /**
   * This function will be called by the tags when they want to store a general
   * non-String object. As the default, it just returns the value.
   *
   * @param key the key of the value to be saved.
   * @param value the value to be added - this will be overridden by what is returned by
   *   this function.
   * @param tag the tag that will be used to save the value.
   * @param pc the page context associated with the tag that is also a parameter. This
   *   will be used to search parameters and contexts (page, session, request, and servlet).
   *
   * @return the lookedup value.
   */
  public Object lookupValue(String key, Object value, TagSupport tag, PageContext pc)
  {
    return value;
  }
}