datatagiteratorusingassigndata.java

这是一个mvc模式

package jsp.tags.dapact.tags.data;

import jsp.tags.dapact.conf.UserClassFactory;
import jsp.tags.dapact.lookup.BaseLookupValue;
import jsp.tags.dapact.tags.data.DataException;
import jsp.tags.dapact.util.TagUtil;
/**
 * 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@
 */

/**
 * This concrete class allows assignment of an object (that implements the
 * RetrieveValueByNameIteratorInf interface) either by looking it up by name or
 * by a subclass assigning it through the {@link #setDataIterateObj(RetrieveValueByNameIteratorInf)}.
 * The system will check the data iterate object property first and then use the
 * {@link #getDataIterateObjName()} method to lookup the data object.
 */
public class DataTagIteratorUsingAssignData extends BaseDataTagIterator
{
  /**
   * Default constructor...
   */
  public DataTagIteratorUsingAssignData()
  {
  }

  /**
   * Called by objects that want to request a value by its name.
   *
   * @param requestor the object requesting the value or the object that the value
   *   is being requested for (like with a lookup: you would pass the TagSupport
   *   object, not the lookup which is what actually calls this function).
   * @param name the name of the value to retrieve.
   *
   * @return the value that was found by the name supplied.
   */
  public Object retrieveValueByName(Object requestor, String name)
  {
    Object result = null;
    RetrieveValueByNameIteratorInf dataIterateObj = getDataIterateObj();
    if (dataIterateObj != null)
    {
      result = dataIterateObj.retrieveValueByName(requestor, name);
    }
    return result;
  }

  /**
   * This function should be called when processing is done or is aborted (so that sub
   * classes can close their resources). This function should be able to handle multiple
   * calls to it without causing an error (so, it the iterator calls it and then the
   * finalize() method calls it, the only exceptions that should occur are in the first
   * call when it tries to close the resources). Subsequent calls should probably be
   * ignored, unless there is a reason to try again.
   */
  public void close() throws DataException
  {
    RetrieveValueByNameIteratorInf dataIterateObj = getDataIterateObj();
    if (dataIterateObj != null)
    {
      dataIterateObj.close();
    }
  }

  /**
   * This function is called to tell the sub class to advance to the next group of
   * data.
   *
   * @return this function should return <code>true</code> until there is no more data,
   *   then it should return <code>false</code>.
   */
  public boolean next() throws DataException
  {
    boolean result = false;
    RetrieveValueByNameIteratorInf dataIterateObj = getDataIterateObj();
    if (dataIterateObj != null)
    {
      result = dataIterateObj.next();
    }
    return result;
  }

  /**
   * Called by the container to free the tags resources - super class calls close().
   */
  public void release()
  {
    super.release();
    dataIterateObj = null;
  }

  /*=============================================================================*/
  /*                           PROPERTIES/ATTRIBUTES                             */
  /*=============================================================================*/
  /**
   * Set the data iterate object to be used to iterate over the set of data and to respond
   * to requests for data. If this is set, it will ignore the data iterate object name.
   */
  public void setDataIterateObj(RetrieveValueByNameIteratorInf dataIterateObj)
  {
    this.dataIterateObj = dataIterateObj;
  }
  /**
   * Get the data iterate object to be used to iterate over the set of data and to respond
   * to requests for data. If this is set, it will ignore the data iterate object name.
   * It will lookup the object (using the data iterate object name) if it is null.
   */
  public RetrieveValueByNameIteratorInf getDataIterateObj()
  {
    // If no data iterate object has been set, look it up.
    if (dataIterateObj == null)
    {
      BaseLookupValue lookup = UserClassFactory.getLookupValueInstance(getLookupValueName());
      if (lookup != null)
      {
        // Set the data iterator from the looked up value.
        try
        {
          dataIterateObj = (RetrieveValueByNameIteratorInf)lookup.lookupValue(getDataIterateObjName(), dataIterateObj, this, pageContext);
        }
        catch (java.lang.ClassCastException e)
        {
          UserClassFactory.getLogger().log("The object referenced by the following name is not of type RetrieveValueByNameIteratorInf: " + getDataIterateObjName(), e);
        }
      }
    }
    return dataIterateObj;
  }

  /**
   * Set the name of the object.
   */
  public void setName(String name)
  {
    super.setName(name);
    RetrieveValueByNameIteratorInf dataIterateObj = getDataIterateObj();
    if (dataIterateObj != null)
    {
      dataIterateObj.setName(name);
    }
  }

  /**
   * A string constant that is used to retrieve and set the value of the Data Iterate Obj Name property.
   */
  public static final String DATA_ITERATE_OBJ_NAME_CONST = TagUtil.HIDE_ATTR_CHAR+"DataIterateObjName";
  /**
   * Get the data iterate object name of the object which is used to find the data object
   * to iterate over (and use to respond to requests for data).
   */
  public String getDataIterateObjName()
  {
    return (String)getValue(DATA_ITERATE_OBJ_NAME_CONST);
  }
  /**
   * Set the data iterate object name of the object which is used to find the data object
   * to iterate over (and use to respond to requests for data).
   */
  public void setDataIterateObjName(String name)
  {
    this.setValue(DATA_ITERATE_OBJ_NAME_CONST, name);
  }

  private RetrieveValueByNameIteratorInf dataIterateObj;
}