messagelooptag.java

这是学习Java必须读懂两套源代码

    } catch(Exception e) {
    }

    if( ft == null ) {
      throw new JspException("Yazd message_loop tag could not find forum.");
    }

    // Get the HTML input parameter begin to setup where message_loop
    // should start
    ServletRequest req = pageContext.getRequest();
    String tmp = req.getParameter("begin");
    if( tmp != null && tmp.length() > 0 ) {
      try {
        begin = Integer.valueOf(tmp).intValue();
      } catch(NumberFormatException e) {
      }
    }

    QueryTag qt = null;
    try {
      qt = (QueryTag)pageContext.getAttribute(query,PageContext.PAGE_SCOPE);
    } catch(Exception e) {
      throw new JspException(
	"Yazd message tag, could not find query tag with id: " + query);
    }
    Map properties = qt.getQuery();
    Query q = ft.getForum().createQuery();
    if( properties.get("beforeDate") != null ) {
      tmp = (String)properties.get("beforeDate");
      try {
        if( tmp != null && tmp.length() > 0 ) {
          Date date = new Date(Long.valueOf(tmp).longValue());
          q.setBeforeDate(date);
        }
      } catch(Exception e) {
	throw new JspException("Yazd message tag, bad query tag beforeDate");
      }
    }
    if( properties.get("afterDate") != null ) {
      tmp = (String)properties.get("afterDate");
      try {
	if( tmp != null && tmp.length() > 0 ) {
          Date date = new Date(Long.valueOf(tmp).longValue());
          q.setAfterDate(date);
        }
      } catch(Exception e) {
        throw new JspException("Yazd message tag, bad query tag afterDate");
      }
    }
    if( properties.get("queryString") != null ) {
      tmp = (String)properties.get("queryString");
      if( tmp == null ) {
	throw new JspException("Yazd message tag, bad query tag queryString");
      }
      if( tmp.length() > 0 )
        q.setQueryString(tmp);
    }
    if( properties.get("userID") != null ) {
      tmp = (String)properties.get("userID");
      try {
        ProfileManager pm = jr.getProfileManager();
        User user = pm.getUser(tmp);
        q.filterOnUser(user);
      } catch(UserNotFoundException ue) {
//	System.out.println("Search Query User: " + tmp + " not found.");
      } catch(Exception e) {
        throw new JspException("Yazd message tag, bad query tag userID:" +
	  e.getMessage());
      }
    }
    mit = q.results(begin,js.getItemsPerPage());

    if( mit == null ) {
      throw new JspException("Yazd message_loop tag could not get Iterator for forum messages.");
    }

    if( !mit.hasNext() )
      return SKIP_BODY;
    cm = (ForumMessage)mit.next();
    message_num++;
    if( !mit.hasNext() ) {
      is_exit = true;
      if( message_num >= js.getItemsPerPage() )
        next_page = true;
    }
    if( begin > 0 )
      prev_page = true;

    return EVAL_BODY_TAG;
  }

  /**
   * Method called at end of each message_loop Tag Body
   *
   * @return an EVAL_BODY_TAG if message_loop should continue, or a SKIP_BODY if message_loop is completed.
   */
  public final int doAfterBody() throws JspException
  {
    is_entry = prev_page = false;
    message_num++;
    if( !mit.hasNext() ) {
      return SKIP_BODY;
    }
    cm = (ForumMessage)mit.next();
    if( !mit.hasNext() ) {
      is_exit = true;
      if( message_num >= js.getItemsPerPage() )
        next_page = true;
    }
    return EVAL_BODY_TAG;
  }

  /**
   * Method called at end of message_loop Tag
   * @return EVAL_PAGE
   */
  public final int doEndTag() throws JspException
  {
    try
    {
      if(bodyContent != null)
        bodyContent.writeOut(bodyContent.getEnclosingWriter());
    } catch(java.io.IOException e)
    {
      throw new JspException("IO Error: " + e.getMessage());
    }
    return EVAL_PAGE;
  }

  /**
   * Set the forum message query to use
   */
  public final void setQuery(String qry)
  {
    query = qry;
  }

  /**
   * Used by <b>message</b> tag to get the current ForumMessage
   *
   * @return ForumMessage
   */
  public final ForumMessage getMessage()
  {
    return cm;
  }

  /**
   * Return total number of messages in thread, required by
   * GetNestedMessage.
   *
   * @return String - thread MessageCount
   */
  public final int getTotal()
  {
    return 0;
  }

  /**
   * Used by <b>on_entry</b> tag to detect if this is the first iteration
   * of the loop.
   *
   * @return true or false
   */
  public final boolean isEntry()
  {
    return is_entry;
  }

  /**
   * Used by <b>on_exit</b> tag to detect if this is the last iteration
   * of the loop.
   *
   * @return true or false
   */
  public final boolean isExit()
  {
    return is_exit;
  }

  /**
   * Used by <b>next_page</b> tag to detect if message listing could continue
   * on another page.
   *
   * @return true or false
   */
  public final boolean isNextPage()
  {
    return next_page;
  }

  /**
   * Used by <b>prev_page</b> tag to detect if message listing
   * has a previous page.
   *
   * @return true or false
   */
  public final boolean isPrevPage()
  {
    return prev_page;
  }

  /**
   * Used by <b>next_item</b> tag to return query portion of an HTML GET href
   * for paging to next list of messages.
   *
   * @return String - query portion of an HTML GET href
   */
  public final String nextItem()
  {
    return "begin=" + (begin+message_num);
  }

  /**
   * Used by <b>prev_item</b> tag to return query portion of an HTML GET href
   * for paging to previous list of messages.
   *
   * @return String - query portion of an HTML GET href
   */
  public final String prevItem()
  {
    int prev = begin - js.getItemsPerPage();
    if( prev < 0 )
      prev = 0;
    return "begin=" + prev;
  }

}