walktag.java

这是学习Java必须读懂两套源代码

/**
 * Copyright (C) 2001 Yasna.com. All rights reserved.
 *
 * ===================================================================
 * The Apache Software License, Version 1.1
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:
 *       "This product includes software developed by
 *        Yasna.com (http://www.yasna.com)."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Yazd" and "Yasna.com" must not be used to
 *    endorse or promote products derived from this software without
 *    prior written permission. For written permission, please
 *    contact [e-mail].
 *
 * 5. Products derived from this software may not be called "Yazd",
 *    nor may "Yazd" appear in their name, without prior written
 *    permission of Yasna.com.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL YASNA.COM OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of Yasna.com. For more information
 * on Yasna.com, please see <http://www.yasna.com>.
 */

/**
 * Copyright (C) 2000 CoolServlets.com. All rights reserved.
 *
 * ===================================================================
 * The Apache Software License, Version 1.1
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:
 *       "This product includes software developed by
 *        CoolServlets.com (http://www.coolservlets.com)."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Jive" and "CoolServlets.com" must not be used to
 *    endorse or promote products derived from this software without
 *    prior written permission. For written permission, please
 *    contact [e-mail].
 *
 * 5. Products derived from this software may not be called "Jive",
 *    nor may "Jive" appear in their name, without prior written
 *    permission of CoolServlets.com.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL COOLSERVLETS.COM OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of CoolServlets.com. For more information
 * on CoolServlets.com, please see <http://www.coolservlets.com>.
 */

package com.Yasna.forum.tags;

import java.io.*;
import java.util.*;
import java.text.*;
import javax.servlet.*;
import javax.servlet.jsp.*;
import javax.servlet.jsp.tagext.*;
import javax.servlet.http.*;
import com.Yasna.forum.*;
import com.Yasna.forum.tags.*;

/**
 * JSP Tag <b>walk</b>, implements a loop used to walk a tree of
 * messages in a thread.
 * <p>
 * Must be nested inside a <b>thread</b> tag.
 * <p>The thread to walk will be the closest parent thread tag unless
 * you specify the optional <b>thread</b> tag to be the <b>id</b>
 * of a different thread tag.
 * <p>
 * Uses the users display preferences <b>messageDepth</b>,
 * <b>threadDepth</b>, and <b>itemsPerPage</b> to determine
 * which messages to display, how to display them, and how
 * many messages to view on a page before triggering paging.
 * <p>
 * The <b>is_parent</b>, <b>is_message</b>, <b>is_summary</b>,
 * <b>is_total</b>, <b>next_page</b>, and <b>prev_page</b> tags
 * can be used to control what formatted content is generated
 * based on user display preferences.
 * <p>
 * The <b>current_depth</b>, <b>while_child</b>, <b>while_new_child</b>,
 * <b>while_parent</b>, and <b>while_new_parent</b> tags can be used
 * to assist JSP page author to propertly format HTML output when
 * displaying a tree of messages in a thread.
 * <p>
 * During each loop the body of the walk tag is processed.
 * <p>
 * The <b>on_entry</b> tag can be used to include content if this is
 * the first time through the loop.
 * <p>
 * The <b>on_exit</b> tag can be used to include content if this is
 * the last time through the loop.
 * <p>
 * The walk tag continues looping until there are no more messages in the
 * thread or the users items_per_page limit has been reached. The <b>next_page</b>
 * tag can be used to determine if the walk tag loop ended due to the
 * users items_per_page limit.  Then the <b>next_item</b> tag can be
 * used to get the query portion of an HTML href so that you can setup
 * an href to page to the next list of messges in this thread.
 * <p>
 * The walk tag can loop back to the previous list of messages
 * after the walk has been paged. The <b>prev_page</b>
 * tag can be used to determine if the walk tag has a previous page.
 * Then the <b>prev_item</b> tag can be used to get the query portion
 * of an HTML href so that you can setup an href to page to the previous
 * list of messages.
 * <p>
 * JSP Tag Lib Descriptor
 * <p><pre>
 *  &lt;name&gt;walk&lt;/name&gt;
 *  &lt;tagclass&gt;com.Yasna.forum.tags.WalkTag&lt;/tagclass&gt;
 *  &lt;bodycontent&gt;JSP&lt;/bodycontent&gt;
 *  &lt;info&gt;Walks a tree of messages in a thread.&lt;/info&gt;
 *  &lt;attribute&gt;
 *    &lt;name&gt;thread&lt;/name&gt;
 *    &lt;required&gt;false&lt;/required&gt;
 *    &lt;rtexprvalue&gt;false&lt;/rtexprvalue&gt;
 *  &lt;/attribute&gt;
 * </pre>
 *
 * @see ThreadTag
 * @see IsParentTag
 * @see IsMessageTag
 * @see IsSummaryTag
 * @see IsTotalTag
 * @see OnEntryTag
 * @see NextPageTag
 * @see NextItemTag
 * @see PrevPageTag
 * @see PrevItemTag
 * @see OnExitTag
 * @see CurrentDepthTag
 * @see WhileChildTag
 * @see WhileNewChildTag
 * @see WhileParentTag
 * @see WhileNewParentTag
 * @see YazdState
 *
 * @author Glenn Nielsen
 */
public class WalkTag extends BodyTagSupport
	implements GetNestedMessage, Paging
{
  private YazdState js = null;
  private String thread = null;
  // WalkData maintains state information for each depth in the tree
  private WalkData wd = null;
  // Used to walk the messages
  private TreeWalker tw = null;
  // Current thread being walked
  private ForumThread ct = null;
  // Current message in the walk
  private ForumMessage cm = null;
  // maintain a stack of WalkData while walking messages
  private LinkedList stack = new LinkedList();
  // variables to maintain state information while walking messages
  private int message_num = 0;
  private int thread_depth = 0;
  private boolean parent_done = false;
  private boolean is_total = false;
  // Did this thread message walk trigger a page
  private boolean next_page = false;
  // Store the href for paging to the next page of messages
  private String next_href = null;
  // Save the query string for the current request
  private String current_href = null;
  // Do we have a previous list of messages that could be displayed
  private boolean prev_page = false;
  // Flag whether this is the first iteration of loop
  private boolean is_entry = true;
  // Flag whether this is the last iteration of loop
  private boolean is_exit = false;
  // deeper and shallower are used by while_new child or parent tags
  private int deeper = 0;
  private int shallower = 0;
  private boolean walk_back = false;

  /**
   * Method called at start of walk Tag, initializes data needed to
   * walk a thread of messages.
   *
   * @return an EVAL_BODY_TAG if walk tag loop should continue, or a SKIP_BODY if walk tag loop is completed.
   */
  public final int doStartTag() throws JspException
  {
    // Get the user state information
    js = (YazdState)pageContext.getAttribute("yazdUserState",
                PageContext.SESSION_SCOPE);
    if( js == null )
      throw new JspException("Yazd walk tag, could not find yazdUserState");

    ThreadTag tt = null;
    // Get the thread from its id
    if( thread != null ) {
      tt = (ThreadTag)pageContext.getAttribute(thread,PageContext.PAGE_SCOPE);
    } else {
      // Get the current thread from closest parent thread tag
      try {
        tt = (ThreadTag)this.findAncestorWithClass(this,
          Class.forName("com.Yasna.forum.tags.ThreadTag"));
      } catch(Exception e) {
      }
    }

    if( tt != null ) {
      ct = tt.getThread();
    }

    if( ct == null ) {
      throw new JspException("Could not find thread tag.");
    }

    tw = ct.treeWalker();

    // Set up the tree of messages to get to current message if
    // previous walk of this thread exceeded itemsPerPage and
    // triggered paging.
    int mesid = -1;
    String tmp;
    ForumMessage next = null;
    HttpServletRequest req = (HttpServletRequest)pageContext.getRequest();
    current_href = req.getQueryString();
    WalkData nw = null;
    cm = tw.getRoot();
    wd = new WalkData();
    wd.setMessage(tw,cm);
    stack.addLast((Object)wd);

    // Get the previous message id's for walking the tree
    for( int i = 1; (tmp = req.getParameter("walk_" + i)) != null; i++ ) {
      try {
        mesid = Integer.valueOf(tmp).intValue();
      } catch( NumberFormatException e ) {
	break;
      }
      try {
        next = ct.getMessage(mesid);
      } catch(ForumMessageNotFoundException e) {
	break;
      }
//      System.out.println("WalkTag Parent: " + mesid);
      nw = new WalkData();
      nw.setMessage(tw,next);
      stack.addLast((Object)nw);
    }
    if( (tmp = req.getParameter("walk_back")) != null ) {
//      System.out.println("Setting walk_back");
      walk_back=true;
    }

    if( stack.size() == 1 && !walk_back ) {
      parent_done = true;
      message_num++;
    } else {
      prev_page = true;
    }

    return EVAL_BODY_TAG;
  }

  /**
   * Method called at end of each walk Tag Body to navigate thread
   * message tree.
   *
   * @return an EVAL_BODY_TAG if walk should continue, or a SKIP_BODY if walk is completed.
   */
  public final int doAfterBody() throws JspException
  {
    is_entry = prev_page = false;
    // If is_exit is true we are all done
    if( is_exit )
      return SKIP_BODY;

    // These get reset each iteration of walk tag loop
    deeper = shallower = 0;
    // Walk the tree of parent messages from the root message
    // until we are viewing the current message
//    System.out.println("** parent_done=" + parent_done);
    if( !parent_done && (thread_depth + 1) < stack.size() ) {
//      System.out.println("Walking parent thread");
      WalkData nw = (WalkData)stack.get(thread_depth+1);
      if( nw == null ) {
//	System.out.println("Could not get next WalkData");
	parent_done = true;
      } else {
	thread_depth++;
	deeper++;
	ForumMessage child = nw.getMessage();
	ForumMessage next = null;
//	System.out.println("cmID: " + cm.getID() + " childID: " + child.getID());
        int i,j;
        j = wd.getChildCount();
//	System.out.println("Found " + j + " children");
	for( i = 0; i < j; i++ ) {
//	  System.out.println("ChildCheckLoop: " + i);
	  next = tw.getChild(cm,i);
	  if( next == null ) {
//	    System.out.println("No more children, parent_done");
	    parent_done = true;
	    wd.setChildIndex(i);
	    break;
	  }
//	  System.out.println("nextID: " + next.getID());
	  if( child.getID() == next.getID() ) {
//	    System.out.println("Setting ChildIndex");
	    wd.setChildIndex(i+1);
//	    System.out.println("thread_depth: " + thread_depth +
//		" stack: " + stack.size() + " walk_back=" + walk_back);
	    if( (thread_depth+1) >= stack.size() && walk_back ) {
//	      System.out.println("Walk Back from Child");
	      cm = null;
	      nw.valid = false;
	      break;
	    }
//	    System.out.println("Displaying parent");
	    wd = nw;
            cm = child;
            return EVAL_BODY_TAG;
	  }
	}
      }
    }

    // Fell through without finding a parent message,
    // start walking messages new to the user
/*
    System.out.println("** Getting new message, is_total:" + is_total +
	" thread_depth: " + thread_depth + " valid=" + wd.valid);
    System.out.println("WalkData cm: " + wd.getMessage().getID() +
	" Count: " + wd.getChildCount() + " Index: " + wd.getChildIndex() );
    if( cm != null ) {
	System.out.println("CurrentMessageID: " + cm.getID() );
    }
*/
    parent_done = true;

    // First see if we have displayed the items_per_page the
    // user wants.
    if( message_num >= js.getItemsPerPage() ) {
//      System.out.println("Exceeded items_per_page");
      cm = null;
    }

    if( cm != null && !is_total ) {

      // First see if this message has any children
      if( tw.getChildCount(cm) > 0 ) {
//	System.out.println("Getting children of current message");
        thread_depth++;
        deeper++;
        if( thread_depth >= js.getThreadDepth() ) {
//          System.out.println("Thread is too deep");
          is_total = true;
	  message_num++;
          return EVAL_BODY_TAG;