errorlooptag.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>error_loop</b>, used to loop through the previous request
 * list of user errors.
 * <p>
 * Requires that attribute <b>id</b> be set to the name of a
 * script variable for later use in JSP to retrieve the next error
 * message using &lt;jsp:getProperty/&gt;.
 * <p>
 * If there is another error message in the list, includes body of tag.
 * <p>
 * The list of errors can be cleared by setting the <b>authorize</b> tag
 * script variable property <b>error</b> equal to "".
 * <p>
 * Example:
 * <p><pre>
 *  &lt;jf:if_error&gt;&lt;hr size="0"&gt;
 *    &lt;center&gt;&lt;b&gt;Errors&lt;/b&gt;&lt;/center&gt;&lt;br&gt;
 *    &lt;jf:error_loop id="errs"&gt;
 *      &lt;li&gt;&lt;jsp:getProperty name="errs" property="error"/&gt;
 *    &lt;/jf:error_loop&gt;
 *    &lt;jsp:setProperty name="req" property="error" value=""/&gt;
 *  &lt;/jf:if_error&gt;
 * <p></pre>
 * JSP Tag Lib Descriptor
 * <p><pre>
 *  &lt;name&gt;error_loop&lt;/name&gt;
 *  &lt;tagclass&gt;com.Yasna.forum.tags.ErrorLoopTag&lt;/tagclass&gt;
 *  &lt;teiclass&gt;com.Yasna.forum.tags.ErrorLoopTEI&lt;/teiclass&gt;
 *  &lt;bodycontent&gt;JSP&lt;/bodycontent&gt;
 *  &lt;info&gt;Loops through all the error messages.&lt;/info&gt;
 *  &lt;attribute&gt;
 *    &lt;name&gt;id&lt;/name&gt;
 *    &lt;required&gt;true&lt;/required&gt;
 *    &lt;rtexprvalue&gt;false&lt;/rtexprvalue&gt;
 *  &lt;/attribute&gt;
 * </pre>
 *
 * @see ErrorTag
 * @see AuthorizeTag
 * @see YazdRequest
 *
 * @author Glenn Nielsen
 */
public class ErrorLoopTag extends BodyTagSupport
{
  private YazdRequest jr = null;
  private List errorlist = null;
  private Iterator errors = null;
  private int index = 0;

  /**
   * Method called at start of error_loop tag.
   *
   * @return EVAL_BODY_TAG if errors exist or SKIP_BODY if there are no errors
   */
  public final int doStartTag() throws JspException
  {
    // Get the user request information
    jr = (YazdRequest)pageContext.getAttribute("yazdUserRequest",
                PageContext.REQUEST_SCOPE);
    if( jr == null )
      throw new JspException("Could not find request");

    // Get an iterator for the list of errors
    errorlist = jr.getErrorList();
    errors = errorlist.iterator();
    if( !errors.hasNext() )
      return SKIP_BODY;

    // Save the script variable so JSP author can get the error message
    pageContext.setAttribute(id,this,PageContext.PAGE_SCOPE);
    return EVAL_BODY_TAG;
  }

  /**
   * Method called at end of each error_loop body.
   *
   * @return EVAL_BODY_TAG if errors exist or SKIP_BODY if there are no more errors
   */
  public final int doAfterBody() throws JspException
  {
    // increment the iterator
    errors.next();
    // See if this is the last error
    if( !errors.hasNext() )
      return SKIP_BODY;
    // There is another error, so loop again
    index++;
    return EVAL_BODY_TAG;
  }

  /**
   * Method called at end of 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;
  }

  /**
   * Error Message property which can be obtained by the JSP page
   * using &lt;jsp:getProperty name=<i>"id"</i> property="error"/&gt;
   *
   * @return String - current error message
   */
  public final String getError()
  {
    StringBuffer next = (StringBuffer)errorlist.get(index);
    return next.toString();
  }

}