Custom JSP Tag - Unrequired-Fields not cleared

[Jeff Schramm]

Hello,

i wrote a custom tag which builds a specific link. Following attributes

    
    <attribute>
      <name>value</name>
      <required>true</required>
      <rtexprvalue>true</rtexprvalue>
    </attribute>
    <attribute>
      <name>label</name>
      <required>false</required>
      <rtexprvalue>true</rtexprvalue>
    </attribute>
    </tag>

The label attribute is not required.

If label is unspecified:

  public int doStartTag() throws JspException {
    try {
    
      if(label == null)
        label = value;

For the first tag of the JSP everything is working, well. But if i use the Tag a second time and the label attribute is again not used in the jsp -> label has the old value from the last tag! Why?

My workaround is to reset all fields at the end of tag execution. Do somebody know a better solution?

Thanks, Jeff

[Eduardo Bueno]

Stupid question: is anything in your tag class static?

[David Newton]

Some containers may cache tags, too.

[Bear Bibeault]

Please post the entire tag handler. Be sure to use code tags.

[Jeff Schramm]

David Newton wrote:Some containers may cache tags, too.

I`m using Tomcat 5.5 -

TagHandler:

public class DynamicFilterLinkHandler extends TagSupport {


  private String key = null;
  private String value = null;
  private String label = null;
  private String linkTitle = null;
  private String styleClass = null;

  public void release() {
        super.release();
        key = null;
        value = null;
        label = null;
        linkTitle = null;
        styleClass = null;
}


  public String getLinkTitle() {
    return linkTitle;
  }

  public String getLabel() {
    return label;
  }

  public String getValue() {
    return value;
  }

  public void setKey(String key) {
    this.key = key;
  }

  public void setLinkTitle(String linkTitle) {
    this.linkTitle = linkTitle;
  }

  public void setLabel(String label) {
    this.label = label;
  }

  public void setValue(String value) {
    this.value = value;
  }

  public void setStyleClass(String styleClass) {
    this.styleClass = styleClass;
  }

  public String getKey() {
    return key;
  }

  public String getStyleClass() {
    return styleClass;
  }

  /**
   *  Description of the Method
   *
   *@return                   Description of the Return Value
   *@exception  JspException  Description of the Exception
   */
  public int doStartTag() throws JspException {
    try {

      if(label == null)
        label = value;

      StringBuffer linkSb = new StringBuffer();

      // Append outer Box & styleClass extension
      linkSb.append("<span class=\"dfContainer "+(styleClass != null ? styleClass : "")+"\">");
      // Append Start & Tooltip
      linkSb.append("<a class=\"dynamicFilter\"  
       null)
        linkSb.append("click to filter for '"+label+"'");
        else
          linkSb.append(linkTitle + " ");

      linkSb.append("\" ");

      // Append JS-Event until start of inner link
       false;\"  rel="nofollow">");

      // Append inner Link stuff
      linkSb.append("<span class=\"dfText\">"+label+"</span>");

      // Append Icon
      linkSb.append("<span class=\"dynamicFilterImage\"> </span></a></span>");

      //Show the link
      this.pageContext.getOut().write(linkSb.toString());

    } catch (Exception e) {
      throw new JspException("DynamicFilterLink Error: " + e.getMessage());
    }finally{
      //this.release();
    }
    return SKIP_BODY;
  }

  /**
   * Default processing of the end tag returning EVAL_PAGE.
   *
   * @returns EVAL_PAGE
   *
   * @see Tag#doEndTag()
   */

  public int doEndTag() throws JspException {
    release();
    return EVAL_PAGE;
  }



}

TLD:

<?xml version="1.0" encoding="UTF-8" ?>
<taglib xmlns="http://java.sun.com/xml/ns/j2ee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee web-jsptaglibrary_2_0.xsd"
    version="2.0">
    <tlib-version>1.0</tlib-version>
    <short-name>et</short-name>
    <uri>http://pms.eventim.ag/calltag/epmsTaglib.tld</uri>

    <tag>
    <name>dfLink</name>
    <tag-class>com.eventim.taglib.DynamicFilterLinkHandler</tag-class>
    <body-content>empty</body-content>
    <display-name>
      Create a dynamic filter link
    </display-name>
    <attribute>
      <name>linkTitle</name>
      <required>false</required>
      <rtexprvalue>true</rtexprvalue>
    </attribute>
    <attribute>
      <name>styleClass</name>
      <required>false</required>
      <rtexprvalue>true</rtexprvalue>
    </attribute>
    <attribute>
      <name>key</name>
      <required>true</required>
      <rtexprvalue>true</rtexprvalue>
    </attribute>
    <attribute>
      <name>value</name>
      <required>true</required>
      <rtexprvalue>true</rtexprvalue>
    </attribute>
    <attribute>
      <name>label</name>
      <required>false</required>
      <rtexprvalue>true</rtexprvalue>
    </attribute>
    </tag>
</taglib>

JSP:

                        <c:forEach var="token" items="${i.keywordArray}" varStatus="loop" >
                            <pms:dfLink key="keyword" value="${token}" styleClass="keyword ${not loop.last ? '' : 'last'}"/>
                        </c:forEach>

If i comment out

  public int doEndTag() throws JspException {
    release();
    return EVAL_PAGE;
  }

the field 'label' will not be cleared for the second iteration!

thanks for your help,
Jeff

[Bear Bibeault]

I did not have to look far to see a problem.

if(label == null)
label = value;

You are modifying an instance variable from within the tag. That's a no no.

The instance variables that represent attribute values can only be set by the container. You muck with them under the covers, and all hell breaks loose.

[Jeff Schramm]

Bear Bibeault wrote:I did not have to look far to see a problem.

if(label == null)
label = value;

You are modifying an instance variable from within the tag. That's a no no.

The instance variables that represent attribute values can only be set by the container. You muck with them under the covers, and all hell breaks loose.

thank you for your advise- i will change it tomorrow

[Bear Bibeault]

This is one of the reasons that Simple Tag handling was introduced in JSP 2.0 -- Classic Tag handling has a lot of "rules" that are easy to fall afoul of.