https://tomcat.apache.org/: JSP package 
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements.  See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License.  You may obtain a copy of the License at
*
*     http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package javax.servlet.jsp.tagext;

import javax.servlet.jsp.JspException;


For a tag to declare that it accepts dynamic attributes, it must implement
this interface.  The entry for the tag in the Tag Library Descriptor must
also be configured to indicate dynamic attributes are accepted.


For any attribute that is not declared in the Tag Library Descriptor for
this tag, instead of getting an error at translation time, the
setDynamicAttribute() method is called, with the name and
value of the attribute.  It is the responsibility of the tag to
remember the names and values of the dynamic attributes.

Since:2.0
/**
 * For a tag to declare that it accepts dynamic attributes, it must implement
 * this interface.  The entry for the tag in the Tag Library Descriptor must
 * also be configured to indicate dynamic attributes are accepted.
 * <br>
 * For any attribute that is not declared in the Tag Library Descriptor for
 * this tag, instead of getting an error at translation time, the
 * <code>setDynamicAttribute()</code> method is called, with the name and
 * value of the attribute.  It is the responsibility of the tag to
 * remember the names and values of the dynamic attributes.
 *
 * @since 2.0
 */
public interface DynamicAttributes {

    
Called when a tag declared to accept dynamic attributes is passed
an attribute that is not declared in the Tag Library Descriptor.

Params:
  • uri – the namespace of the attribute, or null if in the default
    namespace.
  • localName – the name of the attribute being set.
  • value – the value of the attribute
Throws:
  • JspException – if the tag handler wishes to
    signal that it does not accept the given attribute.  The
    container must not call doStartTag() or doTag() for this tag.
/**
     * Called when a tag declared to accept dynamic attributes is passed
     * an attribute that is not declared in the Tag Library Descriptor.
     *
     * @param uri the namespace of the attribute, or null if in the default
     *     namespace.
     * @param localName the name of the attribute being set.
     * @param value the value of the attribute
     * @throws JspException if the tag handler wishes to
     *     signal that it does not accept the given attribute.  The
     *     container must not call doStartTag() or doTag() for this tag.
     */
    public void setDynamicAttribute(
        String uri, String localName, Object value )
        throws JspException;

}