TagData.java

/*
 * 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 java.util.Hashtable;

/**
 * The (translation-time only) attribute/value information for a tag instance.
 * <p>
 * TagData is only used as an argument to the isValid, validate, and getVariableInfo methods of TagExtraInfo, which are
 * invoked at translation time.
 */

public class TagData implements Cloneable {

    /**
     * Distinguished value for an attribute to indicate its value is a request-time expression (which is not yet
     * available because TagData instances are used at translation-time).
     */

    public static final Object REQUEST_TIME_VALUE = new Object();


    /**
     * Constructor for TagData.
     * <p>
     * A typical constructor may be
     *
     * <pre>
     * static final Object[][] att = { { "connection", "conn0" }, { "id", "query0" } };
     * static final TagData td = new TagData(att);
     * </pre>
     *
     * All values must be Strings except for those holding the distinguished object REQUEST_TIME_VALUE.
     *
     * @param atts the static attribute and values. May be null.
     */
    public TagData(Object[] atts[]) {
        if (atts == null) {
            attributes = new Hashtable<>();
        } else {
            attributes = new Hashtable<>(atts.length);
        }

        if (atts != null) {
            for (Object[] att : atts) {
                attributes.put((String) att[0], att[1]);
            }
        }
    }

    /**
     * Constructor for a TagData. If you already have the attributes in a hashtable, use this constructor.
     *
     * @param attrs A hashtable to get the values from.
     */
    public TagData(Hashtable<String,Object> attrs) {
        this.attributes = attrs;
    }

    /**
     * The value of the tag's id attribute.
     *
     * @return the value of the tag's id attribute, or null if no such attribute was specified.
     */

    public String getId() {
        return getAttributeString(TagAttributeInfo.ID);
    }

    /**
     * The value of the attribute. If a static value is specified for an attribute that accepts a request-time attribute
     * expression then that static value is returned, even if the value is provided in the body of a
     * &lt;jsp:attribute&gt; action. The distinguished object REQUEST_TIME_VALUE is only returned if the value is
     * specified as a request-time attribute expression or via the &lt;jsp:attribute&gt; action with a body that
     * contains dynamic content (scriptlets, scripting expressions, EL expressions, standard actions, or custom
     * actions). Returns null if the attribute is not set.
     *
     * @param attName the name of the attribute
     *
     * @return the attribute's value
     */

    public Object getAttribute(String attName) {
        return attributes.get(attName);
    }

    /**
     * Set the value of an attribute.
     *
     * @param attName the name of the attribute
     * @param value   the value.
     */
    public void setAttribute(String attName, Object value) {
        attributes.put(attName, value);
    }

    /**
     * Get the value for a given attribute.
     *
     * @param attName the name of the attribute
     *
     * @return the attribute value string
     *
     * @throws ClassCastException if attribute value is not a String
     */

    public String getAttributeString(String attName) {
        Object o = attributes.get(attName);
        if (o == null) {
            return null;
        }
        return (String) o;
    }

    /**
     * Enumerates the attributes.
     *
     * @return An enumeration of the attributes in a TagData
     */
    public java.util.Enumeration<String> getAttributes() {
        return attributes.keys();
    }

    // private data

    private final Hashtable<String,Object> attributes; // the tagname/value map
}