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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 (int i = 0; i < atts.length; i++) {
		attributes.put(atts[i][0], atts[i][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 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 <jsp:attribute> action.
     * The distinguished object REQUEST_TIME_VALUE is only returned if
     * the value is specified as a request-time attribute expression
     * or via the <jsp:attribute> 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;
	} else {
	    return (String) o;
	}	
    }

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

    // private data

    private Hashtable attributes;	// the tagname/value map
}