AttributeTag.java

/*
 * Copyright 2004 The Apache Software Foundation.
 * 
 * Licensed 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.faces.webapp;

import javax.faces.component.UIComponent;
import javax.faces.context.FacesContext;
import javax.faces.el.ValueBinding;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.Tag;
import javax.servlet.jsp.tagext.TagSupport;

/**
 * see Javadoc of <a href="http://java.sun.com/j2ee/javaserverfaces/1.1_01/docs/api/index.html">JSF Specification</a>
 *
 * @author Manfred Geiler (latest modification by $Author$)
 * @version $Revision$ $Date$
 */
public class AttributeTag
        extends TagSupport
{
    private static final long serialVersionUID = 3147657100171678632L;
    private String _name;
    private String _value;

    public void setName(String name)
    {
        _name = name;
    }

    public void setValue(String value)
    {
        _value = value;
    }

    public int doStartTag() throws JspException
    {
        UIComponentTag componentTag = UIComponentTag.getParentUIComponentTag(pageContext);
        if (componentTag == null)
        {
            throw new JspException("no parent UIComponentTag found");
        }
        UIComponent component = componentTag.getComponentInstance();
        if (component == null)
        {
            throw new JspException("parent UIComponentTag has no UIComponent");
        }
        String name = getName();
        if (component.getAttributes().get(name) == null)
        {
            Object value = getValue();

            if(value != null)
                component.getAttributes().put(name, value);
        }
        return Tag.SKIP_BODY;
    }

    public void release()
    {
        super.release();
        _name = null;
        _value = null;
    }


    private String getName()
    {
        if (UIComponentTag.isValueReference(_name))
        {
            FacesContext facesContext = FacesContext.getCurrentInstance();
            ValueBinding vb = facesContext.getApplication().createValueBinding(_name);
            return (String)vb.getValue(facesContext);
        }
        else
        {
            return _name;
        }
    }

    private Object getValue()
    {
        if (UIComponentTag.isValueReference(_value))
        {
            FacesContext facesContext = FacesContext.getCurrentInstance();
            ValueBinding vb = facesContext.getApplication().createValueBinding(_value);
            return vb.getValue(facesContext);
        }
        else
        {
            return _value;
        }
    }

}