containsheadertag.java

来自「jakarta-taglibs」· Java 代码 · 共 98 行

/*
 * Copyright 1999,2004 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 org.apache.taglibs.response;

import java.util.*;
import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.jsp.*;
import javax.servlet.jsp.tagext.*;

/**
 * JSP Tag <b>containsHeader</b>, used to determine if the Http Response
 * contains the header named <b>name</b>.
 * <p>
 * Includes the body of the tag if the header exists.
 * <p>
 * You can set the optional tag attribute <b>value</b> to <b>true</b> or
 * <b>false</b>.  The body of the tag is included if containsHeader matches
 * the value.
 * <p>
 * JSP Tag Lib Descriptor
 * <p><pre>
 * &lt;name&gt;containsHeader&lt;/name&gt;
 * &lt;tagclass&gt;org.apache.taglibs.response.ContainsHeaderTag&lt;/tagclass&gt;
 * &lt;bodycontent&gt;JSP&lt;/bodycontent&gt;
 * &lt;info&gt;Test whether the HTTP Response contains a header.&lt;/info&gt;
 *   &lt;attribute&gt;
 *     &lt;name&gt;name&lt;/name&gt;
 *     &lt;required&gt;required&lt;/required&gt;
 *     &lt;rtexprvalue&gt;false&lt;/rtexprvalue&gt;
 *   &lt;/attribute&gt;
 *   &lt;attribute&gt;
 *     &lt;name&gt;value&lt;/name&gt;
 *     &lt;required&gt;false&lt;/required&gt;
 *     &lt;rtexprvalue&gt;false&lt;/rtexprvalue&gt;
 *   &lt;/attribute&gt;
 * </pre>
 *
 * @author Glenn Nielsen
 */

public class ContainsHeaderTag extends TagSupport
{
    private String name = null;
    private boolean value = true;

    /**
     * Used to test whether the HTTP Response contains a header.
     *
     * @return SKIP_BODY if containsHeader doesn't match value, EVAL_BODY_INCLUDE if containsHeader matches value
     */
    public final int doStartTag() throws JspException
    {
	boolean result = 
	((HttpServletResponse)pageContext.getResponse()).containsHeader(name);

	if( value == result )
	    return EVAL_BODY_INCLUDE;

	return SKIP_BODY;
    }

    /**   
     * Set the optional tag attribute <b>value</b> to true or false.
     *
     * @param boolean true or false
     */
    public final void setValue(boolean value)
    {
	this.value = value;
    }

    /**
     * Required attribute, name of the header.
     *
     * @param String name
     */
    public final void setName(String nam)
    {
	name = nam;
    }

}