001    /* 
002        Licensed to the Apache Software Foundation (ASF) under one
003        or more contributor license agreements.  See the NOTICE file
004        distributed with this work for additional information
005        regarding copyright ownership.  The ASF licenses this file
006        to you under the Apache License, Version 2.0 (the
007        "License"); you may not use this file except in compliance
008        with the License.  You may obtain a copy of the License at
009    
010           http://www.apache.org/licenses/LICENSE-2.0
011    
012        Unless required by applicable law or agreed to in writing,
013        software distributed under the License is distributed on an
014        "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015        KIND, either express or implied.  See the License for the
016        specific language governing permissions and limitations
017        under the License.  
018     */
019    package org.apache.wiki.tags;
020    
021    import java.io.IOException;
022    
023    import javax.servlet.jsp.JspWriter;
024    import javax.servlet.jsp.JspException;
025    
026    import org.apache.wiki.WikiEngine;
027    import org.apache.wiki.api.exceptions.NoSuchVariableException;
028    import org.apache.wiki.util.TextUtil;
029    
030    /**
031     *  Returns the value of an Wiki variable.
032     *
033     *  <P><B>Attributes</B></P>
034     *  <UL>
035     *    <LI>var - Name of the variable.  Required.
036     *    <LI>default - Revert to this value, if the value of "var" is null.
037     *                  If left out, this tag will produce a concise error message
038     *                  if the named variable is not found. Set to empty (default="")
039     *                  to hide the message.
040     *  </UL>
041     *
042     *  <P>A default value implies <I>failmode='quiet'</I>.
043     *
044     *  @since 2.0
045     */
046    public class VariableTag
047        extends WikiTagBase
048    {
049        private static final long serialVersionUID = 0L;
050    
051        private String m_var      = null;
052        private String m_default  = null;
053    
054        public void initTag()
055        {
056            super.initTag();
057            m_var = m_default = null;
058        }
059    
060        public String getVar()
061        {
062            return m_var;
063        }
064    
065        public void setVar( String arg )
066        {
067            m_var = arg;
068        }
069    
070        public void setDefault( String arg )
071        {
072            m_default = arg;
073        }
074    
075        public final int doWikiStartTag()
076            throws JspException,
077                   IOException
078        {
079            WikiEngine engine   = m_wikiContext.getEngine();
080            JspWriter out = pageContext.getOut();
081            String msg = null;
082            String value = null;
083    
084            try
085            {
086                value = engine.getVariableManager().getValue( m_wikiContext,
087                                                              getVar() );
088            }
089            catch( NoSuchVariableException e )
090            {
091                msg = "No such variable: "+e.getMessage();
092            }
093            catch( IllegalArgumentException e )
094            {
095                msg = "Incorrect variable name: "+e.getMessage();
096            }
097    
098            if( value == null )
099            {
100                value = m_default;
101            }
102    
103            if( value == null )
104            {
105                value = msg;
106            }
107            out.write( TextUtil.replaceEntities(value) );
108            return SKIP_BODY;
109        }
110    }