org.apache.myfaces.shared_tomahawk.resource.ValueExpressionFilterInputStream Maven / Gradle / Ivy

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JSF components and utilities that can be used with any JSF implementation. This library is based on the JSF1.1 version of Tomahawk, but with minor source code and build changes to take advantage of JSF2.1 features. A JSF2.1 implementation is required to use this version of the Tomahawk library.
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/*
 * 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 org.apache.myfaces.shared_tomahawk.resource;

import java.io.IOException;
import java.io.InputStream;
import java.io.PushbackInputStream;
import java.util.ArrayList;
import java.util.List;
import java.util.logging.Level;
import java.util.logging.Logger;

import javax.el.ELContext;
import javax.el.ELException;
import javax.el.ValueExpression;
import javax.faces.context.FacesContext;
import javax.faces.event.ExceptionQueuedEvent;
import javax.faces.event.ExceptionQueuedEventContext;

import org.apache.myfaces.shared_tomahawk.util.io.DynamicPushbackInputStream;

public class ValueExpressionFilterInputStream extends InputStream
{
    private PushbackInputStream delegate;
    private String libraryName;
    private String resourceName;
    
    public ValueExpressionFilterInputStream(InputStream in, String libraryName, String resourceName)
    {
        super();
        delegate = new DynamicPushbackInputStream(in,300);
    }

    @Override
    public int read() throws IOException
    {
        int c1 = delegate.read();
        
        if (c1 == -1)
        {
            return -1;
        }
        
        if ( ((char)c1) == '#')
        {
            int c2 = delegate.read();
            if (c2 == -1)
            {
                return -1;
            }
            if (((char)c2) == '{')
            {
                //It is a value expression. We need
                //to look for a occurrence of } to 
                //extract the expression and evaluate it,
                //the result should be unread.
                List expressionList = new ArrayList();
                int c3 = delegate.read();
                while ( c3 != -1 && ((char)c3) != '}' )
                {
                    expressionList.add(c3);
                    c3 = delegate.read();
                }
                
                if (c3 == -1)
                {
                    //get back the data, because we can't
                    //extract any value expression
                    for (int i = 0; i < expressionList.size(); i++)
                    {
                        delegate.unread(expressionList.get(i));
                    }
                    delegate.unread(c2);
                    return c1;
                }
                else
                {
                    //EL expression found. Evaluate it and pushback
                    //the result into the stream
                    FacesContext context = FacesContext.getCurrentInstance();
                    ELContext elContext = context.getELContext();
                    try
                    {
                        ValueExpression ve = context.getApplication().
                            getExpressionFactory().createValueExpression(
                                    elContext,
                                    "#{"+convertToExpression(expressionList)+"}",
                                    String.class);
                        String value = (String) ve.getValue(elContext);
                        
                        for (int i = value.length()-1; i >= 0 ; i--)
                        {
                            delegate.unread((int) value.charAt(i));
                        }
                    }
                    catch(ELException e)
                    {
                        ExceptionQueuedEventContext equecontext = new ExceptionQueuedEventContext (
                                context, e, null);
                        context.getApplication().publishEvent (context, ExceptionQueuedEvent.class, equecontext);
                        
                        Logger log = Logger.getLogger(ResourceImpl.class.getName());
                        if (log.isLoggable(Level.SEVERE))
                        {
                            log.severe("Cannot evaluate EL expression " + convertToExpression(expressionList)
                                    + " in resource " + (libraryName == null?"":libraryName) + ":" + 
                                    (resourceName == null?"":resourceName));
                        }
                        
                        delegate.unread(c3);
                        for (int i = expressionList.size()-1; i >= 0; i--)
                        {
                            delegate.unread(expressionList.get(i));
                        }
                        delegate.unread(c2);
                        return c1;
                    }
                    
                    //read again
                    return delegate.read();
                }
            }
            else
            {
                delegate.unread(c2);
                return c1;
            }
        }
        else
        {
            //just continue
            return c1;
        }
    }
    
    private String convertToExpression(List expressionList)
    {
        char[] exprArray = new char[expressionList.size()];
        
        for (int i = 0; i < expressionList.size(); i++)
        {
            exprArray[i] = (char) expressionList.get(i).intValue();
        }
        return String.valueOf(exprArray);
    }

    @Override
    public void close() throws IOException
    {
        delegate.close();
    }
}