/*
 * The Apache Software License, Version 1.1
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 * Copyright (c) 1999 The Apache Software Foundation.  All rights 
 * reserved.
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 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
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 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer. 
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 *    notice, this list of conditions and the following disclaimer in
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 *    any, must include the following acknowlegement:  
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package org.apache.taglibs.standard.examples.taglib;

import java.io.*;

import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.jsp.*;
import javax.servlet.jsp.tagext.*;
import org.apache.taglibs.standard.lang.support.ExpressionEvaluatorManager;

import org.apache.taglibs.standard.examples.util.*;

/**
 * <p>Tag handler for &lt;resource&gt;
 *
 * @author Pierre Delisle
 * @version $Revision: 1.1.1.1 $ $Date: 2001/11/21 07:34:25 $
 */
public class ResourceTag extends TagSupport {
    
    //*********************************************************************
    // Instance variables
    
    private String id;
    private String resource;
    
    private Reader reader;
    
    //*********************************************************************
    // Constructors
    
    public ResourceTag() {
        super();
        init();
    }
    
    private void init() {
        id = null;
        resource = null;
    }
    
    //*********************************************************************
    // Tag's properties
    
    /**
     * Tag's 'id' attribute
     */
    public void setId(String id) {
        this.id = id;
    }
    
    /**
     * Tag's 'resource' attribute
     */
    public void setResource(String resource) {
        this.resource = resource;
    }
    
    //*********************************************************************
    // TagSupport methods
    
    public int doStartTag() throws JspException {
        reader = getReaderFromResource((String)eval("resource", resource, String.class));
        exposeVariable(reader);
        return EVAL_BODY_INCLUDE;
    }
    
    public int doEndTag() throws JspException {
        try {
            reader.close();
        } catch (IOException ex) {}
        reader = null;
        return EVAL_PAGE;
    }
    
    /**
     * Releases any resources we may have (or inherit)
     */
    public void release() {
        super.release();
        init();
    }
    
    //*********************************************************************
    // Tag's scific behavior methods
    
    private Reader getReaderFromResource(String name) throws JspException {
        HttpServletRequest request =
        (HttpServletRequest)pageContext.getRequest();
        HttpServletResponse response =
        (HttpServletResponse)pageContext.getResponse();
        RequestDispatcher rd = null;
        
        // The response of the local URL becomes the reader that
        // we export. Need temporary storage.
        IOBean ioBean = new IOBean();
        Writer writer = ioBean.getWriter();
        ServletResponseWrapper responseWrapper =
        new ServletResponseWrapperForWriter(
        response, new PrintWriter(writer));
        rd = pageContext.getServletContext().getRequestDispatcher(name);
        try {
            rd.include(request, responseWrapper);
            return ioBean.getReader();
        } catch (Exception ex) {
            throw new JspException(ex);
        }
    }
    
    //*********************************************************************
    // Utility methods
    
    /**
     * Evaluate elexprvalue
     */
    private Object eval(String attName, String attValue, Class clazz)
    throws JspException {
        Object obj = ExpressionEvaluatorManager.evaluate(
        attName, attValue, clazz, this, pageContext);
        if (obj == null) {
            throw new NullAttributeException("escapeHtml", attName);
        } else {
            return obj;
        }
    }
    
    private void exposeVariable(Reader reader) {
        if (id != null) {
            pageContext.setAttribute(id, reader);
        }
    }
}
