ImportResponseWrapper.java

/*
 * Copyright (c) JForum Team. All rights reserved.
 *
 * The software in this package is published under the terms of the LGPL
 * license a copy of which has been included with this distribution in the
 * license.txt file.
 *
 * The JForum Project
 * http://www.jforum.net
 */
package net.jforum.core.tags;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.PrintWriter;
import java.io.StringWriter;
import java.io.UnsupportedEncodingException;
import java.util.Locale;

import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpServletResponseWrapper;

import org.apache.taglibs.standard.resources.Resources;

/**
 * @author Bill
 *
 */
/** Wraps responses to allow us to retrieve results as Strings. */
public class ImportResponseWrapper extends HttpServletResponseWrapper {

	// ************************************************************
	// Overview

	/*
	 * We provide either a Writer or an OutputStream as requested. We actually
	 * have a true Writer and an OutputStream backing both, since we don't want
	 * to use a character encoding both ways (Writer -> OutputStream -> Writer).
	 * So we use no encoding at all (as none is relevant) when the target
	 * resource uses a Writer. And we decode the OutputStream's bytes using OUR
	 * tag's 'charEncoding' attribute, or ISO-8859-1 as the default. We thus
	 * ignore setLocale() and setContentType() in this wrapper.
	 * 
	 * In other words, the target's asserted encoding is used to convert from a
	 * Writer to an OutputStream, which is typically the medium through with the
	 * target will communicate its ultimate response. Since we short-circuit
	 * that mechanism and read the target's characters directly if they're
	 * offered as such, we simply ignore the target's encoding assertion.
	 */

	// ************************************************************
	// Data
	/** Default character encoding for response. */
	public static final String DEFAULT_ENCODING = "ISO-8859-1";

	private String charEncoding = null; // 'charEncoding' attrib.

	/** The Writer we convey. */
	private StringWriter sw = new StringWriter();

	/** A buffer, alternatively, to accumulate bytes. */
	private ByteArrayOutputStream bos = new ByteArrayOutputStream();

	/** A ServletOutputStream we convey, tied to this Writer. */
	private ServletOutputStream sos = new ServletOutputStream() {
		public void write(int b) throws IOException {
			bos.write(b);
		}
	};

	/** 'True' if getWriter() was called; false otherwise. */
	private boolean isWriterUsed;

	/** 'True if getOutputStream() was called; false otherwise. */
	private boolean isStreamUsed;

	/** The HTTP status set by the target. */
	private int status = 200;

	// ************************************************************
	// Constructor and methods

	/** Constructs a new ImportResponseWrapper. */
	public ImportResponseWrapper(HttpServletResponse response) {
		super(response);
	}

	/** Returns a Writer designed to buffer the output. */
	public PrintWriter getWriter() {
		if (isStreamUsed)
			throw new IllegalStateException(Resources
					.getMessage("IMPORT_ILLEGAL_STREAM"));
		isWriterUsed = true;
		return new PrintWriter(sw);
	}

	/** Returns a ServletOutputStream designed to buffer the output. */
	public ServletOutputStream getOutputStream() {
		if (isWriterUsed)
			throw new IllegalStateException(Resources
					.getMessage("IMPORT_ILLEGAL_WRITER"));
		isStreamUsed = true;
		return sos;
	}

	/** Has no effect. */
	public void setContentType(String x) {
		// ignore
	}

	/** Has no effect. */
	public void setLocale(Locale x) {
		// ignore
	}

	public void setStatus(int status) {
		this.status = status;
	}

	public int getStatus() {
		return status;
	}

	public String getCharEncoding() {
		return charEncoding;
	}

	public void setCharEncoding(String charEncoding) {
		this.charEncoding = charEncoding;
	}

	/**
	 * Retrieves the buffered output, using the containing tag's 'charEncoding'
	 * attribute, or the tag's default encoding, <b>if necessary</b>.
	 */
	// not simply toString() because we need to throw
	// UnsupportedEncodingException
	public String getString() throws UnsupportedEncodingException {
		if (isWriterUsed)
			return sw.toString();
		else if (isStreamUsed) {
			if (charEncoding != null && !charEncoding.equals(""))
				return bos.toString(charEncoding);
			else
				return bos.toString(DEFAULT_ENCODING);
		} else
			return ""; // target didn't write anything
	}
}