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Posted to dev@velocity.apache.org by jv...@locus.apache.org on 2000/11/16 08:06:01 UTC
cvs commit: jakarta-velocity/src/java/org/apache/velocity/io VelocityWriter.java JspWriter.java JspWriterImpl.java
jvanzyl 00/11/15 23:06:01
Added: src/java/org/apache/velocity/io VelocityWriter.java
Removed: src/java/org/apache/velocity/io JspWriter.java
JspWriterImpl.java
Log:
- merged the old JspWriter/JspWriterImpl as the base class mainly
consisted of documentation and a couple of fields. renamed it
to VelocityWriter.
Revision Changes Path
1.1 jakarta-velocity/src/java/org/apache/velocity/io/VelocityWriter.java
Index: VelocityWriter.java
===================================================================
package org.apache.velocity.io;
/*
* $Header: /home/cvs/jakarta-velocity/src/java/org/apache/velocity/io/VelocityWriter.java,v 1.1 2000/11/16 07:06:01 jvanzyl Exp $
* $Revision: 1.1 $
* $Date: 2000/11/16 07:06:01 $
*
* ====================================================================
*
* The Apache Software License, Version 1.1
*
* Copyright (c) 1999 The Apache Software Foundation. All rights
* reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* 3. The end-user documentation included with the redistribution, if
* any, must include the following acknowlegement:
* "This product includes software developed by the
* Apache Software Foundation (http://www.apache.org/)."
* Alternately, this acknowlegement may appear in the software itself,
* if and wherever such third-party acknowlegements normally appear.
*
* 4. The names "The Jakarta Project", "Tomcat", and "Apache Software
* Foundation" must not be used to endorse or promote products derived
* from this software without prior written permission. For written
* permission, please contact apache@apache.org.
*
* 5. Products derived from this software may not be called "Apache"
* nor may "Apache" appear in their names without prior written
* permission of the Apache Group.
*
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
* USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
* ====================================================================
*
* This software consists of voluntary contributions made by many
* individuals on behalf of the Apache Software Foundation. For more
* information on the Apache Software Foundation, please see
* <http://www.apache.org/>.
*
*/
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.Writer;
/**
* <p>
* The actions and template data in a JSP page is written using the
* JspWriter object that is referenced by the implicit variable out which
* is initialized automatically using methods in the PageContext object.
* <p>
* This abstract class emulates some of the functionality found in the
* java.io.BufferedWriter and java.io.PrintWriter classes,
* however it differs in that it throws java.io.IOException from the print
* methods while PrintWriter does not.
* <p><B>Buffering</B>
* <p>
* The initial JspWriter object is associated with the PrintWriter object
* of the ServletResponse in a way that depends on whether the page is or
* is not buffered. If the page is not buffered, output written to this
* JspWriter object will be written through to the PrintWriter directly,
* which will be created if necessary by invoking the getWriter() method
* on the response object. But if the page is buffered, the PrintWriter
* object will not be created until the buffer is flushed and
* operations like setContentType() are legal. Since this flexibility
* simplifies programming substantially, buffering is the default for JSP
* pages.
* <p>
* Buffering raises the issue of what to do when the buffer is
* exceeded. Two approaches can be taken:
* <ul>
* <li>
* Exceeding the buffer is not a fatal error; when the buffer is
* exceeded, just flush the output.
* <li>
* Exceeding the buffer is a fatal error; when the buffer is exceeded,
* raise an exception.
* </ul>
* <p>
* Both approaches are valid, and thus both are supported in the JSP
* technology. The behavior of a page is controlled by the autoFlush
* attribute, which defaults to true. In general, JSP pages that need to
* be sure that correct and complete data has been sent to their client
* may want to set autoFlush to false, with a typical case being that
* where the client is an application itself. On the other hand, JSP
* pages that send data that is meaningful even when partially
* constructed may want to set autoFlush to true; such as when the
* data is sent for immediate display through a browser. Each application
* will need to consider their specific needs.
* <p>
* An alternative considered was to make the buffer size unbounded; but,
* this had the disadvantage that runaway computations would consume an
* unbounded amount of resources.
* <p>
* The "out" implicit variable of a JSP implementation class is of this type.
* If the page directive selects autoflush="true" then all the I/O operations
* on this class shall automatically flush the contents of the buffer if an
* overflow condition would result if the current operation were performed
* without a flush. If autoflush="false" then all the I/O operations on this
* class shall throw an IOException if performing the current operation would
* result in a buffer overflow condition.
*
* @see java.io.Writer
* @see java.io.BufferedWriter
* @see java.io.PrintWriter
*
* Write text to a character-output stream, buffering characters so as
* to provide for the efficient writing of single characters, arrays,
* and strings.
*
* Provide support for discarding for the output that has been
* buffered.
*
* This needs revisiting when the buffering problems in the JSP spec
* are fixed -akv
*
* @author Anil K. Vijendran
*/
public final class VelocityWriter extends Writer
{
/**
* constant indicating that the Writer is not buffering output
*/
public static final int NO_BUFFER = 0;
/**
* constant indicating that the Writer is buffered and is using the implementation default buffer size
*/
public static final int DEFAULT_BUFFER = -1;
/**
* constant indicating that the Writer is buffered and is unbounded; this is used in BodyContent
*/
public static final int UNBOUNDED_BUFFER = -2;
protected int bufferSize;
protected boolean autoFlush;
private Writer writer;
private char cb[];
private int nextChar;
private static int defaultCharBufferSize = 8 * 1024;
private boolean flushed = false;
/**
* Create a buffered character-output stream that uses a default-sized
* output buffer.
*
* @param response A Servlet Response
*/
public VelocityWriter(Writer writer)
{
this(writer, defaultCharBufferSize, true);
}
/**
* private constructor.
*/
private VelocityWriter(int bufferSize, boolean autoFlush)
{
this.bufferSize = bufferSize;
this.autoFlush = autoFlush;
}
/**
* This method returns the size of the buffer used by the JspWriter.
*
* @return the size of the buffer in bytes, or 0 is unbuffered.
*/
public int getBufferSize() { return bufferSize; }
/**
* This method indicates whether the JspWriter is autoFlushing.
*
* @return if this JspWriter is auto flushing or throwing IOExceptions on buffer overflow conditions
*/
public boolean isAutoFlush() { return autoFlush; }
/**
* Create a new buffered character-output stream that uses an output
* buffer of the given size.
*
* @param response A Servlet Response
* @param sz Output-buffer size, a positive integer
*
* @exception IllegalArgumentException If sz is <= 0
*/
public VelocityWriter(Writer writer, int sz, boolean autoFlush)
{
this(sz, autoFlush);
if (sz < 0)
throw new IllegalArgumentException("Buffer size <= 0");
this.writer = writer;
cb = sz == 0 ? null : new char[sz];
nextChar = 0;
}
private final void init( Writer writer, int sz, boolean autoFlush )
{
this.writer= writer;
if( sz > 0 && ( cb == null || sz > cb.length ) )
cb=new char[sz];
nextChar = 0;
this.autoFlush=autoFlush;
this.bufferSize=sz;
}
/**
* Flush the output buffer to the underlying character stream, without
* flushing the stream itself. This method is non-private only so that it
* may be invoked by PrintStream.
*/
private final void flushBuffer() throws IOException
{
if (bufferSize == 0)
return;
flushed = true;
if (nextChar == 0)
return;
writer.write(cb, 0, nextChar);
nextChar = 0;
}
/**
* Discard the output buffer.
*/
public final void clear()
{
nextChar = 0;
}
private final void bufferOverflow() throws IOException
{
throw new IOException("overflow");
}
/**
* Flush the stream.
*
*/
public final void flush() throws IOException
{
flushBuffer();
if (writer != null)
{
writer.flush();
}
}
/**
* Close the stream.
*
*/
public final void close() throws IOException {
if (writer == null)
return;
flush();
}
/**
* @return the number of bytes unused in the buffer
*/
public final int getRemaining()
{
return bufferSize - nextChar;
}
/**
* Write a single character.
*
*/
public final void write(int c) throws IOException
{
if (bufferSize == 0)
{
writer.write(c);
}
else
{
if (nextChar >= bufferSize)
if (autoFlush)
flushBuffer();
else
bufferOverflow();
cb[nextChar++] = (char) c;
}
}
/**
* Our own little min method, to avoid loading java.lang.Math if we've run
* out of file descriptors and we're trying to print a stack trace.
*/
private final int min(int a, int b)
{
if (a < b) return a;
return b;
}
/**
* Write a portion of an array of characters.
*
* <p> Ordinarily this method stores characters from the given array into
* this stream's buffer, flushing the buffer to the underlying stream as
* needed. If the requested length is at least as large as the buffer,
* however, then this method will flush the buffer and write the characters
* directly to the underlying stream. Thus redundant
* <code>DiscardableBufferedWriter</code>s will not copy data unnecessarily.
*
* @param cbuf A character array
* @param off Offset from which to start reading characters
* @param len Number of characters to write
*
*/
public final void write(char cbuf[], int off, int len)
throws IOException
{
if (bufferSize == 0)
{
writer.write(cbuf, off, len);
return;
}
if (len == 0)
{
return;
}
if (len >= bufferSize)
{
/* If the request length exceeds the size of the output buffer,
flush the buffer and then write the data directly. In this
way buffered streams will cascade harmlessly. */
if (autoFlush)
flushBuffer();
else
bufferOverflow();
writer.write(cbuf, off, len);
return;
}
int b = off, t = off + len;
while (b < t)
{
int d = min(bufferSize - nextChar, t - b);
System.arraycopy(cbuf, b, cb, nextChar, d);
b += d;
nextChar += d;
if (nextChar >= bufferSize)
if (autoFlush)
flushBuffer();
else
bufferOverflow();
}
}
/**
* Write an array of characters. This method cannot be inherited from the
* Writer class because it must suppress I/O exceptions.
*/
public final void write(char buf[]) throws IOException
{
write(buf, 0, buf.length);
}
/**
* Write a portion of a String.
*
* @param s String to be written
* @param off Offset from which to start reading characters
* @param len Number of characters to be written
*
*/
public final void write(String s, int off, int len) throws IOException
{
if (bufferSize == 0)
{
writer.write(s, off, len);
return;
}
int b = off, t = off + len;
while (b < t)
{
int d = min(bufferSize - nextChar, t - b);
s.getChars(b, b + d, cb, nextChar);
b += d;
nextChar += d;
if (nextChar >= bufferSize)
if (autoFlush)
flushBuffer();
else
bufferOverflow();
}
}
/**
* Write a string. This method cannot be inherited from the Writer class
* because it must suppress I/O exceptions.
*/
public final void write(String s) throws IOException
{
write(s, 0, s.length());
}
/**
* resets this class so that it can be reused
*
*/
public final void recycle(OutputStreamWriter writer)
{
this.writer = writer;
flushed = false;
clear();
}
}