jspwriterimpl.java

业界著名的tomcat服务器的最新6.0的源代码。

/*
 * 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.jasper.runtime;

import java.io.IOException;
import java.io.Writer;
import java.security.AccessController;
import java.security.PrivilegedAction;

import javax.servlet.ServletResponse;
import javax.servlet.jsp.JspWriter;

import org.apache.jasper.Constants;
import org.apache.jasper.compiler.Localizer;
import org.apache.jasper.security.SecurityUtil;

/**
 * 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 class JspWriterImpl extends JspWriter {
    
    private Writer out;
    private ServletResponse response;    
    private char cb[];
    private int nextChar;
    private boolean flushed = false;
    private boolean closed = false;
    
    public JspWriterImpl() {
        super( Constants.DEFAULT_BUFFER_SIZE, true );
    }
    
    /**
     * Create a buffered character-output stream that uses a default-sized
     * output buffer.
     *
     * @param  response  A Servlet Response
     */
    public JspWriterImpl(ServletResponse response) {
        this(response, Constants.DEFAULT_BUFFER_SIZE, true);
    }
    
    /**
     * 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 JspWriterImpl(ServletResponse response, int sz, 
            boolean autoFlush) {
        super(sz, autoFlush);
        if (sz < 0)
            throw new IllegalArgumentException("Buffer size <= 0");
        this.response = response;
        cb = sz == 0 ? null : new char[sz];
        nextChar = 0;
    }
    
    void init( ServletResponse response, int sz, boolean autoFlush ) {
        this.response= response;
        if( sz > 0 && ( cb == null || sz > cb.length ) )
            cb=new char[sz];
        nextChar = 0;
        this.autoFlush=autoFlush;
        this.bufferSize=sz;
    }
    
    /** Package-level access
     */
    void recycle() {
        flushed = false;
        closed = false;
        out = null;
        nextChar = 0;
        response = null;
    }
    
    /**
     * 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.
     */
    protected final void flushBuffer() throws IOException {
        if (bufferSize == 0)
            return;
        flushed = true;
        ensureOpen();
        if (nextChar == 0)
            return;
        initOut();
        out.write(cb, 0, nextChar);
        nextChar = 0;
    }
    
    private void initOut() throws IOException {
        if (out == null) {
            out = response.getWriter();
        }
    }
    
    private String getLocalizeMessage(final String message){
        if (SecurityUtil.isPackageProtectionEnabled()){
            return (String)AccessController.doPrivileged(new PrivilegedAction(){
                public Object run(){
                    return Localizer.getMessage(message); 
                }
            });
        } else {
            return Localizer.getMessage(message);
        }
    }
    
    /**
     * Discard the output buffer.
     */
    public final void clear() throws IOException {
        if ((bufferSize == 0) && (out != null))
            // clear() is illegal after any unbuffered output (JSP.5.5)
            throw new IllegalStateException(
                    getLocalizeMessage("jsp.error.ise_on_clear"));
        if (flushed)
            throw new IOException(
                    getLocalizeMessage("jsp.error.attempt_to_clear_flushed_buffer"));
        ensureOpen();
        nextChar = 0;
    }
    
    public void clearBuffer() throws IOException {
        if (bufferSize == 0)
            throw new IllegalStateException(
                    getLocalizeMessage("jsp.error.ise_on_clear"));
        ensureOpen();
        nextChar = 0;
    }
    
    private final void bufferOverflow() throws IOException {
        throw new IOException(getLocalizeMessage("jsp.error.overflow"));
    }
    
    /**
     * Flush the stream.
     *
     */
    public void flush()  throws IOException {
        flushBuffer();
        if (out != null) {
            out.flush();
        }
    }
    
    /**
     * Close the stream.
     *
     */
    public void close() throws IOException {
        if (response == null || closed)
            // multiple calls to close is OK
            return;
        flush();
        if (out != null)
            out.close();
        out = null;
        closed = true;
    }
    
    /**
     * @return the number of bytes unused in the buffer
     */
    public int getRemaining() {
        return bufferSize - nextChar;
    }
    
    /** check to make sure that the stream has not been closed */
    private void ensureOpen() throws IOException {
        if (response == null || closed)
            throw new IOException("Stream closed");
    }
    
    
    /**
     * Write a single character.
     */
    public void write(int c) throws IOException {
        ensureOpen();
        if (bufferSize == 0) {
            initOut();
            out.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 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 void write(char cbuf[], int off, int len) 
    throws IOException 
    {
        ensureOpen();
        
        if (bufferSize == 0) {
            initOut();
            out.write(cbuf, off, len);
            return;
        }
        
        if ((off < 0) || (off > cbuf.length) || (len < 0) ||
                ((off + len) > cbuf.length) || ((off + len) < 0)) {
            throw new IndexOutOfBoundsException();
        } else 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();
            initOut();
            out.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();
        }
        
    }
    
    /**