java/jakarta/servlet/ServletOutputStream.java

/*
 * 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 jakarta.servlet;

import java.io.CharConversionException;
import java.io.IOException;
import java.io.OutputStream;
import java.nio.ByteBuffer;
import java.text.MessageFormat;
import java.util.Objects;
import java.util.ResourceBundle;

/**
 * Provides an output stream for sending binary data to the client. A <code>ServletOutputStream</code> object is
 * normally retrieved via the {@link ServletResponse#getOutputStream} method.
 * <p>
 * This is an abstract class that the servlet container implements. Subclasses of this class must implement the
 * <code>java.io.OutputStream.write(int)</code> method.
 *
 * @see ServletResponse
 */
public abstract class ServletOutputStream extends OutputStream {

    private static final String LSTRING_FILE = "jakarta.servlet.LocalStrings";
    private static final ResourceBundle lStrings = ResourceBundle.getBundle(LSTRING_FILE);

    /**
     * Does nothing, because this is an abstract class.
     */
    protected ServletOutputStream() {
        // NOOP
    }

    /**
     * Writes from the given buffer to the output stream.
     * <p>
     * If the output steam is in non-blocking mode, before each invocation of this method {@link #isReady()} must be
     * called and must return {@code true} or the {@link WriteListener#onWritePossible()} call back must indicate that
     * data may be written else an {@link IllegalStateException} must be thrown.
     * <p>
     * Otherwise, if this method is called when {@code buffer} has no data remaining, the method returns immediately and
     * {@code buffer} is unchanged.
     * <p>
     * If the output stream is in non-blocking mode, neither the position, limit nor content of the buffer passed to
     * this method may be modified until a subsequent call to {@link #isReady()} returns true or the
     * {@link WriteListener#onWritePossible()} call back indicates data may be written again. At this point the buffer's
     * limit will be unchanged from the value when passed to this method and the position will be the same as the limit.
     * <p>
     * If the output stream is in blocking mode and {@code buffer} has space remaining, this method blocks until all the
     * remaining data in the buffer has been written. When the method returns, and if data has been written, the
     * buffer's limit will be unchanged from the value when passed to this method and the position will be the same as
     * the limit.
     * <p>
     * Subclasses are strongly encouraged to override this method and provide a more efficient implementation.
     *
     * @param buffer The buffer from which the data is written.
     *
     * @exception IllegalStateException If the output stream is in non-blocking mode and this method is called without
     *                                      first calling {@link #isReady()} and that method has returned {@code true}
     *                                      or {@link WriteListener#onWritePossible()} has not signalled that data may
     *                                      be written.
     * @exception IOException           If the output stream has been closed or if some other I/O error occurs.
     * @exception NullPointerException  If buffer is null.
     *
     * @since Servlet 6.1
     */
    public void write(ByteBuffer buffer) throws IOException {
        Objects.requireNonNull(buffer);

        if (!isReady()) {
            throw new IllegalStateException();
        }

        if (buffer.remaining() == 0) {
            return;
        }

        byte[] b = new byte[buffer.remaining()];

        buffer.get(b);

        write(b);
    }

    /**
     * Writes a <code>String</code> to the client, without a carriage return-line feed (CRLF) character at the end.
     *
     * @param s the <code>String</code> to send to the client
     *
     * @exception IOException if an input or output exception occurred
     */
    public void print(String s) throws IOException {
        if (s == null) {
            s = "null";
        }
        int len = s.length();
        byte[] buffer = new byte[len];

        for (int i = 0; i < len; i++) {
            char c = s.charAt(i);

            //
            // XXX NOTE: This is clearly incorrect for many strings,
            // but is the only consistent approach within the current
            // servlet framework. It must suffice until servlet output
            // streams properly encode their output.
            //
            if ((c & 0xff00) != 0) { // high order byte must be zero
                String errMsg = lStrings.getString("err.not_iso8859_1");
                Object[] errArgs = new Object[1];
                errArgs[0] = Character.valueOf(c);
                errMsg = MessageFormat.format(errMsg, errArgs);
                throw new CharConversionException(errMsg);
            }
            buffer[i] = (byte) (c & 0xFF);
        }
        write(buffer);
    }

    /**
     * Writes a <code>boolean</code> value to the client, with no carriage return-line feed (CRLF) character at the end.
     *
     * @param b the <code>boolean</code> value to send to the client
     *
     * @exception IOException if an input or output exception occurred
     */
    public void print(boolean b) throws IOException {
        String msg;
        if (b) {
            msg = lStrings.getString("value.true");
        } else {
            msg = lStrings.getString("value.false");
        }
        print(msg);
    }

    /**
     * Writes a character to the client, with no carriage return-line feed (CRLF) at the end.
     *
     * @param c the character to send to the client
     *
     * @exception IOException if an input or output exception occurred
     */
    public void print(char c) throws IOException {
        print(String.valueOf(c));
    }

    /**
     * Writes an int to the client, with no carriage return-line feed (CRLF) at the end.
     *
     * @param i the int to send to the client
     *
     * @exception IOException if an input or output exception occurred
     */
    public void print(int i) throws IOException {
        print(String.valueOf(i));
    }

    /**
     * Writes a <code>long</code> value to the client, with no carriage return-line feed (CRLF) at the end.
     *
     * @param l the <code>long</code> value to send to the client
     *
     * @exception IOException if an input or output exception occurred
     */
    public void print(long l) throws IOException {
        print(String.valueOf(l));
    }

    /**
     * Writes a <code>float</code> value to the client, with no carriage return-line feed (CRLF) at the end.
     *
     * @param f the <code>float</code> value to send to the client
     *
     * @exception IOException if an input or output exception occurred
     */
    public void print(float f) throws IOException {
        print(String.valueOf(f));
    }

    /**
     * Writes a <code>double</code> value to the client, with no carriage return-line feed (CRLF) at the end.
     *
     * @param d the <code>double</code> value to send to the client
     *
     * @exception IOException if an input or output exception occurred
     */
    public void print(double d) throws IOException {
        print(String.valueOf(d));
    }

    /**
     * Writes a carriage return-line feed (CRLF) to the client.
     *
     * @exception IOException if an input or output exception occurred
     */
    public void println() throws IOException {
        print("\r\n");
    }

    /**
     * Writes a <code>String</code> to the client, followed by a carriage return-line feed (CRLF).
     *
     * @param s the <code>String</code> to write to the client
     *
     * @exception IOException if an input or output exception occurred
     */
    public void println(String s) throws IOException {
        StringBuilder sb = new StringBuilder();
        sb.append(s);
        sb.append("\r\n");
        print(sb.toString());
    }

    /**
     * Writes a <code>boolean</code> value to the client, followed by a carriage return-line feed (CRLF).
     *
     * @param b the <code>boolean</code> value to write to the client
     *
     * @exception IOException if an input or output exception occurred
     */
    public void println(boolean b) throws IOException {
        StringBuilder sb = new StringBuilder();
        if (b) {
            sb.append(lStrings.getString("value.true"));
        } else {
            sb.append(lStrings.getString("value.false"));
        }
        sb.append("\r\n");
        print(sb.toString());
    }

    /**
     * Writes a character to the client, followed by a carriage return-line feed (CRLF).
     *
     * @param c the character to write to the client
     *
     * @exception IOException if an input or output exception occurred
     */
    public void println(char c) throws IOException {
        println(String.valueOf(c));
    }

    /**
     * Writes an int to the client, followed by a carriage return-line feed (CRLF) character.
     *
     * @param i the int to write to the client
     *
     * @exception IOException if an input or output exception occurred
     */
    public void println(int i) throws IOException {
        println(String.valueOf(i));
    }

    /**
     * Writes a <code>long</code> value to the client, followed by a carriage return-line feed (CRLF).
     *
     * @param l the <code>long</code> value to write to the client
     *
     * @exception IOException if an input or output exception occurred
     */
    public void println(long l) throws IOException {
        println(String.valueOf(l));
    }

    /**
     * Writes a <code>float</code> value to the client, followed by a carriage return-line feed (CRLF).
     *
     * @param f the <code>float</code> value to write to the client
     *
     * @exception IOException if an input or output exception occurred
     */
    public void println(float f) throws IOException {
        println(String.valueOf(f));
    }

    /**
     * Writes a <code>double</code> value to the client, followed by a carriage return-line feed (CRLF).
     *
     * @param d the <code>double</code> value to write to the client
     *
     * @exception IOException if an input or output exception occurred
     */
    public void println(double d) throws IOException {
        println(String.valueOf(d));
    }

    /**
     * Returns {@code true} if it is allowable to call any method that may write data (e.g. {@code write()},
     * {@code print()} or {@code flush}). In blocking mode, this method will always return {@code true}, but a
     * subsequent call to a method that writes data may block. In non-blocking mode this method may return
     * {@code false}, in which case it is illegal to call a method that writes data and an {@link IllegalStateException}
     * MUST be thrown. When {@link WriteListener#onWritePossible()} is called, a call to this method that returned
     * {@code true} is implicit.
     * <p>
     * If this method returns {@code false} and a {@link WriteListener} has been set via
     * {@link #setWriteListener(WriteListener)}, then container will subsequently invoke
     * {@link WriteListener#onWritePossible()} once a write operation becomes possible without blocking. Other than the
     * initial call, {@link WriteListener#onWritePossible()} will only be called if and only if this method is called
     * and returns false.
     *
     * @return {@code true} if data can be written without blocking, otherwise returns {@code false}.
     *
     * @since Servlet 3.1
     */
    public abstract boolean isReady();

    /**
     * Sets the {@link WriteListener} for this {@link ServletOutputStream} and thereby switches to non-blocking IO. It
     * is only valid to switch to non-blocking IO within async processing or HTTP upgrade processing.
     *
     * @param listener The non-blocking IO write listener
     *
     * @throws IllegalStateException If this method is called if neither async nor HTTP upgrade is in progress or if the
     *                                   {@link WriteListener} has already been set
     * @throws NullPointerException  If listener is null
     *
     * @since Servlet 3.1
     */
    public abstract void setWriteListener(WriteListener listener);

    /**
     * {@inheritDoc}
     * <p>
     * If this method is called when the output stream is in non-blocking mode, it will immediately return with the
     * stream effectively closed, even if the stream contains buffered data that is yet to be written to client. The
     * container will write this data out in the background. If this process fails the
     * {@link WriteListener#onError(Throwable)} method will be invoked as normal.
     */
    @Override
    public void close() throws IOException {
        super.close();
    }
}