CommittingOutputStream.java

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package com.sun.jersey.api.client;

import java.io.IOException;
import java.io.OutputStream;

/**
 * A commiting output stream that commits before
 * the first byte is written to the adapted {@link OutputStream}.
 * <p>
 * This class may be overridden to provide the commit functionality.
 * 
 * @author Paul.Sandoz@Sun.Com
 */
public abstract class CommittingOutputStream extends OutputStream {

    private OutputStream o;

    private boolean isCommitted;

    /**
     * Construct a new instance.
     * <p>
     * The method {@link #getOutputStream() } MUST be overridden
     * to return an output stream.
     */
    public CommittingOutputStream() {
    }

    /**
     * Construct a new instance with an output stream to adapt.
     *
     * @param o the adapted output stream.
     * @throws IllegalArgumentException if <code>o</code> is null.
     */
    public CommittingOutputStream(OutputStream o) {
        if (o == null)
            throw new IllegalArgumentException();
        
        this.o = o;
    }

    @Override
    public void write(byte b[]) throws IOException {
        commitWrite();
        o.write(b);
    }

    @Override
    public void write(byte b[], int off, int len) throws IOException {
        commitWrite();
        o.write(b, off, len);
    }

    public void write(int b) throws IOException {
        commitWrite();
        o.write(b);
    }

    @Override
    public void flush() throws IOException {
        commitWrite();
        o.flush();
    }

    @Override
    public void close() throws IOException {
        commitWrite();
        o.close();
    }

    private void commitWrite() throws IOException {
        if (!isCommitted) {
            isCommitted = true;

            commit();

            if (o == null)
                o = getOutputStream();
        }
    }

    /**
     * Get the adapted output stream.
     * <p>
     * This method MUST be overriden if the empty constructor is
     * utilized to construct an instance of this class.
     * 
     * @return the adapted output stream.
     * @throws java.io.IOException
     */
    protected OutputStream getOutputStream() throws IOException {
        throw new IllegalStateException();
    }

    /**
     * Perform the commit functionality.
     * 
     * @throws java.io.IOException
     */
    protected abstract void commit() throws IOException;
};