Commons IO example source code file (ProxyWriter.java)

This example Commons IO source code file (ProxyWriter.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Commons IO tags/keywords

filterwriter, io, ioexception, ioexception, override, override, proxywriter, proxywriter, writer, writer

The Commons IO ProxyWriter.java source code

/*
 * 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.commons.io.output;

import java.io.FilterWriter;
import java.io.IOException;
import java.io.Writer;

/**
 * A Proxy stream which acts as expected, that is it passes the method 
 * calls on to the proxied stream and doesn't change which methods are 
 * being called. It is an alternative base class to FilterWriter
 * to increase reusability, because FilterWriter changes the 
 * methods being called, such as write(char[]) to write(char[], int, int)
 * and write(String) to write(String, int, int).
 * 
 * @author Stephen Colebourne
 * @version $Id: ProxyWriter.java 1003647 2010-10-01 20:53:59Z niallp $
 */
public class ProxyWriter extends FilterWriter {

    /**
     * Constructs a new ProxyWriter.
     * 
     * @param proxy  the Writer to delegate to
     */
    public ProxyWriter(Writer proxy) {
        super(proxy);
        // the proxy is stored in a protected superclass variable named 'out'
    }

    /**
     * Invokes the delegate's <code>append(char) method.
     * @param c The character to write
     * @return this writer
     * @throws IOException if an I/O error occurs
     * @since Commons IO 2.0
     */
    @Override
    public Writer append(char c) throws IOException {
        try {
            beforeWrite(1);
            out.append(c);
            afterWrite(1);
        } catch (IOException e) {
            handleIOException(e);
        }
        return this;
    }

    /**
     * Invokes the delegate's <code>append(CharSequence, int, int) method.
     * @param csq The character sequence to write
     * @param start The index of the first character to write
     * @param end  The index of the first character to write (exclusive)
     * @return this writer
     * @throws IOException if an I/O error occurs
     * @since Commons IO 2.0
     */
    @Override
    public Writer append(CharSequence csq, int start, int end) throws IOException {
        try {
            beforeWrite(end - start);
            out.append(csq, start, end);
            afterWrite(end - start);
        } catch (IOException e) {
            handleIOException(e);
        }
        return this;
    }

    /**
     * Invokes the delegate's <code>append(CharSequence) method.
     * @param csq The character sequence to write
     * @return this writer
     * @throws IOException if an I/O error occurs
     * @since Commons IO 2.0
     */
    @Override
    public Writer append(CharSequence csq) throws IOException {
        try {
            int len = 0;
            if (csq != null) {
                len = csq.length();
            }

            beforeWrite(len);
            out.append(csq);
            afterWrite(len);
        } catch (IOException e) {
            handleIOException(e);
        }
        return this;
    }

    /**
     * Invokes the delegate's <code>write(int) method.
     * @param idx the character to write
     * @throws IOException if an I/O error occurs
     */
    @Override
    public void write(int idx) throws IOException {
        try {
            beforeWrite(1);
            out.write(idx);
            afterWrite(1);
        } catch (IOException e) {
            handleIOException(e);
        }
    }

    /**
     * Invokes the delegate's <code>write(char[]) method.
     * @param chr the characters to write
     * @throws IOException if an I/O error occurs
     */
    @Override
    public void write(char[] chr) throws IOException {
        try {
            int len = 0;
            if (chr != null) {
                len = chr.length;
            }

            beforeWrite(len);
            out.write(chr);
            afterWrite(len);
        } catch (IOException e) {
            handleIOException(e);
        }
    }

    /**
     * Invokes the delegate's <code>write(char[], int, int) method.
     * @param chr the characters to write
     * @param st The start offset
     * @param len The number of characters to write
     * @throws IOException if an I/O error occurs
     */
    @Override
    public void write(char[] chr, int st, int len) throws IOException {
        try {
            beforeWrite(len);
            out.write(chr, st, len);
            afterWrite(len);
        } catch (IOException e) {
            handleIOException(e);
        }
    }

    /**
     * Invokes the delegate's <code>write(String) method.
     * @param str the string to write
     * @throws IOException if an I/O error occurs
     */
    @Override
    public void write(String str) throws IOException {
        try {
            int len = 0;
            if (str != null) {
                len = str.length();
            }

            beforeWrite(len);
            out.write(str);
            afterWrite(len);
        } catch (IOException e) {
            handleIOException(e);
        }
    }

    /**
     * Invokes the delegate's <code>write(String) method.
     * @param str the string to write
     * @param st The start offset
     * @param len The number of characters to write
     * @throws IOException if an I/O error occurs
     */
    @Override
    public void write(String str, int st, int len) throws IOException {
        try {
            beforeWrite(len);
            out.write(str, st, len);
            afterWrite(len);
        } catch (IOException e) {
            handleIOException(e);
        }
    }

    /**
     * Invokes the delegate's <code>flush() method.
     * @throws IOException if an I/O error occurs
     */
    @Override
    public void flush() throws IOException {
        try {
            out.flush();
        } catch (IOException e) {
            handleIOException(e);
        }
    }

    /**
     * Invokes the delegate's <code>close() method.
     * @throws IOException if an I/O error occurs
     */
    @Override
    public void close() throws IOException {
        try {
            out.close();
        } catch (IOException e) {
            handleIOException(e);
        }
    }

    /**
     * Invoked by the write methods before the call is proxied. The number
     * of chars to be written (1 for the {@link #write(int)} method, buffer
     * length for {@link #write(char[])}, etc.) is given as an argument.
     * <p>
     * Subclasses can override this method to add common pre-processing
     * functionality without having to override all the write methods.
     * The default implementation does nothing.
     *
     * @since Commons IO 2.0
     * @param n number of chars to be written
     * @throws IOException if the pre-processing fails
     */
    protected void beforeWrite(int n) throws IOException {
    }

    /**
     * Invoked by the write methods after the proxied call has returned
     * successfully. The number of chars written (1 for the
     * {@link #write(int)} method, buffer length for {@link #write(char[])},
     * etc.) is given as an argument.
     * <p>
     * Subclasses can override this method to add common post-processing
     * functionality without having to override all the write methods.
     * The default implementation does nothing.
     *
     * @since Commons IO 2.0
     * @param n number of chars written
     * @throws IOException if the post-processing fails
     */
    protected void afterWrite(int n) throws IOException {
    }

    /**
     * Handle any IOExceptions thrown.
     * <p>
     * This method provides a point to implement custom exception
     * handling. The default behaviour is to re-throw the exception.
     * @param e The IOException thrown
     * @throws IOException if an I/O error occurs
     * @since Commons IO 2.0
     */
    protected void handleIOException(IOException e) throws IOException {
        throw e;
    }

}