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Groovy example source code file (SystemOutputInterceptor.java)

This example Groovy source code file (SystemOutputInterceptor.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 - Groovy tags/keywords

boolean, boolean, closure, closure, filteroutputstream, io, ioexception, printstream, printstream, string, systemoutputinterceptor, systemoutputinterceptor

The Groovy SystemOutputInterceptor.java source code

/*
 * Copyright 2003-2007 the original author or authors.
 *
 * Licensed 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 groovy.ui;

import groovy.lang.Closure;

import java.io.FilterOutputStream;
import java.io.IOException;
import java.io.PrintStream;

/**
 * Intercepts System.out/System.err. Implementation helper for Console.groovy.
 *
 * @version $Id: SystemOutputInterceptor.java 21223 2010-12-03 21:48:51Z hamletdrc $
 */
public class SystemOutputInterceptor extends FilterOutputStream {

    private Closure callback;
    private boolean output;

    /**
     * Constructor
     *
     * @param callback accepts a string to be sent to std out and returns a Boolean.
     *                 If the return value is true, output will be sent to
     *                 System.out, otherwise it will not.
     */
    public SystemOutputInterceptor(final Closure callback) {
        this(callback, true);
    }

    /**
     * Constructor
     *
     * @param callback accepts a string to be sent to std out and returns a Boolean.
     *                 If the return value is true, output will be sent to
     *                 System.out/System.err, otherwise it will not.
     * @param output   flag that tells whether System.out needs capturing ot System.err
     */
    public SystemOutputInterceptor(final Closure callback, boolean output) {
        super(output ? System.out : System.err);

        assert callback != null;

        this.callback = callback;
        this.output = output;
    }

    /**
     * Starts intercepting System.out/System.err
     */
    public void start() {
        if (output) {
            System.setOut(new PrintStream(this));
        } else {
            System.setErr(new PrintStream(this));
        }
    }

    /**
     * Stops intercepting System.out/System.err, sending output to wherever it was
     * going when this interceptor was created.
     */
    public void stop() {
        if (output) {
            System.setOut((PrintStream) out);
        } else {
            System.setErr((PrintStream) out);
        }
    }

    /**
     * Intercepts output - moret common case of byte[]
     */
    public void write(byte[] b, int off, int len) throws IOException {
        Boolean result = (Boolean) callback.call(new String(b, off, len));
        if (result) {
            out.write(b, off, len);
        }
    }

    /**
     * Intercepts output - single characters
     */
    public void write(int b) throws IOException {
        Boolean result = (Boolean) callback.call(String.valueOf((char) b));
        if (result) {
            out.write(b);
        }
    }
}

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