grails.io.support.SystemOutErrCapturer.groovy Maven / Gradle / Ivy

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/*
 * Copyright 2014 original 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 grails.io.support

import groovy.transform.CompileStatic


/**
 * Utility for capturing the result of calls to System.out / System.err
 */
@CompileStatic
class SystemOutErrCapturer {
    ByteArrayOutputStream out
    ByteArrayOutputStream err
    SystemStreamsRedirector previousState
    
    SystemOutErrCapturer capture() {
        out = new ByteArrayOutputStream()
        err = new ByteArrayOutputStream()
        previousState = SystemStreamsRedirector.create(null, new PrintStream(out, true), new PrintStream(err, true)).redirect()
        this
    }
    
    SystemOutErrCapturer redirectToNull() {
        out = null
        err = null
        OutputStream nullStream = new NullOutputStream()
        previousState = SystemStreamsRedirector.create(null, new PrintStream(nullStream, true), new PrintStream(nullStream, true)).redirect()
        this
    }
    
    void close() {
        if(previousState != null) {
            previousState.redirect()
            previousState = null
        }
    }
    
    public static  T withCapturedOutput(Closure closure) {
        SystemOutErrCapturer capturer = new SystemOutErrCapturer().capture()
        try {
            return closure.call(capturer)
        } finally {
            capturer.close()
        }
    }
    
    public static  T withNullOutput(Closure closure) {
        SystemOutErrCapturer capturer = new SystemOutErrCapturer().redirectToNull()
        try {
            return closure.call(capturer)
        } finally {
            capturer.close()
        }
    }
    
    @CompileStatic
    public static class NullOutputStream extends OutputStream {
        @Override
        public void write(byte[] b) throws IOException {
            
        }       
        
        @Override
        public void write(int b) throws IOException {
            
        }
        
        @Override
        public void write(byte[] b, int off, int len) throws IOException {
            
        }
    }
}