src/test/java/org/apache/maven/plugins/pmd/CapturingPrintStream.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 org.apache.maven.plugins.pmd;

import java.io.PrintStream;

import org.slf4j.impl.MavenSlf4jSimpleFriend;

/**
 * Captures log output from simple slf4j for asserting in unit tests.
 */
class CapturingPrintStream extends PrintStream {
    private boolean quiet;
    private StringBuilder buffer = new StringBuilder();

    private CapturingPrintStream(boolean quiet) {
        super(System.out, true);
        this.quiet = quiet;
    }

    @Override
    public void println(String x) {
        if (!quiet) {
            super.println(x);
        }
        buffer.append(x).append(System.lineSeparator());
    }

    public static void init(boolean quiet) {
        CapturingPrintStream capture = get();
        if (capture != null) {
            capture.buffer.setLength(0);
            capture.quiet = quiet;
        } else {
            capture = new CapturingPrintStream(quiet);
            System.setOut(capture);
            MavenSlf4jSimpleFriend.init();
        }
    }

    public static CapturingPrintStream get() {
        if (System.out instanceof CapturingPrintStream) {
            return (CapturingPrintStream) System.out;
        }
        return null;
    }

    public static String getOutput() {
        CapturingPrintStream stream = get();
        if (stream != null) {
            stream.flush();
            return stream.buffer.toString();
        }
        return "";
    }
}