Resolves #152 - Adds option to redirect program output of exec:exec to the maven logger.

src/main/java/org/codehaus/mojo/exec/ExecMojo.java

@@ -148,6 +148,82 @@ public class ExecMojo
     @Parameter( property = "exec.outputFile" )
     private File outputFile;
 
+    /**
+     * When enabled, program standard and error output will be redirected to the
+     * Maven logger as <i>Info</i> and <i>Error</i> level logs, respectively. If not enabled the
+     * traditional behavior of program output being directed to standard System.out
+     * and System.err is used.<br>
+     * <br>
+     * NOTE: When enabled, to log the program standard out as Maven <i>Debug</i> level instead of
+     * <i>Info</i> level use {@code exec.quietLogs=true}. <br>
+     * <br>
+     * This option can be extremely helpful when combined with multithreaded builds
+     * for two reasons:<br>
+     * <ul>
+     * <li>Program output is suffixed with the owning thread name, making it easier
+     * to trace execution of a specific projects build thread.</li>
+     * <li>Program output will not get jumbled with other maven log messages.</li>
+     * </ul>
+     *
+     * For Example, if using {@code exec:exec} to run a script to echo a count from
+     * 1 to 100 as:
+     *
+     * <pre>
+     * for i in {1..100}
+     * do
+     *   echo "${project.artifactId} - $i"
+     * done
+     * </pre>
+     *
+     * When this script is run multi-threaded on two modules, {@code module1} and
+     * {@code module2}, you might get output such as:
+     *
+     * <pre>
+     * [BuilderThread 1] [INFO] --- exec-maven-plugin:1.6.0:exec (test) @ module1 ---
+     * [BuilderThread 2] [INFO] --- exec-maven-plugin:1.6.0:exec (test) @ module2 ---
+     * ...
+     * module2 - 98
+     * modu
+     * module1 - 97
+     * module1 -
+     * le2 - 9899
+     * ...
+     * </pre>
+     *
+     * With this flag enabled, the output will instead come something similar to:
+     *
+     * <pre>
+     * ...
+     * [Exec Stream Pumper] [INFO] [BuilderThread 2] module2 - 98
+     * [Exec Stream Pumper] [INFO] [BuilderThread 1] module1 - 97
+     * [Exec Stream Pumper] [INFO] [BuilderThread 1] module1 - 98
+     * [Exec Stream Pumper] [INFO] [BuilderThread 2] module2 - 99
+     * ...
+     * </pre>
+     *
+     * NOTE 1: To show the thread in the Maven log, configure the Maven
+     * installations <i>conf/logging/simplelogger.properties</i> option:
+     * {@code org.slf4j.simpleLogger.showThreadName=true}<br>
+     *
+     * NOTE 2: This option is ignored when {@code exec.outputFile} is specified.
+     *
+     * @since 3.0.0
+     * @see java.lang.System#err
+     * @see java.lang.System#in
+     */
+    @Parameter( property = "exec.useMavenLogger", defaultValue = "false" )
+    private boolean useMavenLogger;
+
+    /**
+     * When combined with {@code exec.useMavenLogger=true}, prints all executed
+     * program output at debug level instead of the default info level to the Maven
+     * logger.
+     *
+     * @since 3.0.0
+     */
+    @Parameter( property = "exec.quietLogs", defaultValue = "false" )
+    private boolean quietLogs;
+
     /**
      * <p>
      * A list of arguments passed to the {@code executable}, which should be of type <code>&lt;argument&gt;</code> or
@@ -340,6 +416,42 @@ else if ( !StringUtils.isEmpty( argsProp ) )
                         IOUtil.close( outputStream );
                     }
                 }
+                else if (useMavenLogger)
+                {
+                    getLog().debug("Will redirect program output to Maven logger");
+                    final String parentThreadName = Thread.currentThread().getName();
+                    final String logSuffix = "[" + parentThreadName + "] ";
+                    Invokable<String> mavenOutRedirect = new Invokable<String>()
+                    {
+
+                        @Override
+                        public void accept(String logMessage)
+                        {
+                            if (quietLogs)
+                            {
+                                getLog().debug(logSuffix + logMessage);
+                            }
+                            else
+                            {
+                                getLog().info(logSuffix + logMessage);
+                            }
+                        }
+                    };
+                    Invokable<String> mavenErrRedirect = new Invokable<String>()
+                    {
+
+                        @Override
+                        public void accept(String logMessage)
+                        {
+                            getLog().error(logSuffix + logMessage);
+                        }
+                    };
+
+                    try (OutputStream out = new LineRedirectOutputStream(mavenOutRedirect);
+                            OutputStream err = new LineRedirectOutputStream(mavenErrRedirect)) {
+                        resultCode = executeCommandLine(exec, commandLine, enviro, out, err);
+                    }
+                }
                 else
                 {
                     resultCode = executeCommandLine( exec, commandLine, enviro, System.out, System.err );

src/main/java/org/codehaus/mojo/exec/Invokable.java

@@ -0,0 +1,37 @@
+package org.codehaus.mojo.exec;
+
+/*
+ * 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.
+ */
+
+/**
+ * A simple Java 7 pseudo-class based on the Java 8 {@code Consumer} class. Can and should be
+ * deleted once this project moves to a minimum execution environment of Java 8+.
+ *
+ * @param <T> - The type of object that will be acted upon.
+ * @since 3.0.0
+ */
+interface Invokable<T> {
+
+    /**
+     * Takes some object and acts upon it.
+     * 
+     * @param object - The object that will be taken
+     */
+    void accept(T object);
+}

src/main/java/org/codehaus/mojo/exec/LineRedirectOutputStream.java

@@ -0,0 +1,61 @@
+package org.codehaus.mojo.exec;
+
+/*
+ * 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.
+ */
+
+import java.io.OutputStream;
+
+/**
+ * An output stream that captures one line of output at a time, and then
+ * redirects that line to some {@link Invokable} to act upon as it pleases. This
+ * class is not thread safe and expects to have only one active writer consuming
+ * it at any given time.
+ * 
+ * @since 3.0.0
+ */
+class LineRedirectOutputStream extends OutputStream {
+
+    private StringBuilder currentLine = new StringBuilder();
+    private final Invokable<String> linePrinter;
+
+    public LineRedirectOutputStream(Invokable<String> linePrinter) {
+        this.linePrinter = linePrinter;
+    }
+
+    @Override
+    public void write(final int b) {
+        if ((char) b == '\n') {
+            printAndReset();
+            return;
+        }
+        currentLine.append((char) b);
+    }
+
+    @Override
+    public void flush() {
+        if (currentLine.length() > 0) {
+            printAndReset();
+        }
+    }
+
+    private void printAndReset() {
+        linePrinter.accept(currentLine.toString());
+        currentLine = new StringBuilder();
+    }
+}