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PO"adb start-server", Java, Gradle and apache-commons-exec: how to make it right?
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copied!<p>I am running into various problems when trying to run <code>android start-server</code> from within Java as external process. The Java is called by Gradle. Let me describe to you what is exactly happening in various scenarios:</p> <p><strong>Environment</strong></p> <ul> <li>Windows 7 X64</li> <li>Java 7</li> <li>commons-exec-1.1</li> <li>Gradle 1.6</li> <li>Android API 17</li> <li>IntelliJ IDEA 12.1.4 Community Edition</li> </ul> <p><strong>Assumption</strong><br> adb daemon is killed and will start up when calling <code>adb start-server</code>.</p> <h2>Case 1</h2> <p>This code:</p> <pre class="lang-java prettyprint-override"><code>DefaultExecutor executor = new org.apache.commons.exec.DefaultExecutor(); executor.execute(org.apache.commons.exec.CommandLine.parse("adb start-server")); log.info("Checkpoint!"); </code></pre> <p>When run from Gradle <code>run</code> task of the application plugin, will display the start-server output, i.e.:</p> <pre><code>* daemon not running. starting it now on port 5037 * * daemon started successfully * </code></pre> <p>and then it will hang, i.e. "Checkpoint!" will never be logged. Killing the <code>adb.exe</code> process manually will cause the code to continue execution.</p> <h2>Question 1</h2> <p>Why this call blocks? When <code>adb start-server</code> command is run from terminal, after a couple of seconds the control is returned to the terminal, so why it doesn't happen in the code?</p> <h2>Case 2</h2> <p>If instead I use directly the Java runtime like so:</p> <pre class="lang-java prettyprint-override"><code>Runtime.getRuntime().exec(new String[]{"adb", "start-server"}); log.info("Checkpoint!"); System.exit(0); </code></pre> <p>If calling from Gradle as previously, the "Checkpoint!" will be logged. However, the execution will hang on <code>System.exit(0)</code>. Killing <code>adb.exe</code> manually will again make Gradle call finish.</p> <p>In this case no output of <code>adb start-server</code> is displayed.</p> <p>Interesting thing is that when, instead of Gradle, I run the application from IntelliJ IDEA with build setup mimicking that of Gradle's, everything works fine and the application finishes properly.</p> <h2>Question 2</h2> <p>Why Gradle hangs on <code>System.exit(0)</code> and IntelliJ doesn't? Is this somehow related to the fact that Gradle itself is a process that internally calls Java and in case of IntelliJ, Java is called immediately without any indirection? Why does it matter?</p> <h2>Question 3</h2> <p>Ultimately, I want to be able to run this from Gradle without hangs of any kind. Logging output of <code>adb start-server</code> would be a bonus. I would greatly appreciate any hints how to do this.</p>

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