I recently had the need to execute a .jar file from within an Azure WebJob built with C#. I found a few resources that showed how to upload a .zip file, for instance, and have that run a .bat file as a job. Or, how to create a Java web app. But my webjob needed to do more than just run a .jar, and I didn’t have the time to get up to speed on Java and the Azure Storage SDK for Java. As the Google let me down, here I demonstrate the solution.
It turns out there is indeed a JRE available and you can run java.exe. You can either give it a class name that contains a main entry point, or give it a .jar, exactly a you would do from the command line. The first thing I had to do was determine how to locate java.exe. I made a dump of environment variables and saw that JAVA_HOME was defined.
| StringBuilder sb = new StringBuilder(); | |
| foreach (DictionaryEntry de in Environment.GetEnvironmentVariables()) | |
| { | |
| sb.AppendFormat("{0} : {1}", de.Key.ToString(), de.Value.ToString()).AppendLine(); | |
| } | |
| Console.WriteLine(sb.ToString()); |
With this information, all you need to do is craft and execute the proper Process:
| using Microsoft.Azure.WebJobs; | |
| using System; | |
| using System.Collections.Generic; | |
| using System.Diagnostics; | |
| using System.IO; | |
| namespace TestWebjob | |
| { | |
| public class Functions | |
| { | |
| // This function will get triggered/executed when a new message is written | |
| // on an Azure Queue called queue. | |
| public static void ProcessQueueMessage([QueueTrigger("webjobtestq")] string message, TextWriter log) | |
| { | |
| try | |
| { | |
| var javaHome = Environment.GetEnvironmentVariable("JAVA_HOME"); | |
| ProcessStartInfo psi = new ProcessStartInfo(javaHome + "\\bin\\java", string.Concat(" -jar .\\App_Data\\AzureWebjobJar.jar ", message)) | |
| { | |
| CreateNoWindow = true, | |
| UseShellExecute = false, | |
| RedirectStandardOutput = true | |
| }; | |
| Process javaProcess = Process.Start(psi); | |
| string theOutput = javaProcess.StandardOutput.ReadToEnd(); | |
| javaProcess.WaitForExit(); | |
| //code to craft email of output omitted | |
| } | |
| catch (Exception ex) | |
| { | |
| //code to craft email of exception omitted | |
| } | |
| } | |
| } | |
| } |
Using the Azure Storage Explorer I was easily able to enqueue messages to execute my webjob which is triggered by the queue:
