![]() We have a ton of assets and classes and the whole process takes only a few seconds! Summary That’s it, after you replace files in the PATH_TO_DEPLOYMENT_DIR HotSwapAgent and Wildfly will do the rest really fast. Compile classes and copy them to the PATH_TO_DEPLOYMENT_DIR.Copy all resources like JSP, JavaScript, CSS and copy to the PATH_TO_DEPLOYMENT_DIR,.Create a script that will look for changes in the application directory (this one is interesting: ),.Build your application and deploy it to the PATH_TO_DEPLOYMENT_DIR in the exploded version,.The process should look like this (you can do it in many ways, in our case, it’s pretty specific as our build process is really complicated): I doesn’t really matter which build-tool you use (Ant, Gradle or Maven). Now that we have everything in place, I will explain how to put it all together. If you use Netbeans, Eclipse or Intellij you should check the HotSwapAgent page for some helpful plugins here:, , and. This is well explained here:īasically create a new file, name it hotswap-agent.properties, set all needed configuration inside and add it to the classpath of the application. It’s a good idea to create a configuration file for the HotSwapAgent. ![]() The javagent is just an interceptor on the top of your classes that allows the HotSwapAgent library to manipulate your code on the fly.The altjvm option sets an alternative Java Virtual Machine.XXaltjvm=dcevm -javaagent:PATH_TO_HOTSWAPAGENT_JAR. ![]() The only thing that you need to do is get the JAR and put it anywhere on your hard drive (I recommend to add it to your Java project). Now, download the latest release of the Hotswap agent from here: Make sure you update to the same Java version that you’re going to use to run the Wildfly server. This is not possible with the original Java HotSpot VM. Why it’s needed? It will allow us unlimited redefinition of loaded classes at runtime. We need to download and install the latest release of DCEVM Java patch from here. HotSwapAgent installation and configuration RELATIVE_TO_PATH is, as the name suggests the dir that the PATH_TO_DEPLOYMENT_DIR is relative to. PATH_TO_DEPLOYMENT_DIR is WILDFLY_DIR/standalone/deployments WILDFLY_DIR/standalone/configuration/standalone-full.xml Now, look for the deployment-scanner node in: XX:MetaspaceSize=256M -XX:MaxMetaspaceSize=512m It’s encouraged that you play with these values after completing all steps. Start by configuring the metaspace size we had to increase defaults for our application, but it’s possible that it will be just fine in your case. You can do this in production as well to allow for application changes with zero downtime. We need to use exploded deployment instead of deploying WAR or EAR. Let’s assume that we use the standalone-full.xml configuration file. I will explain how to combine it with Widlfly in order to hot-deploy Java classes as well as how to hot-deploy other resources (Javascript, CSS, images). You can use the open-source version, but then you need to send project statistics to the JRebel server, which is not a viable option for your more serious projects.įortunately, there is an open-source project called HotSwapAgent and it does the same thing as JRebel, for free (thank you, guys!). I know about JRebel, but while it’s a good tool, it’s also pretty expensive. Java development can be really frustrating when you need to re-build your project and restart a server every time you change something.
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