How to Instantly Reload Java Web Apps with JRebel in IntelliJ IDEA
This guide explains how JRebel eliminates the need to restart Tomcat by enabling hot‑deployment of class and Spring configuration changes, covering two installation methods—adding JVM parameters to Tomcat and using the IntelliJ IDEA plugin—plus detailed configuration for Windows, Linux, Mac, Maven, and Gradle.
JRebel Installation
In Java web development, updating a Java file usually requires manually restarting the Tomcat server, which wastes time. JRebel allows immediate hot‑deployment of class changes and Spring configuration updates, greatly improving development efficiency.
Installation Method 1: Add parameters to Tomcat startup
Extract JRebel to a directory and configure Tomcat in IntelliJ IDEA. Select the Tomcat server, choose Local, set the deployment to the project with the exploded option, and remove the default Make step to improve speed.
In the server configuration, enable On 'Update' action and On frame deactivation, and set both to Update classes and resources so that class changes and resources are hot‑deployed correctly.
Configure VM options according to the operating system:
-noverify
-agentpath:D:/dev_env/jrebel/jrebel_running/lib/jrebel64.dllLinux:
-agentpath:/dev_env/jrebel/jrebel_running/lib/libjrebel64.soMac OS:
-agentpath:/dev_env/jrebel/jrebel_running/lib/libjrebel64.dylibAfter setting the VM options, start Tomcat. This method requires reconfiguration for each new project.
Installation Method 2: IntelliJ IDEA plugin
Install the JRebel plugin locally via IntelliJ IDEA settings. After installation, a JRebel configuration appears in the settings panel. When the plugin is valid, two green buttons ( Run and Debug) appear next to the regular run button.
Custom Container Startup
The Tomcat configuration is the same as above, but the VM options field can be left empty. Start the project using the Debug button; successful execution shows JRebel version information in the log.
Maven or Gradle Launch
Open the JRebel panel, select the project or module, and the plugin generates a rebel.xml file in src/main/resources specifying the hot‑deployment folders. Then launch the application via Maven or Gradle tasks using JRebel.
After launching, updating resources and recompiling (Ctrl+Shift+F9) triggers hot deployment. A free activation key can be obtained from the JRebel website.
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