jonasseglare/hotswap-dcevm-clojure-demo

Java class reloading without restarting the REPL

hotswap-dcevm-clojure-demo

To try out Hotswap-agent and DCEVM with Clojure, so that we can reload freshly compiled Java classes without restarting the REPL. This is useful when developing mixed codebases with both Clojure and Java: We might have a REPL running and then we edit a java file that we compile using lein javac. Normally, we would have to restart the repl in order for those changes to be visible, but with DCEVM and hotswap-agent, the recompile class file is automatically imported without having to restart the REPL.

Usage

1. Download and unpack TravaOpenJDK from this page: https://github.com/TravaOpenJDK/trava-jdk-11-dcevm/releases/tag/dcevm-11.0.5%2B4
2. Define JAVA_HOME to point at the unpacked directory.
3. Launch the REPL and load the namespace hotswap-dcevm-clojure-demo.core a few times.
4. Edit the file src/java/Mjao.java and compile it using lein javac.
5. Load the file hotswap-dcevm-clojure-demo.core again.
6. Repeat step 4 and 5...

Mjao result (3): 13
Mjao result (3): 13
Mjao result (3): 13
HOTSWAP AGENT: 13:15:53.645 RELOAD (org.hotswap.agent.config.PluginManager) - Reloading classes [Mjao] (autoHotswap)
Mjao result (3): 103
Mjao result (3): 103
HOTSWAP AGENT: 13:16:08.070 RELOAD (org.hotswap.agent.config.PluginManager) - Reloading classes [Mjao] (autoHotswap)
Mjao result (3): 10003
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Summary

To have automatic class reloading in the REPL, these two things are needed:

• A resources/hotswap-agent.properties file containing the line autoHotswap=true
• JAVA_HOME environment variable pointing at the JDK found here, or newer.

Documentation

• Main page of the project: http://hotswapagent.org/
• Instructions for getting the JDK: http://hotswapagent.org/mydoc_quickstart-jdk11.html
• About the Hotswapper plugin: http://hotswapagent.org/mydoc_plugin_hotswapper.html
• Example file of hotswap-agent.properties: https://github.com/HotswapProjects/HotswapAgent/blob/master/hotswap-agent-core/src/main/resources/hotswap-agent.properties

License

Copyright © 2019 Jonas Östlund

This program and the accompanying materials are made available under the terms of the Eclipse Public License 2.0 which is available at http://www.eclipse.org/legal/epl-2.0.

This Source Code may also be made available under the following Secondary Licenses when the conditions for such availability set forth in the Eclipse Public License, v. 2.0 are satisfied: GNU General Public License as published by the Free Software Foundation, either version 2 of the License, or (at your option) any later version, with the GNU Classpath Exception which is available at https://www.gnu.org/software/classpath/license.html.