This document discusses JRebel, a tool that allows developers to see code changes in web applications without redeploying. It summarizes JRebel's key features, licensing options, and how it works by redefining classes at runtime using instrumentation and bytecode handling to allow reloading updated classes. It then demonstrates how JRebel can be used with GateIn to achieve zero-redeployment of portlets and UI components.

1. Zero redeployment with JRebel
Minh Hoang TO
Portal Team

2. Agenda
1. JRebel
2. GateIn zero-redeployment
3. How does JRebel work?
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3. JRebel
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4. - Developer(s): Zero Turnaround
- Written in: Java
- License: Proprietary
- Highlighted features:
Immediately visible code changes without redeploying
Easy installation and simple configuration
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5. Free license plans
OSS plan
Commiters of Open Source projects have access to free license
Social plan
Free license in exchange of privileged to post on Twitter/Facebook account
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6. GateIn zero-deployment
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7. GateIn code changes in IDE are reflected immediately on browser without the
need of redeploying. Say GOODBYE to tedious redeploy work
Productive dev environment applicable to any eXo product:
Social, Wiki, Forum, ECMS, Platform
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8. Demo
- Targeted Maven artifacts:
exo.portal.webui.portal (basic UI components of GateIn portal)
exo.portlet.exoadmin (core portlets of GateIn)
- Expectation:
Code changes on portal/portlet components from those two artifacts take
effect on browser without the need of redeploying .war to Tomcat
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9. Before demo
1. Customize packaging/tomcat/pkg/src/main/resources/tomcat/bin/gatein-dev.sh
2. Generate rebel.xml in targeted Maven artifacts
3. Build and run GateIn
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10. rebel.xml
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11. rebel.xml
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12. JRebel agent starts
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13. Demo starting ...
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14. How does JRebel work?
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15. Object & Class
MyObject obj = new MyObject();
Class<?> type = obj.getClass();
1. Behavior of method call on 'obj' is determined by 'type'
2. 'type' is identified by MyObject.class bytecode and context ClassLoader of the
code MyObject obj = new MyObject();
3. Once loaded, 'type' could not be unloaded or changed (class loader holds a
vector of loaded classes)
4. JRebel approach to redefine 'type'
Black box as JRebel is not open source! But described as a combination of
Instrumentation API + Byte code handling + Class loader
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16. Class redefinition
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17. MANIFEST.MF
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18. JRebel agent
The code in AgentInstall is likely to be
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