Rapid Java Application Development

JUG.ru25.02.2012

Turnaround Cycle

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Build, deploy,

wait

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dev << PROD

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Turnaround Cycle

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Application deployment

Turnaround Time Sink

Container boot time

OOM

Container Startup Time

http://dow.ngra.de/2010/12/14/jee-oss-container-startup-times-apples-vs-oranges/

http://zeroturnaround.com/java-ee-productivity-report-2011/

Build

Exploded Directory Deployment

Jetty Launcherpublic class Launcher {

public static void main(String[] args) {

Server server = new Server();

SelectChannelConnector connector = new SelectChannelConnector();    connector.setPort(8080);    server.addConnector(connector);

    WebAppContext context = new WebAppContext("war", "/"); server.setHandler(context);    server.start();

}

}

“…I know about JRebel, but I cannot pay for it, so I tried Maven…” - Stackoverflow

This works:mvn jetty:run

others?

MyApp.war

virtual mapping

getResource(“hello.html”) read(“src/main/.../hello.html”)

Build

Build

Why Code Reloading is Hard?Externalized

Temporary

Serializable

Derivative

State

MyObject

MyObject.class

OldClassLoader NewClassLoader

MyObject.class

MyObjectRecreate object

Classes

Libraries

OldClassLoader NewClassLoader

Sevlet New ClassesNew

Libraries

Sevlet

Session Session

init()

App State

App State

Serialize/deserialize

Twin ClassLoader Issues

JVM

Classes

Libraries

OldClassLoader NewClassLoader

Objects and

Code

Classes

Libraries

Objects and

CodeOutOfMemoryErrorClassCastException

…

Old ComponentClassLoader

New Component ClassLoader

Class Object

Component State

NewClass

NewObject

MyObject

MyObject.class

OldClassLoader

Code101000101100010010

Debugger

HotSwap

New code111000100101010010

New code 111000100101010010

Make changes in IDEHotSwap

JRebel vs HotSwapHotSwap JRebel

Changing method bodies + +Adding/removing methods - +Adding/removing constructors - +Adding/removing fields - +Adding/removing classes - +Adding/removing annotations - +Replacing superclass - -Adding/removing implemented interfaces

- -

MyObject

MyObject.class

OldClassLoader

Code101000101100010010 New code

111000100101010010

Make changes in IDE

JRebel

Fram

ewor

k

Configuration(XML, annotations,..)

JRebel

in action

Oh ...The Acid is Kicking In

Take a break!