Editing GAE (section)

==Development Process==

===New Project===
The wizard creates a directory structure for the project, including a src/ directory for Java source files, and a war/ directory for compiled classes and other files for the application, libraries, configuration files, static files such as images and CSS, and other data files. The wizard also creates a servlet source file and two configuration files. The complete directory structure looks like this:

 <Project>/
   src/
     <Project>/
       server/
         <Project>Servlet.java
     META-INF/
       jdoconfig.xml
     log4j.properties
     logging.properties
   war/
     WEB-INF/
       lib/
         ...App Engine JARs...
       [[#appengine-web.xml|appengine-web.xml]]
       [[JEE#Deployment_Descriptor|web.xml]]
     index.html

====Specific Configuration Files====

=====appengine-web.xml=====
appengine-web.xml is specific to App Engine, and is not part of the servlet standard.

 <?xml version="1.0" encoding="utf-8"?>
 <appengine-web-app xmlns="http://appengine.google.com/ns/1.0">
    <application></application>
    <version>1</version>
 </appengine-web-app>

=====persistence.xml=====
* JPA configuration
* general description in [[JavaJEEJPA#persistence.xml|persistence.xml]]

=====jdoconfig.xml=====
It resides in the directory <code>war/WEB-INF/classes/META-INF/</code>.

===Implementation===

====New Servlet====
* New Java Class Wizzard with base javax.servlet.http.HttpServlet
* add Servlet in \war\WEB-INF\web.xml


====JPA====
* create src\META-INF\[[#persistence.xml|persistence.xml]]

=====save an entity=====
 X x = new X();
 x.setA(a);
 javax.persistence.EntityManager em = EMFactory.get().createEntityManager();
 em.persist(x);


=====retrieving entities=====
 javax.persistence.EntityManager em = EMFactory.get().createEntityManager();
 javax.persistence.Query q = em.qreateQuery("SELECT v From <CLASSNAME> v");
 List<CLASSNAME> results = q.getResultList();
 Iterator<CLASSNAME> iter = results.iterator();
 while (iter.hasNext())
 {
   <CLASSNAME> v = iter.next();
 }

===Run/Debug Project===
With Eclipse, you can leave the server running in the debugger while you make changes to source code, JSPs, static files and appengine-web.xml. When you save changes to source code, Eclipse compiles the class automatically, then attempts to insert it into the running web server dynamically. In most cases, you can simply reload the page in your browser to test the new version of the code. Changes to JSPs, static files and appengine-web.xml are recognized by the development server automatically, and also take effect without restarting the server. If you change web.xml or other configuration files, you must stop and start the server for the changes to take effect.

====Run====
*''Project Context Menu -> Run As -> Web Application'' or
*''Project Context Menu -> Run As -> Run Configuration -> Web Application -> <Projectname>''
*Browser http://localhost:<port>/<Appname>

====Debug====
*''Project Context Menu -> Debug As -> Web Application'' or
*''Project Context Menu -> Debug As -> Debug Configuration -> Web Application -> <Projectname>''
*Browser http://localhost:<port>/<Appname>

====Deploy changes====
* according documentation local engine should be updated after save but doesn't work, so go to Debug Perspective, select engine context menu and use 'terminate and relaunch'

===Stop Server===
* switch to Debug perspective
* select application in the debug panel
* press terminate button in button bar