ORB initialization
In a stand-alone Java™ application, the client must create an instance of the ORB.
init(...).
For example: ORB orb = ORB.init(args,props);- A string array containing property-value pairs.
- A Java Properties object.
A similar method is used for an applet. The difference is that a Java Applet is passed instead of the string array.
The first step of ORB initialization is to process the ORB properties.
- First, check in the applet parameter, or application string array.
- Check in the properties parameter, if the parameter exists.
- Check in the system properties.
- Check in any orb.properties file that is found in the <user-home> directory.
- Check in any orb.properties file that is found in the <java-home>/lib directory.
- Finally, use hardcoded default behavior.
From service refresh 3, fix pack 10, the order of precedence is
changed.
The properties are found by searching in the following sequence: - First, check in the applet parameter, or application string array.
- Check in the properties parameter, if the parameter exists.
- Check in the system properties.
- Check in any orb.properties file under the directory that is specified by the JVM property com.ibm.CORBA.ORBPropertyFilePath.
- Check in any orb.properties file that is found in the <user-home> directory.
- Check in any orb.properties file that is found in the <java-home>/lib directory.
- Check in any orb.properties file that is found in the CLASSPATH (including JAR files).
- Finally, use hardcoded default behavior.

Two important properties are ORBClass and ORBSingletonClass. These properties determine which ORB class is created and initialized, or instantiated.
After the ORB is instantiated, it starts and initializes the TCP transport layer. If the ListenerPort property was set, the ORB also opens a server socket to listen for incoming requests. The ListenerPort property is used by a server-side ORB. At the end of the initialization process that is run by the init() method, the ORB is fully functional and ready to support the client application.