Classify the processing into the following three types and then determine whether to use the container extension library. If you do not want to use the container extension library, include the common libraries in the EJB-JAR files, WAR files, or library JARs.

• Business processing
  Include the common libraries in the EJB-JAR files or WAR files because the processing for each business is different. You need not use the container extension library.
  
• Processing shared by the EJB-JAR files and WAR files
  If the Enterprise Beans, servlets, JSPs, and business processing included in multiple EJB-JAR files and WAR files can commonly utilize the processing, use a library JAR. If you cannot use the library JAR, create a common processing class and use the container extension library.
  
• Processing shared by the EAR files
  If the EJB-JARs and WARs included in the multiple EAR files can commonly utilize the processing, use a library JAR. If you cannot use the library JAR, create a common processing class and use the container extension library.
  

Classify the operations of the Enterprise Beans, servlets, and JSPs as follows, and determine whether to use the container extension library for each. The following table describes the guidelines for using the container extension library.

Table 14-3 Guidelines for using the container extension library for each operation

Operations	Container extension library	EJB-JAR file or WAR file	Library JAR
Operations to access the files and directories	Y	N	N
Operations using the JNI#	Y	N	N
Operations for invoking the CORBA objects through Smart Agent	Y	N	N
Operations of the J2EE container functionality	N	Y	N
Class references within the EJB-JAR files and WAR files	N	--	N

Legend:

Y: Included

N: Not included

--: Not applicable

#: If you attempt to load the same native library in J2EE applications or Web applications, UnsatisfiedLinkError is thrown due to the JNI specifications. You can avoid the error by registering the native library that is commonly used by the applications, as the container extension library.

Note

The following access permission is assigned to the container extension library. You cannot change the access permission.

java.security.AllPermission

However, the setSecurityManager access permission of java.lang.RuntimePermission is not assigned.