Comparing the i5/OS Java virtual machine and the IBM Toolbox for Java classes

You always have at least two ways to access an iSeries™ server resource when your Java™ program is running on the IBM^® Developer Kit for Java (i5/OS™) Java virtual machine (JVM).

You can use either of the following interfaces:

Facilities built into Java
An IBM Toolbox for Java class

When deciding which interface to use, consider the following factors:

Location - Where a program runs is the most important factor in deciding which interface set to use. Does the program do the following:
- Run only on the client?
- Run only on the server?
- Run on both client and server, but in both cases the resource is an iSeries server resource?
- Run on one i5/OS JVM and access resources on another iSeries server?
- Run on different kinds of servers?
If the program runs on both client and server (including an iSeries server as a client to a second iSeries server) and accesses only iSeries server resources, it may be best to use the IBM Toolbox for Java interfaces.

If the program must access data on many types of servers, it may be best to use Java native interfaces.
Consistency / Portability - The ability to run IBM Toolbox for Java classes on iSeries servers means that the same interfaces can be used for both client programs and server programs. When you have only one interface to learn for both client programs and server programs, you can be more productive.
Writing to IBM Toolbox for Java interfaces makes your program less server portable, however.

If your program must run to an iSeries server as well as other servers, you may find it better to use the facilities that are built into Java.
Complexity - The IBM Toolbox for Java interface is built especially for easy access to an iSeries server resource. Often, the only alternative to using the IBM Toolbox for Java interface is to write a program that accesses the resource and communicates with that program through Java Native Interface (JNI).
You must decide whether it is more important to have better Java neutrality and write a program to access the resource, or to use the IBM Toolbox for Java interface, which is less portable.
Function - The IBM Toolbox for Java interface often provides more function than the Java interface. For example, the IFSFileOutputStream class of the IBM Toolbox for Java licensed program has more function than the FileOutputStream class of java.io. Using IFSFileOutputStream makes your program specific to iSeries servers, however. You lose server portability by using the IBM Toolbox for Java class.
You must decide whether portability is more important or whether you want to take advantage of the additional function.
Resource - When running on the i5/OS JVM, many of the IBM Toolbox for Java classes still make requests through the host servers. Therefore, a second job (the server job) carries out the request to access a resource.
This request may take more resource than a Java native interface that runs under the job of the Java program.
iSeries server as a client - If your program runs on one iSeries server and accesses data on a second iSeries server, your best choice may be to use IBM Toolbox for Java classes. These classes provide easy access to the resource on the second iSeries server.
An example of this is Data Queue access. The Data Queue interfaces of the IBM Toolbox for Java licensed program provide easy access to the data queue resource.

Using the IBM Toolbox for Java also means your program works on both a client and server to access a data queue on an iSeries server. It also works when running on one iSeries server to access a data queue on another iSeries server.

The alternative is to write a separate program (in C, for example) that accesses the data queue. The Java program calls this program when it needs to access the data queue.

This method is more server-portable; you can have one Java program that handles data queue access and different versions of the program for each server you support.