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also want single sign on for users across various security domains, but, at the

same time, permit access only to employees whose proper access privileges

adhere to company wide rules.

Internal applications may also provide some limited mobile functionality; that

is, they need to be accessible from mobile devices such as PDAs and cellphones.

For example, a travel expense tracking application may want to allow employees

who are on the road to keep track of their expense records. Likewise, enterprises

whose departments are geographically scattered may find it more efficient for

employees to use the Internet for internal communications. Web service interfaces

are particularly useful in these situations, although there are the additional con 

cerns of distributed and multiple security domains.

Often, systems developed for internal use rely on home grown legacy sys 

tems. While systems bought from third party vendors may be integrated using

standard connectors supplied by their vendors or third parties, this is not true for

homegrown systems. These homegrown, or one off, applications must still be

integrated with other applications in the enterprise and accessed from a Web

browser.

6.2

Now that we have examined some common integration scenarios, let's look at the

technologies that are available on the J2EE 1.4 platform to help with these issues.

The J2EE platform provides a set of EIS integration technologies that address the

EIS integration problem. These include relational database integration technologies

(such as JDBC, Enterprise JavaBeans technology container managed persistence,

and Java Data Objects), messaging technologies (such as Java Message Service and

message driven beans), EIS access technologies (particularly the J2EE Connector

architecture), Web services, and XML technologies for manipulating documents. 

Let's briefly examine some of the available integration technologies. The

section  Integration Design Approaches  on page 263 maps these technologies to

different integration problems, illustrating when and how to use them most

effectively.