Chapter Seven. Middleware Types and Application Integration: What Works Where?

In this chapter we take a much deeper dive into the world of middleware and look specifically at what types of middleware work for particular types of application integration problem domains.

This is a very important chapter because when architects attempt to solve application integration problems, the trouble they run into is the use of the wrong type of middleware. For example, distributed objects don't work well for problem domains that require a more information-oriented solution, and message-oriented middleware does not support service-oriented solutions. You'll understand the relationships between middleware and application integration solutions by the end of the chapter.

This is a long chapter, but worth the time.

Continuing our discussion from the last chapter, as you may recall, the evolution of middleware is changing many of the identifying features that once made categorizing middleware such a straightforward task. For example, many MOM products now perform publish and subscribe tasks, provide transactional features, and host application logic. The challenge of appropriately categorizing such a product should be plainly evident.

However, even as we acknowledge the difficulty in categorizing middleware, we note that several types of middleware continue to solve particular types of problems. For the purposes of our application integration discussion, we will describe

• RPCs

• MOM

• Distributed objects

• Database-oriented middleware

• Transactional middleware

• Integration servers (covered in the next chapter)

Of course, you can find more in-depth descriptions in many books that focus only on middleware. This chapter focuses on the application of each middleware type in particular application integration problem domains. In other words, which types of middleware solve which problems?