Apache provides an Application Programming Interface (API) to modules to insulate them from the mechanics of the HTTP protocol and from each other. In this chapter, we explore the main concepts of the API and provide a detailed listing of the functions available to the module author.
In previous editions of this book, we described the Apache 1.x API. As you know, things have moved on since then, and Apache 2.x is upon us. The facilities in 2.x include some radical and exciting improvements over 1.x, and furthermore, 1.x has been frozen, apart from maintenance. So we decided that, unlike the rest of the book, we would document only the new API. (Appendix A provides some coverage of the 1.x API.)
Also, in previous editions, we had an API reference section. Because Apache 2.0 has substantially improved API documentation of its own, and because the API is still moving around as we write, we have decided to concentrate on the concepts and examples and refer you to the Web for the API reference. Part of the work we have done while writing this chapter is to help ensure that the online documentation does actually cover all the important APIs.
In this chapter, we will cover the important concepts needed to understand the API and point you to appropriate documentation. In the next chapter, we will illustrate the use of the API through a variety of example modules.