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Chapter 20. The Apache API
Contents:
Documentation
APR
Pools
Per-Server Configuration
Per-Directory Configuration
Per-Request Information
Access to Configuration and Request Information
Hooks, Optional Hooks, and Optional Functions
Filters, Buckets, and Bucket Brigades
Modules
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.
20.1. Documentation
In Apache 2.0 the Apache Group has gone to great lengths to try to document the API properly. Included in the headers is text that can by used to generate online documentation. Currently it expects to be processed by doxygen, a system similar to javadoc, only designed for use with C and C++. Doxygen can be found at http://www.stack.nl/~dimitri/doxygen/. Doxygen produces a variety of formats, but the only one we actively support is HTML. This format can be made simply by typing:
make dox
in the top Apache directory. The older target "docs" attempts to use scandoc instead of doxygen, but it doesn't work very well.
We do not reproduce information available in the online documentation here, but rather try to present a broader picture. We did consider including a copy of the documentation in the book, but decided against it because it is still changing quite frequently, and anyway it works much better as HTML documents than printed text.
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| 19.6. Testing Cocoon |  | 20.2. APR |
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