Chapter 8. Filter Modules

In terms of application development, the most important innovation in Apache 2 is the filter architecture and the ability to chain multiple different data processing operations at will. In this chapter, we will take a detailed look at the filter chain and develop several illustrative filter modules.

Before going into details, let’s review a few basics. In Chapter 2, we saw that filters operate on a “data” axis, orthogonal to the processing axis familiar from Apache 1 and other webservers (Figure 8-1). But this is not the whole story. Strictly speaking, it is really accurate only for content filters—that is, for those filters that operate on the body of an HTTP request or response. If your application is not concerned ...

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