Writing Apache Modules with Perl and C

4.2. Virtual Documents

The previous sections of this chapter have been concerned with transforming existing files. Now we turn our attention to spinning documents out of thin air. Despite the fact that these two operations seem very different, Apache content handlers are responsible for them both. A content handler is free to ignore the translation of the URI that is passed to it. Apache neither knows nor cares that the document produced by the content handler has no correspondence to a physical file.

We've already seen an Apache content handler that produces a virtual document. Chapter 2, gave the code for Apache::Hello, an Apache Perl module that produces a short HTML document. For convenience, we show it again in Example 4.7. This content handler is essentially identical to the previous content handlers we've seen. The main difference is that the content handler sets the MIME content type itself, calling the request object's content_type() method to set the MIME type to type text/html. This is in contrast to the idiom we used earlier, where the handler allowed Apache to choose the content type for it. After this, the process of emitting the HTTP header and the document itself is the same as we've seen before.

After setting the content type, the handler calls send_http_header() to send the HTTP header to the browser, and immediately exits with an OK status code if header_only() returns true (this is a slight improvement over the original Chapter 2 version of the program). ...