1. 通过apxs生成
1.1 简单版
使用apxs -n helloworld -g可生成helloworld模块：
renz@apache1:~/helloworld$ ls
Makefile mod_helloworld.c modules.mk
生成mod_helloworld.c代码如下：
/*
** mod_helloworld.c -- Apache sample helloworld module
** [Autogenerated via ``apxs -n helloworld -g'']
**
** To play with this sample module first compile it into a
** DSO file and install it into Apache's modules directory
** by running:
**
** $ apxs -c -i mod_helloworld.c
**
** Then activate it in Apache's apache2.conf file for instance
** for the URL /helloworld in as follows:
**
** # apache2.conf
** LoadModule helloworld_module modules/mod_helloworld.so
** <Location /helloworld>
** SetHandler helloworld
** </Location>
**
** Then after restarting Apache via
**
** $ apachectl restart
**
** you immediately can request the URL /helloworld and watch for the
** output of this module. This can be achieved for instance via:
**
** $ lynx -mime_header http://localhost/helloworld
**
** The output should be similar to the following one:
**
** HTTP/1.1 200 OK
** Date: Tue, 31 Mar 1998 14:42:22 GMT
** Server: Apache/1.3.4 (Unix)
** Connection: close
** Content-Type: text/html
**
** The sample page from mod_helloworld.c
*/
#include "httpd.h"
#include "http_config.h"
#include "http_protocol.h"
#include "ap_config.h"
/* The sample content handler */
static int helloworld_handler(request_rec *r)
{
if (strcmp(r->handler, "helloworld")) {
return DECLINED;
}
r->content_type = "text/html";
if (!r->header_only)
ap_rputs("The sample page from mod_helloworld.c\n", r);
return OK;
}
static void helloworld_register_hooks(apr_pool_t *p)
{
ap_hook_handler(helloworld_handler, NULL, NULL, APR_HOOK_MIDDLE);
}
/* Dispatch list for API hooks */
module AP_MODULE_DECLARE_DATA helloworld_module = {
STANDARD20_MODULE_STUFF,
NULL, /* create per-dir config structures */
NULL, /* merge per-dir config structures */
NULL, /* create per-server config structures */
NULL, /* merge per-server config structures */
NULL, /* table of config file commands */
helloworld_register_hooks /* register hooks */
};
代码注释里有helloworld模块实现的步骤，参考执行：apxs -c -i mod_helloworld.c，这一步执行的就是编译了。如果apache不是按照默认目录安装，可能需要修改Makefile文件里的路径。
加载模块，找到apache2.conf配置文件，在里面添加如下配置即可：
LoadModule helloworld_module modules/mod_helloworld
<Location /helloworld>
SetHandler helloworld
</Location>
我这个环境稍有不同，在浏览器登录的欢迎界面就说到：
The configuration layout for an Apache2 web server installation on Ubuntu systems is as follows:
/etc/apache2/
|-- apache2.conf
| `-- ports.conf
|-- mods-enabled
| |-- *.load
| `-- *.conf
|-- conf-enabled
| `-- *.conf
|-- sites-enabled
| `-- *.conf
它把apache的配置文件拆成了小配置文件，在apache2.conf文件里include，mods-enabled文件夹像是用来管理模块的，但是你会发现里面全是mods-available链接过来的文件，so仿照mods-available文件夹里面的文件格式，将helloworld模块的配置文件分成两部分：
helloworld.conf:
<Location /helloworld>
SetHandler helloworld
</Location>
helloworld.load:
LoadModule helloworld_module /usr/lib/apache2/modules/mod_helloworld.so
但是仅仅这样还不行，你还需要将模块链接到mod_available文件夹下面，链接的方法也写在apache服务器的欢迎页面了：
They are activated by symlinking available configuration files from their respective *-available/ counterparts. These should be managed by using our helpers a2enmod, a2dismod,a2ensite, a2dissite,and a2enconf, a2disconf . See their respective man pages for detailed information.
使用sudo a2enmod helloworld完成链接。
重启apache服务器apachectl restart，也可以按照提示使用service apache2 restart，再然后就可以见证奇迹了，在主机浏览器里输入http://192.168.232.129/helloworld，出现The sample page from mod_helloworld.c界面：
apache-hellowrold2.png
代码里可见这个模块只做了很少的事情，检查r-handler是否是helloworld，若不是，返回DECLINED（代表处理器和请求不匹配，拒绝处理该请求）。
1.2 地狱版
获取Apache最常用的三组信息：请求报头、响应抱头和内部环境变量。
修改mod_helloworld.c:
#include "httpd.h"
#include "http_config.h"
#include "http_protocol.h"
#include "ap_config.h"
static int printitem(void *rec, const char *key, const char *value)
{
request_rec *r = rec;
ap_rprintf(r, "<tr><th scope=\"row\">%s</th><td>%s</td></tr>\n",
ap_escape_html(r->pool, key),
ap_escape_html(r->pool, value));
return 1;
}
static void printtable(request_rec *r, apr_table_t *t, const char *caption, const char *keyhead, const char *valhead)
{
ap_rprintf(r, "<table><caption>%s</caption><thead>"
"<tr><th scope=\"col\">%s</th><th scope=\"col\">%s"
"</th></tr></thead><tbody>", caption, keyhead, valhead);
apr_table_do(printitem, r, t, NULL);
ap_rputs("</tbody></table>\n", r);
}
/* The sample content handler */
static int helloworld_handler(request_rec *r)
{
if (!r->handler || strcmp(r->handler, "helloworld") != 0 ) {
return DECLINED;
}
if (r->method_number != M_GET) {
return HTTP_METHOD_NOT_ALLOWED;
}
ap_set_content_type(r, "text/html;charset=ascii");
ap_rputs("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01//EN\">\n"
"<html><head><title>Apache Helloworld Module</title></head>"
"<body><h1>Hello World</h1>"
"<p>This is the Helloworld Module</p>", r);
/*打印表格*/
printtable(r, r->headers_in, "Request Headers", "Header", "Value");
printtable(r, r->headers_out, "Response Headers", "Header", "Value");
printtable(r, r->subprocess_env, "Environment", "Variable", "Value");
ap_rputs("</body></html>", r);
return OK;
}
static void helloworld_register_hooks(apr_pool_t *p)
{
ap_hook_handler(helloworld_handler, NULL, NULL, APR_HOOK_MIDDLE);
}
/* Dispatch list for API hooks */
module AP_MODULE_DECLARE_DATA helloworld_module = {
STANDARD20_MODULE_STUFF,
NULL, /* create per-dir config structures */
NULL, /* merge per-dir config structures */
NULL, /* create per-server config structures */
NULL, /* merge per-server config structures */
NULL, /* table of config file commands */
helloworld_register_hooks /* register hooks */
};
重启后如下图：
apache-helloworld3.png
1.3 其他
printitem回调函数
apr_table_do(func, rec, table, NULL) ;对表进行迭代
ap_escape_html
面向过滤器的I/O
三个步骤：
- 创建一个Bucket brigade
- 加载数据到Brigade
- 把Brigade传递到堆栈（r->output_filters）的第一个输出过滤器中。
2 手动编辑
安装apxs：
apt-get install apache2-dev
DECLINED:
#define DECLINED -1 /**< Module declines to handle */
request_rec:
/** A structure that represents the current request */
struct request_rec {
/** The handler string that we use to call a handler function */
const char *handler; /* What we *really* dispatch on */
/** Request method (eg. GET, HEAD, POST, etc.) */
const char *method;
/** M_GET, M_POST, etc. */
int method_number;
/** The filename on disk corresponding to this response */
char *filename;
}
ap_rputs:
/**
* Output a string for the current request
* @param str The string to output
* @param r The current request
* @return The number of bytes sent
* @deffunc int ap_rputs(const char *str, request_rec *r)
*/
AP_DECLARE(int) ap_rputs(const char *str, request_rec *r);
ap_set_content_length:
/**
* Set the content length for this request
* @param r The current request
* @param length The new content length
* @deffunc void ap_set_content_length(request_rec *r, apr_off_t length)
*/
AP_DECLARE(void) ap_set_content_length(request_rec *r, apr_off_t length);
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