helloworld_mod模块

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
**    
**    SetHandler helloworld
**    
**
**  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

SetHandler helloworld

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:


SetHandler helloworld

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:

helloworld_mod模块_第1张图片
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, "%s%s\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, ""
        "", caption, keyhead, valhead);
    apr_table_do(printitem, r, t, NULL);
    ap_rputs("
%s
%s%s" "
\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("\n" "Apache Helloworld Module" "

Hello World

" "

This is the Helloworld Module

", 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("", 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:


helloworld_mod模块_第2张图片
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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