### 示例: hello handler 模块[](http://tengine.taobao.org/book/chapter_03.html#hello-handler "永久链接至标题") 在前面已经看到了这个hello handler module的部分重要的结构。该模块提供了2个配置指令,仅可以出现在location指令的作用域中。这两个指令是hello_string, 该指令接受一个参数来设置显示的字符串。如果没有跟参数,那么就使用默认的字符串作为响应字符串。 另一个指令是hello_counter,如果设置为on,则会在响应的字符串后面追加Visited Times:的字样,以统计请求的次数。 这里有两点注意一下: 1. 对于flag类型的配置指令,当值为off的时候,使用ngx_conf_set_flag_slot函数,会转化为0,为on,则转化为非0。 1. 另外一个是,我提供了merge_loc_conf函数,但是却没有设置到模块的上下文定义中。这样有一个缺点,就是如果一个指令没有出现在配置文件中的时候,配置信息中的值,将永远会保持在create_loc_conf中的初始化的值。那如果,在类似create_loc_conf这样的函数中,对创建出来的配置信息的值,没有设置为合理的值的话,后面用户又没有配置,就会出现问题。 下面来完整的给出ngx_http_hello_module模块的完整代码。 [](http:// "点击提交Issue,反馈你的意见...") #include <ngx_config.h> #include <ngx_core.h> #include <ngx_http.h> typedef struct { ngx_str_t hello_string; ngx_int_t hello_counter; }ngx_http_hello_loc_conf_t; static ngx_int_t ngx_http_hello_init(ngx_conf_t *cf); static void *ngx_http_hello_create_loc_conf(ngx_conf_t *cf); static char *ngx_http_hello_string(ngx_conf_t *cf, ngx_command_t *cmd, void *conf); static char *ngx_http_hello_counter(ngx_conf_t *cf, ngx_command_t *cmd, void *conf); static ngx_command_t ngx_http_hello_commands[] = { { ngx_string("hello_string"), NGX_HTTP_LOC_CONF|NGX_CONF_NOARGS|NGX_CONF_TAKE1, ngx_http_hello_string, NGX_HTTP_LOC_CONF_OFFSET, offsetof(ngx_http_hello_loc_conf_t, hello_string), NULL }, { ngx_string("hello_counter"), NGX_HTTP_LOC_CONF|NGX_CONF_FLAG, ngx_http_hello_counter, NGX_HTTP_LOC_CONF_OFFSET, offsetof(ngx_http_hello_loc_conf_t, hello_counter), NULL }, ngx_null_command }; /* static u_char ngx_hello_default_string[] = "Default String: Hello, world!"; */ static int ngx_hello_visited_times = 0; static ngx_http_module_t ngx_http_hello_module_ctx = { NULL, /* preconfiguration */ ngx_http_hello_init, /* postconfiguration */ NULL, /* create main configuration */ NULL, /* init main configuration */ NULL, /* create server configuration */ NULL, /* merge server configuration */ ngx_http_hello_create_loc_conf, /* create location configuration */ NULL /* merge location configuration */ }; ngx_module_t ngx_http_hello_module = { NGX_MODULE_V1, &ngx_http_hello_module_ctx, /* module context */ ngx_http_hello_commands, /* module directives */ NGX_HTTP_MODULE, /* module type */ NULL, /* init master */ NULL, /* init module */ NULL, /* init process */ NULL, /* init thread */ NULL, /* exit thread */ NULL, /* exit process */ NULL, /* exit master */ NGX_MODULE_V1_PADDING }; static ngx_int_t ngx_http_hello_handler(ngx_http_request_t *r) { ngx_int_t rc; ngx_buf_t *b; ngx_chain_t out; ngx_http_hello_loc_conf_t* my_conf; u_char ngx_hello_string[1024] = {0}; ngx_uint_t content_length = 0; ngx_log_error(NGX_LOG_EMERG, r->connection->log, 0, "ngx_http_hello_handler is called!"); my_conf = ngx_http_get_module_loc_conf(r, ngx_http_hello_module); if (my_conf->hello_string.len == 0 ) { ngx_log_error(NGX_LOG_EMERG, r->connection->log, 0, "hello_string is empty!"); return NGX_DECLINED; } if (my_conf->hello_counter == NGX_CONF_UNSET || my_conf->hello_counter == 0) { ngx_sprintf(ngx_hello_string, "%s", my_conf->hello_string.data); } else { ngx_sprintf(ngx_hello_string, "%s Visited Times:%d", my_conf->hello_string.data, ++ngx_hello_visited_times); } ngx_log_error(NGX_LOG_EMERG, r->connection->log, 0, "hello_string:%s", ngx_hello_string); content_length = ngx_strlen(ngx_hello_string); /* we response to 'GET' and 'HEAD' requests only */ if (!(r->method & (NGX_HTTP_GET|NGX_HTTP_HEAD))) { return NGX_HTTP_NOT_ALLOWED; } /* discard request body, since we don't need it here */ rc = ngx_http_discard_request_body(r); if (rc != NGX_OK) { return rc; } /* set the 'Content-type' header */ /* *r->headers_out.content_type.len = sizeof("text/html") - 1; *r->headers_out.content_type.data = (u_char *)"text/html"; */ ngx_str_set(&r->headers_out.content_type, "text/html"); /* send the header only, if the request type is http 'HEAD' */ if (r->method == NGX_HTTP_HEAD) { r->headers_out.status = NGX_HTTP_OK; r->headers_out.content_length_n = content_length; return ngx_http_send_header(r); } /* allocate a buffer for your response body */ b = ngx_pcalloc(r->pool, sizeof(ngx_buf_t)); if (b == NULL) { return NGX_HTTP_INTERNAL_SERVER_ERROR; } /* attach this buffer to the buffer chain */ out.buf = b; out.next = NULL; /* adjust the pointers of the buffer */ b->pos = ngx_hello_string; b->last = ngx_hello_string + content_length; b->memory = 1; /* this buffer is in memory */ b->last_buf = 1; /* this is the last buffer in the buffer chain */ /* set the status line */ r->headers_out.status = NGX_HTTP_OK; r->headers_out.content_length_n = content_length; /* send the headers of your response */ rc = ngx_http_send_header(r); if (rc == NGX_ERROR || rc > NGX_OK || r->header_only) { return rc; } /* send the buffer chain of your response */ return ngx_http_output_filter(r, &out); } static void *ngx_http_hello_create_loc_conf(ngx_conf_t *cf) { ngx_http_hello_loc_conf_t* local_conf = NULL; local_conf = ngx_pcalloc(cf->pool, sizeof(ngx_http_hello_loc_conf_t)); if (local_conf == NULL) { return NULL; } ngx_str_null(&local_conf->hello_string); local_conf->hello_counter = NGX_CONF_UNSET; return local_conf; } /* static char *ngx_http_hello_merge_loc_conf(ngx_conf_t *cf, void *parent, void *child) { ngx_http_hello_loc_conf_t* prev = parent; ngx_http_hello_loc_conf_t* conf = child; ngx_conf_merge_str_value(conf->hello_string, prev->hello_string, ngx_hello_default_string); ngx_conf_merge_value(conf->hello_counter, prev->hello_counter, 0); return NGX_CONF_OK; }*/ static char * ngx_http_hello_string(ngx_conf_t *cf, ngx_command_t *cmd, void *conf) { ngx_http_hello_loc_conf_t* local_conf; local_conf = conf; char* rv = ngx_conf_set_str_slot(cf, cmd, conf); ngx_conf_log_error(NGX_LOG_EMERG, cf, 0, "hello_string:%s", local_conf->hello_string.data); return rv; } static char *ngx_http_hello_counter(ngx_conf_t *cf, ngx_command_t *cmd, void *conf) { ngx_http_hello_loc_conf_t* local_conf; local_conf = conf; char* rv = NULL; rv = ngx_conf_set_flag_slot(cf, cmd, conf); ngx_conf_log_error(NGX_LOG_EMERG, cf, 0, "hello_counter:%d", local_conf->hello_counter); return rv; } static ngx_int_t ngx_http_hello_init(ngx_conf_t *cf) { ngx_http_handler_pt *h; ngx_http_core_main_conf_t *cmcf; cmcf = ngx_http_conf_get_module_main_conf(cf, ngx_http_core_module); h = ngx_array_push(&cmcf->phases[NGX_HTTP_CONTENT_PHASE].handlers); if (h == NULL) { return NGX_ERROR; } *h = ngx_http_hello_handler; return NGX_OK; } 通过上面一些介绍,我相信大家都能对整个示例模块有一个比较好的理解。唯一可能感觉有些理解困难的地方在于ngx_http_hello_handler函数里面产生和设置输出。但其实大家在本书的前面的相关章节都可以看到对ngx_buf_t和request等相关数据结构的说明。如果仔细看了这些地方的说明的话,应该对这里代码的实现就比较容易理解了。因此,这里不再赘述解释。