After an object is uploaded, Object Storage Service (OSS) can send a callback request to the application server. To implement a callback, you need to only send a request that contains relevant callback parameters to OSS.
Usage notes
In this topic, the public endpoint of the China (Hangzhou) region is used. If you want to access OSS from other Alibaba Cloud services in the same region as OSS, use an internal endpoint. For more information about OSS regions and endpoints, see Regions and endpoints.
In this topic, an OSSClient instance is created by using an OSS endpoint. If you want to create an OSSClient instance by using custom domain names or Security Token Service (STS), see Initialization.
Examples
The following sample code provides an example on how to configure an upload callback:
#include "oss_api.h"
#include "aos_http_io.h"
/* Specify the endpoint of the region in which the bucket is located. For example, if the bucket is located in the China (Hangzhou) region, set the endpoint to https://oss-cn-hangzhou.aliyuncs.com. */
const char *endpoint = "yourEndpoint";
/* Specify the name of the bucket. Example: examplebucket. */
const char *bucket_name = "examplebucket";
/* Specify the full path of the object. Do not include the bucket name in the full path. Example: exampledir/exampleobject.txt. */
const char *object_name = "exampledir/exampleobject.txt";
const char *object_content = "More than just cloud.";
/* Specify the region in which the bucket is located. For example, if the bucket is located in the China (Hangzhou) region, set the region to cn-hangzhou. */
const char *region = "yourRegion";
void init_options(oss_request_options_t *options)
{
options->config = oss_config_create(options->pool);
/* Use a char* string to initialize data of the aos_string_t type. */
aos_str_set(&options->config->endpoint, endpoint);
/* Obtain access credentials from environment variables. Before you run the sample code, make sure that the OSS_ACCESS_KEY_ID and OSS_ACCESS_KEY_SECRET environment variables are configured. */
aos_str_set(&options->config->access_key_id, getenv("OSS_ACCESS_KEY_ID"));
aos_str_set(&options->config->access_key_secret, getenv("OSS_ACCESS_KEY_SECRET"));
// Specify two additional parameters.
aos_str_set(&options->config->region, region);
options->config->signature_version = 4;
/* Specify whether to use CNAME. The value 0 indicates that CNAME is not used. */
options->config->is_cname = 0;
/* Configure network parameters, such as the timeout period. */
options->ctl = aos_http_controller_create(options->pool, 0);
}
int main(int argc, char *argv[])
{
aos_pool_t *p = NULL;
aos_status_t *s = NULL;
aos_string_t bucket;
aos_string_t object;
aos_table_t *headers = NULL;
oss_request_options_t *options = NULL;
aos_table_t *resp_headers = NULL;
aos_list_t resp_body;
aos_list_t buffer;
aos_buf_t *content;
char *buf = NULL;
int64_t len = 0;
int64_t size = 0;
int64_t pos = 0;
char b64_buf[1024];
int b64_len;
/* Specify the callback parameters in the JSON format. */
/* (Optional) Specify the Host field included in the callback request header. */
char *callback = "{"
"\"callbackUrl\":\"http://oss-demo.aliyuncs.com:23450\","
"\"callbackHost\":\"yourCallbackHost\","
"\"callbackBody\":\"bucket=${bucket}&object=${object}&size=${size}&mimeType=${mimeType}\","
"\"callbackBodyType\":\"application/x-www-form-urlencoded\""
"}";
/* Call the aos_http_io_initialize method in main() to initialize global resources, such as network resources and memory resources. */
if (aos_http_io_initialize(NULL, 0) != AOSE_OK) {
exit(1);
}
/* Initialize the parameters. */
aos_pool_create(&p, NULL);
options = oss_request_options_create(p);
init_options(options);
aos_str_set(&bucket, bucket_name);
aos_str_set(&object, object_name);
aos_list_init(&resp_body);
aos_list_init(&buffer);
content = aos_buf_pack(options->pool, object_content, strlen(object_content));
aos_list_add_tail(&content->node, &buffer);
/* Add the callback to the header. */
b64_len = aos_base64_encode((unsigned char*)callback, strlen(callback), b64_buf);
b64_buf[b64_len] = '\0';
headers = aos_table_make(p, 1);
apr_table_set(headers, OSS_CALLBACK, b64_buf);
/* Configure the upload callback. */
s = oss_do_put_object_from_buffer(options, &bucket, &object, &buffer,
headers, NULL, NULL, &resp_headers, &resp_body);
if (aos_status_is_ok(s)) {
printf("put object from buffer succeeded\n");
} else {
printf("put object from buffer failed\n");
}
/* Obtain the buffer length. */
len = aos_buf_list_len(&resp_body);
buf = (char *)aos_pcalloc(p, (apr_size_t)(len + 1));
buf[len] = '\0';
/* Copy the content in the buffer to the memory. */
aos_list_for_each_entry(aos_buf_t, content, &resp_body, node) {
size = aos_buf_size(content);
memcpy(buf + pos, content->pos, (size_t)size);
pos += size;
}
/* Release the memory pool. This operation releases the memory resources allocated for the request. */
aos_pool_destroy(p);
/* Release the allocated global resources. */
aos_http_io_deinitialize();
return 0;
}