libcurl上传文件实例

libcurl上传文件实例

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Using POST with HTTP 1.1 implies the use of a "Expect: 100-continue" header. You can disable this header with CURLOPT_HTTPHEADER as usual.

When setting CURLOPT_HTTPPOST, it will automatically set CURLOPT_NOBODY to 0 (since 7.14.1).

CURLOPT_POST   --application/x-www-form-urlencoded形式

A non-zero parameter tells the library to do a regular HTTP post. This will also make the library use the a "Content-Type: application/x-www-form-urlencoded" header. (This is by far the most commonly used POST method).

Use one of CURLOPT_POSTFIELDS or CURLOPT_COPYPOSTFIELDS options to specify what data to post and CURLOPT_POSTFIELDSIZE or CURLOPT_POSTFIELDSIZE_LARGE to set the data size.

Optionally, you can provide data to POST using the CURLOPT_READFUNCTION and CURLOPT_READDATA options but then you must make sure to not set CURLOPT_POSTFIELDS to anything but NULL. When providing data with a callback, you must transmit it using chunked transfer-encoding or you must set the size of the data with the CURLOPT_POSTFIELDSIZE or CURLOPT_POSTFIELDSIZE_LARGE option. To enable chunked encoding, you simply pass in the appropriate Transfer-Encoding header, see the post-callback.c example.

You can override the default POST Content-Type: header by setting your own with CURLOPT_HTTPHEADER.

Using POST with HTTP 1.1 implies the use of a "Expect: 100-continue" header. You can disable this header with CURLOPT_HTTPHEADER as usual.

If you use POST to a HTTP 1.1 server, you can send data without knowing the size before starting the POST if you use chunked encoding. You enable this by adding a header like "Transfer-Encoding: chunked" with CURLOPT_HTTPHEADER. With HTTP 1.0 or without chunked transfer, you must specify the size in the request.

When setting CURLOPT_POST to a non-zero value, it will automatically set CURLOPT_NOBODY to 0 (since 7.14.1).

If you issue a POST request and then want to make a HEAD or GET using the same re-used handle, you must explicitly set the new request type using CURLOPT_NOBODY or CURLOPT_HTTPGET or similar.

以上是两种POST方式，具体代码如下:

    ALLUPLOADFILES::iterator iter  =  allFiles.begin();
     // 如果含有文件  // name="files"; filename="file1.txt"    
     if ( bFileFlag )  // 以form-dataf方式post
     {
        for (;iter != allFiles.end();iter++)
        {
            if ( iter->isFile )
            {
                my_bytestr_url_encode(iter->fileName);
                curl_formadd(&post, &last, CURLFORM_COPYNAME , iter->contrlID.c_str(),
                    CURLFORM_BUFFER, iter->fileName.c_str(),
                    CURLFORM_BUFFERPTR,iter->data.c_str(),
                    CURLFORM_END);    
            }
            else
            {
                curl_formadd(&post, &last, CURLFORM_COPYNAME , iter->contrlID.c_str(),
                    CURLFORM_COPYCONTENTS,iter->data.c_str(),
                    CURLFORM_END);    
            }
        }
    }
     else   // 以application/x-www-form-urlencoded方式post
     {
        for (;iter != allFiles.end();iter++)
        {
            my_bytestr_url_encode(iter->contrlID);
            my_bytestr_url_encode(iter->data);
            postbuffer += iter->contrlID;
            postbuffer += "=";
            postbuffer += iter->data;
            postbuffer += "&";
        }
    }


     if  (bFileFlag) 
        curl_easy_setopt(curl, CURLOPT_HTTPPOST,post);
     else  
     {
        curl_easy_setopt(curl, CURLOPT_POST,1);
        curl_easy_setopt(curl, CURLOPT_COPYPOSTFIELDS  , postbuffer.c_str());
    }

    code  =  curl_easy_perform(curl);

对于返回页面，我们可以和上一篇文章所说那样，设置write的回调函数，写入文件即可：

    curl_easy_setopt(curl, CURLOPT_VERBOSE,  1L );
    curl_easy_setopt(curl, CURLOPT_URL, url.c_str());
    curl_easy_setopt(curl, CURLOPT_FOLLOWLOCATION,  1 );
    curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, writer);

long writer(void * data, int size, int nmemb, string  & content)
{
    long sizes = size * nmemb;
    string temp(data,sizes);
    printf("receive data(%d bytes):\r\n%s",  sizes, (char*)data );
    content += temp; 
    return sizes;
}

测试：
我们可以用tomcat写一个jsp上传代码测试一下，其中使用到了smartUpload组件，代码如下：upload.html

< form action = " upload.jsp "  method = " post "  ENCTYPE = " multipart/form-data " >

输入名称: < input type = " type "  name = " name " >< br >

选择要上传的图片:

< input type = " file "  name = " pic " >

< input type = " submit "  value = " 上传 " >

</ form >

upload.jsp如下:

< jsp:useBean id = " smart "  scope = " page "   class = " org.lxh.smart.SmartUpload " />

<%
        // 上传初始化
       smart.initialize(pageContext);
        // 准备上传
       smart.upload();     
        // 保存上传的文件
        // smart.save("/upload");
        // 取得文件的扩展名称
       String ext  =  smart.getFiles().getFile( 0 ).getFileExt();
%>
<%
        // String name=request.getParameter("name"); 表单被封装了,不能用这种方法取值.
       String name = smart.getRequest().getParameter( " name " );
%>  

        // <%=name+"."+ext%>
<%         // 保存文件,包括改名.
       smart.getFiles().getFile( 0 ).saveAs( " /upload/ " + name + " . " + ext);
%>

经测试用libcurl POST文件成功。以上是简单的测试，比较深入的问题还有待进一步研究。
由于我对HTTP协议，WEB这块不是太熟，如果有错误理解不当的地方，还请指正，欢迎大家和我探讨，谢谢！