基于Httpfs访问HDFS的C++实现

Httpfs是hadoop2.x中hdfs项目的内置应用，基于tomcat和jesery，对外提供完备HDFS操作的RESTful接口，无需安装客户端，可方便实现数据交互，如从windows访问存储在hdfs上的文件。本文通过Httpfs说明文档，实现了一个基于libcurl和jsoncpp的httpfs客户端程序（C++）。

1.准备工作

　　1.1 编译jsoncpp

jsoncpp下载地址：https://codeload.github.com/open-source-parsers/jsoncpp/zip/master

使用VS2010打开jsoncpp解压文件夹/makefiles/msvc2010/jsoncpp.sln，选择lib_json，设置项目的属性。具体设置为：1）常规里设置配置类型为.lib,使用多字节字符集C/C++->代码生成中的代码生成选择 /MD(release) /MDd(debug)。编译环境必须与我们开发的工程一致！！！

1.2编译libcurl

libcurl下载地址：https://curl.haxx.se/download/curl-7.47.1.tar.gz

打开curl解压目录\projects\Windows\VC10\curl-all.sln ,选择lib_debug和lib_release编译。vs2010引用静态链接失败解决：

1）给工程添加依赖的库：项目->属性->链接器->输入->附加依赖项，把libcurl.lib ws2_32.lib winmm.lib wldap32.lib添加进去(注意，debug配置用libcurld.lib).

2)、加入预编译选项：项目->属性->c/c++ ->预处理器->预处理器，把;BUILDING_LIBCURL;HTTP_ONLY复制进去（注意不要丢了;）

解决方案来自网络“vc2010使用libcurl静态库遇到连接失败的解决方案”

1.3设置头文件引用

在工程路径下创建一个include目录，将libcurl和jsoncpp中的include文件夹下的文件复制到该include文件夹下，设置为vc++目录引用路径。

2.代码实现

HttpfsClient.H

#pragma once

#include <string>

#include <vector>

using namespace std;

typedef struct FileStatus {

    __int64 accessTime;

    __int64 blocksize;

    string group;

    __int64 length;

    __int64 modificationTime;

    string owner;

    string pathSuffix;

    string permission;

    int replication;

    string type;

}FileStatus;

class CHttpFSClient

{

private:

    string m_hostaddr;    //http://<HOST>:<PORT>/webhdfs/v1/

    string m_username;  //i.e. hadoop

    long m_timeout;

    long m_conntimeout;

public:

    enum HTTP_TYPE{GET=,PUT,POST,DEL};

public:

    CHttpFSClient(string& hostaddr,string& username);

    ~CHttpFSClient(void);

    bool create(string& local_file,string& rem_file,bool overwrite = false);

    bool append(string& local_file,string& rem_file);

    bool mkdirs(string& path);

    bool rename(string& src,string& dst);

    bool del(string& path, bool recursive=false);

    bool read(string& rem_file,string& local_file, long offset=, long length=);

    bool ls(string& rem_path,vector<FileStatus>& results);

protected:

    static size_t fileread_callback(void *ptr, size_t size, size_t nmemb, void *stream);

    static size_t filewrite_data(const char *ptr, size_t size, size_t nmemb, void *stream);

    static size_t memwrite_data(const char *contents, size_t size, size_t nmemb, string *stream);

    static size_t header_callback(const char  *ptr, size_t size, size_t nmemb, std::string *stream);

    void showFileStatus(vector<FileStatus>& results);

};

HttpfsClient.cpp

// HttpfsClient.cpp : 定义控制台应用程序的入口点。

//

#include "stdafx.h"

#include "HttpfsClient.h"

#include <assert.h>

#include <stdio.h>

#include <fcntl.h>

#include <sys/stat.h>

#include <curl/curl.h>

#include <json/json.h>

#include <iostream>

#include <fstream>

using namespace std;

CHttpFSClient::CHttpFSClient(string& hostaddr,string& username)

{

    m_hostaddr = hostaddr;

    m_username = username;

    m_timeout = ;

    m_conntimeout = ;

    /* In windows, this will init the winsock stuff */

    curl_global_init(CURL_GLOBAL_ALL);

}

CHttpFSClient::~CHttpFSClient(void)

{

    curl_global_cleanup();

}

/*

    Create and Write to a File

    @param local_file string

    @param rem_file string

    @param overwirte: ture,false

    @return true/false

    Step 1: Submit a HTTP PUT request without automatically following redirects and without sending the file data.

    curl -i -X PUT "http://<HOST>:<PORT>/webhdfs/v1/<PATH>?op=CREATE                        [&overwrite=<true|false>][&blocksize=<LONG>][&replication=<SHORT>]

                        [&permission=<OCTAL>][&buffersize=<INT>]"

    The request is redirected to a datanode where the file data is to be written:

    HTTP/1.1 307 TEMPORARY_REDIRECT

    Location: http://<DATANODE>:<PORT>/webhdfs/v1/<PATH>?op=CREATE...

    Content-Length: 0

    Step 2: Submit another HTTP PUT request using the URL in the Location header with the file data to be written.

    curl -i -X PUT -T <LOCAL_FILE> "http://<DATANODE>:<PORT>/webhdfs/v1/<PATH>?op=CREATE..."

    The client receives a 201 Created response with zero content length and the WebHDFS URI of the file in the Location header:

    HTTP/1.1 201 Created

    Location: webhdfs://<HOST>:<PORT>/<PATH>

    Content-Length: 0

*/

bool CHttpFSClient::create(string& local_file,string& rem_file,bool overwrite)

{

    string url = m_hostaddr + rem_file + "?op=CREATE&user.name="+m_username;

    if(overwrite) url += "&overwrite=true";

    string szheader_buffer;

    char* redir_url;

    string strredir_url;

    long response_code=;

    bool curlerr = false;

    CURL *curl;

    CURLcode res;

    // get a curl handle

    curl = curl_easy_init();

    if(curl) {

        curl_easy_setopt(curl, CURLOPT_PUT, 1L);

        curl_easy_setopt(curl, CURLOPT_URL, url.c_str());

        curl_easy_setopt(curl, CURLOPT_UPLOAD, 1L);

        curl_easy_setopt(curl, CURLOPT_TIMEOUT, m_timeout);

        curl_easy_setopt(curl, CURLOPT_CONNECTTIMEOUT, m_conntimeout);

        curl_easy_setopt(curl, CURLOPT_FOLLOWLOCATION, 0L);

        curl_easy_setopt(curl, CURLOPT_INFILESIZE, ); //上传的字节数 

        res = curl_easy_perform(curl);

        // Check for errors

        if(res != CURLE_OK)

        {

            fprintf(stderr, "hdfs create first request failed: %s\n",

            curl_easy_strerror(res));

            curlerr = true;

        }

        else

        {

            res = curl_easy_getinfo(curl,CURLINFO_REDIRECT_URL,&redir_url);

            if(res != CURLE_OK)

            {

                fprintf(stderr, "curl_easy_getinfo CURLINFO::CURLINFO_REDIRECT_URL failed: %s\n",

                    curl_easy_strerror(res));

                curlerr = true;

            }

            strredir_url = redir_url;

        }        

    }

    // always cleanup!!!!

    curl_easy_cleanup(curl);

    if(curlerr)

        return false;

    //upload file to hdfs

    struct stat file_info;

    // get the file size of the local file

    stat(local_file.c_str(), &file_info);

    FILE * hd_src;

    hd_src = fopen(local_file.c_str(), "rb");

    if(GetLastError() != )

        return false;

    struct curl_slist *headers = NULL;

    headers = curl_slist_append(headers, "Content-Type:application/octet-stream");

    headers = curl_slist_append(headers, "Content-Type:application/octet-stream");

    curl = curl_easy_init();

    if(curl) {

        // we want to use our own read function

        curl_easy_setopt(curl, CURLOPT_READFUNCTION, CHttpFSClient::fileread_callback);

        // enable uploading

        curl_easy_setopt(curl, CURLOPT_UPLOAD, 1L);

        // HTTP PUT please

        curl_easy_setopt(curl, CURLOPT_PUT, 1L);

        // specify target URL, and note that this URL should include a file    name, not only a directory

        curl_easy_setopt(curl, CURLOPT_URL, strredir_url.c_str());

        // specify content type

        curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers);

        // now specify which file to upload

        curl_easy_setopt(curl, CURLOPT_READDATA, hd_src);

        // provide the size of the upload, we specicially typecast the value to curl_off_t

        // since we must be sure to use the correct data size

        curl_easy_setopt(curl, CURLOPT_INFILESIZE_LARGE,

            (curl_off_t)file_info.st_size);

        // Now run off and do what you've been told!

        res = curl_easy_perform(curl);

        // Check for errors

        if(res != CURLE_OK)

        {

            fprintf(stderr, "upload file to hdfs failed: %s\n",

            curl_easy_strerror(res));

            curlerr = true;

        }

    }

    fclose(hd_src); // close the local file 

    // always cleanup!!!!

    curl_slist_free_all(headers);

    curl_easy_cleanup(curl);

    if(curlerr)

        return false;

    return true;

}

/*

    Append to a File

    @param local_file string

    @param rem_file string

    @return true/false

    Step 1: Submit a HTTP POST request without automatically following redirects and without sending the file data.

    curl -i -X POST "http://<HOST>:<PORT>/webhdfs/v1/<PATH>?op=APPEND[&buffersize=<INT>]"

    The request is redirected to a datanode where the file data is to be appended:

    HTTP/1.1 307 TEMPORARY_REDIRECT

    Location: http://<DATANODE>:<PORT>/webhdfs/v1/<PATH>?op=APPEND...

    Content-Length: 0

    Step 2: Submit another HTTP POST request using the URL in the Location header with the file data to be appended.

    curl -i -X POST -T <LOCAL_FILE> "http://<DATANODE>:<PORT>/webhdfs/v1/<PATH>?op=APPEND..."

    The client receives a response with zero content length:

    HTTP/1.1 200 OK

    Content-Length: 0

*/

bool CHttpFSClient::append(string& local_file,string& rem_file)

{

    string url = m_hostaddr + rem_file + "?op=APPEND&user.name="+m_username;

    char* redir_url;

    string strredir_url;

    long response_code=;

    bool curlerr = false;

    CURL *curl;

    CURLcode res;

    // get a curl handle

    curl = curl_easy_init();

    if(curl) {

        curl_easy_setopt(curl, CURLOPT_POST, 1L);

        curl_easy_setopt(curl, CURLOPT_URL, url.c_str());

        curl_easy_setopt(curl, CURLOPT_TIMEOUT, m_timeout);

        curl_easy_setopt(curl, CURLOPT_FOLLOWLOCATION, 0L);

        curl_easy_setopt(curl, CURLOPT_CONNECTTIMEOUT, m_conntimeout);

        curl_easy_setopt(curl, CURLOPT_POSTFIELDSIZE, );

        res = curl_easy_perform(curl);

        // Check for errors

        if(res != CURLE_OK)

        {

            fprintf(stderr, "hdfs append first request failed: %s\n",

                curl_easy_strerror(res));

            curlerr = true;

        }

        else

        {

            res = curl_easy_getinfo(curl,CURLINFO_REDIRECT_URL,&redir_url);

            if(res != CURLE_OK)

            {

                fprintf(stderr, "curl_easy_getinfo CURLINFO::CURLINFO_REDIRECT_URL failed: %s\n",

                    curl_easy_strerror(res));

                curlerr = true;

            }

            strredir_url = redir_url;

        }        

    }

    // always cleanup!!!!

    curl_easy_cleanup(curl);

    if(curlerr)

        return false;

    // append file to hdfs

    struct curl_slist *headers = NULL;

    headers = curl_slist_append(headers, "Content-Type: application/octet-stream");

    curl = curl_easy_init();

    if(curl) {

        curl_easy_setopt(curl, CURLOPT_POST, 1L);

        curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers);

        curl_easy_setopt(curl, CURLOPT_URL, strredir_url.c_str());

        //curl_easy_setopt(curl, CURLOPT_VERBOSE, 1L); 

        /*//multipart/formdata请求

        struct curl_httppost *formpost = NULL;

        struct curl_httppost *lastptr  = NULL;

        curl_formadd(&formpost, &lastptr, CURLFORM_COPYNAME, "file", CURLFORM_FILE, local_file.c_str(), CURLFORM_CONTENTTYPE, "application/octet-stream", CURLFORM_END);

        curl_easy_setopt(curl, CURLOPT_HTTPPOST, formpost);*/

        //C++代码一次读取文本文件全部内容到string对象

        ifstream fin(local_file.c_str(),ios::in);

        istreambuf_iterator<char> beg(fin), end;

        string strdata(beg, end);

        fin.close();

        curl_easy_setopt(curl,CURLOPT_POSTFIELDS,strdata.c_str());

        res = curl_easy_perform(curl);

        //curl_formfree(formpost);

        // Check for errors

        if(res != CURLE_OK)

        {

            fprintf(stderr, "append file to hdfs failed: %s\n",

                curl_easy_strerror(res));

            curlerr = true;

        }

        else

        {

            res = curl_easy_getinfo(curl,CURLINFO_RESPONSE_CODE,&response_code);

            if(res != CURLE_OK)

            {

                fprintf(stderr, "curl_easy_getinfo CURLINFO::CURLINFO_RESPONSE_CODE failed: %s\n",

                    curl_easy_strerror(res));

                curlerr = true;

            }

        }

    }

    // always cleanup!!!!

    curl_slist_free_all(headers);

    curl_easy_cleanup(curl);

    if(curlerr)

        return false;

    if(response_code == )

        return true;

    else

        return false;

}

/*

    Make a Directory

    Submit a HTTP PUT request.

    curl -i -X PUT "http://<HOST>:<PORT>/<PATH>?op=MKDIRS[&permission=<OCTAL>]"

    The client receives a response with a boolean JSON object:

    HTTP/1.1 200 OK

    Content-Type: application/json

    Transfer-Encoding: chunked

    {"boolean": true}

*/

bool CHttpFSClient::mkdirs(string& path)

{

    string url = m_hostaddr + path + "?op=MKDIRS&user.name="+m_username;

    long response_code=;

    long headerlen = ;

    bool curlerr = false;

    string response_contents;

    CURL *curl;

    CURLcode res;

    // get a curl handle

    curl = curl_easy_init();

    if(curl) {

        // http put

        curl_easy_setopt(curl, CURLOPT_PUT, 1L);

        curl_easy_setopt(curl, CURLOPT_URL, url.c_str());

        curl_easy_setopt(curl, CURLOPT_HEADER, 1L);

        curl_easy_setopt(curl, CURLOPT_TIMEOUT, m_timeout);

        curl_easy_setopt(curl, CURLOPT_CONNECTTIMEOUT, m_conntimeout);

        curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, CHttpFSClient::memwrite_data);

        curl_easy_setopt(curl, CURLOPT_WRITEDATA, &response_contents);

        curl_easy_setopt(curl, CURLOPT_INFILESIZE, );

        res = curl_easy_perform(curl);

        // Check for errors

        if(res != CURLE_OK)

        {

            fprintf(stderr, "hdfs mkdirs failed: %s\n",

                curl_easy_strerror(res));

            curlerr = true;

        }

        else

        {

            res = curl_easy_getinfo(curl,CURLINFO_RESPONSE_CODE,&response_code);

            if(res != CURLE_OK)

            {

                fprintf(stderr, "curl_easy_getinfo CURLINFO::CURLINFO_RESPONSE_CODE failed: %s\n",

                    curl_easy_strerror(res));

                curlerr = true;

            }

            res = curl_easy_getinfo(curl,CURLINFO_HEADER_SIZE,&headerlen);

            if(res != CURLE_OK)

            {

                fprintf(stderr, "curl_easy_getinfo CURLINFO::CURLINFO_HEADER_SIZE failed: %s\n",

                    curl_easy_strerror(res));

                curlerr = true;

            }

        }        

    }

    // always cleanup!!!!

    curl_easy_cleanup(curl);

    if(curlerr)

        return false;

    if(response_code == )

    {

        Json::Reader reader;

        Json::Value root;

        const char *content = response_contents.c_str();

        if(!reader.parse(content+headerlen,content+response_contents.length(),root,false))

            return false;

        return root["boolean"].asBool();

    }

    else

        return false;

}

/*

Rename a File/Directory

Submit a HTTP PUT request.

curl -i -X PUT "<HOST>:<PORT>/webhdfs/v1/<PATH>?op=RENAME&destination=<PATH>"

The client receives a response with a boolean JSON object:

HTTP/1.1 200 OK

Content-Type: application/json

Transfer-Encoding: chunked

{"boolean": true}

*/

bool CHttpFSClient::rename(string& src,string& dst)

{

    string url = m_hostaddr + src + "?op=RENAME&user.name="+m_username+"&destination="+dst;

    long response_code=;

    long headerlen = ;

    bool curlerr = false;

    string response_contents;

    CURL *curl;

    CURLcode res;

    // get a curl handle

    curl = curl_easy_init();

    if(curl) {

        // http put

        curl_easy_setopt(curl, CURLOPT_PUT, 1L);

        curl_easy_setopt(curl, CURLOPT_URL, url.c_str());

        curl_easy_setopt(curl, CURLOPT_HEADER, 1L);

        curl_easy_setopt(curl, CURLOPT_TIMEOUT, m_timeout);

        curl_easy_setopt(curl, CURLOPT_CONNECTTIMEOUT, m_conntimeout);

        curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, CHttpFSClient::memwrite_data);

        curl_easy_setopt(curl, CURLOPT_WRITEDATA, &response_contents);

        curl_easy_setopt(curl, CURLOPT_INFILESIZE, );

        res = curl_easy_perform(curl);

        // Check for errors

        if(res != CURLE_OK)

        {

            fprintf(stderr, "hdfs rename failed: %s\n",

                curl_easy_strerror(res));

            curlerr = true;

        }

        else

        {

            res = curl_easy_getinfo(curl,CURLINFO_RESPONSE_CODE,&response_code);

            if(res != CURLE_OK)

            {

                fprintf(stderr, "curl_easy_getinfo CURLINFO::CURLINFO_RESPONSE_CODE failed: %s\n",

                    curl_easy_strerror(res));

                curlerr = true;

            }

            res = curl_easy_getinfo(curl,CURLINFO_HEADER_SIZE,&headerlen);

            if(res != CURLE_OK)

            {

                fprintf(stderr, "curl_easy_getinfo CURLINFO::CURLINFO_HEADER_SIZE failed: %s\n",

                    curl_easy_strerror(res));

                curlerr = true;

            }

        }        

    }

    // always cleanup!!!!

    curl_easy_cleanup(curl);

    if(curlerr)

        return false;

    if(response_code == )

    {

        Json::Reader reader;

        Json::Value root;

        const char *content = response_contents.c_str();

        if(!reader.parse(content+headerlen,content+response_contents.length(),root,false))

            return false;

        return root["boolean"].asBool();

    }

    else

        return false;

}

/*

    Delete a File/Directory

    @param file string, the file or directory to be deleted

    @return ture/false

    Submit a HTTP DELETE request

    curl -i -X DELETE "http://<host>:<port>/webhdfs/v1/<path>?op=DELETE

                                  [&recursive=<true|false>]"

    The client receives a response with a boolean JSON object:

    HTTP/1.1 200 OK

    Content-Type: application/json

    Transfer-Encoding: chunked

    {"boolean": true}

*/

bool CHttpFSClient::del(string& path, bool recursive)

{

    string url = m_hostaddr + path + "?op=DELETE&user.name="+m_username;

    if(recursive) url+="&recursive=true";

    string response_contents;

    char redir_url[];

    long response_code=;

    long headerlen = ;

    bool curlerr = false;

    CURL *curl;

    CURLcode res;

    // get a curl handle

    curl = curl_easy_init();

    if(curl) {

        // Set the DELETE command

        curl_easy_setopt(curl, CURLOPT_CUSTOMREQUEST, "DELETE");

        curl_easy_setopt(curl, CURLOPT_URL, url.c_str());

        curl_easy_setopt(curl, CURLOPT_HEADER, 1L);

        curl_easy_setopt(curl, CURLOPT_TIMEOUT, m_timeout);

        curl_easy_setopt(curl, CURLOPT_CONNECTTIMEOUT, m_conntimeout);

        curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, CHttpFSClient::memwrite_data);

        curl_easy_setopt(curl,CURLOPT_WRITEDATA,&response_contents);

        res = curl_easy_perform(curl);

        // Check for errors

        if(res != CURLE_OK)

        {

            fprintf(stderr, "hdfs del failed: %s\n",

                curl_easy_strerror(res));

            curlerr = true;

        }

        else

        {

            res = curl_easy_getinfo(curl,CURLINFO_RESPONSE_CODE,&response_code);

            if(res != CURLE_OK)

            {

                fprintf(stderr, "curl_easy_getinfo CURLINFO::CURLINFO_RESPONSE_CODE failed: %s\n",

                    curl_easy_strerror(res));

                curlerr = true;

            }

            res = curl_easy_getinfo(curl,CURLINFO_HEADER_SIZE,&headerlen);

            if(res != CURLE_OK)

            {

                fprintf(stderr, "curl_easy_getinfo CURLINFO::CURLINFO_HEADER_SIZE failed: %s\n",

                    curl_easy_strerror(res));

                curlerr = true;

            }

        }        

    }

    // always cleanup!!!!

    curl_easy_cleanup(curl);

    if(curlerr)

        return false;

    if(response_code == )

    {

        Json::Reader reader;

        Json::Value root;

        const char *content = response_contents.c_str();

        if(!reader.parse(content+headerlen,content+response_contents.length(),root,false))

            return false;

        return root["boolean"].asBool();

    }

    else

        return false;

}

/*

    Open and Read a File of remote an write to local_file

    @param @remote_file

    @param @local_file

    Submit a HTTP GET request with automatically following redirects.

    curl -i -L "http://<HOST>:<PORT>/webhdfs/v1/<PATH>?op=OPEN

                        [&offset=<LONG>][&length=<LONG>][&buffersize=<INT>]"

    The request is redirected to a datanode where the file data can be read:

    HTTP/1.1 307 TEMPORARY_REDIRECT

    Location: http://<DATANODE>:<PORT>/webhdfs/v1/<PATH>?op=OPEN...

    Content-Length: 0

    The client follows the redirect to the datanode and receives the file data:

    HTTP/1.1 200 OK

    Content-Type: application/octet-stream

    Content-Length: 22

    Hello, webhdfs user!

*/

bool CHttpFSClient::read(string& rem_file,string& local_file, long offset, long length)

{

    char url[];

    if(offset !=  && length != )

        sprintf_s(url,,"%s%s?op=OPEN&user.name=%s&offset=%ld&length=%ld",m_hostaddr.c_str(),rem_file.c_str(),m_username.c_str(),offset,length);

    else

        sprintf_s(url,,"%s%s?op=OPEN&user.name=%s",m_hostaddr.c_str(),rem_file.c_str(),m_username.c_str());

    long response_code=;

    bool curlerr = false;

    CURL *curl;

    CURLcode res;

    // get a curl handle

    curl = curl_easy_init();

    if(curl) {

        // HTTP GET please

        curl_easy_setopt(curl, CURLOPT_HTTPGET, 1L);

        // specify target URL, and note that this URL should include a file    name, not only a directory

        curl_easy_setopt(curl, CURLOPT_URL, url);

        /* send all data to this function  */

        curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, CHttpFSClient::filewrite_data);

        FILE * pagefile;

        pagefile = fopen(local_file.c_str(), "wb");

        if(GetLastError() != )

            return false;

        // write the page body to this file handle

        curl_easy_setopt(curl, CURLOPT_WRITEDATA, pagefile);

        // Now run off and do what you've been told!

        res = curl_easy_perform(curl);

        // Check for errors

        if(res != CURLE_OK)

        {

            fprintf(stderr, "get file from hdfs failed: %s\n",

                curl_easy_strerror(res));

            curlerr = true;

        }

        fclose(pagefile); // close the local file

    }

    // always cleanup!!!!

    curl_easy_cleanup(curl);

    if(curlerr)

        return false;

    return true;

}

/*

    list a directory

    @param $dir string, the dir to list

    @return json object

    Submit a HTTP GET request.

    curl -i  "http://<HOST>:<PORT>/webhdfs/v1/<PATH>?op=LISTSTATUS"

    The client receives a response with a FileStatuses JSON object:

    HTTP/1.1 200 OK

    Content-Type: application/json

    Content-Length: 427

    {

      "FileStatuses":

      {

        "FileStatus":

        [

          {

            "accessTime"      : 1320171722771,

            "blockSize"       : 33554432,

            "group"           : "supergroup",

            "length"          : 24930,

            "modificationTime": 1320171722771,

            "owner"           : "webuser",

            "pathSuffix"      : "a.patch",

            "permission"      : "644",

            "replication"     : 1,

            "type"            : "FILE"

          },

          {

            "accessTime"      : 0,

            "blockSize"       : 0,

            "group"           : "supergroup",

            "length"          : 0,

            "modificationTime": 1320895981256,

            "owner"           : "szetszwo",

            "pathSuffix"      : "bar",

            "permission"      : "711",

            "replication"     : 0,

            "type"            : "DIRECTORY"

          },

          ...

        ]

      }

    }

    */

bool CHttpFSClient::ls(string& rem_path,vector<FileStatus>& results)

{

    string url = m_hostaddr + rem_path + "?op=LISTSTATUS&user.name="+m_username;

    long response_code=;

    long headerlen = ;

    bool curlerr = false;

    string response_contents;

    CURL *curl;

    CURLcode res;

    // get a curl handle

    curl = curl_easy_init();

    if(curl) {

        curl_easy_setopt(curl, CURLOPT_HTTPGET, 1L);

        curl_easy_setopt(curl, CURLOPT_URL, url.c_str());

        curl_easy_setopt(curl, CURLOPT_HEADER, 1L);

        curl_easy_setopt(curl, CURLOPT_TIMEOUT, m_timeout);

        curl_easy_setopt(curl, CURLOPT_CONNECTTIMEOUT, m_conntimeout);

        curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, CHttpFSClient::memwrite_data);

        curl_easy_setopt(curl, CURLOPT_WRITEDATA, &response_contents);

        res = curl_easy_perform(curl);

        // Check for errors

        if(res != CURLE_OK)

        {

            fprintf(stderr, "hdfs GETFILESTATUS failed: %s\n",

                curl_easy_strerror(res));

            curlerr = true;

        }

        else

        {

            res = curl_easy_getinfo(curl,CURLINFO_RESPONSE_CODE,&response_code);

            if(res != CURLE_OK)

            {

                fprintf(stderr, "curl_easy_getinfo CURLINFO::CURLINFO_RESPONSE_CODE failed: %s\n",

                    curl_easy_strerror(res));

                curlerr = true;

            }

            res = curl_easy_getinfo(curl,CURLINFO_HEADER_SIZE,&headerlen);

            if(res != CURLE_OK)

            {

                fprintf(stderr, "curl_easy_getinfo CURLINFO::CURLINFO_HEADER_SIZE failed: %s\n",

                    curl_easy_strerror(res));

                curlerr = true;

            }

        }        

    }

    // always cleanup!!!!

    curl_easy_cleanup(curl);

    if(curlerr)

        return false;

    if(response_code == )

    {

        Json::Reader reader;

        Json::Value root;

        const char *content = response_contents.c_str();

        if(!reader.parse(content+headerlen,content+response_contents.length(),root,false))

            return false;

        if(root.empty()) return false;

        Json::Value FileStatuses = root.get("FileStatuses",Json::nullValue);

        if(FileStatuses == Json::nullValue) return false;

        Json::Value FileStatusVec = FileStatuses.get("FileStatus",Json::nullValue);

        if(FileStatusVec == Json::nullValue) return false;

        results.clear();

        int size = FileStatusVec.size();

        for (int i=; i<size; ++i)

        {

            FileStatus fst;

            fst.accessTime = FileStatusVec[i]["accessTime"].asInt64();

            fst.blocksize = FileStatusVec[i]["blockSize"].asInt64();

            fst.group = FileStatusVec[i]["group"].asString();

            fst.length = FileStatusVec[i]["length"].asInt64();

            fst.modificationTime = FileStatusVec[i]["modificationTime"].asInt64();

            fst.owner = FileStatusVec[i]["owner"].asString();

            fst.pathSuffix = FileStatusVec[i]["pathSuffix"].asString();

            fst.permission = FileStatusVec[i]["permission"].asString();

            fst.replication = FileStatusVec[i]["replication"].asInt();

            fst.type = FileStatusVec[i]["type"].asString();

            results.push_back(fst);

        }

        showFileStatus(results);

        return true;

    }

    else

        return false;

}

void CHttpFSClient::showFileStatus(vector<FileStatus>& results)

{

    //print result

    printf("path\towner\tlength\trep\n");

    for (vector<FileStatus>::const_iterator itr = results.begin();itr != results.end(); itr++)

    {

        printf("%s\t%s\t%ld\t%d\n",itr->pathSuffix.c_str(),itr->owner.c_str(),itr->length,itr->replication);

    }

}

size_t CHttpFSClient::fileread_callback(void *ptr, size_t size, size_t nmemb, void *stream)

{

  size_t retcode;

  curl_off_t nread;

  /* in real-world cases, this would probably get this data differently

     as this fread() stuff is exactly what the library already would do

     by default internally */

  retcode = fread(ptr, size, nmemb, (FILE *)stream);

  nread = (curl_off_t)retcode;

  fprintf(stderr, "*** We read %" CURL_FORMAT_CURL_OFF_T

          " bytes from file\n", nread);

  return retcode;

}

size_t CHttpFSClient::filewrite_data(const char *ptr, size_t size, size_t nmemb, void *stream)

{

    size_t written = fwrite(ptr, size, nmemb, (FILE *)stream);

    return written;

}

size_t CHttpFSClient::memwrite_data(const char *contents, size_t size, size_t nmemb, string *stream)

{

    assert(stream != NULL);

    size_t len  = size * nmemb;

    stream->append(contents, len);

    return len;

}

size_t CHttpFSClient::header_callback(const char  *ptr, size_t size, size_t nmemb, std::string *stream)

{

    assert(stream != NULL);

    size_t len  = size * nmemb;

    stream->append(ptr, len);

    return len;

} 

int main(int argc, _TCHAR* argv[])

{

    string hostaddr = "http://192.168.0.111:14000/webhdfs/v1";

    string username = "hadoop";

    CHttpFSClient httpfs(hostaddr,username);

    vector<FileStatus> results;

    string local_file = ".\\test.docx";

    string rem_path = "/test.docx";

    //httpfs.create(local_file,rem_path);

    //httpfs.append(local_file,rem_path);

    httpfs.read(rem_path,local_file);

    //httpfs.ls(rem_path,results);

    //httpfs.del(rem_path);

    getchar();

    return ;

}

3.工程代码下载

http://files.cnblogs.com/files/hikeepgoing/HttpfsClient.rar

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