poco-1.5.1: Facebook GraphAPI JSON question

[ghost]

Hi,

I'm using poco to deal with facebook GraphAPI. I managed to do most of the work but i'm struggling with the latest bit. Here is my code:

try {
    // Target URI
    Poco::URI uri("https://graph.facebook.com/me/friends?access_token=" + AppDelegate::getAccessToken());
    std::string path(uri.getPathEtc());

    // SSL Context
    const Poco::Net::Context::Ptr context(new Poco::Net::Context(Poco::Net::Context::CLIENT_USE, "", "", "", Poco::Net::Context::VERIFY_NONE, 9, true, "ALL:!ADH:!LOW:!EXP:!MD5:@STRENGTH"));

    // HTTP Session
    Poco::Net::HTTPSClientSession session(uri.getHost(), uri.getPort(), context);

    // Request
    Poco::Net::HTTPRequest request(Poco::Net::HTTPRequest::HTTP_GET, path, Poco::Net::HTTPMessage::HTTP_1_1);
    session.sendRequest(request);

    // Response
    Poco::Net::HTTPResponse response;
    std::istream& rs = session.receiveResponse(response);
    std::cout << response.getStatus() << " " << response.getReason() << std::endl;
    for (auto response_header: response) {
      std::cout << response_header.first << " = " << response_header.second << std::endl;
    }

    std::ostringstream responseBody;
    if (response.getStatus() != Poco::Net::HTTPResponse::HTTP_UNAUTHORIZED) {
      Poco::StreamCopier::copyStream(rs, responseBody);
//      Poco::StreamCopier::copyStream(rs, std::cout);
    } else {
      Poco::NullOutputStream null;
      Poco::StreamCopier::copyStream(rs, null);
      return;
    }

    // Parsing JSON response
    Poco::JSON::DefaultHandler handler;
    Poco::JSON::Parser parser;

    parser.setHandler(&handler);
    parser.parse(responseBody.str());
    Poco::DynamicAny result = handler.result();

    Poco::JSON::Object::Ptr obj;
    //if (result.type() == typeid(Poco::JSON::Object::Ptr)) {
      obj = result.extract<Poco::JSON::Object::Ptr>();
    //}

    // Serialize to string
//      std::ostringstream out;
    obj->stringify(std::cout);
  } catch (Poco::Exception& exc) {
    CCLOG("error =  %s", exc.displayText().c_str());
  }

And here is the output:

200 OK 
Access-Control-Allow-Origin = * 
Cache-Control = private, no-cache, no-store, must-revalidate 
Connection = close 
Content-Length = 3149 
Content-Type = text/javascript; charset=UTF-8 
Date = Sun, 13 Jan 2013 10:46:44 GMT 
ETag = "1bfe8dcc4ef3831df52f40d3457c8744b129908a" 
Expires = Sat, 01 Jan 2000 00:00:00 GMT 
Pragma = no-cache 
X-FB-Debug = PzikR8+tz4SyqNBlz0WiHLKUQhql4FsoiTEitZK/EJ0= 
X-FB-Rev = 711202 
{"data":[Cocos2d: error =  Bad cast exception: Can not convert to std::string

As you can see, everything works like a charm except the:

  obj->stringify(std::cout);

Any ideas of what I'm doing wrong ?

Thanks,
BQ.

[aleks-f]

Any ideas of what I'm doing wrong ?

Impossible to tell without seeing the JSON itself. I'm quite sure, though, that at some point during "stringifying" you end up here:

https://github.com/pocoproject/poco/blob/develop/Foundation/include/Poco/Dynamic/VarHolder.h#L460

inline void VarHolder::convert(std::string& /*val*/) const
{
    throw BadCastException("Can not convert to std::string");
}

Franky Braem (https://github.com/fbraem) wrote that library so he is the best source of information on it.

[ghost]

Ok thanks for the info.

Franky, is there any documentation/tutorial demonstrating the use of your JSON library ? The benchmark sample is a good start, however, it's a bit bland let's say.

[aleks-f]

It'll help if you post a sample of JSON that throws.

[fbraem]

Can you send me an example JSON response from the URL you use?

[ghost]

Sure, my bad. Here is the JSON response:

{"data":[{"name":"Frantisek Zacek","id":"518797070"},{"name":"Clem Ne'me","id":"521787019"},{"name":"Ga\u00eblle Legu\u00e9n\u00e9","id":"523167073"},{"name":"Sylvain Astier","id":"532706918"},{"name":"David Quentin","id":"539806978"},{"name":"Flandre Renaud","id":"559169452"},{"name":"Augustin Rieunier","id":"565503436"},{"name":"Julie Legendre","id":"567007562"},{"name":"Sarah Hosking","id":"572717063"},{"name":"Yann P\u00e9zier","id":"584202620"},{"name":"Denis Rousseau","id":"597972372"},{"name":"Benoit Nesme","id":"604647623"},{"name":"Florent Drillon","id":"609952144"},{"name":"Benjamin Villedieu","id":"633548483"},{"name":"Julien Massenet","id":"635685647"},{"name":"Vincent Remy","id":"658644483"},{"name":"Martin Smurthwaite","id":"670111481"},{"name":"Shanta Raj","id":"680831928"},{"name":"Cyrielle Mehl","id":"682324166"},{"name":"Anne-Fleur Drillon","id":"690978943"},{"name":"FX Singer","id":"699407761"},{"name":"Yann Popo","id":"701439716"},{"name":"Murielle Touret","id":"701911151"},{"name":"Celine Laurencin","id":"710495247"},{"name":"Charles Vionnet","id":"718038682"},{"name":"Geraldine Quenin","id":"729326765"},{"name":"Hadrien Gantzer","id":"781456179"},{"name":"Julie Dupr\u00e9","id":"828462523"},{"name":"Smatti Sofian","id":"842429787"},{"name":"Jef Pommier","id":"1002498019"},{"name":"Jean-Guillaume Desanti","id":"1018251414"},{"name":"Patrick Peinoit","id":"1018307198"},{"name":"Damien Brelivet","id":"1044879509"},{"name":"Arnaud Puy","id":"1080510304"},{"name":"Guillaume Cessieux","id":"1096104649"},{"name":"Perroy Damien","id":"1108765447"},{"name":"Alexandre Demailly","id":"1133658539"},{"name":"Benoit Rivollet","id":"1196713537"},{"name":"Bernard Quenin","id":"1205726565"},{"name":"Marilyn Bass","id":"1218525169"},{"name":"Bastien Perret","id":"1272287731"},{"name":"Karim Tadjene","id":"1277063130"},{"name":"Sophie Ladreyt","id":"1278373214"},{"name":"Paola Jacquemin","id":"1311030773"},{"name":"Agnieszka Jacquemot","id":"1387575444"},{"name":"Annie Suel","id":"1399271494"},{"name":"Laurent Cony","id":"1456958012"},{"name":"Didier Trouvel","id":"1459554573"},{"name":"Delphine Juillot","id":"1484902071"},{"name":"C\u00e9dric Martins","id":"1552565132"},{"name":"Aur\u00e9lie Bert Petrucci","id":"1568276408"},{"name":"Rh\u00e9da Bakir","id":"1616376985"},{"name":"Anthony Poignant","id":"100000969207248"},{"name":"Todd Warwaruk","id":"100001547094911"},{"name":"Miguel Herve","id":"100001565258822"},{"name":"Farah Mahir","id":"100002202791306"},{"name":"Marilyn Ssab","id":"100003069216658"},{"name":"S\u00e9bastien Perret","id":"100003533872156"},{"name":"Glob Ideuh","id":"100003585244509"},{"name":"Isabelle Pourquoipas","id":"100004595822764"},{"name":"Cie K\u00e9roz\u00e8ne","id":"100004688318068"}],"paging":{"next":"https:\/\/graph.facebook.com\/100003057316436\/friends?access_token=BAAGcAvILkyUBABh4NGZCJuj1ZCsHpTROdmbFLs5Dyh4tcZBlR1zaqMmj4MIT348XVwBqwUx2vyBtQxUDO0g62XXXXituSmvrhrYLx0BXZBI9Tgjqrvsez1nnSfqxfQzuuaHBJn2hhb3vDWxIHpGdZCTJ797xgLM82RbjLg9xR06I8V5S1Kg6qDI1werXXqtyl6J2UdAmBdYoZAi1DaxX6lAjwoOfL0PV6cu798A1WNCDgZDZD&limit=5000&offset=5000&__after_id=100004688318068"}}

I was just wondering if there was a more substantial example somewhere else, maybe I should file another question then :)

Thanks,
BQ.

[aleks-f]

I can't reproduce the problem. This code parses and stringifies fine:

std::string fbjson = "{\"data\":[{\"name\":\"Frantisek Zacek\",\"id\":\"518797070\"},{\"name\":\"Clem Ne'me\",\"id\":\"521787019\"},{\"name\":\"Ga\\u00eblle Legu\\u00e9n\\u00e9\",\"id\":\"523167073\"},{\"name\":\"Sylvain Astier\",\"id\":\"532706918\"},{\"name\":\"David Quentin\",\"id\":\"539806978\"},{\"name\":\"Flandre Renaud\",\"id\":\"559169452\"},{\"name\":\"Augustin Rieunier\",\"id\":\"565503436\"},{\"name\":\"Julie Legendre\",\"id\":\"567007562\"},{\"name\":\"Sarah Hosking\",\"id\":\"572717063\"},{\"name\":\"Yann P\\u00e9zier\",\"id\":\"584202620\"},{\"name\":\"Denis Rousseau\",\"id\":\"597972372\"},{\"name\":\"Benoit Nesme\",\"id\":\"604647623\"},{\"name\":\"Florent Drillon\",\"id\":\"609952144\"},{\"name\":\"Benjamin Villedieu\",\"id\":\"633548483\"},{\"name\":\"Julien Massenet\",\"id\":\"635685647\"},{\"name\":\"Vincent Remy\",\"id\":\"658644483\"},{\"name\":\"Martin Smurthwaite\",\"id\":\"670111481\"},{\"name\":\"Shanta Raj\",\"id\":\"680831928\"},{\"name\":\"Cyrielle Mehl\",\"id\":\"682324166\"},{\"name\":\"Anne-Fleur Drillon\",\"id\":\"690978943\"},{\"name\":\"FX Singer\",\"id\":\"699407761\"},{\"name\":\"Yann Popo\",\"id\":\"701439716\"},{\"name\":\"Murielle Touret\",\"id\":\"701911151\"},{\"name\":\"Celine Laurencin\",\"id\":\"710495247\"},{\"name\":\"Charles Vionnet\",\"id\":\"718038682\"},{\"name\":\"Geraldine Quenin\",\"id\":\"729326765\"},{\"name\":\"Hadrien Gantzer\",\"id\":\"781456179\"},{\"name\":\"Julie Dupr\\u00e9\",\"id\":\"828462523\"},{\"name\":\"Smatti Sofian\",\"id\":\"842429787\"},{\"name\":\"Jef Pommier\",\"id\":\"1002498019\"},{\"name\":\"Jean-Guillaume Desanti\",\"id\":\"1018251414\"},{\"name\":\"Patrick Peinoit\",\"id\":\"1018307198\"},{\"name\":\"Damien Brelivet\",\"id\":\"1044879509\"},{\"name\":\"Arnaud Puy\",\"id\":\"1080510304\"},{\"name\":\"Guillaume Cessieux\",\"id\":\"1096104649\"},{\"name\":\"Perroy Damien\",\"id\":\"1108765447\"},{\"name\":\"Alexandre Demailly\",\"id\":\"1133658539\"},{\"name\":\"Benoit Rivollet\",\"id\":\"1196713537\"},{\"name\":\"Bernard Quenin\",\"id\":\"1205726565\"},{\"name\":\"Marilyn Bass\",\"id\":\"1218525169\"},{\"name\":\"Bastien Perret\",\"id\":\"1272287731\"},{\"name\":\"Karim Tadjene\",\"id\":\"1277063130\"},{\"name\":\"Sophie Ladreyt\",\"id\":\"1278373214\"},{\"name\":\"Paola Jacquemin\",\"id\":\"1311030773\"},{\"name\":\"Agnieszka Jacquemot\",\"id\":\"1387575444\"},{\"name\":\"Annie Suel\",\"id\":\"1399271494\"},{\"name\":\"Laurent Cony\",\"id\":\"1456958012\"},{\"name\":\"Didier Trouvel\",\"id\":\"1459554573\"},{\"name\":\"Delphine Juillot\",\"id\":\"1484902071\"},{\"name\":\"C\\u00e9dric Martins\",\"id\":\"1552565132\"},{\"name\":\"Aur\\u00e9lie Bert Petrucci\",\"id\":\"1568276408\"},{\"name\":\"Rh\\u00e9da Bakir\",\"id\":\"1616376985\"},{\"name\":\"Anthony Poignant\",\"id\":\"100000969207248\"},{\"name\":\"Todd Warwaruk\",\"id\":\"100001547094911\"},{\"name\":\"Miguel Herve\",\"id\":\"100001565258822\"},{\"name\":\"Farah Mahir\",\"id\":\"100002202791306\"},{\"name\":\"Marilyn Ssab\",\"id\":\"100003069216658\"},{\"name\":\"S\\u00e9bastien Perret\",\"id\":\"100003533872156\"},{\"name\":\"Glob Ideuh\",\"id\":\"100003585244509\"},{\"name\":\"Isabelle Pourquoipas\",\"id\":\"100004595822764\"},{\"name\":\"Cie K\\u00e9roz\\u00e8ne\",\"id\":\"100004688318068\"}],\"paging\":{\"next\":\"https:\\/\\/graph.facebook.com\\/100003057316436\\/friends?access_token=BAAGcAvILkyUBABh4NGZCJuj1ZCsHpTROdmbFLs5Dyh4tcZBlR1zaqMmj4MIT348XVwBqwUx2vyBtQxUDO0g62XXXXituSmvrhrYLx0BXZBI9Tgjqrvsez1nnSfqxfQzuuaHBJn2hhb3vDWxIHpGdZCTJ797xgLM82RbjLg9xR06I8V5S1Kg6qDI1werXXqtyl6J2UdAmBdYoZAi1DaxX6lAjwoOfL0PV6cu798A1WNCDgZDZD&limit=5000&offset=5000&__after_id=100004688318068\"}}";
Parser parser;
DefaultHandler handler;
parser.setHandler(&handler);
parser.parse(fbjson);
Object::Ptr obj = handler.result().extract<Object::Ptr>();
obj->stringify(std::cout);

[ghost]

Strange. I ran your code and I get the same error as above (at least its consistent).

I run this code on an iOS device, do you think that could be a reason ? I'm gonna investigate more.

Thanks for your feedback.
BQ.

[aleks-f]

see if you have this fix in your code:

42d963a#JSON/src/Stringifier.cpp

[ghost]

Yeah, I have the fix.

I found my issue. I messed up my iPhone build configuration file. I forgot to add -std=c++11 to my custom build file.

Here is my build file (if anyone want to use clang c++11/libc++ for iPhone):

#
# $Id: //poco/1.4/build/config/iPhone#3 $
#
# iPhone
#
# Build settings for iPhone OS, using Apple's iPhone SDK
# 

#
# General Settings
#
# iPhone OS does not allow dynamic linking to user libraries
#
LINKMODE ?= STATIC

#
# If the SDK is defined use it
# Otherwise find the latest version installed
#
IPHONE_SDK_VERSION = 6.0

# if IPHONE_SDK_VERSION_MIN is defined use that
# Otherwise use the version found. 

IPHONE_SDK             ?= iPhoneOS
IPHONE_SDK_ROOT        ?= $(shell xcode-select -print-path)/Platforms/$(IPHONE_SDK).platform/Developer/SDKs
IPHONE_SDK_ROOT_DIR     = $(IPHONE_SDK_ROOT)/$(IPHONE_SDK)
IPHONE_SDK_BASE         = $(shell ls -d $(IPHONE_SDK_ROOT_DIR)$(IPHONE_SDK_VERSION)*.sdk | tail -1)
IPHONE_SDK_VERSION_MIN ?= $(patsubst %.sdk,%,$(patsubst $(IPHONE_SDK_ROOT_DIR)%,%,$(IPHONE_SDK_BASE)))

POCO_TARGET_OSNAME     ?= $(IPHONE_SDK)
POCO_TARGET_OSARCH     ?= armv7
TOOL_PREFIX            ?= $(shell xcode-select -print-path)/Platforms/$(IPHONE_SDK).platform/Developer/usr/bin
OSFLAGS                ?= -arch $(POCO_TARGET_OSARCH) -isysroot $(IPHONE_SDK_BASE) -mthumb -miphoneos-version-min=$(IPHONE_SDK_VERSION_MIN)

#
# Tools
#
# If GCC_VER is defined then use it.
# Otherwise select the latest version
#
# CC        = $(shell ls $(TOOL_PREFIX)/llvm-gcc-$(GCC_VER)* | tail -1)
# CXX       = $(shell ls $(TOOL_PREFIX)/llvm-g++-$(GCC_VER)* | tail -1)
CC      = $(shell xcode-select -print-path)/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang
CXX     = $(shell xcode-select -print-path)/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang


LINK    = $(CXX) -bind_at_load
LIB     = libtool -static -o
RANLIB  = ranlib
SHLIB   = $(CXX) $(OSFLAGS) -dynamiclib -Wl,-install_name,$@ -o $@
DYLIB   = $(CXX) $(OSFLAGS) -dynamic -bundle -read_only_relocs suppress -Wl,-bind_at_load -o $@ 
SHLIBLN = $(POCO_BASE)/build/script/shlibln
STRIP   = 
DEP     = $(POCO_BASE)/build/script/makedepend.gcc
SHELL   = sh
RM      = rm -rf
CP      = cp
MKDIR   = mkdir -p

#
# Extension for Shared Libraries
#
SHAREDLIBEXT     = .$(target_version).dylib
SHAREDLIBLINKEXT = .dylib

#
# Compiler and Linker Flags
#
CFLAGS          = $(OSFLAGS)
CFLAGS32        =
CFLAGS64        =
CXXFLAGS        = $(OSFLAGS) -Wall -Wno-sign-compare -std=c++11 -stdlib=libc++
CXXFLAGS32      =
CXXFLAGS64      = 
LINKFLAGS       = $(OSFLAGS)
LINKFLAGS32     =
LINKFLAGS64     =
STATICOPT_CC    =
STATICOPT_CXX   =
STATICOPT_LINK  =
SHAREDOPT_CC    = -fPIC 
SHAREDOPT_CXX   = -fPIC
SHAREDOPT_LINK  = 
DEBUGOPT_CC     = -g -D_DEBUG=$(DEBUGLEVEL)
DEBUGOPT_CXX    = -g -D_DEBUG=$(DEBUGLEVEL) 
DEBUGOPT_LINK   =
RELEASEOPT_CC   = -DNDEBUG -O2
RELEASEOPT_CXX  = -DNDEBUG -O 
RELEASEOPT_LINK =

#
# System Specific Flags
#
SYSFLAGS = -DPOCO_HAVE_IPv6 -DPOCO_NO_FPENVIRONMENT -DPOCO_NO_STAT64 -DPOCO_NO_SHAREDLIBS -DPOCO_NO_NET_IFTYPES

#
# System Specific Libraries
#
SYSLIBS  = -ldl -lc++

Thank you for your help. Sorry I've wasted your time :)
BQ.