Boost Property_tree Parsing JSON

Parsing JSON using boost property_tree

Before using Jsoncpp parsing JSON, now know that boost has a library of analysis, learn about it

Property_tree can parse data in xml,json,ini,info and other formats, and using Property_tree to parse these formats is very similar.

Parsing JSON is simple, and the namespace is boost: The:p Roperty_tree,reson_json function parses a file stream, a string into Ptree,write_json, and outputs the ptree as a string or a file stream. The rest is the operation of the Ptree.

Parsing JSON requires a header file:

#include <boost/property_tree/ptree.hpp>
#include <boost/property_tree/json_parser.hpp>

1. Parsing JSON

Parse the following data:

1. {
2. "Code": 0,
3. "Images":
4. [
5. {
6. "url": "Fmn057/20111221/1130/head_kjoo_05d9000251de125c.jpg"
7. },
8. {
9. "url": "Fmn057/20111221/1130/original_kjoo_05d9000251de125c.jpg"
10. }
11. ]
12. }

{  "code": 0,  "Images":  [    {      "url": "Fmn057/20111221/1130/head_kjoo_05d9000251de125c.jpg"    },    {      "url": "Fmn057/20111221/1130/original_kjoo_05d9000251de125c.jpg"    }  ]}

2. int Parsejson ()
4. {
6. std::string str = "{\" code\ ": 0,\" images\ ": [{\" url\ ": \" Fmn057/20111221/1130/head_kjoo_05d9000251de125c.jpg\ "}, {\ "url\": \ "Fmn057/20111221/1130/original_kjoo_05d9000251de125c.jpg\"}]} ";
8. using namespace boost::p roperty_tree;
12. Std::stringstream SS (str);
14. Ptree pt;
16. try{
18. Read_json (SS, PT);
20. }
22. catch (Ptree_error & E) {
24. return 1;
26. }
30. try{
32. int code = pt.get<int> ("code"); //Get the value of "code"
34. Ptree Image_array = Pt.get_child ("Images"); //Get_child Get Array Object
38. //Traversal array
40. Boost_foreach (boost::p roperty_tree::p tree::value_type &v, Image_array)
42. {
44. Std::stringstream s;
46. Write_json (S, V.second);
48. std::string Image_item = S.str ();
50. }
52. }
54. catch (Ptree_error & E)
56. {
58. return 2;
60. }
62. return 0;
64. }

int Parsejson () {  std::string str = "{\" code\ ": 0,\" images\ ": [{\" url\ ": \" Fmn057/20111221/1130/head_kjoo_ 05d9000251de125c.jpg\ "},{\" url\ ": \" Fmn057/20111221/1130/original_kjoo_05d9000251de125c.jpg\ "}]}";  Using namespace boost::p roperty_tree;  Std::stringstream SS (str);  Ptree pt;  try{        Read_json (SS, PT);  }  catch (Ptree_error & E) {    return 1;   }  try{    int code = pt.get<int> ("code");   Get "code" of value    ptree Image_array = Pt.get_child ("Images");  Get_child get Array Object        //traversal array    Boost_foreach (BOOST::p roperty_tree::p tree::value_type &v, Image_array)    {      std::stringstream s;      Write_json (S, v.second);      std::string Image_item = S.str ();    }  }  catch (Ptree_error & E)  {    return 2;  }  return 0;}

2. Structuring the JSON

2. int Insertjson ()
4. {
6. std::string str = "{\" code\ ": 0,\" images\ ": [{\" url\ ": \" Fmn057/20111221/1130/head_kjoo_05d9000251de125c.jpg\ "}, {\ "url\": \ "Fmn057/20111221/1130/original_kjoo_05d9000251de125c.jpg\"}]} ";
8. using namespace boost::p roperty_tree;
12. Std::stringstream SS (str);
14. Ptree pt;
16. try{
18. Read_json (SS, PT);
20. }
22. catch (Ptree_error & E) {
24. return 1;
26. }
30. //Modify/Add a key-value,key does not exist then increase
32. Pt.put ("Upid", "00001");
36. //Insert an array
38. Ptree Exif_array;
40. Ptree array1, Array2, array3;
42. Array1.put ("make", "NIKON");
44. Array2.put ("DateTime", "2011:05:31 06:47:09");
46. Array3.put ("Software", "ver.1.01");
48. Exif_array.push_back (Std::make_pair ("", array1));
50. Exif_array.push_back (Std::make_pair ("", Array2));
52. Exif_array.push_back (Std::make_pair ("", Array3));
56. Exif_array.push_back (Std::make_pair ("Make", "NIKON"));
58. Exif_array.push_back (Std::make_pair ("DateTime", "2011:05:31 06:47:09"));
60. Exif_array.push_back (Std::make_pair ("Software", "ver.1.01"));
64. Pt.put_child ("ExIFS", Exif_array);
66. Std::stringstream S2;
68. Write_json (S2, PT);
70. std::string outstr = S2.str ();
74. return 0;
76. }

int Insertjson () {std::string str = "{\" code\ ": 0,\" images\ ": [{\" url\ ": \" Fmn057/20111221/1130/head_kjoo_  05d9000251de125c.jpg\ "},{\" url\ ": \" Fmn057/20111221/1130/original_kjoo_05d9000251de125c.jpg\ "}]}";  Using namespace boost::p roperty_tree;  Std::stringstream SS (str);  Ptree pt;  try{Read_json (SS, PT);   } catch (Ptree_error & E) {return 1;  }//Modify/Add a key-value,key does not exist then increase pt.put ("Upid", "00001");  Insert an array ptree exif_array;  Ptree array1, Array2, array3;  Array1.put ("Make", "NIKON");  Array2.put ("DateTime", "2011:05:31 06:47:09");  Array3.put ("Software", "ver.1.01");  Exif_array.push_back (Std::make_pair ("", array1));  Exif_array.push_back (Std::make_pair ("", array2)); Exif_array.push_back (Std::make_pair ("", array3));//Exif_array.push_back (Std::make_pair ("Make", "NIKON");//Exif_ Array.push_back (Std::make_pair ("DateTime", "2011:05:31 06:47:09");//Exif_array.push_back (Std::make_pair ("  Software "," ver.1.01 "));  Pt.put_child ("ExIFS", Exif_array); Std::stringstReam S2;  Write_json (S2, PT);  std::string outstr = S2.str (); return 0;}

Three. Experience with two types of analytic libraries

1. With boost::p Roperty_tree parse string encountered "\" when parsing failed, and Jsoncpp can parse the success, you know '/' preceded by a ' \ ' is the JSON standard format.

2. Boost::p roperty_tree Read_json and Write_json used in multi-threading can cause crashes.

For 1, you can use boost::p Roperty_tree parsing before writing a function to remove the "\" in the "\", for 2, in multi-threaded synchronization can be resolved.

My experience: Using boost::p Roperty_tree not only can parse JSON, but also can parse data in xml,info format. For parsing json, using boost::p Roperty_tree parsing can be tolerated, but parsing XML, because there are too many problems can only be replaced by other libraries.

Boost Property_tree Parsing JSON