Introduction to JSON usage

"Introduction to JSON "

Jsoncpp mainly contains three types of Class:value, Reader, Writer. All objects in Jsoncpp, class names in namespace Json, contain json.h.

"VALUE"

Json::value is the most basic and important class in jsoncpp, used to represent various types of objects, Jsoncpp supported object types are visible Json::valuetype enumeration values.

You can use the Json::value class as follows:

Json::value json_temp; Temporary object for use with the following code

json_temp["name"] = Json::value ("Huchao");

Json_temp["Age" = Json::value (26);

Json::value Root; Represents the entire JSON object

root["key_string"] = Json::value ("value_string"); Create a new Key (named: key_string) and give the string value: "Value_string".

root["Key_number"] = Json::value (12345); Create a new Key (named: key_number) and give the value: 12345.

root["Key_boolean"] = Json::value (false); Create a new Key (named: Key_boolean) and give the bool value: false.

root["key_double"] = Json::value (12.345); Create a new Key (named: key_double) and give the Double value: 12.345.

root["Key_object"] = json_temp; Create a new Key (named: key_object) to give the Json::value object value.

root["Key_array"].append ("array_string"); Create a new Key (named: key_array), type an array, and assign a value to the first element as a string: "Array_string".

root["Key_array"].append (1234); An array of key_array assignments, with the second element assigned a value of: 1234.

Json::valuetype type = Root.type (); Gets the type of root, here is the ObjectValue type.

"WRITER"

The Json::writer class of Jsoncpp is a pure virtual class and cannot be used directly. Here we use Json::writer subclasses: Json::fastwriter, Json::styledwriter, Json::styledstreamwriter.

As the name implies, using Json::fastwriter to deal with Json should be the fastest, let's try.

Json::fastwriter Fast_writer;

Std::cout << fast_writer.write (root) << Std::endl;

The output is:

{"Key_array": ["array_string", 1234], "Key_boolean": false, "key_double": 12.3450, "Key_number": 12345, "Key_object": {" Age ": +," name ":" Huchao "}," key_string ":" Value_string "}

Again as the name implies, with Json::styledwriter is formatted Json, below we see how json::styledwriter is formatted.

Json::styledwriter Styled_writer;

Std::cout << styled_writer.write (root) << Std::endl;

The output is:

{

"Key_array": ["array_string", 1234],

"Key_boolean": false,

"Key_double": 12.3450,

"Key_number": 12345,

"Key_object": {

"Age": 26,

"Name": "Huchao"

},

"Key_string": "Value_string"

}

"VALUE"

Json::reader is used to read, say the exact point, is used to convert a string to a Json::value object.

Let's look at a simple example.

Json::reader Reader;

Json::value Json_object;

Const char* Json_document = "{/" age/": 26,/" name/":/" huchao/"}";

if (!reader.parse (Json_document, Json_object))

return 0;

Std::cout << json_object["name"] << Std::endl;

Std::cout << json_object["age"] << Std::endl;

The output is:

"Huchao"

26

From:http://www.cnblogs.com/tekkaman/archive/2011/10/14/2211404.html

Introduction to JSON usage