Parse json array string using jsoncpp

Question

I have this JSON:

[{"header": "test" , "test2" : "test2"}]

I'm trying to parse this using jsoncpp.

Here's my code snippet:

 Json::CharReaderBuilder builder;
 Json::CharReader *reader = builder.newCharReader();
 Json::Value root;
 bool parseRet = reader->parse(serverResponse.c_str(),serverResponse.c_str() +serverResponse.size(), &root, &errors);

parseRet returns true. But root does not include json data.

How do I parse this?

Answer 1

parseRet returns true. But root does not include JSON data.

This sounds like an issue with the way you're accessing the parsed JSON elements.

---

Below is a complete working example with a raw string literal as JSON input.

A few points:

• Use std::unique_ptr for reader to de-allocate memory appropriately at the end. In your code snippet, it's a memory leak.
• Read the documentation carefully! Accessing an element using a method or operator might return a default value or an exception so handle accordingly. For example, the JSON in root is an array so it should be accessed by index and then each index contains an object i.e. root[0]["header"].

Example (C++11):

#include <iostream>
#include <string>
#include <memory>
#include <jsoncpp/json/json.h>

int main()
{
    const std::string raw_json = R"json([{"header": "test" , "test2" : "test2"}])json";

    Json::CharReaderBuilder builder {};

    // Don't leak memory! Use std::unique_ptr!
    auto reader = std::unique_ptr<Json::CharReader>( builder.newCharReader() );

    Json::Value root {};
    std::string errors {};
    const auto is_parsed = reader->parse( raw_json.c_str(),
                                          raw_json.c_str() + raw_json.length(),
                                          &root,
                                          &errors );
    if ( !is_parsed )
    {
        std::cerr << "ERROR: Could not parse! " << errors << '\n';
        return -1;
    }

    std::cout << "Parsed JSON:\n" << root << "\n\n";

    try
    {
        std::cout << "header: " << root[0]["header"] << '\n';
        std::cout << "test2 : " << root[0]["test2"] << '\n';
    }
    catch ( const Json::Exception& e )
    {
        std::cerr << e.what() << '\n';
    }

    return 0;
}

Output:

Parsed JSON:
[
    {
        "header" : "test",
        "test2" : "test2"
    }
]

header: "test"
test2 : "test2"