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Realization of JSON protocol in mql4 / mql5.You can create JSON object with data of different types and run serialization and deserialization of JSON data.

This repo is fork ofJAson (https://www.mql5.com/en/code/13663) with improvements, refactoring code, unit tests and translating of comments to English.

Download repo and copyJAson/Include/JAson.mqh folder to<TERMINAL DIR>/MQL(4/5)/Include

Add#include <JAson.mqh> and createCJAVal object to work with JSON data. See simple example for easy understand:

#include<JAson.mqh>intOnInit(){CJAValdata;// --- simple structure ---data["a"] =12;data["b"] =3.14;data["c"] ="foo";data["d"] =true;Print(data["a"].ToInt());// 12Print(data["b"].ToDbl());// 3.14Print(data["c"].ToStr());// "foo"Print(data["d"].ToBool());// true// --- array structure ---data["e"].Add("bar");data["e"].Add(2);Print(data["e"][0].ToStr());// "bar"Print(data["e"][1].ToInt());// 2// --- nested structures ---// - as part of array -CJAValsub_data_obj_in_list;sub_data_obj_in_list["k1"] =7;sub_data_obj_in_list["k2"] ="baz";data["e"].Add(sub_data_obj_in_list);Print(data["e"][2]["k1"].ToInt());// 7Print(data["e"][2]["k2"].ToStr());// "baz"// - as object -CJAValsub_data_obj;sub_data_obj["sub_c"] ="muz2";sub_data_obj["sub_d"] =44;data["f"] =sub_data_obj;Print(data["f"]["sub_c"].ToStr());// "muz2"Print(data["f"]["sub_d"].ToInt());// 44}

To get value from Json object, you need use methods:

• ToInt() forinteger type;
• ToDbl() fordouble type;
• ToStr() forstring type;
• ToBool() forboolean type;

For example:

data["a"].ToInt();// 12data["b"].ToDbl();// 3.14data["c"].ToStr();// "foo"data["d"].ToBool();// true

To create array, use.Add()

data["e"].Add("bar");data["e"].Add(2);

To use nested json, create otherCJAVal object and assign to existedCJAVal object. NestedCJAVal object can be value of key or contained in array:

CJAValdata;// - adding as object -CJAValdata_1;data_1["d1_1"] =7;data_1["d1_2"] ="foo";data["a"] =data_1;// - adding as part of array -CJAValdata_2;data_2["d2_1"] =1;data_2["d2_1"] ="bar";data["b"].Add("buz");data["b"].Add(data_2);data["b"].Add("muz");

JAson provides the serialization and deserialization:

#include<JAson.mqh>intOnInit(){stringdata_str;CJAValdata;data["a"] =3.14;data["b"] ="foo";data["c"].Add("bar");data["c"].Add(2);data["c"].Add("baz");Print(data["b"].ToStr());// foodata_str =data.Serialize();Print(data_str);// {"a":3.14000000,"b":"foo","c":["bar",2,"baz"]}CJAValdata_2;data_2.Deserialize(data_str);Print(data_2["a"].ToDbl());// 3.14Print(data_2["b"].ToStr());// fooPrint(data_2["c"][0].ToStr());// barPrint(data_2["c"][1].ToInt());// 2Print(data_2["c"][2].ToStr());// baz}

It can be useful for data saving in a file or send Json object by POST request.

POST request with Json object:

#include<JAson.mqh>#include<requests/requests.mqh>// https://github.com/vivazzi/mql_requestsintOnInit(){CJAValdata;data["a"] =7;data["b"] ="foo";Requestsrequests;Responseresponse =requests.post("https://vivazzi.pro/test-request/",data.Serialize());Print(response.text);// {"status": "OK", "method": "POST", "body": "{"a": 7, "b": "foo"}"}data.Deserialize(response.text);Print(data["status"].ToStr());// "OK"Print(data["method"].ToStr());// "POST"Print(data["body"].ToStr());// {"a": 7, "b": "foo"}// if Json object has value of key as serialized object, you can also deserialize this valueCJAValdata_2;data_2.Deserialize(data["body"].ToStr());Print(data_2["a"].ToInt());// 7Print(data_2["b"].ToStr());// "foo"// also you can join this Json objects to get full structuredata["body"] =data_2;Print(data["body"]["a"].ToInt());Print(data["body"]["b"].ToStr());}

In this example it has been used:mql_requests and online serviceGetest for testing GET and POST requests.

To clearCJAVal object, use methodClear():

#include<JAson.mqh>intOnInit(){CJAValdata;stringdata_str;data["a"] =3.14;data["b"] ="foo";data_str =data.Serialize();Print(data_str);// "{"a":3.14000000,"b":"foo"}"data.Clear();data["c"] =123;data["d"] ="bar";data_str =data.Serialize();Print(data_str);// "{"c":123,"d":"bar"}"}

So if you want to get values of "c" and "d" keys, you need:

Print(data["c"].ToInt())// 123Print(data["d"].ToStr())// "bar"

But if you check "a" and "b" keys, that no longer exist (or never used keys), you get initial values for key:

// old notexistent keysPrint(data["a"].ToDbl())// 0.0Print(data["b"].ToStr())// "" (empty)// never used keysPrint(data["e"].ToStr())// "" (empty)

And this can lead to logical errors - be careful! Always use only a specific set of keys to avoid logical error!

If you use Json, that can be cleaned up, and you use different keys, you can check type of keys. JAson library define next types:

• jtUNDEF, if key is undefined
• jtNULL forNULL
• jtBOOL forboolean
• jtINT forint
• jtDBL fordouble
• jtSTR forstring
• jtARRAY forarray
• jtOB forobj

Then in example above:

// old notexistent keysPrint(data["a"].ToDbl());// 0.0Print(data["a"].type);// jtUNDEFPrint(data["b"].ToStr());// ""Print(data["b"].type);// jtUNDEF// current keysPrint(data["c"].ToInt());// 123Print(data["c"].type);// jtINTPrint(data["d"].ToStr());// "bar"Print(data["d"].type);// jtSTR// never used keysPrint(data["e"].ToStr());// ""Print(data["e"].type);// jtUNDEF

So you can compare key type withjtUNDEF, if you want to check for the existence of a key:

#include<JAson.mqh>intOnInit(){CJAValdata;data["a"] =3.14;data.Clear();data["c"] =123;if (data["a"].type ==jtUNDEF) {// do something    }else {// else do something    }}

• CJAVal data; - CreatesCJAVal (Json) object.
• CJAVal data(CJAVal* a_parent, enJAType a_type); - CreatesCJAVal object with specified type.a_parent - parent for createdCJAVal object (useNULL if no parent).a_type - type ofCJAVal object, available types:jtUNDEF,jtNULL,jtBOOL,jtINT,jtDBL,jtSTR,jtARRAY,jtOBJ.
• CJAVal data(const double v, int precision=-100); - CreatesCJAVal object of double type of specified precision.

• data[key] = some_val; - Addssome_val (int, double, string or anotherCJAVal) to data withkey key.
• data[key].Add(other_data); - Addsother_data (int, double, string or other CJAVal) tokey array.
• data[key].Add(const double v, int precision=-2); - Addsv of double type with specified precision tokey array.

• data.Serialize(); - ConvertCJAVal object to string.
• data.Deserialize(string json, int acp=CP_ACP); - Convertjson string toCJAVal object.data gets result.acp - code page for deserialization.

• data.Clear(enJAType jt=jtUNDEF, bool save_key=false); - ClearsCJAVal object.jt- sets specified type ofCJAVal object.save_key - iftrue, values of all keys will be keys will be cleared, else all keys and values will be cleared.
• data.Size(); - Gets size ofCJAVal object.

• If thedbl_precision value is in the range from 0 to 16, then a string representation of the number with the specified number of decimal places will be obtained.
• If thedbl_precision value is in the range from -1 to -16, then the string representation of the number in scientific format with the specified number of decimal places will be obtained.
• In all other cases, the string representation of the number will contain 8 decimal places.

1. CopyJAson/Scripts/ folder to<TERMINAL DIR>/MQL(4/5)/Scripts/
2. CompileTestJAson.mq4 and runTestJAson.ex4 in terminal in a window of any trading pair.
3. Look test result in<TERMINAL DIR>/MQL(4/5)/Files/TestJAson_unit_test_log.txt

To reporting bugs or suggest improvements, please use theissue tracker.

Thank you very much, that you would like to contribute toJAson. Thanks to thepresent, past and future contributors.

If you think you have discovered a security issue in code, please do not create issue or raise it in any public forum until we have had a chance to deal with it.For security issues usesecurity@vuspace.pro

• Report bugs and suggest improvements:
  • https://github.com/vivazzi/JAson/issues (strongly recommended)
  • https://www.mql5.com/en/code/13663 (not tracked by the repo author)
• Author's site of this repo, Artem Maltsev:https://vivazzi.pro

Copyright © 2021 Alexey Sergeev, Artem Maltsev andcontributors.

MIT licensed.