Convert JSON to Thrift Object in Nodejs

Question

I have the following thrift file:

union D{ 1: string s; }

struct B{ 1: required D d; }

struct C{ 1: required D d; }

union A{ 1: B b; 2: C c; }

service Test { void store(1: A a) }

And I have the following JSON object, which was obtained by parsing a string.

var data_json = {
    'b': {
        'd': {
            's': "hello"
        }
    }
};

I'm trying to write a thrift client in Nodejs which calls the store method with data_json as its argument, but I get the following error when I do so:

/home/aakash/Documents/thrift0/gen-nodejs/test_types.js:225
    this.b.write(output);
           ^
TypeError: Object #<Object> has no method 'write'
    at Object.A.write (/home/aakash/Documents/thrift0/gen-nodejs/test_types.js:225:12)
    at Object.Test_store_args.write (/home/aakash/Documents/thrift0/gen-nodejs/Test.js:57:12)
    at Object.TestClient.send_store (/home/aakash/Documents/thrift0/gen-nodejs/Test.js:113:8)
    at Object.TestClient.store (/home/aakash/Documents/thrift0/gen-nodejs/Test.js:105:8)
    at Object.<anonymous> (/home/aakash/Documents/thrift0/client.js:40:8)
    at Module._compile (module.js:456:26)
    at Object.Module._extensions..js (module.js:474:10)
    at Module.load (module.js:356:32)
    at Function.Module._load (module.js:312:12)
    at Function.Module.runMain (module.js:497:10)

However, it works fine when I pass the following object as argument:

var data_thrift = new ttypes.A({
    'b': new ttypes.B({
        'd': new ttypes.D({
            's': "hello"
        })
    })
});

Is there a way to pass data_json directly to store, or a way to convert data_json to data_thrift ?

score 0 · Accepted Answer · answered Jan 28 '14 at 22:08

I'm trying to write a thrift client in Nodejs which calls the store method with data_json as its argument, but I get the following error when I do so:

/home/aakash/Documents/thrift0/gen-nodejs/test_types.js:225
this.b.write(output);

Is there a way to pass data_json directly to store, or a way to convert data_json to data_thrift ?

TL;DR

Sure. Just provide a write() method for each of your Objects that implements what is generated by Thrift otherwise, or provide an alternative serialization mechanism for your data to produce the exact same output.

Explanation

The code generated by Thrift and the Thrift library provide the necessary infrastructure for using Thrift and to ensure the interoperability of both Thrift RPC calls and serialized data. To achieve this, the serialized data follow a certain predefined structure, which is determined by the protocol you use. All the infrastructure of an RPC and serialization framework, including the generacted code for your data, is just there to provide the means to do this.

If your application holds data in another way internally (which is perfectly ok) you will have to convert them back and forth. The only way to store the data directly would be to generate the exact same JSON output that the Thrift infrastructure would produce for your data, othwerwise the other side will not be able to deserialize your JSON.

But technically, following that path you will end up reinventing the wheel.

But when I do `console.log(data_json)` and `console.log(data_thrift)`, I get the exact same output. Can't I somehow typecast `data_json` into `data_thrift`. — aakashns, Jan 29 '14 at 06:56
Never tried, but even if you would cast `ttypes.A(yourA)`, the childs are still of the old type and will need to be casted too. There's a similar discussion over here http://stackoverflow.com/questions/5873624/parse-json-string-into-a-particular-object-prototype-in-javascript referencing this site http://javascriptweblog.wordpress.com/2010/06/07/understanding-javascript-prototypes/ — JensG, Jan 29 '14 at 23:55

Convert JSON to Thrift Object in Nodejs

1 Answers1

TL;DR

Explanation