node-java typescript import

Question

node-java typescript import

I need to use node-java node_module in my typescript project.

However,

var java = require("java");

does not work in typescript way, and also

import java = module("java");

does not work as it is.

I know we may need a definition file etc. and there's a project like https://github.com/borisyankov/DefinitelyTyped

Having said that, I think it's way too complicated to do by myself.

Is there any easier workaround? Thanks.

node.js
typescript

Answer 1

The best way is use a definition file to node-java API, however, using your first code snippet:

var java = require("java");

you can use a reference to this node typing as following:

/// <reference path="node/node.d.ts" />

var java = require("java");

java.classpath.push("commons-lang3-3.1.jar");
java.classpath.push("commons-io.jar");

var list = java.newInstanceSync("java.util.ArrayList");

java.newInstance("java.util.ArrayList", function(err, list) {
  list.addSync("item1");
  list.addSync("item2");
});

var ArrayList = java.import('java.util.ArrayList');
var list2 = new ArrayList();
list.addSync('item1');

To use the second snippet:

import java = module("java");

you will need a definition file. To a kick start you can create a node-java.d.ts file with the following code:

module "java" {
    export var classpath: { push(jar: string); };
    export function newInstanceSync(type: string);
    export function newInstance(type: string, callback: (err, list) => any);
    export function import(type: string);
    export function newArray(...item: any[]);
    export function callStaticMethodSync(...args: any[]);
}

And use this file as following:

/// <reference path="node-java.d.ts" />

import java = module("java");

java.classpath.push("commons-lang3-3.1.jar");
java.classpath.push("commons-io.jar");

var list = java.newInstanceSync("java.util.ArrayList");

java.newInstance("java.util.ArrayList", function(err, list) {
  list.addSync("item1");
  list.addSync("item2");
});

var ArrayList = java.import('java.util.ArrayList');
var list2 = new ArrayList();
list.addSync('item1');

Having time, I'll send a node-java definition to DefinitelyTyped repository.

Answer 2

When you say that this doesn't work:

var java = require("java");

I'm assuming you get an error directly calling require because it doesn't have type information.

One way to solve this is to add type information for require:

declare var require: (module: string) => any;
var java = require('java');

This is a simplistic example - java won't be typed as the return value of require in my example is any - but if you had type information you could cast it:

declare var require: (module: string) => any;
var java = <JavaDefinition> require('java');