The actual combat series of node. JS Play Java

Over the years, the rise of node. js, JavaScript has changed from "The world's most misunderstood language" to "the world's most popular language." and its development, from the evolution of language itself, the growth of libraries and packages, the improvement of tool support, star project and the emergence of domain solutions, platforms, technology stacks, the expansion of applications, and so on, are not seen before. With Node.js the popularity of services, for the back-end service is the Java company will have a problem, Node.js how to Java communicate with it?

What are you talking about today?

We put aside the architectural design, aside from the http traditional socket , rpc communication protocols, we talk Node.js about how to connect in the application Java API , in other words, Node.js write code directly in Java .

Node-java

Node.jsWant and Java Connect, need a Node-java module.

Environment preparation

• Operating system: Support Osx,linux

• Operating Environment (recommended):

  • Nodejs LTS version Minimum requirements6.x
  • Java JDK1.8 +
  • Liunx GCC4.8.1 +

  Mounting module

  $ npm install java

Liunx If you do not support C + + 11 You need to manually upgrade GCC to gcc 4.8.) Reference Address

If this is a Mac hint: Display needs to install the old Java SE 6 operating environment to open, download JDK 2015

node. JS calls Javahelloworld

• Java

 Public class HelloWorld {  publicstaticvoid  main (string[] args) {      System.out.println ("Hello world!" );  }}

Output: Hello world!

• node. js

Const Java = require (' java '= Java.import (' Java.lang.System ') javaLangSystem.out.printlnSync (' Hello world! ')

Output: Hello world!

Operation Java Mapjava Operation HashMap

ImportJava.util.HashMap;ImportJava.util.Map; Public classHashmapdemo { Public Static voidMain (string[] args) {Map<string, object> map =NewHashmap<>(); Map.put ("Name", "Sunilwang"); Map.put ("Age", 20); String name= (String) map.get ("name"); intAge = (int) Map.get ("Age"); System.out.printf ("Name:%s", name); System.out.println (""); System.out.printf ("Age:%d", age); }}

Output: Name:sunilwang age:20

node. JS synchronizes calls to Java HashMap

Const Java = require (' java '= Java.import (' java.util.HashMap ')//  synchronous operation  New HashMap () hashmap.putsync(' name ', ' Sunilwang ') hashmap.putsync (' age ', Hashmap.getsync (' name '= Hashmap.getsync (' age ') console.log (' name ', name) Console.log ( "Age", age)

Output: Name:sunilwang age:20

node. JS Callback calls Java HashMap

Const Java = require (' java '= Java.import (' java.util.HashMap ')//  callback Operation   New  HashMap () hashmap.put (' name ', ' Sunilwang ', (error, info) = =  {if ( Error) Console.log (' Put name ' ERROR: ', error ')  hashmap.get (' name ', (error, name) = = {     if (Error) Console.log (' Get name error: ', error)    Console.log (' callback name:%s ' , Name)})  })

Output: Callback Name:sunilwang

node. JS Promise calls Java HashMap

Const CO = require (' Co ') const Java= require (' Java ')//the current configuration must be declared at the top of theJava.asyncoptions ={syncsuffix:' Sync ',//Synchronous method name suffixAsyncsuffix: ",//Async method Name suffixPromisesuffix: ' Promise ',//Promise method Name suffixPromisify:require (' Bluebird '). promisify//modules that rely on promise}// ==============Const HASHMAP= Java.import (' Java.util.HashMap ')//Promise OperationCofunction*() {Let HashMap=NewHashMap () yield hashmap.putpromise (' Name ', ' Sunilwang ') yield hashmap.putpromise (' Age ', ' 20 ') let name= Yield hashmap.getpromise (' name ') let-age= Yield hashmap.getpromise (' age ') Console.log (' Name ', name) Console.log (' Age ', Age)})

Two methods of creating Java instances

• Java

Importjava.util.ArrayList;Importjava.util.List; Public classArraylistdemo { Public Static voidMain (string[] args) {List<String> List1 =NewArraylist<>(); List<String> List2 =NewArraylist<>(); List1.add ("Item1"); List2.add ("Item1"); System.out.printf ("Size:%d", list1.size ());//2System.out.println (""); //list1 equals List2:trueSystem.out.printf ("List1 equals List2:%s", List1.equals (List2)); }}

Newinstancesync

Const Java = require (' java '= Java.newinstancesync (' java.util.ArrayList '//  0 List1.addsync (' item1 '//  1

Import & New

Let ArrayList = java. Import (' java.util.ArrayList 'new  ArrayList () list2.addsync (' item1 '=  List2.equalssync (List1) console.log (equalvalue)//  true

Other operations quick new Data group

• Java

 Public class Chararraydemo {  publicstaticvoid  main (string[] args) {      Char [] chararray = "Hello world\n". ToCharArray ();     // Chararray length:12    System.out.printf ("Chararray Length:%d", chararray.length);}  }

• node. js

Let Chararray = Java.newarray (' char ', ' Hello world\n '. Split ('))//  [' H ', ' e ', ' l ', ' l ', ' o ', ', ' W ', ' O ', ' r ', ' L ', ' d ', ' \ n ')//  

Fast new Long Object

• Java

 Public class Longdemo {  publicstaticvoid  main (string[] args) {     New Long ("5");    SYSTEM.OUT.PRINTLN (num);    System.out.println (Num.longvalue ());}  }

• node. js

Let Javalong = Java.newinstancesync (' Java.lang.Long ', 5)//  possibly truncated Long value:5 Console.log (' Possibly truncated Long value:%d ', Javalong)//  Original Long value (as a string): 5console.log (' Original Long value (as a string):%s ', javalong.longvalue)

node. JS calls itself to compile the class

• Java

 Package Com.nearinfinity.nodeJava;  Public class MyClass {  publicstaticint addnumbers (intint  b) {     return A + B;  }}

• node. js

Const Java = require (' java ') Java.classpath.push ('./src '= Java.import (' Com.nearinfinity.nodeJava.MyClass '= Myclass.addnumberssync (1, 2= Java.newinstancesync (' Java.lang.Integer ', 2)//  Quick Call method inside Java Static class result = Java.callstaticmethodsync (' Com.nearinfinity.nodeJava.MyClass ', ' addnumbers ', Javainteger, 3) console.log (Result)

Conclusion

The above method just takes you to understand the node-java tip of the iceberg, the node-java API is very rich, such as,, jvm , and 实例一个类 调用类静态方法 快速实例化一个对象 so on.

The quickest way to learn is to look at the document, document address: Node-java.

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The actual combat series of node. JS Play Java