nodejs request java interface

With the rapid development of Internet technology, the development of Web applications has become more and more popular. Among them, the architectural model of separation of front and back ends has become one of the mainstream models of Web development. Under this architecture, the front end is responsible for rendering pages and interacting with users, and the back end focuses on data processing and logic control. In order to achieve data transfer and interaction between the front and back ends, it is often necessary to use different programming languages ​​and frameworks.

Under the front-end and back-end separation architecture, Java, as a mature back-end language, is often used to implement business logic in web applications. Node.js is a JavaScript running environment based on the Chrome V8 engine, which is widely used in the development of web servers, RESTful APIs and other fields. In actual development, due to the need for front-end and back-end separation architecture, Node.js needs to call Java interfaces to obtain data and process business logic. So, this article will introduce how to use Node.js to request Java interfaces.

1. Node.js request module

In Node.js, there is a very convenient third-party module called "request", which can be used to send messages to other servers HTTP requests, and processing responses. This module can be installed through the following command:

npm install request --save

After the installation is completed, you can use the module in Node.js code, for example:

var request = require('request');
request('https://www.baidu.com', function (error, response, body) {
  if (!error && response.statusCode == 200) {
    console.log(body);
  }
})

In the above code, we pass the request module A GET request was sent to "https://www.baidu.com" and the returned HTML code was output in the callback function. It should be noted here that Node.js is asynchronous and non-blocking, so the program will continue to execute before the request is completed, and the callback function will be executed after the request is completed.

2. How to call the Java interface

In Java, we can use the Spring framework to provide a RESTful style interface for Node.js to call. The Spring framework provides a series of annotations that can implement controller functions on Java methods, for example:

@RestController
public class UserController {
 
    @Autowired
    private UserService userService;
 
    @RequestMapping(value = "/users/{id}", method = RequestMethod.GET)
    public User getUserById(@PathVariable("id") long id){
        return userService.getUserById(id);
    }
}

In the above code, we use the @RestController annotation provided by the Spring framework to identify the class as a controller , and defines a GET request interface "/users/{id}", the interface parameter is the ID parameter on the path, and returns a User object. In the controller, we inject an instance of UserService to handle business logic.

3. Example of Node.js calling Java interface

In practical applications, we can use the request module to send HTTP requests to Java interfaces. For example:

var request = require('request');
var url="http://localhost:8080/users/1";
 
request({
    url: url,
    method: "GET"
}, function(error, response, body) {
    console.log(body);
});

In the above code, we sent a GET request to the local Java interface "/users/1" and output the returned data in the callback function. It should be noted that when we send a request, we need to specify the full path of the interface and include the request method. In the callback function, we can use the returned data parameter "body" for data processing.

4. Notes

When using Node.js to request the Java interface, you need to pay attention to the following matters:

(1) The Java interface must include Domain access processing, otherwise Node.js will not be able to obtain data when it initiates a request.

(2) Node.js needs to know the full path and request method of the Java interface in order to send HTTP requests.

(3) The Java interface needs to return data format that meets the requirements of Node.js, such as data in JSON or XML format.

(4) Node.js requests are asynchronous and non-blocking, so you need to pay attention to the execution order and logic of the callback function.

5. Summary

This article introduces how to use Node.js to request Java interfaces, including examples of using the request module, defining Java interfaces, and Node.js calling Java interfaces and precautions. In actual applications, if we need to display data in Java on the front-end page, or need to transfer front-end user operations to Java to process business logic, we can use this calling method.

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