Implement a simple proxy server function example

Java Dynamic Agent

If you want to understand Java dynamic agent, you must first understand what an agent is. Friends who are familiar with design patterns must know that among the 23 design patterns summarized by Gof, one An object structural pattern called Proxy. The proxy in dynamic proxy refers to this design pattern.

In my opinion, the so-called proxy mode and the "decoration mode" among the 23 design patterns are the same thing. Among the 23 design patterns, they are regarded as two patterns. There are also some articles on the Internet about the similarities and differences of these two patterns. From the details, it is indeed possible to distinguish the two patterns artificially. However, after abstracting to a certain level, I think these two patterns are not the same. The patterns are exactly the same. Therefore, if you learn the proxy mode, you will also master the decoration mode.

Without further ado, let’s start with code:

var express = require('express');
var request = require('request');
var app = express();
app.use('/', function(req, res) {
    var url = 'https://www.baidu.com/' + req.url;
    req.pipe(request(url)).pipe(res);
});
app.listen(process.env.PORT || 3000);

With less than 10 lines of code, a simple proxy server function is implemented. Isn't it amazing?
If you are familiar with Node.js, it should be easy to understand these lines of code. First load the express module, which is a popular framework for creating HTTP servers. Then there is request, which encapsulates various methods of HTTP requests, making it very easy to initiate requests. Next, instantiate an express object and set the access route. Finally listen on port 3000.
Look at the effect first. Save the above code to the file proxy.js, and execute it in the path where the file is located:

node proxy.js
Use a browser to open localhost:3000/

The key code is in the routing processing method.

req.pipe(request(url)).pipe(res);

This pipe method is magical. Just like its name (pipeline), it passes the browser's request data to the request client, and then transmits the response data of the target server back to the browser. This code is so concise!
So, how to achieve scientific Internet access? Yes, just run the code on a server that is not blocked by the network and it will be fine. For example, behind this Rendoso www.rendoso.com is a Google agent.

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