Java Building IP Proxy Pools: The Secret Weapon to Make Web Crawlers More Flexible

In the ocean of Internet data, web crawlers are like fishermen who catch fish, while IP proxy pool is the fish net in their hands. Without a good IP proxy pool, crawlers are like fishing with their bare hands, which is inefficient and easy to be blocked by the website. Today, we will talk about how to use Java to build a powerful IP proxy pool, so that your crawler as a tiger with wings.

What is an IP Proxy Pool?

An IP proxy pool, as the name suggests, is a collection of IP addresses that can be used to make web requests instead of the original IP. The advantage of this is that crawlers can make requests through different IP addresses, thus avoiding being blocked for frequently visiting the same website.

Imagine you go to the same restaurant every day, the owner might get curious about you or even wonder if you are doing something strange. Whereas if you change restaurants every day, the boss won't notice you. This is where IP proxy pooling comes in.

Preparation for Java Implementation of IP Proxy Pools

Before we start building the IP proxy pool, we need some preparation:

• Java Development Environment: Make sure you have installed the JDK and an IDE such as IntelliJ IDEA or Eclipse.
• Proxy IP Source: You need to find some reliable proxy IP providers or get a proxy IP through some free proxy IP websites.
• Web request libraries: we can use Apache HttpClient or OkHttp for web requests.

Basic Steps for Building an IP Proxy Pool

Next, we will implement the construction of the IP proxy pool step by step.

1. Obtain a proxy IP

First, we need to get a batch of proxy IPs from a proxy IP provider.Assuming we have an API interface for proxy IPs, we can get proxy IPs with the following code:

import java.io.BufferedReader;
import java.io.
import java.net.HttpURLConnection; import java.net.
import java.net.URL; import java.util.
import java.util.ArrayList; import java.util.
import java.util.List; import java.util.

public class ProxyFetcher {
public List fetchProxies(String apiUrl) throws Exception {
List proxyList = new ArrayList();
URL url = new URL(apiUrl);
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
HttpURLConnection connection = (HttpURLConnection) url.openConnection(); connection.setRequestMethod("GET");
BufferedReader in = new BufferedReader(new InputStreamReader(connection.getInputStream()));
String inputLine; while ((inputLine = inputLine))
while ((inputLine = in.readLine()) ! = null) {
String inputLine; while ((inputLine = in.readLine()) !
}
in.close(); }
return proxyList; }
}
}

2. Verify proxy IP

After obtaining proxy IPs, we need to verify that they are available. We can verify the validity of the proxy IPs by sending a request to a test site:

import java.net.HttpURLConnection;
import java.net.InetSocketAddress; import java.net.
import java.net.Proxy; import java.net.
import java.net.URL; import java.net.

public class ProxyValidator {
public boolean validateProxy(String proxyAddress) {
String[] parts = proxyAddress.split(":");
String ip = parts[0];
String ip = parts[0]; int port = Integer.parseInt(parts[1]);
try {
Proxy proxy = new Proxy(Proxy.Type.HTTP, new InetSocketAddress(ip, port));
HttpURLConnection connection = (HttpURLConnection) new URL("http://www.google.com").openConnection(proxy);
connection.setConnectTimeout(3000); connection.setReadTimeout(3000)
connection.setConnectTimeout(3000); connection.setReadTimeout(3000);
connection.connect(); return connection.getResponse
return connection.getResponseCode() == 200; } catch (Exception e) { { connection.
} catch (Exception e) {
return false; } catch (Exception e) {
}
}
}

3. Building the agent pool

After verifying the validity of the proxy IPs, we can store these valid proxy IPs into a pool for subsequent use:

import java.util.List;
import java.util.concurrent.CopyOnWriteArrayList;

public class ProxyPool {


public void addProxy(String proxy) {
public void addProxy(String proxy) { proxyList.add(proxy); }
}

public String getProxy() {
if (proxyList.isEmpty()) {
throw new RuntimeException("No valid proxies available"); }
}
return proxyList.remove(0);
}
}

Using IP Proxy Pools for Web Requests

With a proxy pool, we can use these proxy IPs in our network requests. Below is a sample code showing how to make a network request through a proxy pool:

import java.net.HttpURLConnection;
import java.net.InetSocketAddress; import java.net.
import java.net.Proxy; import java.net.
import java.net.URL; import java.net.

public class ProxyHttpClient {
private ProxyPool proxyPool; private class ProxyHttpClient { private ProxyPool proxyPool

public class ProxyHttpClient { private ProxyPool proxyPool; public ProxyHttpClient(ProxyPool proxyPool) {
this.proxyPool = proxyPool; public ProxyHttpClient(ProxyPool proxyPool) { this.
}

public void sendRequest(String targetUrl) {
String proxyAddress = proxyPool.getProxy();
String[] parts = proxyAddress.split(":");
String ip = parts[0];
int port = Integer.parseInt(parts[1]);
try {
Proxy proxy = new Proxy(Proxy.Type.HTTP, new InetSocketAddress(ip, port));
HttpURLConnection connection = (HttpURLConnection) new URL(targetUrl).openConnection(proxy);
connection.setConnectTimeout(3000); connection.setReadTimeout(3000); HttpURLConnection
connection.setConnectTimeout(3000); connection.setReadTimeout(3000);
connection.connect(); System.out.println()
System.out.println("Response Code: " + connection.getResponseCode()); } catch (Exception e) { { connection.setConnectionTimeout(3000)
} catch (Exception e) {
System.err.println("Failed to send request through proxy: " + proxyAddress); }
}
}
}

summarize

With the above steps, we have successfully built a simple IP proxy pool in Java. This proxy pool can help us avoid being banned for frequently visiting the same website when we do web crawling. Although this example is relatively simple, it provides us with a basic framework for us to extend and optimize in real applications.

I hope this article can help you to make your web crawler more flexible and efficient. If you have any questions or suggestions, please feel free to leave them in the comment section and we'll talk about them together!