High-concurrency design and implementation based on the Java asynchronous HTTP client (Design and Implementation of High-Concurrency Web Crawler Based on Java Async HTTP Client)
Based on the design and implementation of the high concurrent network crawler design of the Java asynchronous HTTP client
introduce:
Network crawler is an automated program that provides data for data analysis, search engine index, price comparison and other purposes from the Internet.High -performance cyber crawlers are essential for the rapid collection and processing of massive data.This article will introduce how to use the Java asynchronous HTTP client to design and achieve high concurrent network crawlers.
Design ideas:
In order to achieve high -parallel network crawlers, we will use the Java asynchronous HTTP client to conduct network requests to improve the efficiency and throughput of the program.The asynchronous HTTP client uses non -blocking I/O and callback mechanisms. It can handle other tasks at the same time when waiting for the server to respond to improve the concurrency performance of the program.
1. Set up climb queues:
First, we need to set up a climbing queue to store URLs to be crawled.You can use a secure queue to implement, such as ConcurrenTlinkedQueue.
2. Create asynchronous http client:
Use the Java asynchronous HTTP client library, such as AsynchtpClient to create an asynchronous HTTP client and set up related parameters, such as connecting timeout time, request timeout time, etc.
3. Initiating asynchronous request:
Take out the URL to be crawled from the crawling queue and use the asynchronous HTTP client to send the HTTP request.When sending a request, set the callback function to process the server's response.
The example code is as follows:
import org.asynchttpclient.*;
public class WebCrawler {
private ConcurrentLinkedQueue<String> urlQueue;
private AsyncHttpClient asyncHttpClient;
public WebCrawler() {
urlQueue = new ConcurrentLinkedQueue<>();
asyncHttpClient = Dsl.asyncHttpClient();
}
public void addUrl(String url) {
urlQueue.offer(url);
}
public void startCrawling() {
while (!urlQueue.isEmpty()) {
String url = urlQueue.poll();
if (url != null) {
RequestBuilder requestBuilder = asyncHttpClient.prepareGet(url);
asyncHttpClient.executeRequest(requestBuilder.build(), new AsyncCompletionHandler<Response>() {
@Override
public Response onCompleted(Response response) {
// Processing the logic of the server response
return response;
}
@Override
public void onThrowable(Throwable t) {
// Logic the logic of abnormal conditions
}
});
}
}
}
}
4. Processing server response:
In the `Oncompleted` recovery function, we can handle the server's response.You can analyze HTML content, extract the required information, and add the new URL to the crawling queue to continue to crawl other pages.
5. Dreatment:
In the `ONTHROWABLE` recovery function, we can handle abnormal conditions, such as connecting timeout, request errors, etc. to ensure the stability and reliability of the program.
Summarize:
By using the Java asynchronous HTTP client, we can achieve high -parallel network crawlers, so as to quickly and efficiently collect the required information.It is worth noting that in practical applications, we need to consider anti -climbing measures, data analysis and storage problems to build a complete network crawler system.
