Java uses Selenium to crawl Dynamic web page data
Selenium is a Test automation tool that can simulate the user's operation in the browser to test and verify the site. However, it can also be used to crawl data from Dynamic web page.
Advantages:
1. Can handle JavaScript rendered pages: Selenium can execute JavaScript and wait for the page to fully load before proceeding, so it can crawl web pages that require JavaScript rendering.
2. Support for multiple browsers: Selenium supports multiple browsers, including Chrome, Firefox, Safari, etc., which enables it to run on different browsers.
3. Provide rich APIs: Selenium provides rich APIs to operate web pages, including searching for elements, simulating clicks, inputting text, etc., which can easily simulate user operations.
Disadvantages:
1. Slow running: Due to Selenium simulating user operations, its running speed is relatively slow.
2. Browser dependency: Selenium needs to rely on the browser to perform operations, install browser drivers, and occupy a certain amount of system resources.
When using Selenium for web crawling, the following Maven dependencies need to be added:
<!-- Selenium WebDriver -->
<dependency>
<groupId>org.seleniumhq.selenium</groupId>
<artifactId>selenium-java</artifactId>
<version>3.141.59</version>
</dependency>
<-- Select the corresponding driver based on the browser used -->
<!-- Chrome -->
<dependency>
<groupId>org.seleniumhq.selenium</groupId>
<artifactId>selenium-chrome-driver</artifactId>
<version>3.141.59</version>
</dependency>
<!-- Firefox -->
<dependency>
<groupId>org.seleniumhq.selenium</groupId>
<artifactId>selenium-firefox-driver</artifactId>
<version>3.141.59</version>
</dependency>
<!-- Safari -->
<dependency>
<groupId>org.seleniumhq.selenium</groupId>
<artifactId>selenium-safari-driver</artifactId>
<version>3.141.59</version>
</dependency>
The following is a sample Java code for crawling Dynamic web page data using Selenium:
import org.openqa.selenium.WebDriver;
import org.openqa.selenium.chrome.ChromeDriver;
import org.openqa.selenium.chrome.ChromeOptions;
public class WebScraper {
public static void main(String[] args) {
//Set Browser Driver Path
System.setProperty("webdriver.chrome.driver", "path_to_chrome_driver");
//Create a ChromeDriver instance
ChromeOptions options = new ChromeOptions();
Options. addArguments ("-- headless")// Headless mode without displaying browser interface
WebDriver driver = new ChromeDriver(options);
//Open target webpage
driver.get("http://example.com");
//Perform page operations, such as simulating clicks, entering text, etc
//Crawling the required data
String data = driver.findElement(By.className("data-class")).getText();
System.out.println(data);
//Close browser window
driver.quit();
}
}
The above code first sets the browser driver path through 'System. setProperty', and then creates a ChromeDriver instance` ChromeOptions' can be used to configure browser options, such as setting headless mode '-- headless' to not display the browser interface. Next, use the 'driver. get' method to open the target webpage, and then perform page operations such as searching for elements, simulating clicks, entering text, etc. Finally, close the browser window through 'driver. quit'.
Summary:
Selenium is a powerful Test automation tool that can also be used to crawl data from Dynamic web page. It can simulate user operations in browsers, support multiple browsers, and provide rich APIs to operate web pages. However, Selenium runs slowly and relies on browser drivers.
