我尝试用硒制成网络爬虫。 我的程序触发了StaleElementReferenceException。 我以为那是因为我以递归方式爬行页面，并且当页面没有更多链接时，该功能导航到下一页，而不是先前的父页面。
因此，当当前URL与父URL不相等时，我引入了树数据结构以导航回父URL。但这不是解决我问题的方法。
有人可以帮助我吗？
代码：
public class crawler {
private static FirefoxDriver driver;
private static String main_url = "https://robhammond.co/tools/seo-crawler";
private static List<String> uniqueLinks = new ArrayList<String>();
public static void main(String[] args) {
driver = new FirefoxDriver();
Node<String> root = new Node<>(main_url);
scrap(root, main_url);
}
public static void scrap(Node<String> node, String url) {
if(node.getParent() != null && (!driver.getCurrentUrl().equals(node.getParent().getData()))) {
driver.navigate().to(node.getParent().getData());
}
driver.navigate().to(url);
List<WebElement> allLinks = driver.findElements(By.tagName("a"));
for(WebElement link : allLinks) {
if(link.getAttribute("href").contains(main_url) && !uniqueLinks.contains(link.getAttribute("href")) && link.isDisplayed()) {
uniqueLinks.add(link.getAttribute("href"));
System.out.println(link.getAttribute("href"));
scrap(new Node<>(link.getAttribute("href")), link.getAttribute("href"));
}
}
}
}
这是控制台的输出：
D:\Programme\openjdk-12.0.1_windows-x64_bin\jdk-12.0.1\bin\java.exe "-javaagent:D:\Programme\JetBrains\IntelliJ IDEA 2019.1.2\lib\idea_rt.jar=60461:D:\Programme\JetBrains\IntelliJ IDEA 2019.1.2\bin" -Dfile.encoding=UTF-8 -classpath C:\Users\admin\Desktop\SeleniumWebScraper\out\production\SeleniumWebScraper;D:\Downloads\selenium-server-standalone-3.141.59.jar de.company.crawler.crawler
1557924446770 mozrunner::runner INFO Running command: "C:\\Program Files\\Mozilla Firefox\\firefox.exe" "-marionette" "-foreground" "-no-remote" "-profile" "C:\\Users\\admin\\AppData\\Local\\Temp\\rust_mozprofile.YqmEqE8y1pjv"
1557924447037 addons.webextension.screenshots@mozilla.org WARN Loading extension 'screenshots@mozilla.org': Reading manifest: Invalid extension permission: mozillaAddons
1557924447037 addons.webextension.screenshots@mozilla.org WARN Loading extension 'screenshots@mozilla.org': Reading manifest: Invalid extension permission: resource://pdf.js/
1557924447037 addons.webextension.screenshots@mozilla.org WARN Loading extension 'screenshots@mozilla.org': Reading manifest: Invalid extension permission: about:reader*
1557924448047 Marionette INFO Listening on port 60468
1557924448383 Marionette WARN TLS certificate errors will be ignored for this session
Mai 15, 2019 2:47:28 NACHM. org.openqa.selenium.remote.ProtocolHandshake createSession
INFO: Detected dialect: W3C
JavaScript warning: https://robhammond.co/js/jquery.min.js, line 4: Using //@ to indicate sourceMappingURL pragmas is deprecated. Use //# instead
https://robhammond.co/tools/seo-crawler#content
https://twitter.com/intent/tweet?text=SEO%20Crawler&url=https://robhammond.co/tools/seo-crawler&via=robhammond
Exception in thread "main" org.openqa.selenium.StaleElementReferenceException: The element reference of <a href="/tools/"> is stale; either the element is no longer attached to the DOM, it is not in the current frame context, or the document has been refreshed
For documentation on this error, please visit: https://www.seleniumhq.org/exceptions/stale_element_reference.html
Build info: version: '3.141.59', revision: 'e82be7d358', time: '2018-11-14T08:25:53'
System info: host: 'DESKTOP-admin', ip: '192.168.233.1', os.name: 'Windows 10', os.arch: 'amd64', os.version: '10.0', java.version: '12.0.1'
Driver info: org.openqa.selenium.firefox.FirefoxDriver
Capabilities {acceptInsecureCerts: true, browserName: firefox, browserVersion: 66.0.5, javascriptEnabled: true, moz:accessibilityChecks: false, moz:geckodriverVersion: 0.24.0, moz:headless: false, moz:processID: 19124, moz:profile: C:\Users\admin\AppData\Loca..., moz:shutdownTimeout: 60000, moz:useNonSpecCompliantPointerOrigin: false, moz:webdriverClick: true, pageLoadStrategy: normal, platform: WINDOWS, platformName: WINDOWS, platformVersion: 10.0, rotatable: false, setWindowRect: true, strictFileInteractability: false, timeouts: {implicit: 0, pageLoad: 300000, script: 30000}, unhandledPromptBehavior: dismiss and notify}
Session ID: b3b87675-57c8-4b48-9a20-8df5e4d37503
at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.base/java.lang.reflect.Constructor.newInstanceWithCaller(Constructor.java:500)
at java.base/java.lang.reflect.Constructor.newInstance(Constructor.java:481)
at org.openqa.selenium.remote.http.W3CHttpResponseCodec.createException(W3CHttpResponseCodec.java:187)
at org.openqa.selenium.remote.http.W3CHttpResponseCodec.decode(W3CHttpResponseCodec.java:122)
at org.openqa.selenium.remote.http.W3CHttpResponseCodec.decode(W3CHttpResponseCodec.java:49)
at org.openqa.selenium.remote.HttpCommandExecutor.execute(HttpCommandExecutor.java:158)
at org.openqa.selenium.remote.service.DriverCommandExecutor.execute(DriverCommandExecutor.java:83)
at org.openqa.selenium.remote.RemoteWebDriver.execute(RemoteWebDriver.java:552)
at org.openqa.selenium.remote.RemoteWebElement.execute(RemoteWebElement.java:285)
at org.openqa.selenium.remote.RemoteWebElement.getAttribute(RemoteWebElement.java:134)
at de.company.crawler.crawler.scrap(crawler.java:33)
at de.company.crawler.crawler.scrap(crawler.java:38)
at de.company.crawler.crawler.main(crawler.java:20)
Process finished with exit code 1
答案 0 :(得分：0)
当您离开第一页时，allLinks列表中的所有WebElements都会丢失。
我建议将其从WebElement列表转换为普通Strings列表，例如：
List<String> allLinksHrefs = allLinks.stream().map(link -> link.getAttribute("href")).collect(Collectors.toList());
，然后遍历这个新的allLinksHrefs列表。
uniqueLinks-这样，重复项将被自动消除