多執行緒

簡介

Playwright Java 不是執行緒安全的，也就是說，它的所有方法以及它建立的所有物件（例如 BrowserContext、Browser、Page 等）的方法都應該在建立 Playwright 物件的同一個執行緒上呼叫，或者應該實作適當的同步機制，以確保在任何給定時間只有一個執行緒呼叫 Playwright 方法。話雖如此，在各自的執行緒上建立多個 Playwright 實例是可以的。

這是一個範例，其中在各自的執行緒上建立了三個 Playwright 實例。每個實例都會啟動自己的瀏覽器程序，並針對它執行測試。

package org.example;

import com.microsoft.playwright.*;

import java.nio.file.Paths;

import static java.util.Arrays.asList;

public class PlaywrightThread extends Thread {
  private final String browserName;

  private PlaywrightThread(String browserName) {
    this.browserName = browserName;
  }

  public static void main(String[] args) throws InterruptedException {
    // Create separate playwright thread for each browser.
    for (String browserName: asList("chromium", "webkit", "firefox")) {
      Thread thread = new PlaywrightThread(browserName);
      thread.start();
    }
  }

  @Override
  public void run() {
    try (Playwright playwright = Playwright.create()) {
      BrowserType browserType = getBrowserType(playwright, browserName);
      Browser browser = browserType.launch();
      Page page = browser.newPage();
      page.navigate("https://playwright.dev.org.tw/");
      page.screenshot(new Page.ScreenshotOptions().setPath(Paths.get("user-agent-" + browserName + ".png")));
    }
  }

  private static BrowserType getBrowserType(Playwright playwright, String browserName) {
    switch (browserName) {
      case "chromium":
        return playwright.chromium();
      case "webkit":
        return playwright.webkit();
      case "firefox":
        return playwright.firefox();
      default:
        throw new IllegalArgumentException();
    }
  }
}

同步 API 和事件分發

在同步 Playwright API 中，所有事件只有在 Playwright 執行其訊息迴圈時才會分發。當您呼叫任何 API 方法時，這會自動發生，如果堆疊上沒有作用中的 Playwright 呼叫，則不會發生。如果您需要等待事件，最好的方法是透過其中一個 waitFor* 方法。

Page.waitForTimeout() 與 Thread.sleep()

同步 API 的一個後果是，如果您因為任何原因呼叫 Thread.sleep()，則在執行緒休眠時不會觸發任何事件。如果您希望在程式

執行暫停時，要讓瀏覽器的事件分發，請使用 Page.waitForTimeout() 或 Frame.waitForTimeout()

page.onResponse(response -> System.out.println(response.url()));
page.navigate("https://playwright.dev.org.tw");
System.out.println("-- did navigate --");
// Block current thread for 60s and ensure the events are dispatched.
page.waitForTimeout(60_000);