code4craft/webmagic · critical · IOException

Property ' ' not set!

Error message

Property '%s' not set!

What it means

WebDriverPool.configure() loads the PhantomJS configuration and requires the property "phantomjs_exec_path". When the config Properties object doesn't define it, configure() throws an IOException whose message is "Property 'phantomjs_exec_path' not set!" (formatted with PhantomJSDriverService.PHANTOMJS_EXECUTABLE_PATH_PROPERTY). This happens lazily inside get() when the first WebDriver is requested.

Solutions

1. Set the system/config property before get(): sConfig.setProperty("phantomjs_exec_path", "/usr/local/bin/phantomjs") or add it to the webdriver pool's config file.
2. Install phantomjs at the configured path and confirm the binary is executable.
3. If not using PhantomJS, switch WebDriverPool to the Chrome/Firefox configuration path so the phantomjs property check is skipped.
4. Pre-load the property from an environment variable as a fallback (System.getenv("PHANTOMJS_PATH")).

Example fix

// before
WebDriverPool pool = new WebDriverPool(); // config lacks phantomjs_exec_path
// after
System.setProperty("phantomjs_exec_path", "/usr/local/bin/phantomjs");
WebDriverPool pool = new WebDriverPool();

String path = System.getProperty("phantomjs_exec_path",
        System.getenv("PHANTOMJS_EXEC_PATH"));
if (path == null || !new java.io.File(path).canExecute()) {
    throw new IllegalStateException("phantomjs_exec_path missing or binary not executable: " + path);
}

try {
    WebDriver driver = pool.get(url);
} catch (java.io.IOException e) {
    if (e.getMessage() != null && e.getMessage().contains("not set!")) {
        throw new IllegalStateException("Set phantomjs_exec_path in WebDriverPool config before get()", e);
    }
    throw e;
}

When it happens

Trigger: Calling WebDriverPool.get() without having set the "phantomjs_exec_path" property in the config passed to the pool (or default sConfig file), while using the PhantomJS driver — the pool cannot locate the phantomjs binary.

Common situations: Switching from PhantomJS to Chrome/Firefox or vice versa and leaving config properties mismatched; config file not found so defaults load without the property; deploying to a machine where the phantomjs path was configured in an env-specific file that wasn't copied.

Understand the failure class

Background: "is required", "must be set", "missing required field": configuration validation errors across open-source libraries — this error's family across 36 libraries.

Related errors

• wrong proto type map
• Already closed!
• threadNum should be more than one!
• emptySleepTime should be more than zero!
• init cache scheduler error

AI-assisted analysis of code4craft/webmagic@67816a19d6 (2026-09-08). Data as JSON: /api/errors/549f751fb9406ebb. Report an issue: GitHub.

Appendix: source

Thrown at webmagic-selenium/src/main/java/us/codecraft/webmagic/downloader/selenium/WebDriverPool.java:90

			configFile = System.getProperty("selenuim_config");
		}
		sConfig.load(new FileReader(configFile));

		// Prepare capabilities
		sCaps = new DesiredCapabilities();
		sCaps.setCapability("takesScreenshot", false);

		String driver = sConfig.getProperty("driver", DRIVER_PHANTOMJS);

		// Fetch PhantomJS-specific configuration parameters
		if (driver.equals(DRIVER_PHANTOMJS)) {
			// "phantomjs_exec_path"
			if (sConfig.getProperty("phantomjs_exec_path") != null) {
				sCaps.setCapability(
						PhantomJSDriverService.PHANTOMJS_EXECUTABLE_PATH_PROPERTY,
						sConfig.getProperty("phantomjs_exec_path"));
			} else {
				throw new IOException(
						String.format(
								"Property '%s' not set!",
								PhantomJSDriverService.PHANTOMJS_EXECUTABLE_PATH_PROPERTY));
			}
			// "phantomjs_driver_path"
			if (sConfig.getProperty("phantomjs_driver_path") != null) {
				System.out.println("Test will use an external GhostDriver");
				sCaps.setCapability(
						PhantomJSDriverService.PHANTOMJS_GHOSTDRIVER_PATH_PROPERTY,
						sConfig.getProperty("phantomjs_driver_path"));
			} else {
				System.out
						.println("Test will use PhantomJS internal GhostDriver");
			}
		}

		// Disable "web-security", enable all possible "ssl-protocols" and
		// "ignore-ssl-errors" for PhantomJSDriver

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