core/src/main/java/org/springframework/security/authentication/jaas/JaasAuthenticationProvider.java
private void configureJaasUsingLoop() throws IOException {
		String loginConfigUrl = convertLoginConfigToUrl();
		boolean alreadySet = false;

		int n = 1;
		final String prefix = "login.config.url.";
		String existing;

		while ((existing = Security.getProperty(prefix + n)) != null) {
			alreadySet = existing.equals(loginConfigUrl);

			if (alreadySet) {
				break;
			}

			n++;
		}

		if (!alreadySet) {
			String key = prefix + n;
			log.debug("Setting security property [" + key + "] to: " + loginConfigUrl);
			Security.setProperty(key, loginConfigUrl);
		}
	}
private void configureJaasUsingLoop() throws IOException {
		String loginConfigUrl = convertLoginConfigToUrl();
		boolean alreadySet = false;

		int n = 1;
		final String prefix = "login.config.url.";
		String existing;

		while ((existing = Security.getProperty(prefix + n)) != null) {
			alreadySet = existing.equals(loginConfigUrl);

			if (alreadySet) {
				break;
			}

			n++;
		}

		if (!alreadySet) {
			String key = prefix + n;
			log.debug("Setting security property [" + key + "] to: " + loginConfigUrl);
			Security.setProperty(key, loginConfigUrl);
		}
	}
Loops through the login.config.url.1,login.config.url.2 properties looking for the
login configuration. If it is not set, it will be set to the last available
login.config.url.X property.