Changed as per PR comments

Author: AriPaaWun

core/src/main/java/com/onelogin/saml2/settings/Saml2Settings.java

@@ -30,8 +30,6 @@ public class Saml2Settings {
      */
 	private static final Logger LOGGER = LoggerFactory.getLogger(Saml2Settings.class);
 
-	public static final String DEFAULT_UNIQUE_ID_PREFIX = "ONELOGIN_";
-
 	// Toolkit settings
 	private boolean strict = false;
 	private boolean debug = false;
@@ -75,7 +73,7 @@ public class Saml2Settings {
 	private String signatureAlgorithm = Constants.RSA_SHA1;
 	private String digestAlgorithm = Constants.SHA1;
 	private boolean rejectUnsolicitedResponsesWithInResponseTo = false;
-	private String uniqueIDPrefix = DEFAULT_UNIQUE_ID_PREFIX;
+	private String uniqueIDPrefix = null;
 
 	// Compress
 	private boolean compressRequest = true;

core/src/main/java/com/onelogin/saml2/settings/SettingsBuilder.java

@@ -390,7 +390,7 @@ private String loadUniqueIDPrefix() {
 		if (StringUtils.isNotEmpty(uniqueIDPrefix)) {
 			return uniqueIDPrefix;
 		} else {
-			return Saml2Settings.DEFAULT_UNIQUE_ID_PREFIX;
+			return Util.UNIQUE_ID_PREFIX;
 		}
 	}
 

core/src/main/java/com/onelogin/saml2/util/Util.java

@@ -105,6 +105,7 @@ public final class Util {
 
     private static final DateTimeFormatter DATE_TIME_FORMAT = DateTimeFormat.forPattern("yyyy-MM-dd'T'HH:mm:ss'Z'").withZone(DateTimeZone.UTC);
 	private static final DateTimeFormatter DATE_TIME_FORMAT_MILLS = DateTimeFormat.forPattern("yyyy-MM-dd'T'HH:mm:ss.SSS'Z'").withZone(DateTimeZone.UTC);
+	public static final String UNIQUE_ID_PREFIX = "ONELOGIN_";
 	public static final String RESPONSE_SIGNATURE_XPATH = "/samlp:Response/ds:Signature";
 	public static final String ASSERTION_SIGNATURE_XPATH = "/samlp:Response/saml:Assertion/ds:Signature";
 	/** Indicates if JAXP 1.5 support has been detected. */
@@ -1537,11 +1538,19 @@ private static SecretKey generateSymmetricKey() throws Exception {
 	 * @return A unique string
 	 */
 	public static String generateUniqueID(String prefix) {
-		if (StringUtils.isNotEmpty(prefix)) {
-			return prefix + UUID.randomUUID();
-		} else {
-			throw new IllegalArgumentException("Prefix cannot be null or empty.");
+		if (prefix == null || StringUtils.isEmpty(prefix)) {
+			prefix = Util.UNIQUE_ID_PREFIX;
 		}
+		return prefix + UUID.randomUUID();
+	}
+
+	/**
+	 * Generates a unique string (used for example as ID of assertions)
+	 *
+	 * @return A unique string
+	 */
+	public static String generateUniqueID() {
+		return generateUniqueID(null);
 	}
 
 	/**

core/src/test/java/com/onelogin/saml2/test/util/UtilsTest.java

@@ -1876,19 +1876,30 @@ public void testGenerateNameIdWithoutFormat() throws URISyntaxException, IOExcep
         assertEquals(expectedNameId, nameId);        
 	}
 
+	/**
+	 * Tests the generateUniqueID method
+	 *
+	 * * @see com.onelogin.saml2.util.Util#generateUniqueID
+	 */
+	@Test
+	public void testGenerateUniqueID() {
+		String s1 = Util.generateUniqueID();
+		assertThat(s1, startsWith(Util.UNIQUE_ID_PREFIX));
+	}
+
 	/**
 	 * Tests the generateUniqueID method
 	 * 
 	 * @see com.onelogin.saml2.util.Util#generateUniqueID
 	 */
 	@Test
-	public void testGenerateUniqueID() {
-		String s1 = Util.generateUniqueID(Saml2Settings.DEFAULT_UNIQUE_ID_PREFIX);
+	public void testGenerateUniqueID_withCustomPrefix() {
+		String s1 = Util.generateUniqueID(Util.UNIQUE_ID_PREFIX);
 
-		assertThat(s1, startsWith(Saml2Settings.DEFAULT_UNIQUE_ID_PREFIX));
+		assertThat(s1, startsWith(Util.UNIQUE_ID_PREFIX));
 		assertTrue(s1.length() > 40);
 
-		String s2 = Util.generateUniqueID(Saml2Settings.DEFAULT_UNIQUE_ID_PREFIX);
+		String s2 = Util.generateUniqueID(Util.UNIQUE_ID_PREFIX);
 		String s3 = Util.generateUniqueID("_");
 		assertThat(s3, startsWith("_"));
 
@@ -1898,19 +1909,21 @@ public void testGenerateUniqueID() {
 	}
 
 	/**
-	 * Tests that generateUniqueID method throws when given null
+	 * Tests that generateUniqueID method uses default prefix when given null
 	 */
-	@Test(expected=IllegalArgumentException.class)
-	public void testGenerateUniqueID_throwsOnNullPrefix() {
-		Util.generateUniqueID(null);
+	@Test
+	public void testGenerateUniqueID_usesDefaultOnNull() {
+		String s1 = Util.generateUniqueID(null);
+		assertThat(s1, startsWith(Util.UNIQUE_ID_PREFIX));
 	}
 
 	/**
-	 * Tests that generateUniqueID method throws when given empty String
+	 * Tests that generateUniqueID method uses default prefix when given empty String
 	 */
-	@Test(expected=IllegalArgumentException.class)
-	public void testGenerateUniqueID_throwsOnEmptyPrefix() {
-		Util.generateUniqueID("");
+	@Test
+	public void testGenerateUniqueID_usesDefaultOnEmpty() {
+		String s1 = Util.generateUniqueID("");
+		assertThat(s1, startsWith(Util.UNIQUE_ID_PREFIX));
 	}
 
 	/**

toolkit/src/test/java/com/onelogin/saml2/test/AuthTest.java

@@ -1065,7 +1065,7 @@ public void testLogin() throws IOException, SettingsException, URISyntaxExceptio
 		Auth auth = new Auth(settings, request, response);
 		auth.login();
 		verify(response).sendRedirect(matches("https:\\/\\/pitbulk.no-ip.org\\/simplesaml\\/saml2\\/idp\\/SSOService.php\\?SAMLRequest=(.)*&RelayState=http%3A%2F%2Flocalhost%3A8080%2Finitial.jsp"));
-		assertThat(auth.getLastRequestId(), startsWith(Saml2Settings.DEFAULT_UNIQUE_ID_PREFIX));
+		assertThat(auth.getLastRequestId(), startsWith(Util.UNIQUE_ID_PREFIX));
 	}
 
 	/**
@@ -1251,7 +1251,7 @@ public void testLogout() throws IOException, SettingsException, XMLEntityExcepti
 		auth.logout();
 
 		verify(response).sendRedirect(matches("https:\\/\\/pitbulk.no-ip.org\\/simplesaml\\/saml2\\/idp\\/SingleLogoutService.php\\?SAMLRequest=(.)*&RelayState=http%3A%2F%2Flocalhost%3A8080%2Finitial.jsp"));
-		assertThat(auth.getLastRequestId(), startsWith(Saml2Settings.DEFAULT_UNIQUE_ID_PREFIX));
+		assertThat(auth.getLastRequestId(), startsWith(Util.UNIQUE_ID_PREFIX));
 	}
 
 	/**