Initial commit

src/main/java/org/scribe/utils/Preconditions.java

@@ -0,0 +1,48 @@
+package org.scribe.utils;
+
+import org.scribe.model.OAuthConstants;
+
+public class Preconditions
+{
+  private static final String DEFAULT_MESSAGE = "Received an invalid parameter";
+
+  public static void checkNotNull(Object object, String errorMsg)
+  {
+    check(object != null, errorMsg);
+  }
+
+  public static void checkEmptyString(String string, String errorMsg)
+  {
+    check(string != null && !string.trim().isEmpty(), errorMsg);
+  }
+
+  public static void checkValidUrl(String url, String errorMsg)
+  {
+    checkEmptyString(url, errorMsg);
+    check(isUrl(url), errorMsg);
+  }
+  
+  public static void checkValidOAuthCallback(String url, String errorMsg)
+  {
+    checkEmptyString(url, errorMsg);
+    if(url.toLowerCase().compareToIgnoreCase(OAuthConstants.OUT_OF_BAND) != 0)
+    {
+      check(isUrl(url), errorMsg);  
+    }
+  }
+  
+  static boolean isUrl(String url)
+  {
+    return url.startsWith("http://") || url.startsWith("https://");
+  }
+  
+  private static void check(boolean requirements, String error)
+  {
+    String message = (error == null || error.trim().isEmpty()) ? DEFAULT_MESSAGE : error;
+    if (!requirements)
+    {
+      throw new IllegalArgumentException(message);
+    }
+  }
+  
+}