Migration path for Uri to throw a checked exception: small step #1 (issue210041)

[johnfargo]

Reviewers: shindig.remailer_gmail.com,

Description:
This CL introduces a trivial wrapper UriException class, which wraps
IllegalArgumentException (itself a RuntimeException), and changes the
Uri class to throw it exclusively rather than IllegalArgumentException
or RuntimeException directly.
This allows calling code to wrap relevant methods in
semantically-bounded try/catch blocks without our having to have Uri's
methods throw a checked exception, which in turn would necessitate large
numbers of downstream changes.

In this way, we can slowly phase in use of UriException, to the point
that eventually we may find it relatively easy to change this exception
to a checked version of itself with minimal trouble.

Comments welcome.

Please review this at http://codereview.appspot.com/210041/show

Affected files:
  java/common/src/main/java/org/apache/shindig/common/uri/Uri.java


Index: java/common/src/main/java/org/apache/shindig/common/uri/Uri.java
===================================================================
--- java/common/src/main/java/org/apache/shindig/common/uri/Uri.java	 
(revision 910762)
+++ java/common/src/main/java/org/apache/shindig/common/uri/Uri.java	 
(working copy)
@@ -97,7 +97,17 @@
    * @return A new Uri, parsed into components.
    */
   public static Uri parse(String text) {
-    return parser.parse(text);
+    try {
+      return parser.parse(text);
+    } catch (IllegalArgumentException e) {
+      // This occurs all the time. Wrap the exception in a Uri-specific
+      // exception, yet one that remains a RuntimeException, so that
+      // callers may catch a specific exception rather than a blanket
+      // Exception, as a compromise between throwing a checked exception
+      // here (forcing wide-scale refactoring across the code base) and
+      // forcing users to simply catch abstract Exceptions here and there.
+      throw new UriException(e);
+    }
   }

   /**
@@ -105,7 +115,7 @@
    */
   public static Uri fromJavaUri(URI uri) {
     if (uri.isOpaque()) {
-      throw new IllegalArgumentException("No support for opaque Uris " +  
uri.toString());
+      throw new UriException("No support for opaque Uris " +  
uri.toString());
     }
     return new UriBuilder()
         .setScheme(uri.getScheme())
@@ -124,7 +134,7 @@
       return new URI(toString());
     } catch (URISyntaxException e) {
       // Shouldn't ever happen.
-      throw new IllegalArgumentException(e);
+      throw new UriException(e);
     }
   }

@@ -185,7 +195,7 @@
     if (StringUtils.isEmpty(uri.authority) &&
         StringUtils.isEmpty(uri.path) &&
         StringUtils.isEmpty(uri.query)) {
-      throw new IllegalArgumentException("Invalid scheme-specific part");
+      throw new UriException("Invalid scheme-specific part");
     }
   }

@@ -387,4 +397,14 @@
     if (!(obj instanceof Uri)) {return false;}
     return Objects.equal(text, ((Uri)obj).text);
   }
+
+  public static class UriException extends IllegalArgumentException {
+    private UriException(Exception e) {
+      super(e);
+    }
+
+    private UriException(String msg) {
+      super(msg);
+    }
+  }
 }