An object that implements this interface encapsulates a URI that is guaranteed to be safe to use (with respect to potential Cross-Site-Scripting vulnerabilities) in a URL context, for example in a URL-typed attribute in an HTML document.

Note on usage: SafeUri should be used to ensure user input is not executed in the browser. SafeUri should not be used to sanitize input before sending it to the server: The server cannot rely on the type contract of SafeUri values received from clients, because a malicious client could provide maliciously crafted serialized forms of implementations of this type that violate the type contract.

All implementing classes must maintain the class invariant (by design and implementation and/or convention of use), that invoking {@link #asString()} on any instance will return a string that is safe to assign to a URL-typed DOM or CSS property in a browser (or to use similarly in a "URL context"), in the sense that doing so must not cause unintended execution of script in the browser.

In determining safety of a URL both the value itself as well as its provenance matter. An arbitrary URI, including e.g. a javascript: URI, can be deemed safe in the sense of this type's contract if it is entirely under the program's control (e.g., a string literal, {@see UriUtils#fromSafeConstant}).

All implementations must implement equals() and hashCode() to behave consistently with the result of asString().equals() and asString.hashCode().

Implementations must not return {@code null} from {@link #asString()}.

@see UriUtils

abstract class SafeUri {
 /**
  * Returns this object's contained URI as a string.
  *
  * <p>
  * Based on this class' contract, the returned value will be non-null and a
  * string that is safe to use in a URL context.
  *
  * @return the contents as a String
  */
 String asString();

 /**
  * Compares this string to the specified object. Must be equal to
  * asString().equals().
  *
  * @param anObject the object to compare to
  */
 bool operator ==(Object obj);
}