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The Slice compilers can optionally generate checksums of Slice definitions. For slice2java, the --checksum option causes the compiler to generate a new Java class that adds checksums to a static map member. Assuming we supplied the option --checksum Checksums to slice2java, the generated class Checksums.java looks like this:

public class Checksums
{
    public static java.util.Map<String, String> checksums;
}

The read-only map checksums is initialized automatically prior to first use; no action is required by the application.

In order to verify a server's checksums, a client could simply compare the dictionaries using the equals method. However, this is not feasible if it is possible that the server might return a superset of the client's checksums. A more general solution is to iterate over the local checksums as demonstrated below:

java.util.Map<String, String> serverChecksums = ...
Checksums.checksums.forEach((id, checksum) ->
    {
        String serverChecksum = serverChecksums.get(id);
        if(serverChecksum == null)
        {
            // No match found for type id!
        }
        else if(!checksum.equals(serverChecksum))
        {
            // Checksum mismatch!
        }
    });

In this example, the client first verifies that the server's dictionary contains an entry for each Slice type ID, and then it proceeds to compare the checksums.

See Also

• Slice Checksums