public static String getMapFieldKeyType ( Field field ) { FieldType type = field . getType ( ) ; if ( ! ( type instanceof Message ) ) { throw new IllegalArgumentException ( field . toString ( ) ) ; } Message entryType = ( Message ) type ; ScalarFieldType keyType = ( ScalarFieldType ) entryType . getField ( MAP_ENTRY_KEY ) . getType ( ) ; return ScalarFieldTypeUtil . getWrapperType ( keyType ) ; }
Returns map field key type name .