Reflect (Generic) UDF
A Java class and method often exists to handle the exact function a user would like to use in Hive. Rather than having to write a wrapper UDF to call this method, the majority of these methods can be called using reflect UDF. Reflect uses Java reflection to instantiate and call methods of objects; it can also call static functions. The method must return a primitive type or a type that Hive knows how to serialize.
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SELECT reflect("java.lang.String", "valueOf", 1), reflect("java.lang.String", "isEmpty"), reflect("java.lang.Math", "max", 2, 3), reflect("java.lang.Math", "min", 2, 3), reflect("java.lang.Math", "round", 2.5), reflect("java.lang.Math", "exp", 1.0), reflect("java.lang.Math", "floor", 1.9) FROM src LIMIT 1; 1 true 3 2 3 2.7182818284590455 1.0 |