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| |
| <document> |
| |
| <properties> |
| <title>Hadoop Hive- Reflect User Defined Function</title> |
| <author email="hive-user@hadoop.apache.org">Hadoop Hive Documentation Team</author> |
| </properties> |
| |
| <body> |
| <section name="Reflect (Generic) UDF" href="reflect"> |
| |
| <p>A java class and method often exists to handle the exact function a user would like to use in hive. Rather |
| then 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 primative type |
| or a type that hive knows how to serialize. |
| </p> |
| |
| <source><![CDATA[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]]></source> |
| |
| </section> |
| </body> |
| </document> |
