LowerUDF

package com.XX.udf;


import org.apache.hadoop.hive.ql.exec.UDFArgumentException;
import org.apache.hadoop.hive.ql.exec.UDFArgumentLengthException;
import org.apache.hadoop.hive.ql.metadata.HiveException;
import org.apache.hadoop.hive.ql.udf.generic.GenericUDF;
import org.apache.hadoop.hive.serde2.objectinspector.ObjectInspector;
import org.apache.hadoop.hive.serde2.objectinspector.primitive.PrimitiveObjectInspectorFactory;
import org.apache.hadoop.hive.serde2.objectinspector.primitive.StringObjectInspector;


public class LowerUDF extends GenericUDF {

    StringObjectInspector str ;
    @Override
    public ObjectInspector initialize(ObjectInspector[] arguments) throws UDFArgumentException {
        //判断输入参数个数是否合法
        if (arguments.length != 1) {
            throw new UDFArgumentLengthException("输入参数长度不合法,应该为一个参数");
        }

        //判断输入参数类型是否合法
        if (!(arguments[0] instanceof StringObjectInspector)) {
            throw new UDFArgumentException("输入非法参数，应为字符串类型");
        }

        str=(StringObjectInspector)arguments[0];
        //制定输出类型
        return PrimitiveObjectInspectorFactory.javaStringObjectInspector;
    }

    @Override
    public Object evaluate(DeferredObject[] arguments) throws HiveException {
        String input = str.getPrimitiveJavaObject(arguments[0].get());
        return input.toLowerCase();
    }

    @Override
    public String getDisplayString(String[] children) {
        return "方法的描述信息";
    }
}