hive中udtf如何使用

这篇文章给大家介绍hive中udtf如何使用，内容非常详细，感兴趣的小伙伴们可以参考借鉴，希望对大家能有所帮助。

场景：使用UDTF解析JSON串

废话不多说了，直接上代码

要想写UDTF必须继承GenericUDTF类，并实现initialize，process，close三个方法，initialize定义每行的列名及类型，process方法是对数据的操作，就是把一行拆成多行，注意一行有多列的话，需要是个集合，close方法可以不实现

package dw.udf;

import java.util.ArrayList;import java.util.Iterator;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.GenericUDTF;import org.apache.hadoop.hive.serde2.objectinspector.ObjectInspector;import org.apache.hadoop.hive.serde2.objectinspector.ObjectInspectorFactory;import org.apache.hadoop.hive.serde2.objectinspector.StructObjectInspector;import org.apache.hadoop.hive.serde2.objectinspector.primitive.PrimitiveObjectInspectorFactory;import org.json.JSONArray;import org.json.JSONObject;public class JsonParse extends GenericUDTF {//集成GenericUDTF        @Override        public StructObjectInspector initialize(ObjectInspector[] args) throws UDFArgumentException {                if (args.length != 1) {                        throw new UDFArgumentLengthException("ExplodeMap takes only one argument");                }                if (args[0].getCategory() != ObjectInspector.Category.PRIMITIVE) {                        throw new UDFArgumentException("ExplodeMap takes string as a parameter");                }                        ArrayList fieldNames = new ArrayList();//这里是列的                ArrayList fieldOIs = new ArrayList();                fieldNames.add("containerid");                fieldOIs.add(PrimitiveObjectInspectorFactory.javaStringObjectInspector);                fieldNames.add("first_step");                fieldOIs.add(PrimitiveObjectInspectorFactory.javaStringObjectInspector);                fieldNames.add("second_step");                fieldOIs.add(PrimitiveObjectInspectorFactory.javaStringObjectInspector);                fieldNames.add("third_step");                fieldOIs.add(PrimitiveObjectInspectorFactory.javaStringObjectInspector);                return ObjectInspectorFactory.getStandardStructObjectInspector(fieldNames, fieldOIs);        }        @SuppressWarnings("rawtypes")        @Override        public void process(Object[] args) throws HiveException {                try {                        JSONObject obj = new JSONObject(args[0].toString());                        Iterator it = obj.keys();                        while (it.hasNext()) {                                String key = (String) it.next();                                JSONArray array = obj.getJSONArray(key);                                if (key.indexOf("&") != -1) {                                        key = key.substring(0, key.indexOf("&"));                                }                                String[] outstr = new String[4];                                outstr[0] = key;                                for (int i = 0; i < array.length(); i++) {                                        outstr[i + 1] = array.getString(i);                                }                                forward(outstr);                        }                } catch (Exception e) {                        e.printStackTrace();                }        }        @Override        public void close() throws HiveException {        }}

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