Apache Pig的UDF返回值问题

今天写了关于Pig的EvalFunc UDF函数，结果一执行，发现返回值，总是bag类型，我就纳闷了，我明明指定了返回是String类型，怎么会变成Bag类型呢？经查找，发现拷贝的问题，由于先前写的UDF函数，返回值是多个，而现在的这个是一个，所以导致，我在pig脚本里面，进行强转string类型出错，发现问题后，设置返回类型为DataType.CHARARRAY问题得以解决。


案例（一），输入值为多个参数，返回也为多个参数

package com.easy.pig;

import com.easy.similar.model.ResultModel;
import com.easy.similar.tools.TextBuildID;
import org.apache.pig.EvalFunc;
import org.apache.pig.data.*;
import org.apache.pig.impl.logicalLayer.schema.Schema;

import java.io.IOException;

/**
 * Created by qindongliang on 2015/9/29.
 * 根据一篇内容返回md5和关键词words
 */
public class FingerUDF  extends EvalFunc<DataBag>  {


    /**tuple实例**/
    TupleFactory mTupleFactory = TupleFactory.getInstance();
    /**Bag实例*/
    BagFactory mBagFactory = BagFactory.getInstance();

    /**md5构建**/
     TextBuildID textBuildID = new TextBuildID();





    @Override
    public DataBag exec(Tuple tuple) throws IOException {
        try {
            DataBag output = mBagFactory.newDefaultBag();
            Object o = tuple.get(0);
            //返回多少句子
            int num_sentence = Integer.parseInt(tuple.get(1).toString());
            //返回几个关键词
            int num_words = Integer.parseInt(tuple.get(2).toString());
            //使用指纹算法 1  还是分词算法 2
            int type=Integer.parseInt(tuple.get(3).toString());
            //参与扩展计算的指纹,null的直接返回空
            String ext=tuple.get(4)==null?"":tuple.get(4).toString();
            //设置句子数量
            textBuildID.top_N_Sentence=num_sentence;
            //设置返回指纹数量
            textBuildID.top_N_Words=num_words;
            //设置去重算法类型
            textBuildID.type=type;
            ResultModel ro=textBuildID.buildID(o.toString(),ext);
            output.add(mTupleFactory.newTuple(ro.getMd5()));//获取md5值
            output.add(mTupleFactory.newTuple(ro.getWords()));//获取指纹关键词
            return output;
        } catch (Exception ee) {
            // error handling goes here
            ee.printStackTrace();
        }


        return null;
    }


    /**描述scheaml形式*/
    public Schema outputSchema(Schema input) {
        try{
            Schema bagSchema = new Schema();
            bagSchema.add(new Schema.FieldSchema("token", DataType.CHARARRAY));

            return new Schema(new Schema.FieldSchema(getSchemaName(this.getClass().getName().toLowerCase(), input),
                    bagSchema, DataType.BAG));
        }catch (Exception e){
            return null;
        }
    }


}

案例（二），输入值为String，返回也为String

package com.easy.pig;

import org.apache.pig.EvalFunc;
import org.apache.pig.data.DataType;
import org.apache.pig.data.Tuple;
import org.apache.pig.impl.logicalLayer.schema.Schema;

import java.io.IOException;

/**
 *  处理url
 */
public class UrlCvUDF extends EvalFunc<String>  {


    @Override
    public String exec(Tuple tuple) throws IOException {
        try {

            Object o = tuple.get(0);
            if(o!=null){
                //判断是否为指定url开头的来源
                if((o+"").startsWith("http://www.court.gov.cn")){
                    return "1";
                }else{
                    return "2";
                }
            }
        } catch (Exception ee) {
            ee.printStackTrace();
        }
        //url 为null 则返回0
        return "0";
    }

//
    /**描述scheaml形式*/
    public Schema outputSchema(Schema input) {
        try{
            Schema bagSchema = new Schema();
            bagSchema.add(new Schema.FieldSchema("token", DataType.CHARARRAY));
            //注意此处返回值要与泛型里面的对应
            return new Schema(new Schema.FieldSchema(getSchemaName(this.getClass().getName().toLowerCase(), input),
                    bagSchema, DataType.CHARARRAY));
        }catch (Exception e){
            e.printStackTrace();
            return null;
        }
    }


}

案例一的pig脚本：

--SET debug 'on'

--REGISTER ./aa.jar
REGISTER ./udf-pig-similarty-hbase-1.0-SNAPSHOT-jar-with-dependencies.jar
REGISTER ./pig-udf-extend-1.0.1-SNAPSHOT-jar-with-dependencies.jar

--mkdir /user/webmaster/crawldb/finger/
--rmf /user/webmaster/crawldb/finger/

mkdir /user/webmaster/search/monitor/finger-data;
rmf  /user/webmaster/search/monitor/finger-data;



set job.name 'pig-hbase-build-index'


a = load 'hbase://ETLDB' USING org.apache.pig.backend.hadoop.hbase.HBaseStorage('content:conn content:casenum,meta:isdelete','-loadKey true  ');

--a = foreach a generate FLATTEN(com.easy.pig.FingerUDF((chararray)$1));
-- 4个参数  0：文章内容   1：前n最长的句子数，2：前n关键词，3：判重算法， 1=>指纹 2=>分词
a = foreach a generate $0 as rowkey:chararray , BagToString(com.easy.pig.FingerUDF((chararray)$1,5,8,1,$2),'@') as info:chararray,$2 as casenum:chararray , $3 as isdel:chararray ;
--a = foreach a generate $2 as num:chararray;

--a = limit a 50;

--dump a;
--describe a;
a = foreach a generate $0 as rowkey:chararray , STRSPLIT(info,'@',2).$0 as finger_md5:chararray ,STRSPLIT(info,'@',2).$1 as finger_content:chararray ,casenum,isdel ;

--describe a;

store a into  '/user/webmaster/search/monitor/finger-data'  using com.pig.support.lucene.LuceneStore('row:true:false,finger_md5:true:false,finger_content:true:false,casenum:true:false,isdel:true:false','default');

案例二的pig脚本：

--SET debug 'on'

--REGISTER ./aa.jar
REGISTER ./udf-pig-similarty-hbase-1.0-SNAPSHOT-jar-with-dependencies.jar
REGISTER ./pig-udf-extend-1.0.1-SNAPSHOT-jar-with-dependencies.jar

--mkdir /user/webmaster/crawldb/finger/
--rmf /user/webmaster/crawldb/finger/

mkdir /user/webmaster/search/monitor/finger-data;
rmf  /user/webmaster/search/monitor/finger-data;



set job.name 'pig-hbase-build-index'


a = load 'hbase://ETLDB' USING org.apache.pig.backend.hadoop.hbase.HBaseStorage('content:conn content:casenum meta:isdelete content:url','-loadKey true  ');

--a = foreach a generate FLATTEN(com.easy.pig.FingerUDF((chararray)$1));
-- 4个参数  0：文章内容   1：前n最长的句子数，2：前n关键词，3：判重算法， 1=>指纹 2=>分词
a = foreach a generate $0 as rowkey:chararray , BagToString(com.easy.pig.FingerUDF((chararray)$1,5,8,1,''),'@') as info:chararray,$2 as casenum:chararray , $3 as isdel:chararray,   com.easy.pig.UrlCvUDF((chararray)$4)  as source:chararray   ;
--a = foreach a generate $2 as num:chararray;


a = limit a 11;

dump a;
describe a;
--describe a;
--a = foreach a generate $0 as rowkey:chararray , STRSPLIT(info,'@',2).$0 as finger_md5:chararray ,STRSPLIT(info,'@',2).$1 as finger_content:chararray ,casenum,isdel ;

--describe a;

--store a into  '/user/webmaster/search/monitor/finger-data'  using com.pig.support.lucene.LuceneStore('row:true:false,finger_md5:true:false,finger_content:true:false,casenum:true:false,isdel:true:false','default');