HiveUDF读取HDFS上的资源文件

背景：
在hive中编写UDF时，我们可能会加载外部的资源文件，可以将资源打到Jar中 ，将资源放在hdfs上，在使用UDF时通过参数就可以加载到。

代码

public class TransformCodeToCode extends GenericUDF {

    private MapredContext context;

    private Configuration conf;

    private FileSystem fileSystem;

    private boolean parseFlag = false;

    private Map<String,String> codeToCodeMap = new HashMap();

    @Override
    public void configure(MapredContext context) {
        //通过context 我们可以获取到外部传入的配置即：-hiveconf 传入的变量值
        this.context = context;
    }

    //基本类型（Primitive），集合（List），键值对映射（Map），结构体（Struct），联合体（Union）。
    @Override
    public ObjectInspector initialize(ObjectInspector[] objectInspectors) throws UDFArgumentException {
        //校验参数长度是否为2
        if (objectInspectors == null || objectInspectors.length != 2) {
            throw new IllegalArgumentException("The function transform accepts 2 parameters.");
        }
        //校验参数是否为PRIMITIVE类型
        ObjectInspector inspectorOne = objectInspectors[0];
        if (!ObjectInspector.Category.PRIMITIVE.equals(inspectorOne.getCategory())) {
            throw new UDFArgumentException("Desired parameter type:PRIMITIVE, actual parameter type:" + inspectorOne.getTypeName());
        }
        ObjectInspector inspectorTwo = objectInspectors[1];
        if (!ObjectInspector.Category.PRIMITIVE.equals(inspectorTwo.getCategory())) {
            throw new UDFArgumentException("Desired parameter type:PRIMITIVE, actual parameter type:" + inspectorTwo.getTypeName());
        }
        return PrimitiveObjectInspectorFactory.javaStringObjectInspector;
    }

    @Override
    public Object evaluate(DeferredObject[] deferredObjects) throws HiveException {
        String fieldValue = String.valueOf(deferredObjects[0].get());
        String filename = String.valueOf(deferredObjects[1].get());
        FSDataInputStream open = null;
        BufferedReader bf = null;
        String returnStr;
        try {
            //如果解析过，先从map中获取
            if(parseFlag){
                returnStr = codeToCodeMap.get(fieldValue);
                if(returnStr != null){
                    return returnStr;
                }else {
                    return fieldValue;
                }
            }
            //初始化conf
            if(conf == null){
                if (context != null) {
                    conf = context.getJobConf();
                } else {
                    conf = SessionState.get().getConf();
                }
            }
            //读取hdfs上的文件
            String filePath = "/data/resource/" + filename + ".txt";
            fileSystem = FileSystem.get(conf);
            open = fileSystem.open(new Path(filePath));
            bf = new BufferedReader(new InputStreamReader(open));
            String lineStr;
            String frontStr;
            String laterStr = "";
            //遍历文件内容，放入map
            while ((lineStr = bf.readLine()) != null) {
                String[] strArr = lineStr.split("\\|\\^\\|");
                int length = strArr.length;
                if(length < 1){
                    continue;
                }
                frontStr = strArr[0];
                if(length >= 3){
                    laterStr = strArr[2];
                }
                codeToCodeMap.put(frontStr, laterStr);
            }
            parseFlag = true;
            returnStr = codeToCodeMap.get(fieldValue);
            if(returnStr != null){
                return returnStr;
            }else {
                return fieldValue;
            }
        } catch (Exception e) {
           throw new HiveException("reader hdfs file Exception" + e.getMessage());
        } finally {
            try {
                if (open != null) {
                    open .close();
                }
                if (bf != null) {
                    bf.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

   @Override
    public void close() throws IOException {
        fileSystem.close();
    }

    @Override
    public String getDisplayString(String[] strings) {
        return "TransformCodeToCode(" + strings[0] + "," + strings[1] + ")";
    }
}