Question

我想从猪的时间戳中获取月份名称（Jan-Dec）。我用Java编写了一个UDF（我的第一个UDF），它看起来像这样：

package pig.data.preprocess;

import java.io.IOException;
import java.util.HashMap;
import java.util.Map;

import org.apache.pig.EvalFunc;
import org.apache.pig.data.Tuple;

public class ColNameToTypeMap extends EvalFunc<String> {

    @Override
    public String exec(Tuple input) throws IOException {
        Map<Integer, String> monthNamesMap = new HashMap<Integer, String>();
        monthNamesMap.put(1, "Jan");
        monthNamesMap.put(2, "Feb");
        monthNamesMap.put(3, "Mar");
        monthNamesMap.put(4, "Apr");
        monthNamesMap.put(5, "May");
        monthNamesMap.put(6, "Jun");
        monthNamesMap.put(7, "Jul");
        monthNamesMap.put(8, "Aug");
        monthNamesMap.put(9, "Sep");
        monthNamesMap.put(10, "Oct");
        monthNamesMap.put(11, "Nov");
        monthNamesMap.put(12, "Dec");
        int monthId = (Integer)input.get(0);
        return monthNamesMap.get(monthId);
    }

}

以下是使用上述UDF的猪脚本：

register '<path-to-jar>/month-name.jar';
DEFINE month_name pig.data.preprocess.ColNameToTypeMap();
month_n = FOREACH only_dates GENERATE id, month_name(GetMonth(ToDate(ts)));
DUMP month_n;

当我运行此脚本时，它会给我以下异常：

ERROR 1200: could not instantiate 'pig.data.preprocess.ColNameToTypeMap' with arguments 'null'

Failed to parse: could not instantiate 'pig.data.preprocess.ColNameToTypeMap' with arguments 'null'
    at org.apache.pig.parser.QueryParserDriver.parse(QueryParserDriver.java:201)
    at org.apache.pig.PigServer$Graph.validateQuery(PigServer.java:1707)
    at org.apache.pig.PigServer$Graph.registerQuery(PigServer.java:1680)
    at org.apache.pig.PigServer.registerQuery(PigServer.java:623)
    at org.apache.pig.tools.grunt.GruntParser.processPig(GruntParser.java:1082)
    at org.apache.pig.tools.pigscript.parser.PigScriptParser.parse(PigScriptParser.java:505)
    at org.apache.pig.tools.grunt.GruntParser.parseStopOnError(GruntParser.java:230)
    at org.apache.pig.tools.grunt.GruntParser.parseStopOnError(GruntParser.java:205)
    at org.apache.pig.tools.grunt.Grunt.run(Grunt.java:66)
    at org.apache.pig.Main.run(Main.java:565)
    at org.apache.pig.Main.main(Main.java:177)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:606)
    at org.apache.hadoop.util.RunJar.run(RunJar.java:221)
    at org.apache.hadoop.util.RunJar.main(RunJar.java:136)
Caused by: java.lang.RuntimeException: could not instantiate 'pig.data.preprocess.ColNameToTypeMap' with arguments 'null'
    at org.apache.pig.impl.PigContext.instantiateFuncFromSpec(PigContext.java:772)
    at org.apache.pig.newplan.logical.expression.UserFuncExpression.getFieldSchema(UserFuncExpression.java:222)
    at org.apache.pig.newplan.logical.optimizer.FieldSchemaResetter.execute(SchemaResetter.java:264)
    at org.apache.pig.newplan.logical.expression.AllSameExpressionVisitor.visit(AllSameExpressionVisitor.java:143)
    at org.apache.pig.newplan.logical.expression.UserFuncExpression.accept(UserFuncExpression.java:113)
    at org.apache.pig.newplan.ReverseDependencyOrderWalker.walk(ReverseDependencyOrderWalker.java:70)
    at org.apache.pig.newplan.PlanVisitor.visit(PlanVisitor.java:52)
    at org.apache.pig.newplan.logical.optimizer.SchemaResetter.visitAll(SchemaResetter.java:67)
    at org.apache.pig.newplan.logical.optimizer.SchemaResetter.visit(SchemaResetter.java:122)
    at org.apache.pig.newplan.logical.relational.LOGenerate.accept(LOGenerate.java:245)
    at org.apache.pig.newplan.DependencyOrderWalker.walk(DependencyOrderWalker.java:75)
    at org.apache.pig.newplan.logical.optimizer.SchemaResetter.visit(SchemaResetter.java:114)
    at org.apache.pig.parser.LogicalPlanBuilder.buildForeachOp(LogicalPlanBuilder.java:1055)
    at org.apache.pig.parser.LogicalPlanGenerator.foreach_clause(LogicalPlanGenerator.java:15896)
    at org.apache.pig.parser.LogicalPlanGenerator.op_clause(LogicalPlanGenerator.java:1933)
    at org.apache.pig.parser.LogicalPlanGenerator.general_statement(LogicalPlanGenerator.java:1102)
    at org.apache.pig.parser.LogicalPlanGenerator.statement(LogicalPlanGenerator.java:560)
    at org.apache.pig.parser.LogicalPlanGenerator.query(LogicalPlanGenerator.java:421)
    at org.apache.pig.parser.QueryParserDriver.parse(QueryParserDriver.java:191)
    ... 16 more
Caused by: java.lang.IllegalAccessException: Class org.apache.pig.impl.PigContext can not access a member of class pig.data.preprocess.ColNameToTypeMap with modifiers ""
    at sun.reflect.Reflection.ensureMemberAccess(Reflection.java:110)
    at java.lang.Class.newInstance(Class.java:377)
    at org.apache.pig.impl.PigContext.instantiateFuncFromSpec(PigContext.java:742)
    ... 34 more

我花了很多时间，但我无法弄清楚问题。如果有人以前解决了类似的问题，请帮忙。

Answer 1

使用ANT / Maven构建jar时，jar中应包含所有必需的库。看来，有些图书馆遗失了。

确保所有依赖项都存在。

确保注册jar并在脚本中声明所有变量，如'ts'。

错误1200：无法使用参数'null'实例化<udf name =“”>

1 个答案: