pig job failed after register a jar

I write a simplest pig scripts for testing.
But after I register a jar, it failed, even i didn't use any function in the jar.
Is there any specific requirements for the jar when i build it?

org.apache.pig.backend.executionengine.ExecException: ERROR 2244: Job failed, hadoop does not return any error message
at org.apache.pig.tools.grunt.GruntParser.executeBatch(GruntParser.java:145)
at org.apache.pig.tools.grunt.GruntParser.parseStopOnError(GruntParser.java:198)
at org.apache.pig.tools.grunt.GruntParser.parseStopOnError(GruntParser.java:170)
at org.apache.pig.tools.grunt.Grunt.exec(Grunt.java:84)
at org.apache.pig.Main.run(Main.java:475)
at org.apache.pig.Main.main(Main.java:157)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.apache.hadoop.util.RunJar.main(RunJar.java:208)

register user_digest_hbase-1.0.0.jar;

RMF /tmp/lei.wang/userdigest/mergeout;

file_data = LOAD '$fileinput' USING PigStorage('\u0001') AS (json:chararray);
STORE file_data INTO '/tmp/lei.wang/userdigest/mergeout/' USING PigStorage('\t');

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