[FLINK-4793] Using a local method with :: notation in Java 8 causes index out of bounds

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 1.2.0
• Assignee: Timo Walther
• Reporter: Ted Dunning
• Created: 11/Oct/16 01:37
• Updated: 12/Oct/16 09:06
• Resolved: 12/Oct/16 09:06

Description

I tried to use the toString method on an object as a map function:

                .<String>map(Trade::toString)

This caused an index out of bounds error:

java.lang.ArrayIndexOutOfBoundsException: -1
	at org.apache.flink.api.java.typeutils.TypeExtractor.getUnaryOperatorReturnType(TypeExtractor.java:351)
	at org.apache.flink.api.java.typeutils.TypeExtractor.getUnaryOperatorReturnType(TypeExtractor.java:305)
	at org.apache.flink.api.java.typeutils.TypeExtractor.getMapReturnTypes(TypeExtractor.java:120)
	at org.apache.flink.streaming.api.datastream.DataStream.map(DataStream.java:506)
	at com.mapr.aggregate.AggregateTest.testAggregateTrades(AggregateTest.java:81)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
	at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
	at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
	at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
	at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
	at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:68)

On the other hand, if I use a public static method, like this:

                .<Trade>map(Trade::fromString)

All is good. fromString and toString are defined like this:

    public static Trade fromString(String s) throws IOException {
        return mapper.readValue(s, Trade.class);
    }

    @Override
    public String toString() {
        return String.format("{\"%s\", %d, %d, %.2f}", symbol, time, volume, price);
    }

This might be a viable restriction on what functions I can use, but there certainly should be a better error message, if so.

Issue Links

• links to: GitHub Pull Request #2621