Package org.apache.flink.testutils.junit

Class SharedObjects

  • All Implemented Interfaces:
    org.junit.rules.TestRule
    @NotThreadSafe
public class SharedObjects
extends org.junit.rules.ExternalResource
    This rule allows objects to be used both in the main test case as well as in UDFs by using serializable SharedReferences. Usage: 
    
    @Rule
     public final SharedObjects sharedObjects = SharedObjects.create();

    @Test
     public void test() throws Exception {
         StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();
        SharedReference<Queue<Long>> listRef = sharedObjects.add(new ConcurrentLinkedQueue<>());
         int n = 10000;
         env.setParallelism(100);
         env.fromSequence(0, n).map(i -> listRef.get().add(i));
         env.execute();
         assertEquals(n + 1, listRef.get().size());
         assertEquals(
                 LongStream.rangeClosed(0, n).boxed().collect(Collectors.toList()),
                 listRef.get().stream().sorted().collect(Collectors.toList()));
     }

    The main idea is that shared objects are bound to the scope of a test case instead of a class. That allows us to:

    • Avoid all kinds of static fields in test classes that only exist since all fields in UDFs need to be serializable.
    • Hopefully make it easier to reason about the test setup
    • Facilitate to share more test building blocks across test classes.
    • Fully allow tests to be rerun/run in parallel without worrying about static fields

    Note that since the shared objects are accessed through multiple threads, they need to be thread-safe or accessed in a thread-safe manner.

    • Method Detail

      • create

        public static SharedObjects create()
        Creates a new instance. Usually that should be done inside a JUnit test class as an instance-field annotated with Rule.

      • add

        public <T> SharedReference<T> add​(T object)
        Adds a new object to this SharedObjects. Although not necessary, it is recommended to only access the object through the returned SharedReference.

      • before

        protected void before()
               throws Throwable
        Overrides:
        before in class org.junit.rules.ExternalResource
        Throws:
        Throwable

      • after

        protected void after()
        Overrides:
        after in class org.junit.rules.ExternalResource

      • hashCode

        public int hashCode()
        Overrides:
        hashCode in class Object