Avoid setting null values with GemFire's Cache Region put(key, value) operation when GemFire is used as the caching provider in Spring's Cache Abstraction (@Cacheable).

    @Cacheable("ExampleRegion")
    public Integer get(final String key) {
      return repository.get(key);
    }

java.lang.NullPointerException: value must not be null
	at com.gemstone.gemfire.internal.cache.LocalRegion.newUpdateEntryEvent(LocalRegion.java:1745)
	at com.gemstone.gemfire.internal.cache.LocalRegion.put(LocalRegion.java:1706)
	at com.gemstone.gemfire.internal.cache.AbstractRegion.put(AbstractRegion.java:286)
	at org.spring.cache.CachingWithGemFireIntegrationTest.testRegionCacheHit(CachingWithGemFireIntegrationTest.java:50)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
	at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47)
	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44)
	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
	at org.springframework.test.context.junit4.statements.RunBeforeTestMethodCallbacks.evaluate(RunBeforeTestMethodCallbacks.java:74)
	at org.springframework.test.context.junit4.statements.RunAfterTestMethodCallbacks.evaluate(RunAfterTestMethodCallbacks.java:83)
	at org.springframework.test.context.junit4.statements.SpringRepeat.evaluate(SpringRepeat.java:72)
	at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:231)
	at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:88)
	at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)
	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)
	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
	at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)
	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)
	at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)
	at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:71)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
	at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:174)
	at org.junit.runner.JUnitCore.run(JUnitCore.java:160)
	at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:74)
	at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:211)
	at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:67)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
	at com.intellij.rt.execution.application.AppMain.main(AppMain.java:134)