Custom UnmodifiableSetMixin Fails in Jackson 2.7+ but works in Jackson 2.6 #1392
Description
I'd like to be able to deserialize an UnmodifiableSet with default typing enabled. To do this I have created an UnmodifiableSetMixin as shown below:
NOTE: You can find a minimal project with all the source code to reproduce this issue at https://github.com/rwinch/jackson-unmodifiableset-mixin
import com.fasterxml.jackson.annotation.JsonCreator;
import com.fasterxml.jackson.annotation.JsonTypeInfo;
import java.util.Set;
@JsonTypeInfo(use = JsonTypeInfo.Id.CLASS, include = JsonTypeInfo.As.PROPERTY)
public abstract class UnmodifiableSetMixin {
@JsonCreator
public UnmodifiableSetMixin(Set<?> s) {}
}I then try to use this to deserialize an empty set.
public class UnmodifiableSetMixinTest {
static final String EXPECTED_JSON = "[\"java.util.Collections$UnmodifiableSet\",[]]";
ObjectMapper mapper;
@Before
public void setup() {
mapper = new ObjectMapper();
mapper.enableDefaultTyping(ObjectMapper.DefaultTyping.NON_FINAL, JsonTypeInfo.As.PROPERTY);
mapper.addMixIn(Collections.unmodifiableSet(Collections.<String>emptySet()).getClass(), UnmodifiableSetMixin.class);
}
@Test
@SuppressWarnings("unchecked")
public void read() throws Exception {
Set<String> foo = mapper.readValue(EXPECTED_JSON, Set.class);
assertThat(foo).isEmpty();
}
}The test passes with Jackson 2.6, but fails using Jackson 2.7+ (including Jackson 2.8.3) with the following stack trace:
java.lang.IllegalStateException: No default constructor for [collection type; class java.util.Collections$UnmodifiableSet, contains [simple type, class java.lang.Object]]
at com.fasterxml.jackson.databind.deser.std.StdValueInstantiator.createUsingDefault(StdValueInstantiator.java:240)
at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:249)
at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:26)
at com.fasterxml.jackson.databind.jsontype.impl.AsArrayTypeDeserializer._deserialize(AsArrayTypeDeserializer.java:110)
at com.fasterxml.jackson.databind.jsontype.impl.AsArrayTypeDeserializer.deserializeTypedFromArray(AsArrayTypeDeserializer.java:50)
at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserializeWithType(CollectionDeserializer.java:310)
at com.fasterxml.jackson.databind.deser.impl.TypeWrappedDeserializer.deserialize(TypeWrappedDeserializer.java:42)
at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:3788)
at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:2779)
at sample.UnmodifiableSetMixinTest.read(UnmodifiableSetMixinTest.java:36)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
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.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
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.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:86)
at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:459)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:678)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:382)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:192)
This seems like a passivity issue. Is there a workaround for this problem?