自定义 UnmodifiableSet Mixin 在 Jackson 2.7+ 中失败
Custom UnmodifiableSetMixin Fails in Jackson 2.7+
我希望能够在启用默认类型的情况下反序列化 UnmodifiableSet。为此，我创建了一个 UnmodifiableSetMixin，如下所示：
注意：您可以在 https://github.com/rwinch/jackson-unmodifiableset-mixin
找到一个包含所有源代码的最小项目来重现此问题
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) {}
}
然后我尝试使用它来反序列化一个空集。
public class UnmodifiableSetMixinTest {
static final String EXPECTED_JSON = "[\"java.util.Collections$UnmodifiableSet\",[]]";
ObjectMapper mapper;
@Before
public void setup() {
mapper = new ObjectMapper();
mapper.enableDefaultTyping(ObjectMapper.DefaultTyping.NON_FINAL, JsonTypeInfo.As.PROPERTY);
mapper.addMixIn(Collections.unmodifiableSet(Collections.<String>emptySet()).getClass(), UnmodifiableSetMixin.class);
}
@Test
@SuppressWarnings("unchecked")
public void read() throws Exception {
Set<String> foo = mapper.readValue(EXPECTED_JSON, Set.class);
assertThat(foo).isEmpty();
}
}
测试通过 Jackson 2.6，但使用 Jackson 2.7+ 失败，堆栈跟踪如下：
java.lang.IllegalStateException: No default constructor for [collection type; class java.util.Collections$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.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.run(ParentRunner.java:290)
at org.junit.runners.ParentRunner.schedule(ParentRunner.java:71)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
at org.junit.runners.ParentRunner.access[=14=]0(ParentRunner.java:58)
at org.junit.runners.ParentRunner.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)
谁能帮我修复 Jackson 2.7+ 的测试（我希望它适用于 Jackson 2.8.3）？
要使混入工作，必须在该内部 class 上有一个单参数 (*) 构造函数；如果不是，则混入不会关联。
但是您绝对需要使用这个 JDK 内部 class 吗？如果没有，您可以添加映射以指示您想要使用标准 Collection 实现之一，而不是使用 SimpleModule.addAbstractTypeMapping(abstractType, concreteType) 反序列化，注册该模块。
(*) EDIT 一开始我说 "zero-argument" 构造函数；但是有问题的构造函数确实有一个参数。
原来这是杰克逊的退步。我创建了 https://github.com/FasterXML/jackson-databind/issues/1392 来确认错误。
通过 #4078 向我提供了使用自定义解串器的解决方法。例如：
@JsonTypeInfo(use = JsonTypeInfo.Id.CLASS, include = JsonTypeInfo.As.PROPERTY)
@JsonDeserialize(using = UnmodifiableSetDeserializer.class)
public abstract class UnmodifiableSetMixin {
@JsonCreator
public UnmodifiableSetMixin(Set<?> s) {}
}
public class UnmodifiableSetDeserializer extends JsonDeserializer<Set> {
@Override
public Set deserialize(JsonParser jp, DeserializationContext ctxt) throws IOException, JsonProcessingException {
ObjectMapper mapper = (ObjectMapper) jp.getCodec();
JsonNode node = mapper.readTree(jp);
Set<Object> resultSet = new HashSet<Object>();
if (node != null) {
if (node instanceof ArrayNode) {
ArrayNode arrayNode = (ArrayNode) node;
Iterator<JsonNode> nodeIterator = arrayNode.iterator();
while (nodeIterator.hasNext()) {
JsonNode elementNode = nodeIterator.next();
resultSet.add(mapper.readValue(elementNode.toString(), Object.class));
}
} else {
resultSet.add(mapper.readValue(node.toString(), Object.class));
}
}
return Collections.unmodifiableSet(resultSet);
}
}
我希望能够在启用默认类型的情况下反序列化 UnmodifiableSet。为此，我创建了一个 UnmodifiableSetMixin，如下所示：
注意：您可以在 https://github.com/rwinch/jackson-unmodifiableset-mixin
找到一个包含所有源代码的最小项目来重现此问题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) {}
}
然后我尝试使用它来反序列化一个空集。
public class UnmodifiableSetMixinTest {
static final String EXPECTED_JSON = "[\"java.util.Collections$UnmodifiableSet\",[]]";
ObjectMapper mapper;
@Before
public void setup() {
mapper = new ObjectMapper();
mapper.enableDefaultTyping(ObjectMapper.DefaultTyping.NON_FINAL, JsonTypeInfo.As.PROPERTY);
mapper.addMixIn(Collections.unmodifiableSet(Collections.<String>emptySet()).getClass(), UnmodifiableSetMixin.class);
}
@Test
@SuppressWarnings("unchecked")
public void read() throws Exception {
Set<String> foo = mapper.readValue(EXPECTED_JSON, Set.class);
assertThat(foo).isEmpty();
}
}
测试通过 Jackson 2.6，但使用 Jackson 2.7+ 失败，堆栈跟踪如下：
java.lang.IllegalStateException: No default constructor for [collection type; class java.util.Collections$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.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.run(ParentRunner.java:290)
at org.junit.runners.ParentRunner.schedule(ParentRunner.java:71)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
at org.junit.runners.ParentRunner.access[=14=]0(ParentRunner.java:58)
at org.junit.runners.ParentRunner.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)
谁能帮我修复 Jackson 2.7+ 的测试（我希望它适用于 Jackson 2.8.3）？
要使混入工作，必须在该内部 class 上有一个单参数 (*) 构造函数；如果不是，则混入不会关联。
但是您绝对需要使用这个 JDK 内部 class 吗？如果没有，您可以添加映射以指示您想要使用标准 Collection 实现之一，而不是使用 SimpleModule.addAbstractTypeMapping(abstractType, concreteType) 反序列化，注册该模块。
(*) EDIT 一开始我说 "zero-argument" 构造函数；但是有问题的构造函数确实有一个参数。
原来这是杰克逊的退步。我创建了 https://github.com/FasterXML/jackson-databind/issues/1392 来确认错误。
通过 #4078 向我提供了使用自定义解串器的解决方法。例如：
@JsonTypeInfo(use = JsonTypeInfo.Id.CLASS, include = JsonTypeInfo.As.PROPERTY)
@JsonDeserialize(using = UnmodifiableSetDeserializer.class)
public abstract class UnmodifiableSetMixin {
@JsonCreator
public UnmodifiableSetMixin(Set<?> s) {}
}
public class UnmodifiableSetDeserializer extends JsonDeserializer<Set> {
@Override
public Set deserialize(JsonParser jp, DeserializationContext ctxt) throws IOException, JsonProcessingException {
ObjectMapper mapper = (ObjectMapper) jp.getCodec();
JsonNode node = mapper.readTree(jp);
Set<Object> resultSet = new HashSet<Object>();
if (node != null) {
if (node instanceof ArrayNode) {
ArrayNode arrayNode = (ArrayNode) node;
Iterator<JsonNode> nodeIterator = arrayNode.iterator();
while (nodeIterator.hasNext()) {
JsonNode elementNode = nodeIterator.next();
resultSet.add(mapper.readValue(elementNode.toString(), Object.class));
}
} else {
resultSet.add(mapper.readValue(node.toString(), Object.class));
}
}
return Collections.unmodifiableSet(resultSet);
}
}