Java、DynamoDB：是否可以自定义编组 Set？

Question

我需要注释一个具有Set<UUID>属性的类。编组标量UUID很好，我可以使用@DynamoDBMarshalling注释来指定我的转换器，一切正常。

尝试在 上使用相同的转换器时Set<UUID>，我收到“DynamoDBMappingException: Expected SS in value”。我已经尝试创建一个期望的自定义​​转换器Set<UUID>，但同样的问题仍然存在。

是否可以自定义编组集？

@DynamoDBTable(tableName="djones-test")
public class UUIDRecommendation {
    private UUID id;
    private Set<UUID> recommendations;

    @DynamoDBHashKey
    @DynamoDBMarshalling(marshallerClass=UuidConverter.class)
    public UUID getId() {
        return id;
    }

    public void setId(UUID id) {
        this.id = id;
    }

    //Neither this nor UuidConverter.class work here    
    @DynamoDBMarshalling(marshallerClass=SetUuidConverter.class)
    public Set<UUID> getRecommendations() {
        return recommendations;
    }

    public void setRecommendations(Set<UUID> recommendations) {
        this.recommendations = recommendations;
    }
}

这是堆栈跟踪：

com.amazonaws.services.dynamodb.datamodeling.DynamoDBMappingException: Expected SS in value {SS: [1a841b97-ab9d-4425-a2c0-f9a81bebf0b4, 1a841b97-ab9d-4425-a2c0-f9a81bebf0b4, 1a841b97-ab9d-4425-a2c0-f9a81bebf0b4], } when invoking public void com.company.model.UUIDRecommendation.setRecommendations(java.util.Set)
    at com.amazonaws.services.dynamodb.datamodeling.SUnmarshaller.typeCheck(SUnmarshaller.java:26)
    at com.amazonaws.services.dynamodb.datamodeling.DynamoDBMapper.setValue(DynamoDBMapper.java:329)
    at com.amazonaws.services.dynamodb.datamodeling.DynamoDBMapper.marshallIntoObject(DynamoDBMapper.java:302)
    at com.amazonaws.services.dynamodb.datamodeling.DynamoDBMapper.load(DynamoDBMapper.java:253)
    at com.amazonaws.services.dynamodb.datamodeling.DynamoDBMapper.load(DynamoDBMapper.java:196)
    at com.mendeley.service.data.DynamoRecommendedItemsDataServiceTest.testObjectMapper(DynamoRecommendedItemsDataServiceTest.java:65)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:45)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:42)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20)
    at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:28)
    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.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:47)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:231)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:60)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:229)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:50)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:222)
    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:300)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:174)
    at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50)
    at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)

Answer 1

哦天哪-看起来客户编组员的集是不可能的。AWS 开发工具包经过硬编码，仅处理单个字符串值 (SUnmarshaller())。

AWS 开发工具包 1.3.13 第 185 行中的 DynamoDBReflector：

if ( isCustomMarshaller(getter) ) {
    unmarshaller = new SUnmarshaller() {

        @Override
        public Object unmarshall(AttributeValue value) {
            return getCustomMarshalledValue(toReturn, getter, value);
        }
    };
}

更新

作为一个完全肮脏的黑客，我通过复制/粘贴整个类拼凑了一些东西:(这就是为什么私有静态最终实用程序服务不好，而依赖注入很好。

这将起作用，因此您可以使用一个客户转换器（在我的例子中）来返回一个或多个实例UuidConverter的 getter 。UUID Set<UUID>

我添加了一个名为 getCustomMarshalledValueSet 的方法，该方法迭代 value.getSS() 返回的 List，为每个值调用自定义编组器，并将结果添加到它返回的 Set 中。

    @SuppressWarnings({ "rawtypes", "unchecked" })
    private <T> T getCustomMarshalledValueSet(T toReturn, Method getter, AttributeValue value) {
    DynamoDBMarshalling annotation = getter.getAnnotation(DynamoDBMarshalling.class);
    Class<? extends DynamoDBMarshaller<? extends Object>> marshallerClass = annotation.marshallerClass();

    DynamoDBMarshaller marshaller;
    try {
        marshaller = marshallerClass.newInstance();
    } catch (InstantiationException e) {
        throw new DynamoDBMappingException("Couldn't instantiate marshaller of class " + marshallerClass, e);
    } catch (IllegalAccessException e) {
        throw new DynamoDBMappingException("Couldn't instantiate marshaller of class " + marshallerClass, e);
    }

    Set<T> set = new HashSet<T>();

    for (String part : value.getSS()) {
        set.add((T) marshaller.unmarshall(getter.getReturnType(), part));
    }

    return (T) set;
}

此外，getArgumentUnmarshaller 已更改为在条件之前进行 isCollection 检查，以决定使用哪种类型的解组器，并更改了自定义编组器块以选择正确的排序。

            if (isCustomMarshaller(getter)) {
                if (isCollection) {
                    unmarshaller = new SSUnmarshaller() {

                        @Override
                        public Object unmarshall(AttributeValue value) {
                            return getCustomMarshalledValueSet(toReturn, getter, value);
                        }
                    };
                } else {
                    unmarshaller = new SUnmarshaller() {

                        @Override
                        public Object unmarshall(AttributeValue value) {
                            return getCustomMarshalledValue(toReturn, getter, value);
                        }
                    };
                }

            }