如何在Morphia（MongoDB）字段中映射是一个任意嵌套的文档？

Question

我试过了：

@Entity
public class Test {

    @Id
    public ObjectId id;
    public Date createdAt;
    public Document data;

}

插入这样的实体工作正常：

Test t = new Test();
        t.createdAt = new Date();
        t.data = new Document("qwe", 12).append("wer", asList("123", "345", "dsf"));
        datastore.save(t);

但有两个问题：

1）在节目开始时有一条温暖的信息：

06:33:47 [main] WARN  org.mongodb.morphia.mapping.validation.MappingValidator - MapKeyDifferentFromString complained about test.Test.data : Maps cannot be keyed by Object (Map<Object,?>); Use a parametrized type that is supported (Map<String/Enum/Long/ObjectId/..., ?>)

2）我无法收回这样的实体datastore.createQuery(Test.class).asList())产生错误：

Exception in thread "main" java.lang.ClassCastException: org.bson.Document cannot be cast to java.util.List
    at org.mongodb.morphia.mapping.DefaultCreator.createList(DefaultCreator.java:131)
    at org.mongodb.morphia.converters.IterableConverter.createNewCollection(IterableConverter.java:122)
    at org.mongodb.morphia.converters.IterableConverter.decode(IterableConverter.java:32)
    at org.mongodb.morphia.converters.Converters.decode(Converters.java:85)

如何在Morphia实体中保留任意嵌套文档？