blocks|key|4212664|text|我们最终解决了这个问题，实现了一个自定义的集合反序列化程序，它简单地从集合中删除了“重复”对象。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4212665|我不认为它是理想的，但它完美地满足了我们的需求。|4212666|在这里发布代码，以防对其他人有用。|4212667|public+class+UniqueCollectionDeserializer+extends+CollectionDeserializer+{
++++public+UniqueCollectionDeserializer(
++++++++JavaType+collectionType,
++++++++JsonDeserializer<Object>+valueDeser,
++++++++TypeDeserializer+valueTypeDeser,
++++++++ValueInstantiator+valueInstantiator
++++)+{
++++++++super(collectionType,+valueDeser,+valueTypeDeser,+valueInstantiator);
++++}

++++protected+UniqueCollectionDeserializer(
++++++++JavaType+collectionType,
++++++++JsonDeserializer<Object>+valueDeser,
++++++++TypeDeserializer+valueTypeDeser,
++++++++ValueInstantiator+valueInstantiator,
++++++++JsonDeserializer<Object>+delegateDeser,
++++++++NullValueProvider+nuller,
++++++++Boolean+unwrapSingle
++++)+{
++++++++super(collectionType,+valueDeser,+valueTypeDeser,+valueInstantiator,+delegateDeser,+nuller,+unwrapSingle);
++++}

++++public+UniqueCollectionDeserializer(CollectionDeserializer+defaultDeserializer)+{
++++++++super(defaultDeserializer);
++++}

++++@Override
++++public+Collection<Object>+deserialize(JsonParser+jsonParser,+DeserializationContext+context)+throws+IOException,+JsonProcessingException+{
++++++++return+removeDuplicates(super.deserialize(jsonParser,+context));
++++}

++++@Override
++++public+Collection<Object>+deserialize(JsonParser+p,+DeserializationContext+ctxt,+Collection<Object>+result)+throws+IOException+{
++++++++return+removeDuplicates(super.deserialize(p,+ctxt,+result));
++++}

++++@SuppressWarnings("unchecked")
++++@Override
++++protected+CollectionDeserializer+withResolved(
++++++++JsonDeserializer<?>+dd,
++++++++JsonDeserializer<?>+vd,
++++++++TypeDeserializer+vtd,
++++++++NullValueProvider+nuller,
++++++++Boolean+unwrapSingle
++++)+{
++++++++return+new+UniqueCollectionDeserializer(_containerType,+(JsonDeserializer<Object>)+vd,+vtd,+_valueInstantiator,+(JsonDeserializer<Object>)+dd,+nuller,+unwrapSingle);
++++}

++++private+Collection<Object>+removeDuplicates(Collection<Object>+data)+{
++++++++return+data.stream()
++++++++++++++++.distinct()
++++++++++++++++.collect(Collectors.toList());
++++}
}|code-block|syntax|javascript|4212668|从BeanDeserializerModifier调用它，如下所示：|4212669|public+JsonDeserializer<?>+modifyCollectionDeserializer(DeserializationConfig+config,+CollectionType+type,+BeanDescription+beanDesc,+JsonDeserializer<?>+deserializer)+{
++++return+new+UniqueCollectionDeserializer((CollectionDeserializer)+deserializer);
}|4212670|entityMap^0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|R|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|S|8|@]|9|@]|A|$]]|$1|F|3|G|5|H|7|T|8|@]|9|@]|A|$I|J]]|$1|K|3|L|5|6|7|U|8|@]|9|@]|A|$]]|$1|M|3|N|5|H|7|V|8|@]|9|@]|A|$I|J]]|$1|O|3|-4|5|6|7|W|8|@]|9|@]|A|$]]]|P|$]]

We ended up solving this by implementing a custom collection deserializer that simply removes the "duplicate" object from the collection.

I don't think it's ideal but works perfectly for our needs.

Posting the code here in case it's of use to someone else.

<pre><code>public class UniqueCollectionDeserializer extends CollectionDeserializer {
 public UniqueCollectionDeserializer(
 JavaType collectionType,
 JsonDeserializer&lt;Object&gt; valueDeser,
 TypeDeserializer valueTypeDeser,
 ValueInstantiator valueInstantiator
 ) {
 super(collectionType, valueDeser, valueTypeDeser, valueInstantiator);
 }

 protected UniqueCollectionDeserializer(
 JavaType collectionType,
 JsonDeserializer&lt;Object&gt; valueDeser,
 TypeDeserializer valueTypeDeser,
 ValueInstantiator valueInstantiator,
 JsonDeserializer&lt;Object&gt; delegateDeser,
 NullValueProvider nuller,
 Boolean unwrapSingle
 ) {
 super(collectionType, valueDeser, valueTypeDeser, valueInstantiator, delegateDeser, nuller, unwrapSingle);
 }

 public UniqueCollectionDeserializer(CollectionDeserializer defaultDeserializer) {
 super(defaultDeserializer);
 }

 @Override
 public Collection&lt;Object&gt; deserialize(JsonParser jsonParser, DeserializationContext context) throws IOException, JsonProcessingException {
 return removeDuplicates(super.deserialize(jsonParser, context));
 }

 @Override
 public Collection&lt;Object&gt; deserialize(JsonParser p, DeserializationContext ctxt, Collection&lt;Object&gt; result) throws IOException {
 return removeDuplicates(super.deserialize(p, ctxt, result));
 }

 @SuppressWarnings("unchecked")
 @Override
 protected CollectionDeserializer withResolved(
 JsonDeserializer&lt;?&gt; dd,
 JsonDeserializer&lt;?&gt; vd,
 TypeDeserializer vtd,
 NullValueProvider nuller,
 Boolean unwrapSingle
 ) {
 return new UniqueCollectionDeserializer(_containerType, (JsonDeserializer&lt;Object&gt;) vd, vtd, _valueInstantiator, (JsonDeserializer&lt;Object&gt;) dd, nuller, unwrapSingle);
 }

 private Collection&lt;Object&gt; removeDuplicates(Collection&lt;Object&gt; data) {
 return data.stream()
 .distinct()
 .collect(Collectors.toList());
 }
}
</code></pre>

Called it from a BeanDeserializerModifier like so:

<pre><code>public JsonDeserializer&lt;?&gt; modifyCollectionDeserializer(DeserializationConfig config, CollectionType type, BeanDescription beanDesc, JsonDeserializer&lt;?&gt; deserializer) {
 return new UniqueCollectionDeserializer((CollectionDeserializer) deserializer);
}
</code></pre>

We are implementing Jackson 2.9's @JsonMerge annotation.

As per the documentation "Merging of Collections is simple: entries are appended; no checks for existence applied".

However, because we are merging JPA entities, we cannot use Set (due to issues with lazy loading), we must use List.

The question is, how can we check for existence when using a Collection?

@JsonMerge check existence with List

我们正在实现Jackson 2.9的@JsonMerge注解。根据文档“集合的合并很简单:附加条目；不检查是否存在”。然而，因为我们正在合并JPA实体，所以我们不能使用Set (由于延迟加载的问题)，我们必须使用List。问题是，在使用Collection时，我们如何检查是否存在？

问@JsonMerge使用列表检查是否存在
EN

社区

活动

资源

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问@JsonMerge使用列表检查是否存在EN

社区

活动

资源

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问@JsonMerge使用列表检查是否存在
EN