在序列化Hibernate对象时引发奇怪的杰克逊异常 [英] Strange Jackson exception being thrown when serializing Hibernate object

问题描述

杰克逊抛出了一个奇怪的例外，我不知道该如何解决。我使用Spring，Hibernate和Jackson。

我已经认为懒加载导致了这个问题，但我已经采取措施告诉Jackson不要处理各种属性如下：

pre $ @ $ $ c $ @ @JsonIgnoreProperties（{sentMessages，receivedMessages，educationFacility}）
public class Director扩展UserAccount implements EducationFacilityUser {
....
}

I对所有其他UserAccount子类也做了同样的事情。

这是抛出的异常：

  org.codehaus.jackson.map.JsonMappingException：找不到类org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer的序列化程序，没有发现创建BeanSerializer的属性（以避免异常，禁用SerializationConfig。 Feature.FAIL_ON_EMPTY_BEANS））（通过引用链：java.util.ArrayList [46]  - > jobprep.domain.educationfacility.Director _ $$ _ javassis t_2 [handler]）
 at org.codehaus.jackson.map.ser.StdSerializerProvider $ 1.serialize（StdSerializerProvider.java:62）
 at org.codehaus.jackson.map.ser.BeanPropertyWriter。 serializeAsField（BeanPropertyWriter.java:268）
位于org.codehaus.jackson.map.ser.BeanSerializer.serializeFields（BeanSerializer.java:146）
位于org.codehaus.jackson.map.ser.BeanSerializer。 （org.codehaus.jackson.map.ser.ContainerSerializers 
）org.codehaus.jackson.map.ser上的
 $ IndexedListSerializer.serializeContents（ContainerSerializers.java:236）
。 ContainerSerializers $ IndexedListSerializer.serializeContents（ContainerSerializers.java:189）
 at org.codehaus.jackson.map.ser.ContainerSerializers $ AsArraySerializer.serialize（ContainerSerializers.java:111）
 at org.codehaus.jackson。 map.ser.StdSerializerProvider._serializeValue（StdSerializerProvider.java:296）
位于org.codehaus.jackson.map.ser.StdSerializerProvider.serializeValue（StdSeria lizerProvider.java:224）
 at org.codehaus.jackson.map.ObjectMapper.writeValue（ObjectMapper.java:925）
 at org.springframework.http.converter.json.MappingJacksonHttpMessageConverter.writeInternal（MappingJacksonHttpMessageConverter。 java：153）
  

有关如何获取更多信息以查看导致此问题的建议？任何人都知道如何解决它？

编辑：我发现getHander（）和其他get *（）方法存在于代理对象上。 GRR！有什么方法可以告诉杰克逊不处理代理上的任何事情，或者我是否可以解决？这很奇怪，因为吐出JSON的方法在某些情况下只会崩溃，而不是所有的时间。尽管如此，这是由于代理对象上的get *（）方法。

旁白：代理是邪恶的。他们扰乱了Jackson，equals（）和其他常规Java编程的其他部分。我试图完全抛弃Hibernate：它不是理想的，但是你可以禁用Jackson的JSON属性自动发现功能，在课堂上使用 @JsonAutoDetect 。这将阻止它试图处理Javassist的东西（和失败）。

这意味着你必须手动注释每个getter（使用 @JsonProperty ），但这不一定是坏事，因为它使事情明确。

Jackson is throwing a weird exception that I don't know how to fix. I'm using Spring, Hibernate and Jackson.

I have already considered that lazy-loading is causing the problem, but I have taken measures to tell Jackson to NOT process various properties as follows:

@JsonIgnoreProperties({ "sentMessages", "receivedMessages", "educationFacility" })
public class Director extends UserAccount implements EducationFacilityUser {
   ....
}

I have done the same thing for all the other UserAccount subclasses as well.

Here's the exception being thrown:

org.codehaus.jackson.map.JsonMappingException: No serializer found for class org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationConfig.Feature.FAIL_ON_EMPTY_BEANS) ) (through reference chain: java.util.ArrayList[46]->jobprep.domain.educationfacility.Director_$$_javassist_2["handler"])
    at org.codehaus.jackson.map.ser.StdSerializerProvider$1.serialize(StdSerializerProvider.java:62)
    at org.codehaus.jackson.map.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:268)
    at org.codehaus.jackson.map.ser.BeanSerializer.serializeFields(BeanSerializer.java:146)
    at org.codehaus.jackson.map.ser.BeanSerializer.serialize(BeanSerializer.java:118)
    at org.codehaus.jackson.map.ser.ContainerSerializers$IndexedListSerializer.serializeContents(ContainerSerializers.java:236)
    at org.codehaus.jackson.map.ser.ContainerSerializers$IndexedListSerializer.serializeContents(ContainerSerializers.java:189)
    at org.codehaus.jackson.map.ser.ContainerSerializers$AsArraySerializer.serialize(ContainerSerializers.java:111)
    at org.codehaus.jackson.map.ser.StdSerializerProvider._serializeValue(StdSerializerProvider.java:296)
    at org.codehaus.jackson.map.ser.StdSerializerProvider.serializeValue(StdSerializerProvider.java:224)
    at org.codehaus.jackson.map.ObjectMapper.writeValue(ObjectMapper.java:925)
    at org.springframework.http.converter.json.MappingJacksonHttpMessageConverter.writeInternal(MappingJacksonHttpMessageConverter.java:153)

Suggestions on how I can get more info to see what's causing this? Anyone know how to fix it?

EDIT: I discovered that getHander() and other get*() methods exist on the proxy object. GRR!! Is there any way I can tell Jackson to not process anything on the proxy, or am I sol? This is really weird because the method that spits out the JSON only crashes under certain circumstances, not all the time. Nonetheless, it's due to the get*() methods on the proxy object.

Aside: Proxies are evil. They disrupt Jackson, equals() and many other parts of regular Java programming. I am tempted to ditch Hibernate altogether :/

解决方案

It's not ideal, but you could disable Jackson's auto-discovery of JSON properties, using @JsonAutoDetect at the class level. This would prevent it from trying to handle the Javassist stuff (and failing).

This means that you then have to annotate each getter manually (with @JsonProperty), but that's not necessarily a bad thing, since it keeps things explicit.

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