无法编写 JSON：找不到类 org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer 的序列化程序答案

【问题标题】：Could not write JSON: No serializer found for class org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer无法编写 JSON：找不到类 org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer 的序列化程序
【发布时间】：2016-03-23 21:33:58
【问题描述】：

当我尝试获取一个用户详细信息时，我在 POSTMAN 客户端中收到以下错误。

<html><head><title>Apache Tomcat/7.0.47 - Error report</title><style><!--H1 {font-family:Tahoma,Arial,sans-serif;color:white;background-color:#525D76;font-size:22px;} H2 {font-family:Tahoma,Arial,sans-serif;color:white;background-color:#525D76;font-size:16px;} H3 {font-family:Tahoma,Arial,sans-serif;color:white;background-color:#525D76;font-size:14px;} BODY {font-family:Tahoma,Arial,sans-serif;color:black;background-color:white;} B {font-family:Tahoma,Arial,sans-serif;color:white;background-color:#525D76;} P {font-family:Tahoma,Arial,sans-serif;background:white;color:black;font-size:12px;}A {color : black;}A.name {color : black;}HR {color : #525D76;}--></style> </head><body><h1>HTTP Status 500 - Could not write JSON: No serializer found for class org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationConfig.SerializationFeature.FAIL_ON_EMPTY_BEANS) ) (through reference chain: com.entity.Person_$$_jvstfa5_0[&quot;handler&quot;]); nested exception is com.fasterxml.jackson.databind.JsonMappingException: No serializer found for class org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationConfig.SerializationFeature.FAIL_ON_EMPTY_BEANS) ) (through reference chain: com.entity.Person_$$_jvstfa5_0[&quot;handler&quot;])</h1><HR size="1" noshade="noshade"><p><b>type</b> Exception report</p><p><b>message</b> <u>Could not write JSON: No serializer found for class org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationConfig.SerializationFeature.FAIL_ON_EMPTY_BEANS) ) (through reference chain: com.entity.Person_$$_jvstfa5_0[&quot;handler&quot;]); nested exception is com.fasterxml.jackson.databind.JsonMappingException: No serializer found for class org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationConfig.SerializationFeature.FAIL_ON_EMPTY_BEANS) ) (through reference chain: com.entity.Person_$$_jvstfa5_0[&quot;handler&quot;])</u></p><p><b>description</b> <u>The server encountered an internal error that prevented it from fulfilling this request.</u></p><p><b>exception</b> <pre>org.springframework.http.converter.HttpMessageNotWritableException: Could not write JSON: No serializer found for class org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationConfig.SerializationFeature.FAIL_ON_EMPTY_BEANS) ) (through reference chain: com.entity.Person_$$_jvstfa5_0[&quot;handler&quot;]); nested exception is com.fasterxml.jackson.databind.JsonMappingException: No serializer found for class org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationConfig.SerializationFeature.FAIL_ON_EMPTY_BEANS) ) (through reference chain: com.entity.Person_$$_jvstfa5_0[&quot;handler&quot;])
    org.springframework.http.converter.json.MappingJackson2HttpMessageConverter.writeInternal(MappingJackson2HttpMessageConverter.java:213)
    org.springframework.http.converter.AbstractHttpMessageConverter.write(AbstractHttpMessageConverter.java:207)
    org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodProcessor.writeWithMessageConverters(AbstractMessageConverterMethodProcessor.java:148)
    org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodProcessor.writeWithMessageConverters(AbstractMessageConverterMethodProcessor.java:90)
    org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor.handleReturnValue(RequestResponseBodyMethodProcessor.java:193)
    org.springframework.web.method.support.HandlerMethodReturnValueHandlerComposite.handleReturnValue(HandlerMethodReturnValueHandlerComposite.java:71)
    org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:122)
    org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:748)
    org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:689)
    org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:83)
    org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:945)
    org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:876)
    org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:931)
    org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:822)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:621)
    org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:807)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
    org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:51)
</pre></p><p><b>root cause</b> <pre>com.fasterxml.jackson.databind.JsonMappingException: No serializer found for class org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationConfig.SerializationFeature.FAIL_ON_EMPTY_BEANS) ) (through reference chain: com.entity.Person_$$_jvstfa5_0[&quot;handler&quot;])
    com.fasterxml.jackson.databind.ser.impl.UnknownSerializer.failForEmpty(UnknownSerializer.java:51)
    com.fasterxml.jackson.databind.ser.impl.UnknownSerializer.serialize(UnknownSerializer.java:25)
    com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:464)
    com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:504)
    com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:117)
    com.fasterxml.jackson.databind.ser.DefaultSerializerProvider.serializeValue(DefaultSerializerProvider.java:108)
    com.fasterxml.jackson.databind.ObjectMapper.writeValue(ObjectMapper.java:1596)
    org.springframework.http.converter.json.MappingJackson2HttpMessageConverter.writeInternal(MappingJackson2HttpMessageConverter.java:210)
    org.springframework.http.converter.AbstractHttpMessageConverter.write(AbstractHttpMessageConverter.java:207)
    org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodProcessor.writeWithMessageConverters(AbstractMessageConverterMethodProcessor.java:148)
    org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodProcessor.writeWithMessageConverters(AbstractMessageConverterMethodProcessor.java:90)
    org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor.handleReturnValue(RequestResponseBodyMethodProcessor.java:193)
    org.springframework.web.method.support.HandlerMethodReturnValueHandlerComposite.handleReturnValue(HandlerMethodReturnValueHandlerComposite.java:71)
    org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:122)
    org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:748)
    org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:689)
    org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:83)
    org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:945)
    org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:876)
    org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:931)
    org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:822)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:621)
    org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:807)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
    org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:51)
</pre></p><p><b>note</b> <u>The full stack trace of the root cause is available in the Apache Tomcat/7.0.47 logs.</u></p><HR size="1" noshade="noshade"><h3>Apache Tomcat/7.0.47</h3></body></html>

单个Id调用一个用户的实现类方法-

@Override
    public Person getPerson(int personId) {
        assignSessionLocalVariable();
        Person person= (Person) session.load(Person.class, personId);
        person.setLast_accessed(new Date());
        try{
                Transaction tx=session.beginTransaction();
                session.update(person);
                tx.commit();
        }catch(Exception e){
            logger.error("#3 Error while updating time in getPerson ####["+e+"]");
        }
        person=null;
        person=(Person) session.get(Person.class, personId);
        logger.info("## Returning the records ##["+person+"]");
        session.close();
        return person;
    }

控制器类-

@RequestMapping(value="/person/all",method = RequestMethod.GET,headers="Accept=application/json")
     public List<Person> getAllPerson(){
         List<Person> persons=personDAO.getAllPerson();
         logger.info("## Returning the persons !!!"+persons);
         logger.info("## Size of list is :["+persons.size()+"]");
         return persons;
     }

我正在正确获取日志并且数据库操作正确，请检查以下内容，但在 Postman 客户端中显示数据时，出现错误。我应该怎么做才能在 PostMan 客户端中获得正确的 json 响应。

日志 -

  17:26:24,532  INFO PersonDAOImpl:64 - ## Returning the records ##[Person [id=2, name=Ravikant, last_accessed=Thu Dec 17 17:26:23 IST 2015]]
  17:26:24,558  INFO PersonController:38 - ## Returning the person with personId...2

【问题讨论】：

留意this
@ankur-singhal 我检查了您的解决方案并将@JsonIgnoreProperties({"hibernateLazyInitializer", "handler"}) 应用于 POJO 类的 GET 方法，但找不到解决方案。我仍然遇到同样的问题。
尝试初始化对象Hibernate.initialize(<your getter method>);
@ankur-singhal 在哪里初始化 POJO 类或实现类？我不明白你想说什么。看看我何时向 PostMan 客户端发送对象列表，然后我没有遇到任何问题。在第一次获得所有用户getAllUsers() 之后，如果我给一个用户打电话getOneUser()，那么结果就很好了。但是，当我第二次调用相同的 api getOneUser() 时，我遇到了问题。

标签： java spring hibernate spring-mvc

【解决方案1】：

我在网上查看并得到了解决方案，我下载了 jar 文件并从下面的链接导入到我的项目中，并在我的项目中创建了一个类 HibernateAwareObjectMapper 并在 xml 中添加了注释配置。然后，它完成了，我现在不会再遇到这样的异常了。

这是一个链接 - https://github.com/FasterXML/jackson-datatype-hibernate

【讨论】：