杰克逊系列化/树形结构的反序列化

问题描述：

@XmlAccessorType(XmlAccessType.FIELD) 
@XmlType(name = "Folder", propOrder = { 
    "id", 
    "parent" 
}) 
@XmlSeeAlso({ 
    FolderTree.class 
}) 
public class Folder 
{  
    protected int id; 
    protected int parent; 

    getters, setters... 
}

和

@XmlAccessorType(XmlAccessType.FIELD) 
@XmlType(name = "FolderTree", propOrder = { 
    "subFolders" 
}) 
@XmlRootElement(name = "folderTree") 
public class FolderTree extends Folder 
{ 
    @XmlElement(name = "subFolder", type = Folder.class) 
    protected List<Folder> subFolders; 

    getter... 
}

和包装：

@XmlAccessorType(XmlAccessType.FIELD) 
@XmlType(name = "Folders", propOrder = { 
    "folders" 
}) 
@XmlRootElement(name = "folders") 
public class Folders 
{ 
    @XmlElement(name = "folder", type = Folder.class) 
    protected List<Folder> folders; 

    getter... 
}

我需要序列化和反序列化他们在XML和JSON中。 XML工作正常，但在JSON以下结构串行化：

{ 
    "folder": [ 
     { 
      "subFolder": [ 
       { 
        "subFolder": [], 
        "id": 2, 
        "parent": 1 

       }, 
       { 
        "subFolder": [], 
        "id": 3, 
        "parent": 1 
       } 
      ], 
      "id": 1, 
      "parent": null    
     } 
    ] 
}

解串器不能识别该子文件夹对象（“子文件夹”：[]）内的第二场的子文件夹。有没有办法让它只在父文件夹中包含子文件夹字段？或者可以做些什么来使杰克逊反序列化这个对象？

我无法更改POJO类，因为它们是由jaxb创建的，并且所有工作都可以正确使用XML。

答

解决方案。

为了在没有孩子的情况下摆脱空的subFiolder数组，我禁用了序列化功能中的WRITE_EMPTY_JSON_ARRAYS。我使用Spring和bean看起来是这样的：

<bean id="objectMapper" class="org.springframework.http.converter.json.Jackson2ObjectMapperFactoryBean"> 
    <property name="annotationIntrospector" ref="jaxbAnnotationIntrospector" /> 
    <property name="featuresToDisable"> 
     <list> 
      <value type="com.fasterxml.jackson.databind.SerializationFeature">WRITE_EMPTY_JSON_ARRAYS</value> 
     </list> 
    </property> 
</bean>

反序列化，因为我无法修改POJO类，我添加了一个混入了文件夹类：

@JsonTypeInfo( 
     use = JsonTypeInfo.Id.NAME, 
     include = JsonTypeInfo.As.PROPERTY, 
     property = "folder", 
     defaultImpl = FolderTree.class) 
public class FolderMixin { 

}

最后，我伸出ObjectMapper设置MixInAnnotations：

public class CustomObjectMapper extends ObjectMapper 
{ 
    public CustomObjectMapper() 
    { 
     super(); 
     customize(); 
    } 

    protected void customize() 
    { 
     registerModule(new SimpleModule() { 
      private static final long serialVersionUID = 1L; 

      public void setupModule(SetupContext context) { 
       super.setupModule(context); 
       context.setMixInAnnotations(Folder.class, FolderMixin.class); 
      }   
     }); 
    } 
}

我增加了对反序列化都AnnotationIntrospectors：

<bean id="customObjectMapper" class="path.to.my.CustomObjectMapper"> 
    <property name="annotationIntrospector" ref="introspectors" /> 
</bean> 

<!-- introspectors --> 
<bean id="xmlAnnotation" class="com.fasterxml.jackson.module.jaxb.JaxbAnnotationIntrospector"> 
    <constructor-arg value="#{customObjectMapper.getTypeFactory()}" /> 
</bean> 

<bean id="jsonAnnotation" class="com.fasterxml.jackson.databind.introspect.JacksonAnnotationIntrospector" /> 

<bean id="introspectors" class="com.fasterxml.jackson.databind.introspect.AnnotationIntrospectorPair"> 
    <constructor-arg ref="xmlAnnotation" /> 
    <constructor-arg ref="jsonAnnotation" /> 
</bean> 
<!-- end of introspectors --> 

<bean id="jsonConverter" class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter"> 
    <property name="objectMapper" ref="customObjectMapper"/> 
</bean>

我使用杰克逊2.4.0。

杰克逊系列化/树形结构的反序列化

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