Jackson exclude field from serialization


  • Using Jackson for JSON Serialization and Deserialization
  • Solving the XML Problem with Jackson
  • Flexible immutability with Jackson and Lombok
  • Spring Boot – Customize the Jackson ObjectMapper
  • Jackson Annotations for JSON
  • Dynamically exclude JSON fields with GSON from Object
  • Using Jackson for JSON Serialization and Deserialization

    If you want to override this behavior, you can use the JsonProperty annotation on the fields. It takes a String attribute that specifies the name that should be mapped to the field during serialization. You can also use JsonProperty annotation during deserialization when the property names of the JSON and the field names of the Java object do not match.

    Let us consider an example Java class that uses the JsonProperty annotation. JsonFormat The JsonFormat annotation is used to tell Jackson that the format in which the value for a field is serialized. It specifies the format using the JsonFormat. Shape enum. Let us consider an example Java class that uses the JsonFormat annotation to modify the Date and Time format of an activeDate field. JsonFormat; import com. JsonProperty; import java. JsonUnwrapped The JsonUnwrapped annotation unwraps the values during serialization and deserialization.

    It helps in rendering the values of a composed class as if they belonged to the parent class. Let us consider an example of Java class that uses the JsonUnwrapped annotation. Without the JsonUnwrapped annotation, the serialized Java object would be similar to this. The test code to test the JsonUnwrapped annotation is this. As you can see, the Address object is unwrapped and is displayed as the properties of the parent class UnwrappedDemoBean. JsonView The JsonView annotation is used to include or exclude a property dynamically during serialization and deserialization, and tells the view in which the properties are rendered.

    Let us consider an example Java class that uses the JsonView annotation with Public and Internal views. JsonProperty; import com.

    The output of running the test in IntelliJ is this. When the JSON is generated in the public view, only personId and name fields are serialized omitting the gender field. However, when JSON is generated in the internal view, all the fields are serialized. Without this annotation, you get an error like this. JsonBackReference; import java.

    ArrayList; import java. As you can see, the field marked with JsonManagedReference is the forward reference which will be included during serialization. The field marked with JsonBackReference is the back reference and is usually omitted during serialization.

    This annotation works similar to the JsonManagedReference and JsonBackReference annotations with the difference that JsonIdentityInfo includes the back reference object. JsonIdentityInfo; import com.

    ObjectIdGenerators; import java. As you can see, the output gives the information about the employee with his manager details and information about the employees under the manager. JsonFilter The JsonFilter annotation is used to tell Jackson to use a custom defined filter to serialize the Java object. To define your filter, you need to use the FilterProvider class.

    This provider gets the actual filter instance to use. The filter is then configured by assigning the FilterProvider to ObjectMapper. Let us consider an example of Java class that uses the JsonFilter annotation. As you can see, the custom filter declared as the arguments of the JsonFilter annotation extract only the name and filters out the other properties of the bean during serialization.

    You can download the source code of this post from here.

    Solving the XML Problem with Jackson

    These annotations allow us to control the XML namespace and local name for elements, including the root element, whether a field is rendered in an element or as plain text, whether the content of an element is rendered in a CData wrapper, and whether a collection should use a wrapper element or not.

    JacksonXmlProperty JacksonXmlProperty can be applied to any field in a bean to control the details of the element that is being rendered. This annotation allows us to determine the namespace, the local name, and whether the field is serialized as an Element or an Attribute.

    This can only adjust the Namespace and Local name — since the root element can never be serialized as an attribute. Simply put, this indicates that an element should be rendered as plain text without another element containing it.

    This can be used in conjunction with the JacksonXmlText if desired to produce a CData wrapper without an element tag. This can ensure that a collection either does or does not use a wrapper element, and can control what the wrapper element uses for namespace and local name. This functionality is an additional module that needs to be added in for it to work.

    This cool functionality gives us a lot of flexibility to work with existing XML documents and integrate with these cleanly and easily. Generating XML The XmlMapper is able to serialize an entire Java bean into a document that is currently being produced, allowing Jackson to integrate and construct the document along with other external actors.

    This also gives some ability to support constructs that Jackson cannot handle natively — for example, the XML Prolog. This can be especially useful if we only care to have Java bean representations for data in the middle of a larger object — for example, if we are parsing an Atom wrapper around the data we are interested in.

    In order to do this, the XmlMapper needs to be called to read values from the XMLStreamReader object — the same as if we were reading from any other Reader. Note that, unlike with JSON, the outermost object must be a bean type — it can not be a primitive or wrapper type, an enumeration, or a collection. By default, Jackson will always use a wrapper element for collections, which is also different to how JAXB works.

    Of course, the behavior can be configured, using the JacksonXmlElementWrapper annotation for one field or the setDefaultUseWrapper configuration setting on the XmlMapper globally. Jackson also has no support for working with specific XML Schemas. Note that this can be solved to an extent by using the JAXB annotation support and generating the beans using the standard xjc tool. If we need this level of support then we should instead use a more full-featured XML solution.

    Typically, this has to be handled using two different libraries with entirely separate configurations. Finally, beyond flexibility and ease-of-use, the Jackson team has historically placed a strong emphasis on performance.

    And given that marshalling and unmarshalling of data is a large part of most web applications, choosing the right library to handle all of that work is critical. That, plus a performance monitoring tool such as Retrace will allow you to get the most out of your app.

    Flexible immutability with Jackson and Lombok

    JsonIgnore is required in order to avoid serializing the isAdult method. I can use myInstance.

    Spring Boot – Customize the Jackson ObjectMapper

    Flexibility This satisfies requirements 1 through 3. Furthermore, note that the JsonAnySetter is private. When doing this, make sure that you reuse your ObjectMapper.

    Dependencies The Maven dependencies involved for this setup are as follows: com. The implementation of all these examples and code snippets can be found on my Github repository here. Generating XML The XmlMapper is able to serialize an entire Java bean into a document that is currently being produced, allowing Jackson to integrate and construct the document along with other external actors.

    This also gives some ability to support constructs that Jackson cannot handle natively — for example, the XML Prolog. This can be especially useful if we only care to have Java bean representations for data in the middle of a larger object — for example, if we are parsing an Atom wrapper around the data we are interested in.

    Jackson Annotations for JSON

    In order to do this, the XmlMapper needs to be called to read values from the XMLStreamReader object — the same as if we were reading from any other Reader. Note that, unlike with JSON, the outermost object must be a bean type — it can not be a primitive or wrapper type, an enumeration, or a collection.

    By default, Jackson will always use a wrapper element for collections, which is also different to how JAXB works. Of course, the behavior can be configured, using the JacksonXmlElementWrapper annotation for one field or the setDefaultUseWrapper configuration setting on the XmlMapper globally.

    The Expose annotation is useful in a style of programming where you want to explicitly specify all fields that should get considered for serialization or deserialization. How to use Expose Expose is optional and offers two configuration parameters : serialize — If true, the field marked with this annotation is written out in the JSON while serializing.

    Dynamically exclude JSON fields with GSON from Object

    Creating Gson instance If we created Gson with new Gsonand execute the toJson and fromJson methods then Expose will not have any effect on serialization and deserialization.

    Exclude fields with modifiers 2. Remember that it is not capable of blocking one way transformation.


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