How to Dynamically Exclude Fields from JSON Serialization in Spring MVC?

Dynamically Excluding Fields from JSON Serialization in Spring MVC

In scenarios where sensitive or irrelevant data needs to be excluded from JSON responses, Spring MVC provides a flexible mechanism to ignore specific fields during the serialization process.

@JsonIgnoreProperties Annotation

The @JsonIgnoreProperties annotation allows you to exclude specific fields from being serialized into JSON. Applied to a POJO, it takes a list of field names as arguments, omitting those fields from the JSON representation. For example, if you want to exclude the createdBy and updatedBy fields from the User object described in the question:

@Entity
@Table(name = "user")
@JsonIgnoreProperties(ignoreUnknown = true, value = {"createdBy", "updatedBy"})
public class User {
    // Class variables and methods
}

With this annotation, the JSON response will only include the fields explicitly specified in the value parameter, namely userId, userName, and emailId.

@JsonIgnore Annotation

Another option is to use the @JsonIgnore annotation on individual fields. This annotation indicates that the field should be ignored during both serialization and deserialization. It is useful when the list of excluded fields is dynamic and may change based on runtime conditions. For example, if you want to exclude the encryptedPwd field dynamically:

@Entity
@Table(name = "user")
@JsonIgnoreProperties(ignoreUnknown = true)
public class User {
    // Other class variables and methods
    
    @JsonIgnore
    private String encryptedPwd;
}

By setting @JsonIgnore on the encryptedPwd field, it will be excluded from the JSON serialization even if it is included in the get method of the POJO.

Github Example

A practical implementation of these techniques can be found in this GitHub repository: https://github.com/spring-projects/spring-framework/tree/main/spring-webmvc/src/test/java/org/springframework/web/servlet/config/annotation/WebMvcAnnotationConfigTests.

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