JsonIdentityReference with alwaysAsId true with null property throws Null Pointer Exception

Question

I have two classes PaymentDetailsDTO and UserDTO. I want to serialize only the id field (a Long) of UserDTO present inside PaymentDetailsDTO. I am using Jackson annotations @JsonIdentityInfo and @JsonIdentityReference(alwaysAsId = true).

The problem is when the id inside UserDTO is null, serialization ends with a null pointer exception (but works when the id is not null).

Not sure if that's how it's supposed to behave (if so, why) or am I missing something.

Instead what I expect is that if the id is null, just write null or don't include the key (depending upon whether the @JsonInclude annotation allows null).

Following is the code in question.

PaymentDetailsDTO

@Data
@Builder
@NoArgsConstructor
@AllArgsConstructor
@JsonInclude(JsonInclude.Include.NON_NULL)
public class PaymentDetailsDTO {

    private Long id;
    @NotNull
    @Builder.Default
    private Long appId = 10151L;

    // Represents user of payment system with information to find it on client
    @JsonProperty("userId")
    @JsonIdentityReference(alwaysAsId = true)
    private UserDTO userDTO;

    // Removed for normalization
    @JsonProperty(access = Access.READ_ONLY)
    private int reqId;

    // @DecimalMin("1.00")
    @NotNull
    private double amountDue;
    
    ...
}

UserDTO

@Data
@Builder(toBuilder = true)
@NoArgsConstructor
@AllArgsConstructor
@JsonIdentityInfo(
    generator = ObjectIdGenerators.PropertyGenerator.class,
    property = "id"
)
public class UserDTO {
    private Long id;
    // userId of the user on specific client
    @NotNull
    private Long clientUserId;
    // clientName like "eYRC", "eYIC", "mooc"
    @NotBlank
    private String clientName;
    @NotBlank
    private String name;
    private String emailId;
   
    ...
}

And this is the exception

com.fasterxml.jackson.databind.JsonMappingException: (was java.lang.NullPointerException) (through reference chain: com.eyantra.payment.features.payment.data.dto.PaymentDetailsDTO["userId"])

    at com.fasterxml.jackson.databind.JsonMappingException.wrapWithPath(JsonMappingException.java:394)
    at com.fasterxml.jackson.databind.JsonMappingException.wrapWithPath(JsonMappingException.java:353)
    at com.fasterxml.jackson.databind.ser.std.StdSerializer.wrapAndThrow(StdSerializer.java:316)
    at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:730)
    at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:166)
    at com.fasterxml.jackson.databind.ser.DefaultSerializerProvider._serialize(DefaultSerializerProvider.java:480)
    at com.fasterxml.jackson.databind.ser.DefaultSerializerProvider.serializeValue(DefaultSerializerProvider.java:319)
    at com.fasterxml.jackson.databind.ObjectMapper._configAndWriteValue(ObjectMapper.java:4094)
    at com.fasterxml.jackson.databind.ObjectMapper.writeValueAsString(ObjectMapper.java:3404)
    at com.eyantra.payment.features.payment.data.dto.PaymentDetailsDTOTest.Serialize_IncludeOnlyUserID_ReturnsJson(PaymentDetailsDTOTest.java:27)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    ...
    at com.intellij.junit5.JUnit5IdeaTestRunner.startRunnerWithArgs(JUnit5IdeaTestRunner.java:69)
    at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:33)
    at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:230)
    at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:58)
Caused by: java.lang.NullPointerException
    at com.fasterxml.jackson.databind.ser.std.NumberSerializers$LongSerializer.serialize(NumberSerializers.java:194)
    at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase._serializeWithObjectId(BeanSerializerBase.java:624)
    at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:159)
    at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:727)
    at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:722)
    ... 57 more



Process finished with exit code 255

JsonIdentityReference with alwaysAsId true with null property throws Null Pointer Exception

0 Answers0