How to Format ZonedDateTime to ISO 8601 in Spring Data JPA JSON Serialization?

Spring Data JPA: Formatting ZonedDateTime in JSON Serialization

Spring Data JPA supports the mapping of Java 8 date and time types to database columns. However, the default JSON serialization format for ZonedDateTime can produce verbose output. This article explores how to format ZonedDateTime to ISO format during JSON serialization.

Problem Statement

Despite using the @DateTimeFormat annotation with iso = DateTimeFormat.ISO.DATE_TIME, the JSON serialization of ZonedDateTime still produces a detailed object. The goal is to format ZonedDateTime to a more concise ISO format.

Solution

The JSON serialization problem is likely caused by Jackson, which handles JSON serialization in Spring Data JPA. To resolve this, Jackson's module for the Java 8 date and time API needs to be added.

Dependency Addition

Add the following dependency to your pom.xml:

<dependency>
    <groupId>com.fasterxml.jackson.datatype</groupId>
    <artifactId>jackson-datatype-jsr310</artifactId>
    <version>2.6.0</version>
</dependency>

Module Registration

After adding the dependency, register the JavaTimeModule with Jackson:

ObjectMapper objectMapper = new ObjectMapper();
objectMapper.registerModule(new JavaTimeModule());

Formatter Customization

The @JsonFormat annotation on the ZonedDateTime getter method can be used to customize the date format during serialization. For example:

@JsonFormat(shape = JsonFormat.Shape.STRING, pattern = "yyyy-MM-dd'T'HH:mm:ss.SSSZ")
public ZonedDateTime getTime() {
    return time;
}

This will format the ZonedDateTime to the ISO format: yyyy-MM-dd'T'HH:mm:ss.SSSZ.

Example

The following example demonstrates the usage of the JavaTimeModule and format customization:

public static void main(String[] args) throws JsonProcessingException {
    ObjectMapper objectMapper = new ObjectMapper();
    objectMapper.registerModule(new JavaTimeModule());
    System.out.println(objectMapper.writeValueAsString(new Entity()));
}

static class Entity {
    ZonedDateTime time = ZonedDateTime.now();

    @JsonFormat(shape = JsonFormat.Shape.STRING, pattern = "yyyy-MM-dd'T'HH:mm:ss.SSSZ")
    public ZonedDateTime getTime() {
        return time;
    }
}

The output of this example would be:

{"time":"2015-07-25T23:09:01.795+0700"}

Conclusion

By adding Jackson's JavaTimeModule and using the @JsonFormat annotation, you can control the JSON serialization format of ZonedDateTime and prevent the transfer of unnecessary data, optimizing the performance and reducing the size of JSON payloads.

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