Generating LocalTime From OpenAPI Specification Using Openapi-generator

When building APIs with OpenAPI, managing date and time formats efficiently is crucial. If you need to generate Java models with LocalTime fields instead of the default OffsetDateTime for date-time values, this guide is for you. In this post, you’ll learn how to customize your OpenAPI generation process with openapi-generator to create models that use Java’s LocalTime from the java.time package.

Why Use LocalTime?

LocalTime is ideal for representing a time-of-day without any time-zone information. It’s particularly useful for applications that require scheduling or logging times that are independent of geographic location. By using openapi-generator with the right configurations, you can ensure that your generated Java classes are clean, type-safe, and align with your project’s requirements.

OpenAPI Specification & Date Formats

OpenAPI supports several built-in formats for date and date-time strings. However, it does not natively support a pure time format (e.g., “HH:mm:ss”). Typically, using the date-time format produces a Java type such as OffsetDateTime when using the default configurations. To generate a LocalTime field, you need to leverage the generator’s customization options.

Customizing openapi-generator for LocalTime

The solution is simple. You can instruct openapi-generator to map a custom format (for example, time) to LocalTime by using type mappings and import mappings. Here’s how you can do it:

Command Line Example

Run the openapi-generator-cli with the following parameters:

openapi-generator-cli generate -g java \
  --type-mappings time=LocalTime \
  --import-mappings LocalTime=java.time.LocalTime

This command tells the generator that any schema field defined with type: string and format: time should be generated as a LocalTime field in Java. The --import-mappings option ensures that the necessary import (java.time.LocalTime) is added to the generated class.

Example OpenAPI Schema

Consider the following OpenAPI schema snippet for a Visit object:

Visit:
  type: object
  properties:
    visitor:
      type: string
    timeOfVisit:
      type: string
      format: time

With the type mappings in place, the generated Java class will look similar to this:

public class Visit {
    private String visitor;
    private LocalTime timeOfVisit;

    // Getters and setters
}

Using Maven Plugin Configuration

If you’re using Maven, you can configure the plugin directly in your pom.xml file to apply these settings automatically:

<configuration>
  <typeMappings>
    <typeMapping>time=LocalTime</typeMapping>
  </typeMappings>
  <importMappings>
    <importMapping>LocalTime=java.time.LocalTime</importMapping>
  </importMappings>
</configuration>

This configuration integrates seamlessly into your build process, ensuring that every generation of your Java models adheres to your custom date and time type requirements.

Keywords and Best Practices

OpenAPI LocalTime generation
openapi-generator LocalTime mapping
Java LocalTime OpenAPI customization
OpenAPI specification time format
OpenAPI generator type mappings

These keywords can help you quickly find relevant discussions and documentation on implementing custom date and time formats with openapi-generator.

Conclusion

Generating LocalTime fields from an OpenAPI specification is straightforward with the right configuration. By leveraging type mappings and import mappings in openapi-generator, you can customize your Java model classes to meet your application’s specific needs. This approach not only improves type safety but also aligns your generated code with modern Java best practices.

Feel free to share your experiences or ask questions in the comments below if you have any issues implementing this solution.

Meta Description: Learn how to generate LocalTime fields from your OpenAPI specification using openapi-generator. This guide covers command line and Maven configurations for Java projects.

Generating LocalTime from OpenAPI Specification Using openapi-generator