Map snake_case JSON Keys with Jackson @JsonProperty

Bridging Naming Conventions with @JsonProperty

Java fields use camelCase. Many JSON APIs (Stripe, GitHub, Slack, AWS) use snake_case. The Jackson @JsonProperty annotation tells the deserializer which JSON key maps to which Java field.

Example JSON

{
  "user_id": 42,
  "first_name": "Alice",
  "last_name": "Williams",
  "is_active": true
}

Generated Java with @JsonProperty

package com.example.model;

import com.fasterxml.jackson.annotation.JsonProperty;

public class User {
    @JsonProperty("user_id")
    private Integer userId;

    @JsonProperty("first_name")
    private String firstName;

    @JsonProperty("last_name")
    private String lastName;

    @JsonProperty("is_active")
    private Boolean isActive;
    // accessors
}

The generator only emits the annotation when the JSON key actually differs from the camelCase Java field name. A key like email does not get an annotation; user_id does.

Alternative: @JsonNaming

If your entire payload uses snake_case, a single class-level annotation is more concise:

@JsonNaming(PropertyNamingStrategies.SnakeCaseStrategy.class)
public class User {
    private Integer userId;
    private String firstName;
    // ...
}

This applies the strategy to every field, removing the per-field annotations entirely. @JsonProperty overrides @JsonNaming on a case-by-case basis when you need exceptions.

Global Configuration

You can also configure the strategy globally on the ObjectMapper:

ObjectMapper mapper = new ObjectMapper();
mapper.setPropertyNamingStrategy(PropertyNamingStrategies.SNAKE_CASE);

When to Use Each Approach

• Per-field @JsonProperty — when only some keys differ from camelCase, or when keys do not follow a consistent strategy.
• @JsonNaming — when the whole class uses one consistent strategy (snake_case, kebab-case, UPPER_CAMEL_CASE).
• Global ObjectMapper config — when every payload in your application uses the same convention.

Other Useful Jackson Annotations

• @JsonIgnore — exclude a field from serialization
• @JsonInclude(NON_NULL) — drop null fields from output
• @JsonAlias — accept multiple incoming key names
• @JsonFormat — control date and number formatting