How to Map Nested JSON Values to Properties Using Jackson Annotations

How can I map a nested value from a JSON response to a property in my Java class using Jackson annotations?

@JsonProperty("brand.name")

Mapping nested JSON values in Java using Jackson annotations can be done effectively by utilizing custom annotations or by creating a simplified model. Although you may want to avoid creating a full class for every nested object, there are efficient solutions to extract the required fields.

public class ProductTest {
    private int productId;
    private String productName;
    private String brandName;

    @JsonProperty("id")
    public int getProductId() {
        return productId;
    }

    public void setProductId(int productId) {
        this.productId = productId;
    }

    @JsonProperty("name")
    public String getProductName() {
        return productName;
    }

    public void setProductName(String productName) {
        this.productName = productName;
    }

    @JsonIgnore
    public String getBrandName() {
        return brandName;
    }

    // Custom method to populate brandName from the brand JSON object
    @JsonProperty
    public void setBrand(JsonNode brandNode) {
        this.brandName = brandNode.get("name").asText();
    }
}

Causes

• Using dot notation in the @JsonProperty annotation doesn't work for nested properties directly.
• Jackson requires an accessible structure to deserialize nested JSON directly into Java objects.

Solutions

• Create a custom getter method for the nested property that fetches the value from the nested JSON object.
• Use the @JsonUnwrapped annotation to unwrap nested properties.

Mistake: Using dot notation in @JsonProperty for nested properties.

Solution: Use a custom method to set the value by extracting it from the nested JSON object.

Mistake: Neglecting to check for null values when accessing nested properties.

Solution: Always validate JSON nodes to avoid NullPointerExceptions.