Master JSON Control in Spring Boot 3: Practical Guide to @JsonProperty, @JsonView & Mix‑ins

1. Introduction

In Spring Boot development, the design of REST API JSON responses directly impacts client experience and data security. By default, Jackson serializes fields based on public getter methods, but many scenarios require finer control such as hiding sensitive fields, renaming fields, forcing null output, or formatting dates and numbers. This article introduces how to use @JsonProperty, @JsonFormat, @JsonView, and Mix‑ins to customize JSON output without modifying original classes.

2. Practical Cases

2.1 Controlling JSON Field Output

Jackson determines the JSON content from class fields and methods, selecting public getters by default. Fields without getters are ignored unless explicitly configured.

public class Customer {
  private String name;
  private String email;
  private Integer age;

  public String getName() { return name; }
  public String getEmail() { return email; }
  public Integer getAge() { return age; }
}

Serializing an instance of this class yields:

{
  "name": "Spring Boot3实战案例200讲",
  "email": "[email protected]",
  "age": 33
}

If a field such as private String address; has no getter, it will not appear in the JSON output.

2.2 Renaming Fields

To expose a field under a different name without changing the source code, use @JsonProperty.

public class Customer {
  // ...
  @JsonProperty("address")
  private String homeAddress;
}

2.3 Outputting Null Fields

Annotate a field with @JsonInclude(JsonInclude.Include.ALWAYS) or configure the ObjectMapper to always include null values.

@JsonInclude(JsonInclude.Include.ALWAYS)
public class Customer { }

ObjectMapper mapper = new ObjectMapper();
mapper.setSerializationInclusion(JsonInclude.Include.ALWAYS);

Spring Boot can also be configured via properties:

spring:
  jackson:
    default-property-inclusion: always

2.4 Formatting Dates and Numbers

Use @JsonFormat to specify date patterns or to serialize numbers as strings.

public class User {
  @JsonFormat(pattern = "yyyy-MM-dd HH:mm:ss", timezone = "GMT+8")
  private LocalDateTime createTime;
}

Resulting JSON: {\n "createTime": "2025-08-10 07:30:30"\n} For numeric fields, applying @JsonFormat(shape = JsonFormat.Shape.STRING) forces string output, avoiding rounding issues in JavaScript.

@JsonFormat(shape = JsonFormat.Shape.STRING)
private BigDecimal price;

2.5 Controlling Fields with @JsonView

Define view interfaces to expose different subsets of fields for public and internal APIs.

public class User {
  @JsonView(Public.class)
  private Long id;
  @JsonView(Public.class)
  private String username;

  @JsonView(Internal.class)
  private String password;

  public interface Public {}
  public interface Internal extends Public {}
}

Apply the view in a controller method:

@GetMapping("/{id}")
@JsonView(User.Public.class)
public User queryUser(@PathVariable Long id) {
  return new User(666L, "Pack_xg", "123123");
}

2.6 Using Mix‑ins

When you cannot modify a third‑party class, create a Mix‑in to add annotations externally.

public abstract class UserMixIn {
  @JsonIgnoreProperties(value = {"password"})
  // rename field
  @JsonProperty("emailAddress")
  abstract String getEmail();

  @JsonFormat(shape = JsonFormat.Shape.STRING, pattern = "yyyy-MM", timezone = "GMT+8")
  abstract Date getBirth();
}

Register the Mix‑in with a customizer:

@Component
public class PackJackson2ObjectMapperBuilderCustomizer implements Jackson2ObjectMapperBuilderCustomizer {
  @Override
  public void customize(Jackson2ObjectMapperBuilder builder) {
    builder.mixIn(User.class, UserMixIn.class);
  }
}

2.7 Controller Example

@GetMapping("/query")
public ResponseEntity<?> query() {
  return ResponseEntity.ok(new User("pack", "123123", new Date(), "[email protected]"));
}

2.8 Result

The endpoint returns JSON according to the configured Mix‑in and view settings.