5 Powerful Techniques to Mask Sensitive Fields in Spring Boot 3

1. Introduction

In real‑world projects, sensitive fields like personal ID numbers, bank card numbers, detailed addresses, phone numbers, and passwords often appear. If these fields are transmitted or displayed without masking, data leaks can cause financial loss, privacy exposure, or identity theft. Masking replaces or hides parts of the data while keeping it usable for analysis.

2. Practical Cases

The following five techniques implement field‑level masking in Spring Boot 3 (environment: SpringBoot 3.4.2).

2.1 Custom Json Serializer

public class CommonMaskSerializer extends JsonSerializer<String> {
    @Override
    public void serialize(String value, JsonGenerator gen, SerializerProvider serializers) throws IOException {
        if (value == null || value.length() < 6) {
            gen.writeString("***");
            return;
        }
        String masked = MaskUtils.maskString(value);
        gen.writeString(masked);
    }
}

public class User {
    @JsonSerialize(using = CommonMaskSerializer.class)
    private String phone;
    @JsonSerialize(using = CommonMaskSerializer.class)
    private String idNo;
}

Result: