Q1. How does Spring handle JSON serialization/deserialization?
Spring uses HttpMessageConverter implementations. The MappingJackson2HttpMessageConverter (provided by Jackson) automatically converts Java objects to JSON and vice versa when @ResponseBody or @RequestBody is used. Jackson is included by default in Spring Boot.
Q2. How can you customize JSON serialization with Jackson?
You can use Jackson annotations like @JsonIgnore, @JsonProperty, @JsonFormat, @JsonInclude. For global configuration, you can customize ObjectMapper bean. In Spring Boot, properties like spring.jackson.* can be set.
Q3. What is @JsonIgnore used for?
@JsonIgnore is used to mark a property to be excluded from JSON serialization and deserialization. Useful for hiding sensitive data like passwords or avoiding circular references.
Q4. How do you handle date formatting in JSON?
Use @JsonFormat annotation:
@JsonFormat(shape = JsonFormat.Shape.STRING, pattern = "yyyy-MM-dd HH:mm:ss")
private Date createdDate;
Q5. What is the difference between @JsonIgnore and @JsonIgnoreProperties?
@JsonIgnore is used on fields, getters, or setters to ignore a single property. @JsonIgnoreProperties is used at class level to ignore multiple properties, e.g., @JsonIgnoreProperties({"id", "version"}). It can also be used to ignore unknown properties during deserialization.