Spring MVC 数据格式化

Spring MVC提供了数据格式化机制，自动完成字符串与日期、数字等类型的转换。

日期格式化

@DateTimeFormat注解

@Data
public class UserDTO {

    @DateTimeFormat(pattern = "yyyy-MM-dd")
    private Date birthday;

    @DateTimeFormat(pattern = "yyyy-MM-dd HH:mm:ss")
    private Date createTime;

    @DateTimeFormat(iso = ISO.DATE)    // yyyy-MM-dd
    private LocalDate birthDate;

    @DateTimeFormat(iso = ISO.DATE_TIME)    // yyyy-MM-dd'T'HH:mm:ss
    private LocalDateTime registerTime;
}

ISO格式枚举

数字格式化

@NumberFormat注解

@Data
public class ProductDTO {

    @NumberFormat(style = Style.NUMBER)
    private Integer quantity;

    @NumberFormat(style = Style.CURRENCY, pattern = "#,##0.00")
    private BigDecimal price;

    @NumberFormat(style = Style.PERCENT)
    private Double discount;

    @NumberFormat(pattern = "#,###")
    private Long sales;
}

Style枚举

Controller接收格式化数据

@RestController
@RequestMapping("/api/user")
public class UserController {

    @PostMapping
    public User create(@RequestBody UserDTO dto) {
        // 日期字符串自动转换为Date类型
        return userService.create(dto);
    }

    @GetMapping("/search")
    public List<User> search(
            @RequestParam @DateTimeFormat(pattern = "yyyy-MM-dd") Date startDate,
            @RequestParam @DateTimeFormat(pattern = "yyyy-MM-dd") Date endDate) {
        return userService.search(startDate, endDate);
    }
}

配置全局格式化

@Configuration
public class WebMvcConfig implements WebMvcConfigurer {

    @Override
    public void addFormatters(FormatterRegistry registry) {
        // 添加日期格式化器
        DateTimeFormatterRegistrar registrar = new DateTimeFormatterRegistrar();
        registrar.setDateFormatter(DateTimeFormatter.ofPattern("yyyy-MM-dd"));
        registrar.setTimeFormatter(DateTimeFormatter.ofPattern("HH:mm:ss"));
        registrar.setDateTimeFormatter(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss"));
        registrar.registerFormatters(registry);

        // 添加数字格式化器
        NumberFormatterRegistrar numberRegistrar = new NumberFormatterRegistrar();
        numberRegistrar.registerFormatters(registry);
    }
}

自定义格式化器

Formatter接口

public interface Formatter<T> extends Printer<T>, Parser<T> {

    String print(T object, Locale locale);    // 对象转字符串

    T parse(String text, Locale locale) throws ParseException;    // 字符串转对象
}

自定义日期格式化器

@Component
public class CustomDateFormatter implements Formatter<Date> {

    private static final String PATTERN = "yyyy年MM月dd日";

    @Override
    public String print(Date date, Locale locale) {
        return new SimpleDateFormat(PATTERN).format(date);
    }

    @Override
    public Date parse(String text, Locale locale) throws ParseException {
        return new SimpleDateFormat(PATTERN).parse(text);
    }
}

注册自定义格式化器

@Configuration
public class WebMvcConfig implements WebMvcConfigurer {

    @Autowired
    private CustomDateFormatter customDateFormatter;

    @Override
    public void addFormatters(FormatterRegistry registry) {
        registry.addFormatter(customDateFormatter);
    }
}

自定义枚举格式化器

@Component
public class StatusFormatter implements Formatter<Status> {

    @Override
    public String print(Status status, Locale locale) {
        return status.getCode();
    }

    @Override
    public Status parse(String text, Locale locale) {
        return Status.fromCode(text);
    }
}

public enum Status {
    ACTIVE("active"),
    INACTIVE("inactive");

    private final String code;

    Status(String code) { this.code = code; }

    public String getCode() { return code; }

    public static Status fromCode(String code) {
        for (Status status : values()) {
            if (status.code.equals(code)) {
                return status;
            }
        }
        throw new IllegalArgumentException("Unknown status: " + code);
    }
}

AnnotationFormatterFactory

根据注解创建格式化器：

@Component
public class DateFormatAnnotationFormatterFactory
        implements AnnotationFormatterFactory<DateFormat> {

    @Override
    public Set<Class<?>> getFieldTypes() {
        return Set.of(Date.class, LocalDate.class, LocalDateTime.class);
    }

    @Override
    public Printer<?> getPrinter(DateFormat annotation, Class<?> fieldType) {
        return new DateFormatter(annotation.pattern());
    }

    @Override
    public Parser<?> getParser(DateFormat annotation, Class<?> fieldType) {
        return new DateFormatter(annotation.pattern());
    }
}

// 自定义注解
@Target({ElementType.FIELD, ElementType.PARAMETER})
@Retention(RetentionPolicy.RUNTIME)
public @interface DateFormat {
    String pattern() default "yyyy-MM-dd";
}

响应数据格式化

使用@ResponseBody返回格式化数据

@RestController
public class UserController {

    @GetMapping("/user/{id}")
    public User getUser(@PathVariable Long id) {
        User user = userService.findById(id);
        // 日期字段使用@JsonFormat格式化输出
        return user;
    }
}

@JsonFormat注解

@Data
public class User {

    private Long id;
    private String name;

    @JsonFormat(pattern = "yyyy-MM-dd HH:mm:ss", timezone = "GMT+8")
    private Date createTime;

    @JsonFormat(pattern = "yyyy-MM-dd", timezone = "GMT+8")
    private LocalDate birthday;

    @JsonFormat(shape = JsonFormat.Shape.STRING, pattern = "#,##0.00")
    private BigDecimal balance;
}

ConversionService与Formatter

@Configuration
public class WebMvcConfig implements WebMvcConfigurer {

    @Bean
    public ConversionService conversionService() {
        DefaultFormattingConversionService service = new DefaultFormattingConversionService();

        // 添加默认格式化器
        service.addFormatterForFieldType(Date.class, new DateFormatter("yyyy-MM-dd"));
        service.addFormatterForFieldType(LocalDate.class, new TemporalFormatter());

        return service;
    }
}

前端到后端格式化流程

前端字符串 → FormatterRegistry → Formatter.parse() → Java对象 → Controller

后端到前端格式化流程

Controller返回对象 → @JsonFormat/Formatter.print() → JSON字符串 → 前端

日期格式化配置对比

要点总结

• @DateTimeFormat用于请求参数日期格式化
• @JsonFormat用于响应JSON日期格式化
• @NumberFormat用于数字格式化
• 通过WebMvcConfigurer.addFormatters注册自定义格式化器
• Formatter接口实现print和parse方法
• ISO枚举提供标准日期格式