深入理解 ResponseBodyAdvice 及其应用

ResponseBodyAdvice 是 Spring MVC 提供的一个强大接口，允许你在响应体被写入 HTTP 响应之前对其进行全局处理。

下面我将全面介绍它的工作原理、使用场景和最佳实践。

基本概念

接口定义

public interface ResponseBodyAdvice<T> {boolean supports(MethodParameter returnType, Class<? extends HttpMessageConverter<?>> converterType);@NullableT beforeBodyWrite(@Nullable T body, MethodParameter returnType, MediaType selectedContentType, Class<? extends HttpMessageConverter<?>> selectedConverterType,ServerHttpRequest request, ServerHttpResponse response);
}

核心方法

1. supports()

   • 决定是否对该方法的返回值应用 advice

   • 参数：

     • returnType: 控制器方法的返回类型信息

     • converterType: 将用于序列化响应体的消息转换器类型

2. beforeBodyWrite()

   • 在消息转换器写入响应体之前对其进行处理

   • 参数：

     • body: 控制器返回的原始响应体

     • 其他参数与 supports() 相同

     • request/response: 当前请求和响应对象

典型应用场景

1. 统一响应封装

最常见的用途是将所有控制器的返回值包装成统一格式：

@RestControllerAdvice
public class UnifiedResponseAdvice implements ResponseBodyAdvice<Object> {@Overridepublic boolean supports(MethodParameter returnType, Class<? extends HttpMessageConverter<?>> converterType) {return true;}@Overridepublic Object beforeBodyWrite(Object body, MethodParameter returnType, MediaType selectedContentType,Class<? extends HttpMessageConverter<?>> selectedConverterType,ServerHttpRequest request, ServerHttpResponse response) {if (body instanceof ApiResponse) {return body;}return ApiResponse.success(body);}
}

2. 响应数据脱敏

对敏感数据进行自动处理：

@Override
public Object beforeBodyWrite(Object body, MethodParameter returnType, MediaType selectedContentType,Class<? extends HttpMessageConverter<?>> selectedConverterType,ServerHttpRequest request, ServerHttpResponse response) {if (body instanceof UserInfo) {UserInfo user = (UserInfo) body;user.setIdCard(desensitize(user.getIdCard()));}return body;
}

3. 响应数据缓存

缓存特定响应：

@Override
public Object beforeBodyWrite(Object body, MethodParameter returnType, MediaType selectedContentType,Class<? extends HttpMessageConverter<?>> selectedConverterType,ServerHttpRequest request, ServerHttpResponse response) {if (request.getURI().getPath().contains("/api/cacheable")) {cacheManager.put(generateCacheKey(request), body);}return body;
}

高级用法与最佳实践

1. 精确控制应用范围

通过 supports() 方法精确控制哪些方法需要处理：

@Override
public boolean supports(MethodParameter returnType, Class<? extends HttpMessageConverter<?>> converterType) {// 只处理标注了@ResponseWrap注解的方法return returnType.hasMethodAnnotation(ResponseWrap.class);// 或者排除特定包下的控制器// return !returnType.getDeclaringClass().getPackage().getName().startsWith("org.springdoc");
}

2. 处理特殊情况

处理String类型返回值

@Override
public Object beforeBodyWrite(Object body, MethodParameter returnType, MediaType selectedContentType,Class<? extends HttpMessageConverter<?>> selectedConverterType,ServerHttpRequest request, ServerHttpResponse response) {if (body instanceof String) {response.getHeaders().setContentType(MediaType.APPLICATION_JSON);return objectMapper.writeValueAsString(ApiResponse.success(body));}// 其他处理...
}

处理文件下载等非JSON响应

@Override
public boolean supports(MethodParameter returnType, Class<? extends HttpMessageConverter<?>> converterType) {// 排除文件下载等场景return !ResourceHttpMessageConverter.class.isAssignableFrom(converterType);
}

3. 性能优化

@RestControllerAdvice
public class CustomResponseAdvice implements ResponseBodyAdvice<Object> {// 重用ObjectMapper实例private static final ObjectMapper objectMapper = new ObjectMapper();// 预定义的成功响应private static final ApiResponse<?> EMPTY_SUCCESS = ApiResponse.success(null);@Overridepublic Object beforeBodyWrite(Object body, MethodParameter returnType, MediaType selectedContentType,Class<? extends HttpMessageConverter<?>> selectedConverterType,ServerHttpRequest request, ServerHttpResponse response) {if (body == null) {return EMPTY_SUCCESS;}// 其他处理...}
}

常见问题解决方案

1. 与Swagger的兼容性问题

@Override
public boolean supports(MethodParameter returnType, Class<? extends HttpMessageConverter<?>> converterType) {// 排除Swagger相关的控制器return !returnType.getDeclaringClass().getPackage().getName().startsWith("springfox.documentation");
}

2. 循环引用问题

当包装的对象存在循环引用时，需要在ObjectMapper中配置：

objectMapper.configure(SerializationFeature.FAIL_ON_EMPTY_BEANS, false);
objectMapper.configure(SerializationFeature.FAIL_ON_SELF_REFERENCES, false);

3. 异常处理

虽然ResponseBodyAdvice不处理异常，但可以与@ExceptionHandler配合使用：

@ExceptionHandler(Exception.class)
public ApiResponse<?> handleException(Exception e) {return ApiResponse.failure(e.getMessage());
}

完整示例

@RestControllerAdvice
public class GlobalResponseAdvice implements ResponseBodyAdvice<Object> {private final ObjectMapper objectMapper;public GlobalResponseAdvice(ObjectMapper objectMapper) {this.objectMapper = objectMapper;}@Overridepublic boolean supports(MethodParameter returnType, Class<? extends HttpMessageConverter<?>> converterType) {// 排除Swagger和Actuator端点return !(returnType.getDeclaringClass().getName().contains("springfox") || returnType.getDeclaringClass().getName().contains("org.springframework.boot.actuate"));}@Overridepublic Object beforeBodyWrite(Object body, MethodParameter returnType, MediaType selectedContentType,Class<? extends HttpMessageConverter<?>> selectedConverterType,ServerHttpRequest request, ServerHttpResponse response) {// 非JSON响应不处理if (!selectedContentType.includes(MediaType.APPLICATION_JSON)) {return body;}// 已经是包装类型不处理if (body instanceof ApiResponse) {return body;}// 处理String类型返回值if (body instanceof String) {try {response.getHeaders().setContentType(MediaType.APPLICATION_JSON);return objectMapper.writeValueAsString(ApiResponse.success(body));} catch (JsonProcessingException e) {throw new RuntimeException("JSON序列化失败", e);}}// 空值处理if (body == null) {return ApiResponse.success();}// 默认包装return ApiResponse.success(body);}@Data@NoArgsConstructor@AllArgsConstructorpublic static class ApiResponse<T> {private int code;private String message;private T data;private long timestamp = System.currentTimeMillis();public static <T> ApiResponse<T> success() {return new ApiResponse<>(200, "success", null);}public static <T> ApiResponse<T> success(T data) {return new ApiResponse<>(200, "success", data);}}
}

通过合理使用ResponseBodyAdvice，你可以实现响应处理的集中管理，使代码更加整洁和一致。