springboot返回结果统一处理
一般来说异常统一处理都知道，@RestControllerAdvice和@ControllerAdive，然后使用@ExceptionHandler注解处理异常统一处理即可。如今前后端分离情况居多，返回给前端的我们也需要统一包装一下，比方说：
package com.lhf.fvscommon.result; import lombok.Data; import java.io.Serializable; /** * <p></p> * * @author lhf * @since 2020/10/22 10:26 */ @Data public class Result<T> { private int code; private T t; private String mes; public Result(int code, T t, String mes) { this.code = code; this.t = t; this.mes = mes; } public static <T> Result<T> success() { Status success = Status.SUCCESS; return new Result<>(success.code, null, success.mes); } /** * 请求成功默认返回 * * @param t * @param <T> * @return */ public static <T> Result<T> success(T t) { Status success = Status.SUCCESS; return new Result<>(success.code, t, success.mes); } /** * 请求成功自定义状态返回 * * @param t * @param status * @param <T> * @return */ public static <T> Result<T> success(T t, Status status) { return new Result<>(status.code, t, status.mes); } /** * 请求失败默认返回 * * @param <T> * @return */ public static <T> Result<T> failure() { Status failure = Status.FAILURE; return new Result<>(failure.code, null, failure.mes); } /** * 自定义失败返回状态，返回信息 * * @param <T> * @return */ public static <T> Result<T> failure(Status status, String mes) { return new Result<>(status.code, null, mes); } /** * 请求失败自定义状态 * * @param status * @param <T> * @return */ public static <T> Result<T> failure(Status status) { return new Result<>(status.code, null, status.mes); } /** * 构建 * * @param <T> * @return */ public static <T> Builder<T> builder() { return new Builder<>(); } public static class Builder<T> { private int code; private T t; private String mes; public Builder<T> code(int code) { this.code = code; return this; } public Builder<T> t(T t) { this.t = t; return this; } public Builder<T> mes(String mes) { this.mes = mes; return this; } public Result<T> build() { return new Result<>(this.code, this.t, this.mes); } } }
上诉代码就是一个基本的返回统一处理的类，相比大家都不陌生，不过恶心的就是每次返回都需要手动包装啊，这个就有点恶心了啊!能不能简单点？
期间我想过aop，但是aop环绕增强返回的一定是实际返回的一个子类，于是要么我们使用一个公共类，Result继承这个公共类，并且所有的返回前端数据对象都继承他，好像也不是很好。而且还有一个潜在的问题就是万一返回的是个String拿不完犊子？要么，实际返回就是一个Object，那这样的话代码可读性就比较差了(别人读你的代码的时候并不知道你返回的是什么啊!!!),于是有改变策略使用了一下过滤器，但是我发现也不是很好(不太好处理)。最后我吧目标放到Springboot自带的Json处理上，因为他的处理和我们要的结果好像是类似！
然后我就debug，跟了好几次终于确定了位置:看下边的代码(代码有点长哈)
protected <T> void writeWithMessageConverters(@Nullable T value, MethodParameter returnType, ServletServerHttpRequest inputMessage, ServletServerHttpResponse outputMessage) throws IOException, HttpMediaTypeNotAcceptableException, HttpMessageNotWritableException { Object body; Class<?> valueType; Type targetType; if (value instanceof CharSequence) { body = value.toString(); valueType = String.class; targetType = String.class; } else { body = value; valueType = getReturnValueType(body, returnType); targetType = GenericTypeResolver.resolveType(getGenericType(returnType), returnType.getContainingClass()); } if (isResourceType(value, returnType)) { outputMessage.getHeaders().set(HttpHeaders.ACCEPT_RANGES, "bytes"); if (value != null && inputMessage.getHeaders().getFirst(HttpHeaders.RANGE) != null && outputMessage.getServletResponse().getStatus() == 200) { Resource resource = (Resource) value; try { List<HttpRange> httpRanges = inputMessage.getHeaders().getRange(); outputMessage.getServletResponse().setStatus(HttpStatus.PARTIAL_CONTENT.value()); body = HttpRange.toResourceRegions(httpRanges, resource); valueType = body.getClass(); targetType = RESOURCE_REGION_LIST_TYPE; } catch (IllegalArgumentException ex) { outputMessage.getHeaders().set(HttpHeaders.CONTENT_RANGE, "bytes */" + resource.contentLength()); outputMessage.getServletResponse().setStatus(HttpStatus.REQUESTED_RANGE_NOT_SATISFIABLE.value()); } } } MediaType selectedMediaType = null; MediaType contentType = outputMessage.getHeaders().getContentType(); boolean isContentTypePreset = contentType != null && contentType.isConcrete(); if (isContentTypePreset) { if (logger.isDebugEnabled()) { logger.debug("Found 'Content-Type:" + contentType + "' in response"); } selectedMediaType = contentType; } else { HttpServletRequest request = inputMessage.getServletRequest(); List<MediaType> acceptableTypes = getAcceptableMediaTypes(request); List<MediaType> producibleTypes = getProducibleMediaTypes(request, valueType, targetType); if (body != null && producibleTypes.isEmpty()) { throw new HttpMessageNotWritableException( "No converter found for return value of type: " + valueType); } List<MediaType> mediaTypesToUse = new ArrayList<>(); for (MediaType requestedType : acceptableTypes) { for (MediaType producibleType : producibleTypes) { if (requestedType.isCompatibleWith(producibleType)) { mediaTypesToUse.add(getMostSpecificMediaType(requestedType, producibleType)); } } } if (mediaTypesToUse.isEmpty()) { if (body != null) { throw new HttpMediaTypeNotAcceptableException(producibleTypes); } if (logger.isDebugEnabled()) { logger.debug("No match for " + acceptableTypes + ", supported: " + producibleTypes); } return; } MediaType.sortBySpecificityAndQuality(mediaTypesToUse); for (MediaType mediaType : mediaTypesToUse) { if (mediaType.isConcrete()) { selectedMediaType = mediaType; break; } else if (mediaType.isPresentIn(ALL_APPLICATION_MEDIA_TYPES)) { selectedMediaType = MediaType.APPLICATION_OCTET_STREAM; break; } } if (logger.isDebugEnabled()) { logger.debug("Using '" + selectedMediaType + "', given " + acceptableTypes + " and supported " + producibleTypes); } } if (selectedMediaType != null) { selectedMediaType = selectedMediaType.removeQualityValue(); for (HttpMessageConverter<?> converter : this.messageConverters) { GenericHttpMessageConverter genericConverter = (converter instanceof GenericHttpMessageConverter ? (GenericHttpMessageConverter<?>) converter : null); if (genericConverter != null ? ((GenericHttpMessageConverter) converter).canWrite(targetType, valueType, selectedMediaType) : converter.canWrite(valueType, selectedMediaType)) { body = getAdvice().beforeBodyWrite(body, returnType, selectedMediaType, (Class<? extends HttpMessageConverter<?>>) converter.getClass(), inputMessage, outputMessage); if (body != null) { Object theBody = body; LogFormatUtils.traceDebug(logger, traceOn -> "Writing [" + LogFormatUtils.formatValue(theBody, !traceOn) + "]"); addContentDispositionHeader(inputMessage, outputMessage); if (genericConverter != null) { genericConverter.write(body, targetType, selectedMediaType, outputMessage); } else { ((HttpMessageConverter) converter).write(body, selectedMediaType, outputMessage); } } else { if (logger.isDebugEnabled()) { logger.debug("Nothing to write: null body"); } } return; } } } if (body != null) { Set<MediaType> producibleMediaTypes = (Set<MediaType>) inputMessage.getServletRequest() .getAttribute(HandlerMapping.PRODUCIBLE_MEDIA_TYPES_ATTRIBUTE); if (isContentTypePreset || !CollectionUtils.isEmpty(producibleMediaTypes)) { throw new HttpMessageNotWritableException( "No converter for [" + valueType + "] with preset Content-Type '" + contentType + "'"); } throw new HttpMediaTypeNotAcceptableException(this.allSupportedMediaTypes); } }
重点我们看第二个红色的部分：getAdvice()返回的是RequestResponseBodyAdviceChain，呦吼看着名字应该是责任链模式了。当然这不是重点，偶尔皮一下，就不那么无聊了。那么重点是这个类了，
从图片上不难看出，这个玩意儿就是处理返回的呀。我们再来看看ResponseBodyAdvice，毕竟我们重点关注的也应该是这个！！！
他就两个方法supports和beforeBodyWrite，supports：此组件是否支持给定的控制器方法返回类型和所选的{@code HttpMessageConverter}类型，但是spring源码并没有给出这个方法的实现而是直接抛出一个异常（当然一定是有处理的，往后看啦）
就很憨憨呀，来看下一个beforeBodyWrite：从方法名字不难发现，响应体写入之前的操作。
可以看到这个返回处理的类是数组，也就是说我能不能继承一个，重写一个beforeBodyWrite呢?
以上变这段代码看来，可以看到一个ControllerAdviceBean，从名字来看，不难发现应该是一个@ControllerAdvice标记的Bean对象没错了。availableAdvice变量是什么，追踪源码发现就是ResponseBodyAdvice集合，最终我得出的结论就是我们自定义的ResponseBodyAdvice类将是一个@ControllerAdvice标记的类。现在来试一下吧!!!
1 package com.lhf.fvscore.result.advice; 2 3 import com.fasterxml.jackson.core.JsonProcessingException; 4 import com.fasterxml.jackson.databind.ObjectMapper; 5 import com.lhf.fvscommon.result.Result; 6 import com.lhf.fvscore.annotation.ResultBody; 7 import org.springframework.core.MethodParameter; 8 import org.springframework.http.MediaType; 9 import org.springframework.http.server.ServerHttpRequest; 10 import org.springframework.http.server.ServerHttpResponse; 11 import org.springframework.web.bind.annotation.*; 12 import org.springframework.web.servlet.mvc.method.annotation.ResponseBodyAdvice; 13 14 import java.lang.reflect.AnnotatedElement; 15 import java.util.Arrays; 16 17 /** 18 * <p> 19 * 20 * </p> 21 * 22 * @author lhf 23 * @since 2020/11/6 14:30 24 */ 25 @ControllerAdvice(annotations = {ResultBody.class}) 26 public class ResultAdvise implements ResponseBodyAdvice<Object> { 27 28 private final ThreadLocal<ObjectMapper> threadLocal = ThreadLocal.withInitial(ObjectMapper::new); 29 30 private static final Class[] annos = { 31 RequestMapping.class, 32 GetMapping.class, 33 PostMapping.class, 34 DeleteMapping.class, 35 PutMapping.class, 36 PatchMapping.class 37 }; 38 39 @Override 40 public boolean supports(MethodParameter methodParameter, Class aClass) { 41 return this.validateMethod(methodParameter); 42 } 43 44 @Override 45 public Object beforeBodyWrite(Object body, MethodParameter methodParameter, MediaType mediaType, Class aClass, ServerHttpRequest request, ServerHttpResponse response) { 46 47 Object out; 48 ObjectMapper mapper = threadLocal.get(); 49 response.getHeaders().setContentType(MediaType.APPLICATION_JSON); 50 if (body instanceof Result) { 51 out = body; 52 } else if (body instanceof String) { 53 Result<Object> result = Result.success(body); 54 try { 55 out = mapper.writeValueAsString(result); 56 } catch (JsonProcessingException e) { 57 out = Result.failure(); 58 } 59 } else { 60 out = Result.success(body); 61 } 62 return out; 63 64 } 65 66 private boolean validateMethod(MethodParameter methodParameter) { 67 AnnotatedElement element = methodParameter.getAnnotatedElement(); 68 return Arrays.stream(annos).anyMatch(anno -> anno.isAnnotation() && element.isAnnotationPresent(anno)); 69 } 70 71 }
还记得上边有翻译或supports方法的注释吗?此组件是否支持给定的控制器方法返回类型和所选的{@code HttpMessageConverter}类型,但是我们在这里并不关心后半部分，是不是HttpMessageConverter类型在封装json的时候框架本身回去验证（AbstractMappingJacksonResponseBodyAdvice.java）我们所关心的应该是，这个方法是不是@RequestMapping标记的，所以我只验证了这一点。
当然，我这里用的自定义注解，没有什么特殊的需求可以直接拦截@RestController即可
/** * <p></p> * * @author lhf * @since 2020/11/5 8:42 */ @Documented @Target({ElementType.METHOD, ElementType.TYPE}) @Retention(RetentionPolicy.RUNTIME) public @interface ResultBody { }
接下来就是测试了:
完美(当然期间遇到很多坑，差点就死了)
欢迎大佬吐槽
