一、PRE Filter

前置過濾器一般用來區分請求來源、轉換數據格式、debug日志、校驗權限，增加請求裝飾標識等待操作。

有一下幾個重要方法：

（1）filterType 確定過濾器類型

（2）filterOrder 過濾器執行順序??

ServletDetectionFilter：-3

Servlet30WrapperFilter：-2

FormBodyWrapperFilter：-1

DebugFilter：1

PreDecorationFilter：5

（3）shouldFilter 是否調用run方法

（4）run 執行過濾動作

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二、自定義前置過濾器

本文前置過濾器用來裝飾請求，給請求參數添加version字段，請求頭加過濾器類型

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三、實現代碼

@Component @Slf4j public class PreFilter extends ZuulFilter {//按類型對過濾器進行分類。Zuul中的標準類型是"pre"用于預路由篩選，"route"用于路由到原點，"post"用于后路由篩選，"error"用于錯誤處理。//我們還支持靜態響應的"static"類型請參閱StaticResponseFilter。可以通過調用FilterProcessor.runFilters(type)//前置過濾器必須返回pre@Overridepublic String filterType() {return FilterConstants.PRE_TYPE;}//必須為過濾器定義filterOrder。如果優先級對篩選器不重要，則過濾器可能具有相同的過濾器順序//過濾器順序不需要是連續的@Overridepublic int filterOrder() {return FilterConstants.PRE_DECORATION_FILTER_ORDER + 10;}//默認情況下，zuulfilter是靜態的；它們不攜帶狀態。這可以通過將isStaticFilter屬性重寫為false來重寫@Overridepublic boolean isStaticFilter() {return super.isStaticFilter();}//要禁用此篩選器的Archaius屬性的名稱。默認情況下，它是zuul.[classname].[filtertype].disable@Overridepublic String disablePropertyName() {return super.disablePropertyName();}//如果為true，則過濾器已被archaius禁用，不會運行@Overridepublic boolean isFilterDisabled() {return super.isFilterDisabled();}//此方法返回的"true"表示應該調用run方法//如果應該調用run方法，則返回true。false不會調用run方法@Overridepublic boolean shouldFilter() {RequestContext ctx = RequestContext.getCurrentContext();return !ctx.containsKey(FilterConstants.FORWARD_TO_KEY) // a filter has already forwarded&& !ctx.containsKey(FilterConstants.SERVICE_ID_KEY); // a filter has already determined serviceId}//如果shouldFilter方法為true，則將調用此方法。這種方法是ZuulFilter的核心方法//返回一些可以返回的任意工件。當前的實現忽略了它。//如果在執行期間發生錯誤，則引發ZuulException@Overridepublic Object run() throws ZuulException {RequestContext ctx = RequestContext.getCurrentContext();try {HttpServletRequest request = ctx.getRequest();ctx.addZuulRequestHeader("X-Forwarded-Filter", "pre");//header添加String method = request.getMethod();// GET請求方法if("GET".equalsIgnoreCase(method)) {Map<String, List<String>> requestQueryParams = ctx.getRequestQueryParams();if (requestQueryParams == null) {requestQueryParams = new HashMap<>();}requestQueryParams.put("version", Arrays.asList("1.0"));//添加參數ctx.setRequestQueryParams(requestQueryParams);}else if("POST".equalsIgnoreCase(method)) {//post方法String contentType = request.getContentType();if (contentType == null) {return null;}byte[] bodyBytes;MediaType mediaType = MediaType.valueOf(contentType);if(mediaType == null){return null;}if(MediaType.APPLICATION_JSON.includes(mediaType)) {//請求jsonString charset = request.getCharacterEncoding();InputStream in = ctx.getRequest().getInputStream();String body = StreamUtils.copyToString(in, Charset.forName(charset));log.info("method POST body:{}", body);Object obj = JSON.parse(body);if (obj instanceof JSONObject) {JSONObject jsonObject = (JSONObject) obj;jsonObject.put("version", "1.0");//添加參數body = jsonObject.toJSONString();}bodyBytes = body.getBytes(charset);}else if (MediaType.APPLICATION_FORM_URLENCODED.includes(mediaType)|| (request.getAttribute(DispatcherServlet.WEB_APPLICATION_CONTEXT_ATTRIBUTE) != null&& MediaType.MULTIPART_FORM_DATA.includes(mediaType))) {//form請求MultiValueMap<String, Object> builder = RequestContentDataExtractor.extract(request);builder.add("version", "1.0");//添加參數//轉換字節流ByteArrayOutputStream output = new ByteArrayOutputStream();HttpMessageConverter converter = new AllEncompassingFormHttpMessageConverter();HttpOutputMessage httpOutputMessage = new HttpOutputMessage() {private HttpHeaders headers = new HttpHeaders();@Overridepublic HttpHeaders getHeaders() {return headers;}@Overridepublic OutputStream getBody() {return output;}};converter.write(builder, mediaType, httpOutputMessage);bodyBytes = output.toByteArray();}else {return null;}//包裝新請求request = new HttpServletRequestWrapper(request) {@Overridepublic ServletInputStream getInputStream() {return new ServletInputStreamWrapper(bodyBytes);}@Overridepublic int getContentLength() {return bodyBytes.length;}@Overridepublic long getContentLengthLong() {return bodyBytes.length;}};//重寫請求ctx.setRequest(request);}} catch (Exception e) {ctx.setSendZuulResponse(false);e.printStackTrace();throw new ZuulException(e, 500, "pre filter handle exception");}return null;}}

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