SpringCloud Finchley Gateway 缓存请求Body和Form表单的实现

在接入spring-cloud-gateway时，可能有需求进行缓存json-body数据或者form-urlencoded数据的情况。

由于spring-cloud-gateway是以webflux为基础的响应式架构设计，所以在原有zuul基础上迁移过来的过程中，传统的编程思路，并不适合于reactor stream的开发。

网络上有许多缓存案例，但是在测试过程中出现各种bug问题，在缓存body时，需要考虑整体的响应式操作，才能更合理的缓存数据

下面提供缓存json-body数据或者form-urlencoded数据的具体实现方案，该方案经测试，满足各方面需求，以及避免了网络上其他缓存方案所出现的问题

定义一个gatewaycontext类，用于存储请求中缓存的数据

import lombok.getter;
import lombok.setter;
import lombok.tostring;
import org.springframework.util.linkedmultivaluemap;
import org.springframework.util.multivaluemap;

@getter
@setter
@tostring
public class gatewaycontext {

  public static final string cache_gateway_context = "cachegatewaycontext";

  /**
   * cache json body
   */
  private string cachebody;
  /**
   * cache formdata
   */
  private multivaluemap<string, string> formdata;
  /**
   * cache reqeust path
   */
  private string path;
}

实现globalfilter和ordered接口用于缓存请求数据

1 . 该示例只支持缓存下面3种mediatype

• application_json--json数据
• application_json_utf8--json数据
• application_form_urlencoded--formdata表单数据

2 . 经验总结:

• 在缓存body时,不能够在filter内部直接进行缓存，需要按照响应式的处理方式，在异步操作路途上进行缓存body，由于body只能读取一次，所以要读取完成后要重新封装新的request和exchange才能保证请求正常传递到下游
• 在缓存formdata时，formdata也只能读取一次，所以在读取完毕后，需要重新封装request和exchange,这里要注意，如果对formdata内容进行了修改，则必须重新定义header中的content-length已保证传输数据的大小一致

import com.choice.cloud.architect.usergate.option.filterorderenum;
import com.choice.cloud.architect.usergate.support.gatewaycontext;
import io.netty.buffer.bytebufallocator;
import lombok.extern.slf4j.slf4j;
import org.springframework.cloud.gateway.filter.gatewayfilterchain;
import org.springframework.cloud.gateway.filter.globalfilter;
import org.springframework.core.ordered;
import org.springframework.core.io.bytearrayresource;
import org.springframework.core.io.buffer.databuffer;
import org.springframework.core.io.buffer.databufferutils;
import org.springframework.core.io.buffer.nettydatabufferfactory;
import org.springframework.http.httpheaders;
import org.springframework.http.mediatype;
import org.springframework.http.codec.httpmessagereader;
import org.springframework.http.server.reactive.serverhttprequest;
import org.springframework.http.server.reactive.serverhttprequestdecorator;
import org.springframework.util.multivaluemap;
import org.springframework.web.reactive.function.server.handlerstrategies;
import org.springframework.web.reactive.function.server.serverrequest;
import org.springframework.web.server.serverwebexchange;
import reactor.core.publisher.flux;
import reactor.core.publisher.mono;

import java.io.unsupportedencodingexception;
import java.net.urlencoder;
import java.nio.charset.charset;
import java.nio.charset.standardcharsets;
import java.util.list;
import java.util.map;

@slf4j
public class gatewaycontextfilter implements globalfilter, ordered {

  /**
   * default httpmessagereader
   */
  private static final list<httpmessagereader<?>> messagereaders = handlerstrategies.withdefaults().messagereaders();

  @override
  public mono<void> filter(serverwebexchange exchange, gatewayfilterchain chain) {
    /**
     * save request path and serviceid into gateway context
     */
    serverhttprequest request = exchange.getrequest();
    string path = request.getpath().pathwithinapplication().value();
    gatewaycontext gatewaycontext = new gatewaycontext();
    gatewaycontext.getallrequestdata().addall(request.getqueryparams());
    gatewaycontext.setpath(path);
    /**
     * save gateway context into exchange
     */
    exchange.getattributes().put(gatewaycontext.cache_gateway_context,gatewaycontext);
    httpheaders headers = request.getheaders();
    mediatype contenttype = headers.getcontenttype();
    long contentlength = headers.getcontentlength();
    if(contentlength>0){
      if(mediatype.application_json.equals(contenttype) || mediatype.application_json_utf8.equals(contenttype)){
        return readbody(exchange, chain,gatewaycontext);
      }
      if(mediatype.application_form_urlencoded.equals(contenttype)){
        return readformdata(exchange, chain,gatewaycontext);
      }
    }
    log.debug("[gatewaycontext]contenttype:{},gateway context is set with {}",contenttype, gatewaycontext);
    return chain.filter(exchange);

  }


  @override
  public int getorder() {
    return integer.min_value;
  }

  /**
   * readformdata
   * @param exchange
   * @param chain
   * @return
   */
  private mono<void> readformdata(serverwebexchange exchange,gatewayfilterchain chain,gatewaycontext gatewaycontext){
    httpheaders headers = exchange.getrequest().getheaders();
    return exchange.getformdata()
        .doonnext(multivaluemap -> {
          gatewaycontext.setformdata(multivaluemap);
          log.debug("[gatewaycontext]read formdata:{}",multivaluemap);
        })
        .then(mono.defer(() -> {
          charset charset = headers.getcontenttype().getcharset();
          charset = charset == null? standardcharsets.utf_8:charset;
          string charsetname = charset.name();
          multivaluemap<string, string> formdata = gatewaycontext.getformdata();
          /**
           * formdata is empty just return
           */
          if(null == formdata || formdata.isempty()){
            return chain.filter(exchange);
          }
          stringbuilder formdatabodybuilder = new stringbuilder();
          string entrykey;
          list<string> entryvalue;
          try {
            /**
             * remove system param ,repackage form data
             */
            for (map.entry<string, list<string>> entry : formdata.entryset()) {
              entrykey = entry.getkey();
              entryvalue = entry.getvalue();
              if (entryvalue.size() > 1) {
                for(string value : entryvalue){
                  formdatabodybuilder.append(entrykey).append("=").append(urlencoder.encode(value, charsetname)).append("&");
                }
              } else {
                formdatabodybuilder.append(entrykey).append("=").append(urlencoder.encode(entryvalue.get(0), charsetname)).append("&");
              }
            }
          }catch (unsupportedencodingexception e){
            //ignore urlencode exception
          }
          /**
           * substring with the last char '&'
           */
          string formdatabodystring = "";
          if(formdatabodybuilder.length()>0){
            formdatabodystring = formdatabodybuilder.substring(0, formdatabodybuilder.length() - 1);
          }
          /**
           * get data bytes
           */
          byte[] bodybytes = formdatabodystring.getbytes(charset);
          int contentlength = bodybytes.length;
          serverhttprequestdecorator decorator = new serverhttprequestdecorator(
              exchange.getrequest()) {
            /**
             * change content-length
             * @return
             */
            @override
            public httpheaders getheaders() {
              httpheaders httpheaders = new httpheaders();
              httpheaders.putall(super.getheaders());
              if (contentlength > 0) {
                httpheaders.setcontentlength(contentlength);
              } else {
                httpheaders.set(httpheaders.transfer_encoding, "chunked");
              }
              return httpheaders;
            }

            /**
             * read bytes to flux<databuffer>
             * @return
             */
            @override
            public flux<databuffer> getbody() {
              return databufferutils.read(new bytearrayresource(bodybytes),new nettydatabufferfactory(bytebufallocator.default),contentlength);
            }
          };
          serverwebexchange mutateexchange = exchange.mutate().request(decorator).build();
          log.debug("[gatewaycontext]rewrite form data :{}",formdatabodystring);
          return chain.filter(mutateexchange);
        }));
  }

  /**
   * readjsonbody
   * @param exchange
   * @param chain
   * @return
   */
  private mono<void> readbody(serverwebexchange exchange,gatewayfilterchain chain,gatewaycontext gatewaycontext){
    /**
     * join the body
     */
    return databufferutils.join(exchange.getrequest().getbody())
        .flatmap(databuffer -> {
          /**
           * read the body flux<databuffer>
           */
          databufferutils.retain(databuffer);
          flux<databuffer> cachedflux = flux.defer(() -> flux.just(databuffer.slice(0, databuffer.readablebytecount())));
          /**
           * repackage serverhttprequest
           */
          serverhttprequest mutatedrequest = new serverhttprequestdecorator(exchange.getrequest()) {
            @override
            public flux<databuffer> getbody() {
              return cachedflux;
            }
          };
          /**
           * mutate exchage with new serverhttprequest
           */
          serverwebexchange mutatedexchange = exchange.mutate().request(mutatedrequest).build();
          /**
           * read body string with default messagereaders
           */
          return serverrequest.create(mutatedexchange, messagereaders)
              .bodytomono(string.class)
              .doonnext(objectvalue -> {
                gatewaycontext.setcachebody(objectvalue);
                log.debug("[gatewaycontext]read jsonbody:{}",objectvalue);
              }).then(chain.filter(mutatedexchange));
        });
  }

}

在后续filter中，可以直接从serverexchange中获取gatewaycontext，就可以获取到缓存的数据，如果需要缓存其他数据，则可以根据自己的需求，添加到gatewaycontext中即可

gatewaycontext gatewaycontext = exchange.getattribute(gatewaycontext.cache_gateway_context);

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。