JDK的HttpURLConnection强制把GET请求转成了POST

/**
     * 查询房间信息
     *
     * @param roomQueryParam
     * @return
     */
@Headers(HttpConstants.HEADER_CONTENT_TYPE_JSON)
@RequestLine("GET /room/queryRooms")
List<RoomDTO> queryRooms(@Valid RoomQueryParam roomQueryParam);

/**
     * 查询房间信息
     *
     * @param roomQueryParam
     * @return
     */
@Override
@RequestMapping(value = "/queryRooms", method = RequestMethod.POST)
@ApiOperation(value = "条件查询房间信息", httpMethod = "POST", produces = "application/json;charset=UTF-8", consumes = "application/json;")
public List<RoomDTO> queryRooms(
  @Valid @NotNull @RequestBody @ApiParam(value = "房间查询参数", required = true) RoomQueryParam roomQueryParam) {
  return roomService.queryRooms(roomQueryParam);
}

2020-05-12 22:20:59.051 INFO [pms-api,de87cf7f069503a3,de87cf7f069503a3,true] --- [o-10026-exec-14] http.consumer.log                        : [GalaxyRoomRemote#queryRooms]
GET http://192.168.16.212:10024/room/queryRooms HTTP/1.1
Content-Type: application/json;charset=UTF-8
Content-Length: 86
appCode: pms

{
  "chainId" : 114,
  "roomNo" : "8235",
  "roomTypeId" : [ ],
  "cleanState" : [ ]
}
 <--- HTTP/1.1 200  elapsed : 13 ms
connection: keep-alive
content-type: application/json;charset=UTF-8
date: Tue, 12 May 2020 14:20:59 GMT
keep-alive: timeout=20
transfer-encoding: chunked
zipkin-trace-id: de2d912a29ae1a91
 <--- END HTTP (468-byte body)

2020-05-12 22:20:59.050 INFO [galaxy,de2d912a29ae1a91,de2d912a29ae1a91,false] --- [io-10024-exec-7] http.request.response.log                :
POST http://192.168.16.212:10024/room/queryRooms?
content-type: application/json;charset=UTF-8
appcode: pms
accept: */*
cache-control: no-cache
pragma: no-cache
user-agent: Java/1.8.0_171
host: 192.168.16.212:10024
connection: keep-alive

{  "chainId" : 114,  "roomNo" : "8235",  "roomTypeId" : [ ],  "cleanState" : [ ]}

ret code 200, start time 1589293259041 --> end time 1589293259050, cost: 9

$ sudo tcpdump -n -S -s 0 -A    dst port 8182   | grep "queryRooms"  -C40 --color

01:02:45.933534 IP 192.168.6.212.38430 > 192.168.1.3.vmware-fdm: Flags [P.], seq 1572827156:1572827402, ack 904633996, win 981, options [nop,nop,TS val 1568347176 ecr 3383828365], length 246
E..*..@.@.*.............].p.5.......r......
]{.(....POST /room/queryRooms HTTP/1.1
Content-Type: application/json;charset=UTF-8
appCode: pms
Accept: */*
Cache-Control: no-cache
Pragma: no-cache
User-Agent: Java/1.8.0_171
Host: 192.168.1.3:8182
Connection: keep-alive
Content-Length: 89

// sun.net.www.protocol.http.HttpURLConnection#getOutputStream0
 private synchronized OutputStream getOutputStream0() throws IOException {
        try {
            if (!doOutput) {
                throw new ProtocolException("cannot write to a URLConnection"
                               + " if doOutput=false - call setDoOutput(true)");
            }

            if (method.equals("GET")) {
                method = "POST"; // Backward compatibility
            }
          // 省略
}

// feign.Client.Default#convertAndSend
 HttpURLConnection convertAndSend(Request request, Options options) throws IOException {
   // 每次打开一个连接   
   final HttpURLConnection
          connection =
          (HttpURLConnection) new URL(request.url()).openConnection();
      if (connection instanceof HttpsURLConnection) {
        HttpsURLConnection sslCon = (HttpsURLConnection) connection;
        if (sslContextFactory != null) {
          sslCon.setSSLSocketFactory(sslContextFactory);
        }
        if (hostnameVerifier != null) {
          sslCon.setHostnameVerifier(hostnameVerifier);
        }
      }
      connection.setConnectTimeout(options.connectTimeoutMillis());
      connection.setReadTimeout(options.readTimeoutMillis());
      connection.setAllowUserInteraction(false);
      connection.setInstanceFollowRedirects(true);
      connection.setRequestMethod(request.method());

      Collection<String> contentEncodingValues = request.headers().get(CONTENT_ENCODING);
      boolean
          gzipEncodedRequest =
          contentEncodingValues != null && contentEncodingValues.contains(ENCODING_GZIP);
      boolean
          deflateEncodedRequest =
          contentEncodingValues != null && contentEncodingValues.contains(ENCODING_DEFLATE);

      boolean hasAcceptHeader = false;
      Integer contentLength = null;
      for (String field : request.headers().keySet()) {
        if (field.equalsIgnoreCase("Accept")) {
          hasAcceptHeader = true;
        }
        for (String value : request.headers().get(field)) {
          if (field.equals(CONTENT_LENGTH)) {
            if (!gzipEncodedRequest && !deflateEncodedRequest) {
              contentLength = Integer.valueOf(value);
              connection.addRequestProperty(field, value);
            }
          } else {
            connection.addRequestProperty(field, value);
          }
        }
      }
      // Some servers choke on the default accept string.
      if (!hasAcceptHeader) {
        connection.addRequestProperty("Accept", "*/*");
      }

      if (request.body() != null) {
        if (contentLength != null) {
          connection.setFixedLengthStreamingMode(contentLength);
        } else {
          connection.setChunkedStreamingMode(8196);
        }
        connection.setDoOutput(true);
        OutputStream out = connection.getOutputStream();
        if (gzipEncodedRequest) {
          out = new GZIPOutputStream(out);
        } else if (deflateEncodedRequest) {
          out = new DeflaterOutputStream(out);
        }
        try {
          out.write(request.body());
        } finally {
          try {
            out.close();
          } catch (IOException suppressed) { // NOPMD
          }
        }
      }
      return connection;
    }