190306-SpringCloud之Feign请求参数包装异常问题定位

<spring.boot.version>2.0.1.RELEASE</spring.boot.version>
<spring.cloud.version>Finchley.RELEASE</spring.cloud.version>

<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-openfeign</artifactId>
    <version>2.0.0.RELEASE</version>
</dependency>

<groupId>io.github.openfeign</groupId>
<artifactId>feign-core</artifactId>
<version>9.5.1</version>

@RequestMapping(value = "getMarketDailySummary")
BaseRsp<MarketDailySummaryDTO> getMarketDailySummary(@RequestParam("datetime") Long datetime,
         @RequestParam(value = "coinIds") List<Integer> coinIds,
         @RequestParam(value = "pairIds") List<Integer> pairIds);

marketDailyReportService.getMarketDailySummary(1551836411000L, Arrays.asList(1, 2, 3, 10), Arrays.asList());

@Component
@WebFilter(value = "/**")
public class ReqFilter implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain)
            throws IOException, ServletException {
        try {
            System.out.println(servletRequest.getParameterMap());
        } finally {
            filterChain.doFilter(servletRequest, servletResponse);
        }

    }

    @Override
    public void destroy() {

    }
}

@RequestMapping(value = "getMarketDailySummary")
BaseRsp<MarketDailySummaryDTO> getMarketDailySummary(@RequestParam("datetime") Long datetime,
       @RequestParam(value = "coinIds", required = false) List<Integer> coinIds,
       @RequestParam(value = "pairIds", required = false) List<Integer> pairIds);

// feign.SynchronousMethodHandler#invoke
 @Override
public Object invoke(Object[] argv) throws Throwable {
  // 下面这一行为目标逻辑，创建请求模板类，请求参数封装肯定是在里面了
  RequestTemplate template = buildTemplateFromArgs.create(argv);
  Retryer retryer = this.retryer.clone();
  while (true) {
    try {
      return executeAndDecode(template);
    } catch (RetryableException e) {
      retryer.continueOrPropagate(e);
      if (logLevel != Logger.Level.NONE) {
        logger.logRetry(metadata.configKey(), logLevel);
      }
      continue;
    }
  }
}

// feign.ReflectiveFeign.BuildTemplateByResolvingArgs#resolve
protected RequestTemplate resolve(Object[] argv, RequestTemplate mutable,
                                  Map<String, Object> variables) {
    // Resolving which variable names are already encoded using their indices
    Map<String, Boolean> variableToEncoded = new LinkedHashMap<String, Boolean>();
    for (Entry<Integer, Boolean> entry : metadata.indexToEncoded().entrySet()) {
      Collection<String> names = metadata.indexToName().get(entry.getKey());
      for (String name : names) {
        variableToEncoded.put(name, entry.getValue());
      }
    }
    
    // 核心逻辑了，使用请求参数来替换模板中的占位
    return mutable.resolve(variables, variableToEncoded);
  }
}

// feign.RequestTemplate#replaceQueryValues(java.util.Map<java.lang.String,?>, java.util.Map<java.lang.String,java.lang.Boolean>)
void replaceQueryValues(Map<String, ?> unencoded, Map<String, Boolean> alreadyEncoded) {
  Iterator<Entry<String, Collection<String>>> iterator = queries.entrySet().iterator();
  while (iterator.hasNext()) {
    Entry<String, Collection<String>> entry = iterator.next();
    if (entry.getValue() == null) {
      continue;
    }
    Collection<String> values = new ArrayList<String>();
    for (String value : entry.getValue()) {
      if (value.indexOf('{') == 0 && value.indexOf('}') == value.length() - 1) {
        Object variableValue = unencoded.get(value.substring(1, value.length() - 1));
        // only add non-null expressions
        if (variableValue == null) {
          // 如果请求参数为null，也不会凭借到url参数中
          continue;
        }
        if (variableValue instanceof Iterable) {
          // 将目标集中在这里，如果请求参数时空集合，下面的for循环不会走到，所以也就不会拼接在url参数中
          for (Object val : Iterable.class.cast(variableValue)) {
            String encodedValue = encodeValueIfNotEncoded(entry.getKey(), val, alreadyEncoded);
            values.add(encodedValue);
          }
        } else {
          String encodedValue = encodeValueIfNotEncoded(entry.getKey(), variableValue, alreadyEncoded);
          values.add(encodedValue);
        }
      } else {
        values.add(value);
      }
    }
    if (values.isEmpty()) {
      iterator.remove();
    } else {
      entry.setValue(values);
    }
  }
}