Optimize:optimize TransHeadersTransfer.

spring-cloud-starter-tencent-metadata-transfer/src/main/java/com/tencent/cloud/metadata/core/EncodeTransferMetadataZuulFilter.java

@@ -20,9 +20,6 @@ package com.tencent.cloud.metadata.core;
 
 import java.io.UnsupportedEncodingException;
 import java.net.URLEncoder;
-import java.util.Arrays;
-import java.util.Enumeration;
-import java.util.HashMap;
 import java.util.Map;
 
 import com.netflix.zuul.ZuulFilter;
@@ -33,13 +30,9 @@ import com.tencent.cloud.common.util.JacksonUtils;
 
 import org.springframework.util.CollectionUtils;
 
-import javax.servlet.http.HttpServletRequest;
-
 import static com.tencent.cloud.common.constant.ContextConstant.UTF_8;
 import static com.tencent.cloud.common.constant.MetadataConstant.HeaderName.CUSTOM_DISPOSABLE_METADATA;
 import static com.tencent.cloud.common.constant.MetadataConstant.HeaderName.CUSTOM_METADATA;
-import static com.tencent.cloud.common.metadata.MetadataContext.FRAGMENT_RAW_TRANSHEADERS;
-import static com.tencent.cloud.common.metadata.MetadataContext.FRAGMENT_RAW_TRANSHEADERS_KV;
 import static org.springframework.cloud.netflix.zuul.filters.support.FilterConstants.RIBBON_ROUTING_FILTER_ORDER;
 import static org.springframework.cloud.netflix.zuul.filters.support.FilterConstants.ROUTE_TYPE;