fix not found error when refresh ui. (#7403)

* fix not found error when refresh ui.

* add CHANGES.md

* Update CHANGES.md
Co-authored-by: 吴晟 Wu Sheng <wu.sheng@foxmail.com>

CHANGES.md

@@ -19,6 +19,8 @@ Release Notes.
 
 #### UI
 
+* Fix not found error when refresh UI.
+
 #### Documentation
 
 All issues and pull requests are [here](https://github.com/apache/skywalking/milestone/96?closed=1)

apm-webapp/src/main/java/org/apache/skywalking/apm/webapp/GlobalErrorWebExceptionHandler.java

+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package org.apache.skywalking.apm.webapp;
+
+import java.io.IOException;
+import lombok.extern.slf4j.Slf4j;
+import org.springframework.boot.web.reactive.error.ErrorWebExceptionHandler;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.core.annotation.Order;
+import org.springframework.core.io.ClassPathResource;
+import org.springframework.core.io.buffer.DataBufferFactory;
+import org.springframework.http.MediaType;
+import org.springframework.http.server.reactive.ServerHttpResponse;
+import org.springframework.util.StreamUtils;
+import org.springframework.web.server.ServerWebExchange;
+import reactor.core.publisher.Mono;
+
+@Slf4j
+@Order(-1)
+@Configuration
+public class GlobalErrorWebExceptionHandler implements ErrorWebExceptionHandler {
+
+    @Override
+    public Mono<Void> handle(ServerWebExchange exchange, Throwable ex) {
+        ServerHttpResponse response = exchange.getResponse();
+        response.getHeaders().setContentType(MediaType.TEXT_HTML);
+        return response.writeWith(Mono.fromSupplier(() -> {
+            DataBufferFactory bufferFactory = response.bufferFactory();
+            try {
+                return bufferFactory.wrap(StreamUtils.copyToByteArray(
+                    new ClassPathResource("/public/index.html").getInputStream()));
+            } catch (IOException e) {
+                log.error("There was an error completing the action.", ex);
+                return bufferFactory.wrap(new byte[0]);
+            }
+        }));
+    }
+}
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