基于transmittable-thread-local的请求参数传递，如traceid，版本等-Toy模板网

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场景

在系统中对请求链路根据版本信息进行服务调度，保证请求发送的请求链路的不同的版本服务上。

方案

有很多开源组件支持链路追踪，如spring cloud sleuth。但支持场景有限，需要另行开发，故使用阿里的transmittable-thread-local进行实现，如默认的异步线程支持，rocketmq的数据传递等。文章来源地址https://www.toymoban.com/news/detail-725157.html

实现

引入transmittable-thread-local组件

        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>transmittable-thread-local</artifactId>
            <version>2.14.2</version>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-openfeign</artifactId>
        </dependency>

创建请求拦截器并设置线程中的数据

import com.lizz.GrayHttpProperties;
import com.lizz.GrayParamHolder;
import org.apache.commons.lang.StringUtils;
import org.slf4j.MDC;
import org.springframework.web.servlet.HandlerInterceptor;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class CustomHeaderInterceptor implements HandlerInterceptor {

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        String traceId = request.getHeader("traceId");
        if (StringUtils.isNotBlank(traceId)) {
            GrayParamHolder.putValue(GrayParamHolder.TRACE_ID, traceId);
            // traceId添加到日志输出中
            MDC.put(GrayParamHolder.TRACE_ID, traceId);
        }
        return true;
    }
    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse         response, Object handler, Exception ex) throws Exception {
        GrayParamHolder.clearValue();
        MDC.clear();
    }
}

添加拦截器到webmvc中

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

@Configuration
public class InterceptorConfig implements WebMvcConfigurer {
    @Bean
    public CustomHeaderInterceptor customHeaderInterceptor() {
        return new CustomHeaderInterceptor();
    }

    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(customHeaderInterceptor());
    }
}

线程数据管理工具

import com.alibaba.ttl.TransmittableThreadLocal;

import java.util.HashMap;
import java.util.Map;
import java.util.Objects;

public class GrayParamHolder {

    public static final String TRACE_ID = "traceId";
    private static ThreadLocal<Map<String, String>> paramLocal = new TransmittableThreadLocal();

    public static String getValue(String key) {
        Map<String, String> paramMap = GrayParamHolder.paramLocal.get();
        if (Objects.nonNull(paramMap) && !paramMap.isEmpty()) {
            return paramMap.get(key);
        }
        return null;
    }

    public static void putValue(String key, String value) {
        Map<String, String> paramMap = GrayParamHolder.paramLocal.get();
        if (Objects.isNull(paramMap) || paramMap.isEmpty()) {
            paramMap = new HashMap<>();
            GrayParamHolder.paramLocal.set(paramMap);
        }
        paramMap.put(key, value);
    }

    public static void clearValue() {
        GrayParamHolder.paramLocal.remove();
    }

}

在Feign请求中增加数据传递

import feign.RequestInterceptor;
import lombok.extern.slf4j.Slf4j;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.util.StringUtils;

@Configuration
@Slf4j
public class FeignClientConfiguration {
    @Bean
    public RequestInterceptor requestInterceptor() {
        return requestTemplate -> {
            // 添加您的自定义标头
             String traceId = GrayParamHolder.getValue(GrayParamHolder.TRACE_ID);
        if (StringUtils.isNotBlank(traceId)) {
            requestTemplate.header(GrayParamHolder.TRACE_ID, traceId);
        }
        };
    }
}

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