前言：本文主要介绍SpringMvc集成Sentinel，作者查阅了Sentinel官网、51CTO、CSDN、码农家园、博客园、神灯等很多技术文章都没有很准确的springmvc集成Sentinel的示例

SpringMvc集成Sentinel

一、Sentinel 介绍

随着微服务的流行，服务和服务之间的稳定性变得越来越重要。Sentinel 是面向分布式、多语言异构化服务架构的流量治理组件，主要以流量为切入点，从流量路由、流量控制、流量整形、熔断降级、系统自适应过载保护、热点流量防护等多个维度来帮助开发者保障微服务的稳定性。

GitHub主页：https://github.com/alibaba/Sentinel

中文文档：https://sentinelguard.io/zh-cn/docs/introduction.html

控制台文档：https://sentinelguard.io/zh-cn/docs/dashboard.html

核心类解析：https://github.com/alibaba/Sentinel/wiki/Sentinel-%E6%A0%B8%E5%BF%83%E7%B1%BB%E8%A7%A3%E6%9E%90

Sentinel示例项目：https://github.com/alibaba/Sentinel/tree/master/sentinel-demo

https://github.com/alibaba/spring-cloud-alibaba/tree/master/spring-cloud-alibaba-examples/sentinel-example

二、Sentinel 基本概念

资源

资源是 Sentinel 的关键概念。它可以是 Java 应用程序中的任何内容，例如，由应用程序提供的服务，或由应用程序调用的其它应用提供的服务，甚至可以是一段代码。在接下来的文档中，我们都会用资源来描述代码块。

只要通过 Sentinel API 定义的代码，就是资源，能够被 Sentinel 保护起来。大部分情况下，可以使用方法签名，URL，甚至服务名称作为资源名来标示资源。

规则

围绕资源的实时状态设定的规则，可以包括流量控制规则、熔断降级规则以及系统保护规则。所有规则可以动态实时调整。

三、springMVC集成Sentinel

这里用的是spring

<spring.version>5.3.18</spring.version>

<servlet.api.version>2.5</servlet.api.version>
<sentinel.version>1.8.6</sentinel.version>

1、springmvc项目引入依赖pom

        <!-- 这是sentinel的核心依赖 -->
        <dependency>
            <groupId>com.alibaba.csp</groupId>
            <artifactId>sentinel-core</artifactId>
            <version>${sentinel.version}</version>
        </dependency>
        <!-- 这是将自己项目和sentinel-dashboard打通的依赖 -->
        <dependency>
            <groupId>com.alibaba.csp</groupId>
            <artifactId>sentinel-transport-simple-http</artifactId>
            <version>${sentinel.version}</version>
        </dependency>
        <!-- 这是使用sentinel对限流资源进行AOP -->
        <dependency>
            <groupId>com.alibaba.csp</groupId>
            <artifactId>sentinel-annotation-aspectj</artifactId>
            <version>${sentinel.version}</version>
        </dependency>
        <!--这是使用sentinel适配Web Servlet的依赖-->
        <dependency>
            <groupId>com.alibaba.csp</groupId>
            <artifactId>sentinel-web-servlet</artifactId>
            <version>${sentinel.version}</version>
        </dependency>
        <!-- 这是使用sentinel热点参数限流功能依赖 -->
        <dependency>
            <groupId>com.alibaba.csp</groupId>
            <artifactId>sentinel-parameter-flow-control</artifactId>
            <version>${sentinel.version}</version>
        </dependency>

2、添加配置文件

在application.properties下创建同级文件sentinel.properties，内容如下

# 集成到sentinel的项目名称
project.name=spring-sentinel-demo
# 对应的sentinel-dashboard地址
csp.sentinel.dashboard.server=localhost:8080

3、添加配置类引入配置文件

创建配置类SentinelAspectConfiguration并引入配置文件sentinel.properties

import com.alibaba.csp.sentinel.annotation.aspectj.SentinelResourceAspect;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.PropertySource;
import org.springframework.context.annotation.PropertySources;

@Configuration
@PropertySources({@PropertySource("classpath:/sentinel.properties")})
public class SentinelAspectConfiguration {

    @Bean
    public SentinelResourceAspect sentinelResourceAspect() {
        return new SentinelResourceAspect();
    }
}

4、web.xml新增如下过滤器配置

 <filter>
        <filter-name>SentinelCommonFilter</filter-name>
        <filter-class>com.alibaba.csp.sentinel.adapter.servlet.CommonFilter</filter-class>
    </filter>

    <filter-mapping>
        <filter-name>SentinelCommonFilter</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>

接入 filter 之后，所有访问的 Web URL 就会被自动统计为 Sentinel 的资源---来源于 https://sentinelguard.io/zh-cn/docs/open-source-framework-integrations.html

开源框架适配的Web 适配下的Web Servlet

5、创建Controller接口

@Controller
public class WebMvcTestController {

    @GetMapping("/hello")
    @ResponseBody
    public String apiHello(String id) {
        System.out.println("id = " + id);
        Date date = new Date();
        System.out.println("date = " + date);
        return "Hello!";
    }

    @GetMapping("/doBusiness")
    @ResponseBody
    public String doBusiness(String id) {
        System.out.println("doBusiness = ");
        return "Oops...";
    }
 }

6、下载控制台-即图形化实时监控平台

参考 https://sentinelguard.io/zh-cn/docs/dashboard.html Sentinel 控制台的下载和启动

访问 https://github.com/alibaba/Sentinel/releases/tag/1.8.6

点击下载

7、运行控制台

java -Dserver.port=8080 -Dcsp.sentinel.dashboard.server=localhost:8080 -Dproject.name=sentinel-dashboard -jar sentinel-dashboard.jar

运行控制台后运行springmvc项目，然后访问某一个路径，就可以在控制台看到了，实时监控如果这个路径没有被访问是显示不出来的

这个时候我们配置限流为即Qps为2

8、测试限流

这里我们用postman进行压测，填写请求的路径保存。并点击run调出压测执行器

执行后查看结果如下

四、自定义异常返回

1、定义如下接口(这里只进行了常见的url定义方式的定义)

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.*;

@Controller
@RequestMapping("/test")
public class WebMvcTestController {
  
    /**
     * 1.未配置流控规则 1000次请求没有间隔发起请求，应该在1秒中完成09:44:33
     * @param id
     * @return
     */
    @RequestMapping("/RequestMapping")
    @ResponseBody
    public String RequestMapping(String id) {
        return "RequestMapping!";
    }

    @GetMapping("/GetMapping")
    @ResponseBody
    public String GetMapping(String id) {
        return "GetMapping...";
    }

    @PostMapping("/PostMapping")
    @ResponseBody
    public String PostMapping(String id) {
        return "PostMapping...";
    }

    /*
    * 路径变量（Path Variables）：使用花括号 {} 来标记路径中的变量，并通过 @PathVariable 注解将其绑定到方法参数上
    * */
    @GetMapping("/GetMapping/{id}")
    @ResponseBody
    public String apiFoo(@PathVariable("id") Long id) {
        return "Hello " + id;
    }

    /*
    * Ant风格的路径匹配：
    *   使用 ? 表示任意单个字符，
    *   * 表示任意多个字符（不包含路径分隔符 /），
    *   ** 表示任意多个字符（包含路径分隔符 /）。
    * */
    @GetMapping("/Ant/*/{id}")
    @ResponseBody
    public String Ant(@PathVariable("id") Long id) {
        return "Ant " + id;
    }

    /*
    * 正则表达式路径匹配：使用 @RequestMapping 注解的 value 属性结合正则表达式来定义请求路径。
    * */
    @GetMapping(value = "/users/{id:\\d+}")
    @ResponseBody
    public String pattern(@PathVariable("id") int id) {
        return "Ant " + id;
    }
}

2、自定义限流返回处理Handler

import com.alibaba.csp.sentinel.adapter.servlet.callback.UrlBlockHandler;
import com.alibaba.csp.sentinel.slots.block.BlockException;
import com.alibaba.csp.sentinel.slots.block.authority.AuthorityException;
import com.alibaba.csp.sentinel.slots.block.degrade.DegradeException;
import com.alibaba.csp.sentinel.slots.block.flow.FlowException;
import com.alibaba.csp.sentinel.slots.block.flow.param.ParamFlowException;
import com.alibaba.csp.sentinel.slots.system.SystemBlockException;
import com.alibaba.fastjson.JSON;
import org.springframework.context.ApplicationContext;
import org.springframework.web.method.HandlerMethod;
import org.springframework.web.servlet.mvc.condition.PatternsRequestCondition;
import org.springframework.web.servlet.mvc.method.RequestMappingInfo;
import org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping;
import org.springframework.web.util.UrlPathHelper;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.*;


public class SentinelExceptionHandler implements UrlBlockHandler {

    @Override
    public void blocked(HttpServletRequest request, HttpServletResponse httpServletResponse, BlockException e) throws IOException {
        String contextPath = request.getContextPath();
        String servletPath = request.getServletPath();
        String requestURI = request.getRequestURI();
        String url = request.getRequestURL().toString();
        System.out.println("servletPath = " + servletPath);
        System.out.println("requestURI = " + requestURI);
        System.out.println("url = " + url);
        if (contextPath == null) {
            contextPath = "";
        }
        ApplicationContext controllerApplicationContext = LiteFlowApplicationContext.getControllerApplicationContext();
        RequestMappingHandlerMapping handlerMapping = controllerApplicationContext.getBean(RequestMappingHandlerMapping.class);
        // 查找匹配的处理方法
        Class<?> returnType = null;
        Map<RequestMappingInfo, HandlerMethod> handlerMethods = handlerMapping.getHandlerMethods();
        for (Map.Entry<RequestMappingInfo, HandlerMethod> entry : handlerMethods.entrySet()) {
            RequestMappingInfo requestMappingInfo = entry.getKey();
            HandlerMethod handlerMethod = entry.getValue();
            //匹配url
            if (requestMappingInfo.getPatternsCondition().getPatterns().contains(requestURI)) {
                System.out.println("Controller: " + handlerMethod.getBeanType().getName());
                System.out.println("Method: " + handlerMethod.getMethod().getName());
                System.out.println("getReturnType: " + handlerMethod.getMethod().getReturnType());
                returnType = handlerMethod.getMethod().getReturnType();
                break;
            }
            //匹配路径带参数的url
            UrlPathHelper pathHelper = new UrlPathHelper();
            String lookupPath = pathHelper.getPathWithinApplication(request);
            PatternsRequestCondition patternsCondition = requestMappingInfo.getPatternsCondition();
            if (patternsCondition != null && patternsCondition.getMatchingPatterns(lookupPath).size() > 0) {
                System.out.println("Controller1111: " + handlerMethod.getBeanType().getName());
                System.out.println("Method111: " + handlerMethod.getMethod().getName());
                System.out.println("getReturnType: " + handlerMethod.getMethod().getReturnType());
                returnType = handlerMethod.getMethod().getReturnType();
                break;
            }
        }
        httpServletResponse.setContentType("application/json;charset=utf-8");
        ResponseData data = null;
        if (returnType != null) {
            if (returnType == String.class) {
                String str = "返回类型为字符串方法限流";
                httpServletResponse.getWriter().write(str);
                return;
            } else if (returnType == Integer.class) {
                httpServletResponse.getWriter().write(new Integer(1));
                return;
            } else if (returnType == Long.class) {
                httpServletResponse.getWriter().write(2);
                return;
            } else if (returnType == Double.class) {

            } else if (returnType == Boolean.class) {

            } else if (returnType == Float.class) {

            } else if (returnType == Byte.class) {

            }
        }
        //BlockException 异常接口,包含Sentinel的五个异常
        // FlowException 限流异常
        // DegradeException 降级异常
        // ParamFlowException 参数限流异常
        // AuthorityException 授权异常
        // SystemBlockException 系统负载异常
        if (e instanceof FlowException) {
            data = new ResponseData(-1, "流控规则被触发......");
        } else if (e instanceof DegradeException) {
            data = new ResponseData(-2, "降级规则被触发...");
        } else if (e instanceof AuthorityException) {
            data = new ResponseData(-3, "授权规则被触发...");
        } else if (e instanceof ParamFlowException) {
            data = new ResponseData(-4, "热点规则被触发...");
        } else if (e instanceof SystemBlockException) {
            data = new ResponseData(-5, "系统规则被触发...");
        }
        httpServletResponse.getWriter().write(JSON.toJSONString(data));
    }
}

3、使用自定义限流处理类

import com.alibaba.csp.sentinel.adapter.servlet.callback.WebCallbackManager;
import org.springframework.context.annotation.Configuration;

@Configuration
public class SentinelConfig {


    public SentinelConfig() {
        WebCallbackManager.setUrlBlockHandler(new SentinelExceptionHandler());
    }
}

4、配置限流并测试结果

当开启限流后访问触发自定义UrlBlockHandler后结果如下

访问对应得url后控制台打印

servletPath = /test/RequestMapping
requestURI = /test/RequestMapping
url = http://localhost:8081/test/RequestMapping
Controller: org.example.WebMvcTestController
Method: RequestMapping
getReturnType: class java.lang.String
servletPath = /test/GetMapping
requestURI = /test/GetMapping
url = http://localhost:8081/test/GetMapping
Controller: org.example.WebMvcTestController
Method: GetMapping
getReturnType: class java.lang.String
servletPath = /test/PostMapping
requestURI = /test/PostMapping
url = http://localhost:8081/test/PostMapping
Controller: org.example.WebMvcTestController
Method: PostMapping
getReturnType: class java.lang.String
servletPath = /test/GetMapping/4
requestURI = /test/GetMapping/4
url = http://localhost:8081/test/GetMapping/4
Controller1111: org.example.WebMvcTestController
Method111: apiFoo
getReturnType: class java.lang.String
servletPath = /test/Ant/a/5
requestURI = /test/Ant/a/5
url = http://localhost:8081/test/Ant/a/5
Controller1111: org.example.WebMvcTestController
Method111: Ant
getReturnType: class java.lang.String
servletPath = /test/users/5
requestURI = /test/users/5
url = http://localhost:8081/test/users/5
Controller1111: org.example.WebMvcTestController
Method111: pattern
getReturnType: class java.lang.String