SPRING CLOUD微服务实战笔记--声明式服务调用:Spring Cloud Feign

骑猪看日落 2022-02-27 05:54 216阅读 0赞

### Spring Cloud Feign ###

*  快速入门
 *  参数绑定
 *  继承特性
 *  Ribbon配置
 *   *  全局配置
     *  指定服务配置
 *  Hystrix配置
 *   *  全局配置
     *  禁用Hystrix
 *  其他配置
 *   *  请求压缩
     *  日志配置

# 快速入门 #

通过Spring Cloud Feign提供的声明式服务绑定功能来实现对该服务接口的调用

*  创建Spring Boot工程,在pom.xml中引入依赖

<dependency>
    	<groupId>org.springframework.cloud</groupId>
    	<artifactId>spring-cloud-starter-feign</artifactId>
    	<version>1.4.6.RELEASE</version>
    </dependency>

*  创建应用主类,并通过@EnableFeignClients注解开启Spring Cloud Feign的支持功能

@EnableFeignClients
    @EnableEurekaClient
    @SpringBootApplication
    public class HelloApplication { 
    	public static void main(String[] args) { 
    		SpringApplication.run(HelloApplication.class, args);
    	}
    }

*  定义HelloService接口,通过@FeignClient注解指定服务名来绑定服务,然后再使用SpringMVC的注解绑定具体该服务提供的REST接口

@FeignClient("hello-service")
    public interface HelloService { 
        @RequestMapping("/hello")
        String hello();
    }

*  创建一个ConsumerController来实现Feign客户端的调用

@RestController
    public class ConsumerController { 
        @Autowired
        HelloService helloService;
        @RequestMapping(value = "/feign-consumer" , method = RequestMethod.GET)
        public String helloConsumer(){ 
            return helloService.hello();
        }
    }

*  在application.properties中指定服务注册中心

spring.application.name=feign-consumer
    server.port=9003
    eureka.client.service-url.defaultZone=http://localhost:1111/eureka/

测试验证  
访问`http://localhost:9003/feign-consumer`,页面如下:  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3poZW5nZG9uZzEyMzQ1_size_16_color_FFFFFF_t_70]

# 参数绑定 #

第一步:改造服务提供方的服务  
服务提供方修改服务,增加接口定义,分别带有Request参数的请求,带有Header信息的请求,带有RequestBody的请求

@RequestMapping(value = "/hello1",method = RequestMethod.GET)
        public String hello(@RequestParam String name){ 
            return "Hello " + name;
        }
    
        @RequestMapping(value = "/hello2",method = RequestMethod.GET)
        public User hello(@RequestHeader String name,@RequestHeader Integer age){ 
            return new User(name,age);
        }
    
        @RequestMapping(value = "/hello3" , method = RequestMethod.POST)
        public String hello(@RequestBody User user){ 
            return "Hello " + user.getName() + ", " + user.getAge();
        }

User对象定义如下:

public class User { 
        private String name;
        private Integer age;
        public User(){ }
        public User(String name,Integer age){ 
            this.name = name;
            this.age = age;
        }
    //省略getter和setter方法
        @Override
        public String toString(){ 
            return "name=" + name + ",age=" + age;
        }
    }

第二步:改造服务消费端的请求绑定

*  在feign-consumer中添加和上面一样的User类
 *  在HelloService中增加三个新增接口的绑定声明

@FeignClient("hello-service")
    public interface HelloService { 
            @RequestMapping("/hello")
            String hello();
            @RequestMapping(value="/hello1",method = RequestMethod.GET)
            String hello(@RequestParam("name") String name);
            @RequestMapping(value = "/hello2",method = RequestMethod.GET)
            User hello(@RequestHeader("name") String name,@RequestHeader("age") Integer age);
            @RequestMapping(value = "/hello3",method = RequestMethod.POST)
            String hello(@RequestBody User user);
    }

*  在ConsumerController中新增一个/feign-consumer2接口,对新增接口进行调用

@RequestMapping(value = "/feign-consumer2",method = RequestMethod.GET)
        public String helloConsumer2(){ 
            StringBuilder sb = new StringBuilder();
            sb.append(helloService.hello()).append("\n");
            sb.append(helloService.hello("DIDI")).append("\n");
            sb.append(helloService.hello("DIDI",30)).append("\n");
            sb.append(helloService.hello(new User("DIDI",30))).append("\n");
            return sb.toString();
        }

测试验证  
访问`http://localhost:9003/feign-consumer2`,返回如下:

Hello World! Hello DIDI name=DIDI,age=30 Hello DIDI, 30

# 继承特性 #

通过Spring Cloud Feign的继承特性来实现REST接口定义的复用  
先新建一个Maven工程:

*  创建一个Maven工程,命名为hello-service-api
 *  修改工程的pom,引入依赖

<modelVersion>4.0.0</modelVersion>
    	<groupId>com.didispace</groupId>
    	<artifactId>hello-service-api</artifactId>
    	<packaging>jar</packaging>
    	<version>0.0.1-SNAPSHOT</version>
    	<name>hello-service-api</name>
    	<description>Demo project for Spring Boot</description>
    	<parent>
    		<groupId>org.springframework.boot</groupId>
    		<artifactId>spring-boot-starter-parent</artifactId>
    		<version>1.3.7.RELEASE</version>
    		<relativePath></relativePath>
    	</parent>
    	<properties>
    		<java.version>1.8</java.version>
    	</properties>
    	<dependencies>
    		<dependency>
    			<groupId>org.springframework.boot</groupId>
    			<artifactId>spring-boot-starter-web</artifactId>
    		</dependency>
    	</dependencies>

*  将上一节实现的User对象复制到hello-service-api工程中
 *  在Maven工程中添加HelloService

@RequestMapping("/refactor")
    public interface HelloService { 
        @RequestMapping(value = "/hello4",method = RequestMethod.GET)
        public String hello(@RequestParam String name);
        @RequestMapping(value = "/hello5",method = RequestMethod.GET)
        public User hello(@RequestHeader String name, @RequestHeader Integer age);
        @RequestMapping(value = "/hello6" , method = RequestMethod.POST)
        public String hello(@RequestBody User user);
    }

再修改服务提供方,对其进行重构

*  修改pom.xml,新增对hello-service-api的依赖

<dependency>
    	<groupId>com.didispace</groupId>
    	<artifactId>hello-service-api</artifactId>
    	<version>0.0.1-SNAPSHOT</version>
    </dependency>

*  创建RefactorHelloController类继承hello-service-api中定义HelloService接口,并实现这个接口中的方法

@RestController
    public class RefactorHelloController implements HelloService { 
        @Override
        public String hello(@RequestParam("name") String name) { 
            return "Hello " + name;
        }
        @Override
        public User hello(@RequestHeader("name") String name,@RequestHeader("age") Integer age) { 
            return new User(name,age);
        }
        @Override
        public String hello(@RequestBody User user) { 
            return "Hello " + user.getName() + ", " + user.getAge();
        }
    }

最后修改服务消费者

*  修改pom.xml,新增对hello-service-api的依赖

<dependency>
    	<groupId>com.didispace</groupId>
    	<artifactId>hello-service-api</artifactId>
    	<version>0.0.1-SNAPSHOT</version>
    </dependency>

*  创建RefactorHelloService接口,并继承hello-service-api包中的HelloService接口,然后添加@FeignClient注解来绑定服务

@FeignClient(value = "HELLO-SERVICE")
    public interface RefactorHelloService extends com.didispace.service.HelloService{ 
    }

*  在ConsumerController中,注入RefactorHelloService的实例,并新增一个请求/feign-consumer3来触发RefactorHelloService的实例

@RequestMapping(value = "/feign-consumer3",method = RequestMethod.GET)
        public String helloConsumer3(){ 
            StringBuilder sb = new StringBuilder();
            sb.append(refactorHelloService.hello("MIMI")).append("\n");
            sb.append(refactorHelloService.hello("MIMI",30)).append("\n");
            sb.append(refactorHelloService.hello(new com.didispace.User.User("MIMI",20))).append("\n");
            return sb.toString();
        }

遇到的问题:  
将项目引入到maven私服库的时候,项目中调用接口不能识别,原来之前为了打包将pom中的编译插件换了,导致执行`mvn install`命令时编译有问题

<build>
    	<plugins>
    		<plugin>
    			<groupId>org.springframework.boot</groupId>
    			<artifactId>spring-boot-maven-plugin</artifactId>
    			<version>2.0.3.RELEASE</version>
    			<executions>
    				<execution>
    					<goals>
    						<goal>repackage</goal>
    					</goals>
    				</execution>
    			</executions>
    		</plugin>
    	</plugins>
    </build>

将上面这段从pom中删除,重新执行`mvn install`后成功

# Ribbon配置 #

## 全局配置 ##

通过使用ribbon.=方式来设置ribbon的各项默认参数,比如修改默认的客户端调用超时时间:

ribbon.ConnectTimeout = 500
    ribbon.ReadTimeout=5000

## 指定服务配置 ##

有时需要个性化配置,采用.ribbon.key=value的格式进行设置  
使用@FeignClient(value = “HELLO-SERVICE”)来创建Feign客户端的时候,同时也创建了一个名为HELLO-SERVICE的Ribbon客户端

HELLO-SERVICE.ribbon.ConnectTimeout=500
    HELLO-SERVICE.ribbon.ReadTimeout=2000

# Hystrix配置 #

## 全局配置 ##

Hystrix的全局配置采用默认配置前缀`hystrix.command.default`就可以设置,比如设置全局的超时时间:

hystrix.command.default.execution.isolation.thread.timeoutInMilliseconds=5000

通过`feign.hystrix.enabled=false`来全局关闭Hystrix功能  
通过`feign.command.default.execution.timeout.enabled=false`来关闭熔断功能

## 禁用Hystrix ##

@Scope(“prototype”)注解为指定的客户端配置Feign.Builder实例

*  构建一个Hystrix配置类

@Configuration
    public class DisableHystrixConfiguration{ 
    	@Bean
    	@Scope("prototype")
    	public Feign.Builder feignBuilder(){ 
    		return Feign.builder();
    	}
    }

*  在HelloService的@FeignClient注解中,通过configuration参数引入上面实现的配置

@FeignClient(name="HELLO-SERVICE",configuration =DisableHystrixConfiguration.class)
    public interface HelloService{ 
    }

# 其他配置 #

## 请求压缩 ##

SpringCloudFeign支持对请求与响应进行GZIP压缩,以减少通信过程中的性能损耗

feign.compression.request.enabled=true
    feign.compression.response.enabled=true

同时还可以进行更加细化的配置

feign.compression.request.enabled=true;
    //指定压缩请求数据类型
    feign.comresstion.request.mime-types=text/xml,application/xml,application/json
    //请求压缩的大小下限,只有查过这个大小的请求才会对其进行压缩
    feign.compression.request.min-request-size=2048

## 日志配置 ##

可以在application.properties文件中使用`logging.level.<FeignClient>`的参数配置格式来开启指定Feign客户端的DEBUG日志,其中`<FeignClient>`为Feign客户端定义接口的完整路径,比如:

logging.level.com.didispace.web.HelloService=DEBUG

同时调整全局的日志级别,可以在应用主类中直接加入Logger.Level的Bean创建,具体如下:

@EnableFeignClients
    @EnableEurekaClient
    @SpringBootApplication
    public class HelloApplication { 
    	@Bean
    	Logger.Level feignLoggerLevel(){ 
    		return Logger.Level.FULL;
    	}
    	public static void main(String[] args) { 
    		SpringApplication.run(HelloApplication.class, args);
    	}
    }

对于Feign的Logger级别主要有如下4类,可以根据实际需要进行调整使用

*  NONE:不记录任何信息
 *  BASIC:仅记录请求方法,URL以及响应状态码和执行时间
 *  HEADERS:除了记录BASIC级别的信息之外,还会记录请求和响应的头信息
 *  FULL:记录所有请求与响应的明细,包括头信息,请求体和元数据等

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