SpringCloud – (二)服务消费者

SpringCloud - (二)服务消费者
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Spring cloud有两种服务调用方式:

一种是ribbon+restTemplate
一种是feign

ribbon+restTemplate

ribbon

ribbon是一个负载均衡客户端,可以很好的控制http和tcp的一些行为。

RestTemplate

RestTemplate是Spring提供的用于访问Rest服务的客户端,RestTemplate提供了多种便捷访问远程Http服务的方法,能够大大提高客户端的编写效率。
RestTemplate的用法

下面进行实践
首先是项目总览:
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eureka-server (注册中心)
eureka-provider-one (提供服务)
eureka-consumer-ribbon (ribbon方式消费)
eureka-consumer-feign (feign方式消费)
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创建eureka-consumer-ribbon项目
选中项目>>右键,New>>Module
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在这里插入图片描述创建完成
在这里插入图片描述项目的pom.xml如下(不需要修改):

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.1.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.wy</groupId>
    <artifactId>eureka-consumer-ribbon</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>eureka-consumer-ribbon</name>
    <description>Demo project for Spring Boot</description>

    <properties>
        <java.version>1.8</java.version>
        <spring-cloud.version>Greenwich.RC2</spring-cloud.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-ribbon</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>${
   spring-cloud.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

    <repositories>
        <repository>
            <id>spring-milestones</id>
            <name>Spring Milestones</name>
            <url>https://repo.spring.io/milestone</url>
        </repository>
    </repositories>

</project>

项目启动类
通过@EnableDiscoveryClient向服务中心注册
并且向程序的ioc注入一个bean: restTemplate;并通过@LoadBalanced注解表明这个restRemplate开启负载均衡的功能

package com.wy.eurekaconsumerribbon;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.context.annotation.Bean;
import org.springframework.web.client.RestTemplate;

@SpringBootApplication
@EnableDiscoveryClient
public class EurekaConsumerRibbonApplication {
   

    public static void main(String[] args) {
   
        SpringApplication.run(EurekaConsumerRibbonApplication.class, args);
    }

    /** * 注入restTemplate, 并且开启负载均衡 */
    @Bean
    @LoadBalanced
    public RestTemplate createRestTemplate() {
   
        return new RestTemplate();
    }



}


项目配置application.yml

# 配置服务器端口
server:
  port: 8920
spring:
  application:
    name: cloud-eureka-consumer-robbon
# 注册服务
eureka:
  client:
    service-url:
      defaultZone: http://localhost:8000/eureka/

依次启动
eureka-server,
eureka-provider-one,
eureka-consumer-ribbon
访问http://localhost:8000/

说明eureka 已经发现了服务提供者和服务消费者

http://localhost:8910/hello/index/wy
在这里插入图片描述说明服务没问题

访问http://localhost:8920/ribbon/hello/wy
在这里插入图片描述说明通过 ribbon+restTemplate访问服务已经成功。

feign

Feign是一个声明式的Web Service客户端,它使得编写Web Serivce客户端变得更加简单。我们只需要使用Feign来创建一个接口并用注解来配置它既可完成。它具备可插拔的注解支持,包括Feign注解和JAX-RS注解。Feign也支持可插拔的编码器和解码器。Spring Cloud为Feign增加了对Spring MVC注解的支持,还整合了Ribbon和Eureka来提供均衡负载的HTTP客户端实现。

深入理解Feign之源码解析
首先在eureka-provider-one项目添加一个hello服务

package com.wy.eurekaproviderone.controller;

import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

@RestController
@RequestMapping("/hello")
public class HelloController {
   

    @RequestMapping("/index/{name}")
    public String index(@PathVariable("name") String name) {
   
        return "hello "+name+",this is first messge";
    }


    @RequestMapping("/test")
    public String index() {
   
        return "hello this is first messge";
    }

    @RequestMapping("/hello")
    public String hello(@RequestParam String name) {
   
        return "hello "+name+",this is first messge";
    }

}

创建eureka-consumer-feign项目
选中项目>>右键,New>>Module

在这里插入图片描述在这里插入图片描述在这里插入图片描述
创建完成
pom.xml不需要修改,如下:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.1.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.wy</groupId>
    <artifactId>eureka-consumer-feign</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>eureka-consumer-feign</name>
    <description>Demo project for Spring Boot</description>

    <properties>
        <java.version>1.8</java.version>
        <spring-cloud.version>Greenwich.RC2</spring-cloud.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-openfeign</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>${
   spring-cloud.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

    <repositories>
        <repository>
            <id>spring-milestones</id>
            <name>Spring Milestones</name>
            <url>https://repo.spring.io/milestone</url>
        </repository>
    </repositories>

</project>

项目启动类,添加@EnableDiscoveryClient,@EnableFeignClients

package com.wy.eurekaconsumerfeign;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.openfeign.EnableFeignClients;

@SpringBootApplication
@EnableDiscoveryClient
@EnableFeignClients
public class EurekaConsumerFeignApplication {
   

    public static void main(String[] args) {
   
        SpringApplication.run(EurekaConsumerFeignApplication.class, args);
    }

}



声明一个接口,HelloService

package com.wy.eurekaconsumerfeign.remote;


import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;

@FeignClient(name = "CLOUD-EUREKA-PROVIDER")
    public interface HelloService {
   

    @RequestMapping(value = "/hello/hello")
    String hello(@RequestParam(value = "name") String name);

    @RequestMapping(value = "/hello/test")
    String test();
}

在controller写一个TestController ,如下:

package com.wy.eurekaconsumerfeign.controller;


import com.wy.eurekaconsumerfeign.remote.HelloService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
@RequestMapping("/feign")
public class TestController {
   
    @Autowired
    HelloService helloService;

    @RequestMapping("/hello/{name}")
    public String hello(@PathVariable("name") String name) {
   
        return helloService.hello(name);
    }


    @RequestMapping("/test")
    public String index() {
   
        return helloService.test();
    }

}

依次启动
eureka-server,
eureka-provider-one,
eureka-consumer-feign

访问http://localhost:8921/feign/hello/wy
在这里插入图片描述
到这里说明feign条用服务成功。

ps:在途中遇到一个小问题,eureka-consumer-feign调服务的时候报

feign.FeignException: status 404 reading HelloService#hello(String)
	at feign.FeignException.errorStatus(FeignException.java:78) ~[feign-core-10.1.0.jar:na]
	at feign.codec.ErrorDecoder$Default.decode(ErrorDecoder.java:93) ~[feign-core-10.1.0.jar:na]
	at feign.SynchronousMethodHandler.executeAndDecode(SynchronousMethodHandler.java:149) ~[feign-core-10.1.0.jar:na]
	at feign.SynchronousMethodHandler.invoke(SynchronousMethodHandler.java:78) ~[feign-core-10.1.0.jar:na]
	at feign.ReflectiveFeign$FeignInvocationHandler.invoke(ReflectiveFeign.java:103) ~[feign-core-10.1.0.jar:na]
	at com.sun.proxy.$Proxy77.hello(Unknown Source) ~[na:na]
	at com.wy.eurekaconsumerfeign.controller.TestController.hello(TestController.java:18) ~[classes/:na]
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_171]
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_171]
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_171]
	at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_171]
	at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:189) ~[spring-web-5.1.3.RELEASE.jar:5.1.3.RELEASE]
	at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:138) ~[spring-web-5.1.3.RELEASE.jar:5.1.3.RELEASE]
	at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:102) ~[spring-webmvc-5.1.3.RELEASE.jar:5.1.3.RELEASE]
	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:895) ~[spring-webmvc-5.1.3.RELEASE.jar:5.1.3.RELEASE]
	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:800) ~[spring-webmvc-5.1.3.RELEASE.jar:5.1.3.RELEASE]
	at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.1.3.RELEASE.jar:5.1.3.RELEASE]
	at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1038) ~[spring-webmvc-5.1.3.RELEASE.jar:5.1.3.RELEASE]
	at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:942) ~[spring-webmvc-5.1.3.RELEASE.jar:5.1.3.RELEASE]
	at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1005) ~[spring-webmvc-5.1.3.RELEASE.jar:5.1.3.RELEASE]
	at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:897) ~[spring-webmvc-5.1.3.RELEASE.jar:5.1.3.RELEASE]
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:634) ~[tomcat-embed-core-9.0.13.jar:9.0.13]
	at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:882) ~[spring-webmvc-5.1.3.RELEASE.jar:5.1.3.RELEASE]
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:741) ~[tomcat-embed-core-9.0.13.jar:9.0.13]

原因是eureka-provider-one提供的服务如下:

@RequestMapping("/index/{name}")
    public String index(@PathVariable("name") String name) {
   
        return "hello "+name+",this is first messge";
    }

eureka-consumer-feign的调用方法如下:

@RequestMapping(value = "/hello/index")
    String hello(@RequestParam(value = "name") String name);

这时候就报上面那个404错误了,于是我看了下ribbon调用的方式:

 @Override
    public String hello(String name) {
   
        return restTemplate.getForObject("http://CLOUD-EUREKA-PROVIDER/hello/index/"+name, String.class);
    }

ribbon通过url接‘/’后面直接接参数可以调用,feign通过@RequestParam传参就不行

解决办法是:
在eureka-provider-one写一个服务如下:

@RequestMapping("/hello")
    public String hello(@RequestParam String name) {
   
        return "hello "+name+",this is first messge";
    }

这样feign就可以调用这个服务了。

本文来源wySama0830,由架构君转载发布,观点不代表Java架构师必看的立场,转载请标明来源出处:https://javajgs.com/archives/14176

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