In the previous article, we introduced the construction of the registration center, including that of the cluster environment. This article introduces how to use the registration center, create a service provider, and use a simple client to call the services provided by the server.
In this article, there are three roles: service provider, service consumer, and the protagonist of the previous article, the registration center Eureka (just use the stand-alone version, and the example in this article will also use the stand-alone version of Eureka).
The overall process is as follows:
- Start the registration center Eureka first
- The provider that starts the service will provide the service and register the service with Eureka, the registry
- The consumer who starts the service, finds the service in the registry and completes the consumption
1. Service provider
1. pom.xml<?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>2.1.6.RELEASE</version> <relativePath/> <!-- lookup parent from repository --> </parent> <groupId>com.springcloud</groupId> <artifactId>producer</artifactId> <version>0.0.1-SNAPSHOT</version> <name>producer</name> <description>Demo project for Spring Boot</description> <properties> <java.version>1.8</java.version> <spring-cloud.version>Greenwich.SR1</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.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>$</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> </project>2. Configuration file application.yml
server: port: 8080 spring: application: name: spring-cloud-producer eureka: client: service-url: defaultZone: http://localhost:8761/eureka/3. Startup class ProducerApplication.java
Add @ EnableEurekaClient. Other registries can use the annotation @ EnableDiscoveryClient to register services
package com.springcloud.producer; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; import org.springframework.cloud.netflix.eureka.EnableEurekaClient; @SpringBootApplication @EnableEurekaClient public class ProducerApplication { public static void main(String[] args) { SpringApplication.run(ProducerApplication.class, args); } }4. Controller
package com.springcloud.producer.controller; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RequestParam; import org.springframework.web.bind.annotation.RestController; /** * Created with IntelliJ IDEA. * * @Date: 2019/7/2 * @Time: 0:02 * @email: [email protected] * Description: */ @RestController public class HelloController { @RequestMapping("/hello") public String hello(@RequestParam String name) { return "hello "+name+"，producer is ready"; } }
First, you can start the Eureka of the stand-alone version in the previous article, and then start the producer service provider that we just wrote. After the startup is successful, visit the link http://localhost : 8761 /, you can see that our service provider producer has successfully registered in the registry.
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At this point, the provider of the service has been configured.
2. Service consumers
1. pom.xml<?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>2.1.6.RELEASE</version> <relativePath/> <!-- lookup parent from repository --> </parent> <groupId>com.springcloud</groupId> <artifactId>consumers</artifactId> <version>0.0.1-SNAPSHOT</version> <name>consumers</name> <description>Demo project for Spring Boot</description> <properties> <java.version>1.8</java.version> <spring-cloud.version>Greenwich.SR1</spring-cloud.version> </properties> <dependencies> <dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId> </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> <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>$</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> </project>
Spring boot starter Web: this package is a general web development package, which includes spring web, spring webmvc and other packages
Spring Cloud starter openfeign: this package is the encapsulation of feign by Spring Cloud. Feign is a declarative Web service client. It supports feign's own annotations, JAX-RS annotations, and spring MVC annotations. Spring Cloud integrates Ribbon and Eureka to provide a load balanced http client when using feign.
2. Configuration file application.ymlserver: port: 8081 spring: application: name: spring-cloud-consumers eureka: client: service-url: defaultZone: http://localhost:8761/eureka/3. Startup class ConsumersApplication.java
As above, add @ EnableEurekaClient. Other registries can use the annotation @ EnableDiscoveryClient to register services
package com.springcloud.consumers; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; import org.springframework.cloud.netflix.eureka.EnableEurekaClient; import org.springframework.cloud.openfeign.EnableFeignClients; @SpringBootApplication @EnableEurekaClient @EnableFeignClients public class ConsumersApplication { public static void main(String[] args) { SpringApplication.run(ConsumersApplication.class, args); } }
@Enable feignclients: this annotation tells spring boot to scan the classes decorated by @ FeignClient when it is started. The @ FeignClient annotation will be used when making remote calls.
4. Feign remote callFeign is a declarative Web Service client. Using feign can make it easier to write a Web Service client. Its use method is to define an interface, and then add comments on it. At the same time, it also supports JAX-RS standard comments. Feign also supports pluggable encoders and decoders. Spring Cloud encapsulates feign to support Spring MVC standard annotations and HttpMessageConverters. Feign can be combined with Eureka and Ribbon to support load balancing.
Create a remote interface
package com.springcloud.consumers.remote; import org.springframework.cloud.openfeign.FeignClient; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RequestParam; /** * @Author: shiyao.wei * @Date: 2019/7/2 11:14 * @Version: 1.0 * @Desc: */ @FeignClient(name= "spring-cloud-producer") public interface HelloRemote { @RequestMapping(value = "/hello") String hello(@RequestParam(value = "name") String name); }
- Name: remote service name, and spring.application.name Name of the configuration
- The method names and parameters in this class should be consistent with those in the container in the remote service
package com.springcloud.consumers.controller; import com.springcloud.consumers.remote.HelloRemote; 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; /** * @Author: shiyao.wei * @Date: 2019/7/2 11:25 * @Version: 1.0 * @Desc: */ @RestController public class HelloController { @Autowired HelloRemote helloRemote; @RequestMapping("/hello/") public String index(@PathVariable("name") String name) { return helloRemote.hello(name); } }
Now, a simple example of service registration and invocation is completed.
3. Test
Simple callLaunch three projects successively: eureka, producer and consumer
After the startup is successful, enter the http://localhost:8080/hello?name=springcloud
You can see the page display: hello springcloud, producer is ready
It proves that our producer has started normally and the services provided are normal
Next, we test the service consumer and enter: http://localhost:8081/hello/spring
You can see the page display: hello spring, producer is ready
It indicates that the client has successfully called the remote service hello through feign and returned the result to the browser.
load balancingMake a copy of the above producer, change the name to producer 2, and modify pom.xml \ \ in is producer2, modify the Controller in it:
package com.springcloud.producer.controller; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RequestParam; import org.springframework.web.bind.annotation.RestController; /** * Created with IntelliJ IDEA. * * @Date: 2019/7/2 * @Time: 0:02 * @email: [email protected] * Description: */ @RestController public class HelloController { @RequestMapping("/hello") public String hello(@RequestParam String name) { return "hello "+name+"，producer2 is ready"; } }
modify application.yml Profile start port is 8082
Start the producer 2 that we just copied. Now you can take a look at the registration center Eureka. Now we have two producer services.
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Then we will visit: http://localhost:8081/hello/spring
The first returned result: hello spring, producer is ready
The second return result: hello spring, producer 2 is ready
Refresh the page continuously, and the two results will appear alternately, indicating that the registry provides the service load balancing function. When the number of services is increased to N, it will be found that the test results are the same, and the request will be automatically polled to each server for processing.