SpringCloud学习笔记(3):使用Feign实现声明式服务调用
简介
feign是一个声明式的web service客户端,它简化了web服务客户端的编写操作,相对于ribbon+resttemplate的方式,开发者只需通过简单的接口和注解来调用http api。它支持spring mvc注解和jax-rs注解,还支持可插拔式的编码器和解码器。整合了eureka,ribbon和hystrix,具有可插拔、基于注解、负载均衡、服务熔断等一系列便捷功能。
项目介绍
- sc-parent,父模块(请参照springcloud学习笔记(1):eureka注册中心)
- sc-eureka,注册中心(请参照springcloud学习笔记(1):eureka注册中心)
- sc-provider,提供者(请参照springcloud学习笔记(1):eureka注册中心)
- sc-consumer-feign,基于feign声明式调用的消费者
基于feign声明式调用的消费者
1.在父模块下创建子模块项目sc-consumer-feign,pom.xml:
<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>com.cf</groupid> <artifactid>sc-parent</artifactid> <version>0.0.1-snapshot</version> </parent> <artifactid>sc-consumer-feign</artifactid> <dependencies> <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> </dependencies> </project>
2.创建启动类feign.feignapplication:
package feign; import org.springframework.boot.springapplication; import org.springframework.boot.autoconfigure.springbootapplication; import org.springframework.cloud.openfeign.enablefeignclients; @springbootapplication @enablefeignclients public class feignapplication { public static void main(string[] args) { springapplication.run(feignapplication.class, args); } }
3.创建feign声明式接口:feign.inter.bookservice
package feign.inter; import org.springframework.cloud.openfeign.feignclient; import org.springframework.web.bind.annotation.getmapping; @feignclient("sc-provider") public interface bookservice { @getmapping("/book/list") public string getbooklist(); }
4.创建调用提供者服务的controller:
package provider.controller; import org.springframework.web.bind.annotation.getmapping; import org.springframework.web.bind.annotation.requestmapping; import org.springframework.web.bind.annotation.restcontroller; @requestmapping("/book") @restcontroller public class bookcontroller { @getmapping("/list") public string getbooklist(){ return "[\"java入门到放弃\",\"c++入门到放弃\",\"python入门到放弃\",\"c入门到放弃\"]"; } }
5.创建application.yml:
server: port: 8084 spring: application: name: sc-consumer-feign eureka: client: registerwitheureka: false serviceurl: defaultzone: http://localhost:8080/eureka/
6.依次启动注册中心sc-eureka、提供者sc-provider、消费者sc-consumer-feign,并访问http://localhost:8084/feign/getbooklist:
feign基于ribbon实现,也具有ribbon负载均衡的特性,可以将调用的提供者服务换成sc-provider-random(请参照springcloud学习笔记(2):使用ribbon负载均衡)来测试。
带参数的请求
上面例子没有涉及到参数的传递,接下来测试下如何使用feign构造带参数的请求,首先对提供者和消费者做如下更改:
//提供者controller添加了两个参数,并打印到控制台。 @requestmapping("/book") @restcontroller public class bookcontroller { @getmapping("/list") public string getbooklist(string param1, integer param2){ system.out.println(param1 + ":" + param2); return "[\"java入门到放弃\",\"c++入门到放弃\",\"python入门到放弃\",\"c入门到放弃\"]"; } } //消费者feign接口和controller添加参数 @feignclient("sc-provider") public interface bookservice { @getmapping("/book/list") public string getbooklist(string param1, integer param2); } @requestmapping("/feign") @restcontroller public class feigncontroller { @autowired private bookservice bookservice; @getmapping("/getbooklist") public string getbooklist(){ return bookservice.getbooklist("java", 520); } }
依次启动注册中心sc-eureka、提供者sc-provider、消费者sc-consumer-feign,启动消费者sc-consumer-feign时会启动失败:
java.lang.illegalstateexception: method has too many body parameters: public abstract java.lang.string feign.inter.bookservice.getbooklist(java.lang.string,java.lang.integer)
解决方法1
更改feign接口,为参数添加@requestparam注解:
@feignclient("sc-provider") public interface bookservice { @getmapping("/book/list") public string getbooklist(@requestparam("param1") string param1, @requestparam("param2") integer param2); }
解决方法2
将参数封装到map里,更改消费者feign接口和controller:
@feignclient("sc-provider") public interface bookservice { @getmapping("/book/list") public string getbooklist(@requestparam map<string, object> parammap); } @requestmapping("/feign") @restcontroller public class feigncontroller { @autowired private bookservice bookservice; @getmapping("/getbooklist") public string getbooklist(){ map<string,object> parammap = new hashmap<string, object>(); parammap.put("param1", "java"); parammap.put("param2", 520); return bookservice.getbooklist(parammap); } }
在参数较多的情况下,该方式可以简化feign接口的编写。
自定义类型的参数
openfeign的@querymap注解支持将自定义类型用于get参数映射,由于@querymap和spring不兼容,spring cloud openfeign提供了一个等价的@springquerymap注解,可以用于自定义类型和map类型的参数映射。下面将使用自定义类型params作为参数,使用@springquerymap注解来处理自定义类型的参数映射。
1.分别在提供者和消费者中创建类params(可以建一个公共模块,然后在提供者和消费者中添加依赖):
public class params { private string param1; private integer param2; public string getparam1() { return param1; } public void setparam1(string param1) { this.param1 = param1; } public integer getparam2() { return param2; } public void setparam2(integer param2) { this.param2 = param2; } @override public string tostring() { return "params [param1=" + param1 + ", param2=" + param2 + "]"; } public params(string param1, integer param2) { this.param1 = param1; this.param2 = param2; } public params() {} }
2.更改提供者和消费者相关类
//提供者 @requestmapping("/book") @restcontroller public class bookcontroller { @getmapping("/list") public string getbooklist(params params){ system.out.println(params.tostring()); return "[\"java入门到放弃\",\"c++入门到放弃\",\"python入门到放弃\",\"c入门到放弃\"]"; } } //消费者 @feignclient("sc-provider") public interface bookservice { @getmapping("/book/list") public string getbooklist(@springquerymap params params); } @requestmapping("/feign") @restcontroller public class feigncontroller { @autowired private bookservice bookservice; @getmapping("/getbooklist") public string getbooklist(){ params params = new params("java", 520); return bookservice.getbooklist(params); } }
3.依次启动注册中心sc-eureka、提供者sc-provider、消费者sc-consumer-feign,并访问http://localhost:8084/feign/getbooklist,提供者控制台输出:
params [param1=java, param2=520]