概述
Feign能干什么
feign旨在使编写java http客户端变的更容易
前面在使用Ribbon+RestTemplate时，利用RestTemplate对http请求的封装处理，形成了一套膜版画的调用方法。但是在实际开发中，由于对服务依赖的调用可能不止一处，往往一个接口会被多处调用，所以通常都会针对每个微服务自行封装一些客户端类来包装这些依赖服务的调用。所以，Feign在此基础上做了进一步封装，由他来帮助我们定义和实现依赖服务接口的定义。在Feign的实现下，我们只需要创建一个接口并使用注解的方式来配置他(以前是在DAO接口上面标注Mapper注解，现在是在一个微服务接口上面标注一个Feign注解即可),即可完成对服务提供方的接口绑定，简化了使用Spring cloud Ribbon时，自动封装服务调用客户端的开发量。
Feign集成了Ribbon
利用Ribbon维护了SPRINGBOOT-MYBATIS-PROVIDER-001的服务列表信息，并且通过轮询实现了客户端的负载均衡。而与Ribbon不同额是，通过feign只需要定义服务绑定接口且以声明式的方法，优雅而简单的实现了服务调用
公共api中包括要提供出去的服务接口以及实体类，在此先上一些踩过的坑
当api项目的pom.xml中依赖的是下面代码中的包时
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-feign</artifactId>
<version>1.4.7.RELEASE</version>
</dependency>
服务提供者依赖了api包，启动类启动时报如下错误
org.springframework.beans.factory.BeanDefinitionStoreException: Failed to process import candidates for configuration class [com.hc.config.SwaggerConfig]; nested exception is java.io.FileNotFoundException: class path resource [org/springframework/boot/autoconfigure/web/ServerPropertiesAutoConfiguration.class] cannot be opened because it does not exist
at org.springframework.context.annotation.ConfigurationClassParser.processImports(ConfigurationClassParser.java:596) ~[spring-context-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.context.annotation.ConfigurationClassParser.access$900(ConfigurationClassParser.java:108) ~[spring-context-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.context.annotation.ConfigurationClassParser$DeferredImportSelectorGroupingHandler.lambda$processGroupImports$1(ConfigurationClassParser.java:805) ~[spring-context-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at java.util.ArrayList.forEach(ArrayList.java:1257) ~[na:1.8.0_191]
at org.springframework.context.annotation.ConfigurationClassParser$DeferredImportSelectorGroupingHandler.processGroupImports(ConfigurationClassParser.java:801) ~[spring-context-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.context.annotation.ConfigurationClassParser$DeferredImportSelectorHandler.process(ConfigurationClassParser.java:771) ~[spring-context-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.context.annotation.ConfigurationClassParser.parse(ConfigurationClassParser.java:185) ~[spring-context-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.context.annotation.ConfigurationClassPostProcessor.processConfigBeanDefinitions(ConfigurationClassPostProcessor.java:315) ~[spring-context-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.context.annotation.ConfigurationClassPostProcessor.postProcessBeanDefinitionRegistry(ConfigurationClassPostProcessor.java:232) ~[spring-context-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.context.support.PostProcessorRegistrationDelegate.invokeBeanDefinitionRegistryPostProcessors(PostProcessorRegistrationDelegate.java:275) ~[spring-context-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.context.support.PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(PostProcessorRegistrationDelegate.java:95) ~[spring-context-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.context.support.AbstractApplicationContext.invokeBeanFactoryPostProcessors(AbstractApplicationContext.java:705) ~[spring-context-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:531) ~[spring-context-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:140) ~[spring-boot-2.1.6.RELEASE.jar:2.1.6.RELEASE]
at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:742) [spring-boot-2.1.6.RELEASE.jar:2.1.6.RELEASE]
at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:389) [spring-boot-2.1.6.RELEASE.jar:2.1.6.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:311) [spring-boot-2.1.6.RELEASE.jar:2.1.6.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1213) [spring-boot-2.1.6.RELEASE.jar:2.1.6.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1202) [spring-boot-2.1.6.RELEASE.jar:2.1.6.RELEASE]
at com.hc.ApplicationProvider001.main(ApplicationProvider001.java:90) [classes/:na]
Caused by: java.io.FileNotFoundException: class path resource [org/springframework/boot/autoconfigure/web/ServerPropertiesAutoConfiguration.class] cannot be opened because it does not exist
at org.springframework.core.io.ClassPathResource.getInputStream(ClassPathResource.java:180) ~[spring-core-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.core.type.classreading.SimpleMetadataReader.<init>(SimpleMetadataReader.java:51) ~[spring-core-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.core.type.classreading.SimpleMetadataReaderFactory.getMetadataReader(SimpleMetadataReaderFactory.java:103) ~[spring-core-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.boot.type.classreading.ConcurrentReferenceCachingMetadataReaderFactory.createMetadataReader(ConcurrentReferenceCachingMetadataReaderFactory.java:86) ~[spring-boot-2.1.6.RELEASE.jar:2.1.6.RELEASE]
at org.springframework.boot.type.classreading.ConcurrentReferenceCachingMetadataReaderFactory.getMetadataReader(ConcurrentReferenceCachingMetadataReaderFactory.java:73) ~[spring-boot-2.1.6.RELEASE.jar:2.1.6.RELEASE]
at org.springframework.core.type.classreading.SimpleMetadataReaderFactory.getMetadataReader(SimpleMetadataReaderFactory.java:81) ~[spring-core-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.context.annotation.ConfigurationClassParser.asSourceClass(ConfigurationClassParser.java:682) ~[spring-context-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.context.annotation.ConfigurationClassParser$SourceClass.getRelated(ConfigurationClassParser.java:1074) ~[spring-context-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.context.annotation.ConfigurationClassParser$SourceClass.getAnnotationAttributes(ConfigurationClassParser.java:1055) ~[spring-context-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.context.annotation.ConfigurationClassParser.collectImports(ConfigurationClassParser.java:538) ~[spring-context-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.context.annotation.ConfigurationClassParser.getImports(ConfigurationClassParser.java:511) ~[spring-context-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.context.annotation.ConfigurationClassParser.doProcessConfigurationClass(ConfigurationClassParser.java:302) ~[spring-context-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.context.annotation.ConfigurationClassParser.processConfigurationClass(ConfigurationClassParser.java:242) ~[spring-context-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.context.annotation.ConfigurationClassParser.processImports(ConfigurationClassParser.java:586) ~[spring-context-5.1.8.RELEASE.jar:5.1.8.RELEASE]
... 19 common frames omitted
最终经查证，发现feign的包应该依赖如下：
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-openfeign</artifactId>
<version>2.1.2.RELEASE</version>
</dependency>
-----------end----------最终解决了提供者启动报错问题。
=================================================================
springboot-mybatis-consumer-feign中的代码如下：
启动类
package com.hc;
import org.apache.log4j.Logger;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.openfeign.EnableFeignClients;
@SpringBootApplication(exclude= {DataSourceAutoConfiguration.class})
@EnableDiscoveryClient
@EnableFeignClients(basePackages = {"com.hc"}) //使用feign代替ribbon
public class AppUserConsumerFeign001 {
private static Logger logger = Logger.getLogger(AppUserConsumerFeign001.class);
/**
* Start
*/
public static void main(String[] args) {
SpringApplication.run(AppUserConsumerFeign001.class, args);
// logger.info("SpringBoot Start Success");
}
}
controller类
package com.hc.controller;
import com.hc.model.User;
import com.hc.service.UserClientService;
import org.apache.log4j.Logger;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.cloud.client.ServiceInstance;
import org.springframework.cloud.client.discovery.DiscoveryClient;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.client.RestTemplate;
import java.util.List;
/**
*/
@Controller
@RequestMapping("/consumerFeign001")
public class UserClientController {
private Logger logger = Logger.getLogger(UserClientController.class);
@Autowired
UserClientService userClientService;
@RequestMapping("/getUsers")
@ResponseBody
public List<User> getUsers() {
return userClientService.getUsers();
}
}
依赖的公共接口提供模块api(spring-mybatis-api)，代码如下：
@FeignClient(value="SPRINGBOOT-MYBATIS-PROVIDER-001")
public interface UserClientService {
@RequestMapping("/getUsers")
List<User> getUsers();
}
服务提供者(springboot-mybatis-provider)controller中代码如下：
@RequestMapping("/getUserInfo")
@ResponseBody
public List<User> getUserInfo() {
List<User> userList = userService.getUserInfo();
if(userList!=null){
System.out.println("user.getName():"+userList.get(0).getName());
logger.info("user.getAge():"+userList.get(0).getAge());
}
return userList;
}
方法名不规范，请忽略，此方法是查询所有用户的
首次访问结果如下：
报错信息
排查原因------------------------start--------------------------------------
发现api中提供的接口路径与提供者提供的接口路径不一致，如下：
#api中service中代码片段
@FeignClient(value="SPRINGBOOT-MYBATIS-PROVIDER-001")
public interface UserClientService {
@RequestMapping("/getUsers")
List<User> getUsers();
}
#提供者controller中代码片段
@RequestMapping("/getUserInfo")
@ResponseBody
public List<User> getUserInfo() {
List<User> userList = userService.getUserInfo();
if(userList!=null){
System.out.println("user.getName():"+userList.get(0).getName());
logger.info("user.getAge():"+userList.get(0).getAge());
}
return userList;
}
结果发现两者的路径不同，然后将api中的路径与提供者controller中的路径进行统一
#api中service中代码片段
@FeignClient(value="SPRINGBOOT-MYBATIS-PROVIDER-001")
public interface UserClientService {
@RequestMapping("/getUserInfo")
List<User> getUsers();
}
#提供者controller中代码片段
@RequestMapping("/getUserInfo")
@ResponseBody
public List<User> getUserInfo() {
List<User> userList = userService.getUserInfo();
if(userList!=null){
System.out.println("user.getName():"+userList.get(0).getName());
logger.info("user.getAge():"+userList.get(0).getAge());
}
return userList;
}
再次访问，结果如下：
默认feign使用的是轮询算法
排查原因------------------------end--------------------------------------
注意：此处也给大家展示一个涛哥踩得大坑，这个坑是真的坑，而且是稍不注意就会导致大家话费很长的时间来找，并且不一定能找到的坑
api（springb-mybatis-api）中的原代码，会导致springboot-mybatis-feign的启动报错
报错信息是这样的
org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'userConsumerFeign002Controller': Unsatisfied dependency expressed through field 'userClientService'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'com.hc.service.UserClientService': FactoryBean threw exception on object creation; nested exception is java.lang.IllegalStateException: PathVariable annotation was empty on param 0.
at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:596) ~[spring-beans-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:90) ~[spring-beans-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessProperties(AutowiredAnnotationBeanPostProcessor.java:374) ~[spring-beans-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1411) ~[spring-beans-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:592) ~[spring-beans-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:515) ~[spring-beans-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:320) ~[spring-beans-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222) ~[spring-beans-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:318) ~[spring-beans-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:199) ~[spring-beans-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:845) ~[spring-beans-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:877) ~[spring-context-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:549) ~[spring-context-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:140) ~[spring-boot-2.1.6.RELEASE.jar:2.1.6.RELEASE]
at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:742) [spring-boot-2.1.6.RELEASE.jar:2.1.6.RELEASE]
at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:389) [spring-boot-2.1.6.RELEASE.jar:2.1.6.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:311) [spring-boot-2.1.6.RELEASE.jar:2.1.6.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1213) [spring-boot-2.1.6.RELEASE.jar:2.1.6.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1202) [spring-boot-2.1.6.RELEASE.jar:2.1.6.RELEASE]
at com.hc.ApplicationConsumerfeign002.main(ApplicationConsumerfeign002.java:20) [classes/:na]
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'com.hc.service.UserClientService': FactoryBean threw exception on object creation; nested exception is java.lang.IllegalStateException: PathVariable annotation was empty on param 0.
at org.springframework.beans.factory.support.FactoryBeanRegistrySupport.doGetObjectFromFactoryBean(FactoryBeanRegistrySupport.java:178) ~[spring-beans-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.beans.factory.support.FactoryBeanRegistrySupport.getObjectFromFactoryBean(FactoryBeanRegistrySupport.java:101) ~[spring-beans-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.beans.factory.support.AbstractBeanFactory.getObjectForBeanInstance(AbstractBeanFactory.java:1674) ~[spring-beans-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.getObjectForBeanInstance(AbstractAutowireCapableBeanFactory.java:1249) ~[spring-beans-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:257) ~[spring-beans-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:199) ~[spring-beans-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.beans.factory.config.DependencyDescriptor.resolveCandidate(DependencyDescriptor.java:277) ~[spring-beans-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.beans.factory.support.DefaultListableBeanFactory.addCandidateEntry(DefaultListableBeanFactory.java:1474) ~[spring-beans-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.beans.factory.support.DefaultListableBeanFactory.findAutowireCandidates(DefaultListableBeanFactory.java:1431) ~[spring-beans-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1214) ~[spring-beans-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1171) ~[spring-beans-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:593) ~[spring-beans-5.1.8.RELEASE.jar:5.1.8.RELEASE]
... 19 common frames omitted
Caused by: java.lang.IllegalStateException: PathVariable annotation was empty on param 0.
at feign.Util.checkState(Util.java:130) ~[feign-core-10.2.3.jar:na]
at org.springframework.cloud.openfeign.annotation.PathVariableParameterProcessor.processArgument(PathVariableParameterProcessor.java:52) ~[spring-cloud-openfeign-core-2.1.2.RELEASE.jar:2.1.2.RELEASE]
at org.springframework.cloud.openfeign.support.SpringMvcContract.processAnnotationsOnParameter(SpringMvcContract.java:292) ~[spring-cloud-openfeign-core-2.1.2.RELEASE.jar:2.1.2.RELEASE]
at feign.Contract$BaseContract.parseAndValidateMetadata(Contract.java:110) ~[feign-core-10.2.3.jar:na]
at org.springframework.cloud.openfeign.support.SpringMvcContract.parseAndValidateMetadata(SpringMvcContract.java:188) ~[spring-cloud-openfeign-core-2.1.2.RELEASE.jar:2.1.2.RELEASE]
at feign.Contract$BaseContract.parseAndValidatateMetadata(Contract.java:66) ~[feign-core-10.2.3.jar:na]
at feign.ReflectiveFeign$ParseHandlersByName.apply(ReflectiveFeign.java:154) ~[feign-core-10.2.3.jar:na]
at feign.ReflectiveFeign.newInstance(ReflectiveFeign.java:52) ~[feign-core-10.2.3.jar:na]
at feign.Feign$Builder.target(Feign.java:251) ~[feign-core-10.2.3.jar:na]
at org.springframework.cloud.openfeign.HystrixTargeter.target(HystrixTargeter.java:36) ~[spring-cloud-openfeign-core-2.1.2.RELEASE.jar:2.1.2.RELEASE]
at org.springframework.cloud.openfeign.FeignClientFactoryBean.loadBalance(FeignClientFactoryBean.java:238) ~[spring-cloud-openfeign-core-2.1.2.RELEASE.jar:2.1.2.RELEASE]
at org.springframework.cloud.openfeign.FeignClientFactoryBean.getTarget(FeignClientFactoryBean.java:267) ~[spring-cloud-openfeign-core-2.1.2.RELEASE.jar:2.1.2.RELEASE]
at org.springframework.cloud.openfeign.FeignClientFactoryBean.getObject(FeignClientFactoryBean.java:247) ~[spring-cloud-openfeign-core-2.1.2.RELEASE.jar:2.1.2.RELEASE]
at org.springframework.beans.factory.support.FactoryBeanRegistrySupport.doGetObjectFromFactoryBean(FactoryBeanRegistrySupport.java:171) ~[spring-beans-5.1.8.RELEASE.jar:5.1.8.RELEASE]
... 30 common frames omitted
产生这个错误的原因如下
@FeignClient(value="SPRINGBOOT-MYBATIS-PROVIDER-001")
UserClientServiceFallbackFactory.class)
public interface UserClientService {
@RequestMapping("/getUserInfo")
List<User> getUsers();
@RequestMapping(value = "/getRealUserInfo/{id}" , method = RequestMethod.GET)
// 原先不规范写法会导致消费端启动报错，大家一定要注意
User getRealUserInfo(@PathVariable Integer id);
// 规范的写法
// User getRealUserInfo(@PathVariable("id") Integer id);
}
