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This article mainly explains "what are the common questions about Spring Cloud Feign". Interested friends may wish to take a look. The method introduced in this paper is simple, fast and practical. Let's let the editor take you to learn what are the common problems in Spring Cloud Feign.

If the FeignClient interface uses @ PathVariable, you must specify the value attribute

/ / in some earlier versions, the "id" in @ PathVariable ("id"), that is, the value property, must be specified and cannot be omitted. FeignClient ("microservice-provider-user") public interface UserFeignClient {@ RequestMapping (value = "/ simple/ {id}", method = RequestMethod.GET) public User findById (@ PathVariable ("id") Long id);.}

Attention points and pits of custom Feign Client in Java code

@ FeignClient (name = "microservice-provider-user", configuration = UserFeignConfig.class) public interface UserFeignClient {@ GetMapping ("/ users/ {id}") User findById (@ PathVariable ("id") Long id);} / * * the configuration class of the FeignClient. Note: * 1. This class can be independent; * 2. You can also add @ Configuration to this class to declare that it is a configuration class; * you can also add @ Configuration annotation to the configuration class to declare that it is a configuration class; * but do not put this in the package scanned by the main application context @ ComponentScan at this time, * otherwise, the configuration will be shared by all Feign Client, and fine-grained configuration cannot be achieved! * personal advice: like me, do not add @ Configuration annotation * * @ author zhouli * / class UserFeignConfig {@ Bean public Logger.Level logger () {return Logger.Level.FULL;}}

The @ Configuraiton annotation can also be added to the configuration class to declare that this is a configuration class, but do not place this in the package scanned by the main application context @ ComponentScan at this time, otherwise, the configuration will be shared by all Feign Client (equivalent to becoming a general configuration, but in essence, it is still a problem caused by overlapping Spring parent-child context scanning packages), and fine-grained configuration cannot be achieved!

* * personal advice: * * like me, without the @ Configuration annotation, you don't have to enter the hole.

* * Best practice: * * customize the configuration of Feign with configuration attributes as much as possible!

@ FeignClient Annotation Properties

/ / @ FeignClient (name = "microservice-provider-user") / / in earlier versions of Spring Cloud, there is no need to provide the name attribute. Starting with the Brixton version, @ FeignClient must provide the name attribute, otherwise the application will not start properly! / / in addition, name, url and other attributes support placeholders. For example: @ FeignClient (name = "${feign.name}", url = "${feign.url}")

Class-level @ RequestMapping will be loaded by Spring MVC

RequestMapping ("/ users") @ FeignClient (name = "microservice-user") public class TestFeignClient {/ /...}

The @ RequestMapping annotation on the class is also loaded by Spring MVC. This problem has been resolved. In the earlier version, there are two solutions: * * scenario 1, "RequestMapping" * does not annotate the class, and * * scenario 2, add the following code:

Configuration@ConditionalOnClass ({Feign.class}) public class FeignMappingDefaultConfiguration {@ Bean public WebMvcRegistrations feignWebRegistrations () {return new WebMvcRegistrationsAdapter () {@ Override public RequestMappingHandlerMapping getRequestMappingHandlerMapping () {return new FeignFilterRequestMappingHandlerMapping ();}} } private static class FeignFilterRequestMappingHandlerMapping extends RequestMappingHandlerMapping {@ Override protected boolean isHandler (Class beanType) {return super.isHandler (beanType) & &! beanType.isInterface ();}

The first request failed Ribbon's Hunger load (eager-load) mode

If you need to generate Hystrix Stream monitoring information, you need to do some additional operations. Feign itself has integrated Hystrix. You can directly use @ FeignClient (value = "microservice-provider-user", fallback = XXX.class) to specify the fallback class. The fallback class inherits the interface marked by @ FeignClient.

However, if you need to use Hystrix Stream for monitoring, by default, accessing http://IP:PORT/actuator/hystrix.stream will return 404. This is because although Feign integrates Hystrix, it does not integrate Hystrix monitoring. How to add monitoring support? The following steps are required:

Step 1: add dependencies, example:

Org.springframework.cloud spring-cloud-starter-hystrix

Step 2: add @ EnableCircuitBreaker annotation to the startup class, for example:

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

Step 3: add the following to the application.yml to expose the hystrix.stream endpoint:

Management: endpoints: web: exposure: include: 'hystrix.stream'

In this way, after accessing the API of any Feign Client interface, and then accessing http://IP:PORT/actuator/hystrix.stream, a lot of Hystrix monitoring data will be displayed.

Original link: http://www.itmuch.com/spring-cloud-sum/feign-problems/

Feign uploads files

Add dependence

Io.github.openfeign.form feign-form 3.0.3 io.github.openfeign.form feign-form-spring 3.0.3

Write Feign Client

FeignClient (name = "ms-content-sample", configuration = UploadFeignClient.MultipartSupportConfig.class) public interface UploadFeignClient {@ RequestMapping (value = "/ upload", method = RequestMethod.POST, produces = {MediaType.APPLICATION_JSON_UTF8_VALUE}, consumes = MediaType.MULTIPART_FORM_DATA_VALUE) @ ResponseBody String handleFileUpload (@ RequestPart (value = "file") MultipartFile file) Class MultipartSupportConfig {@ Bean public Encoder feignFormEncoder () {return new SpringFormEncoder ();} as shown in the code, in this Feign Client, we refer to the configuration class MultipartSupportConfig, and in MultipartSupportConfig, we instantiate SpringFormEncoder. So that the Feign Client can be uploaded. Note that produeces and consumes cannot be reduced in the RequestMapping comments; @ RequestMapping (value = "/ upload", method = RequestMethod.POST, produces = {MediaType.APPLICATION_JSON_UTF8_VALUE}, consumes = MediaType.MULTIPART_FORM_DATA_VALUE)

The annotation @ RequestPart (value = "file") in the interface definition cannot be written as @ RequestParam (value = "file").

It is best to set the Hystrix timeout a little longer, such as 5 seconds, otherwise the Hystrix may time out before the file has been uploaded, resulting in an error on the client side.

Original link: http://www.itmuch.com/spring-cloud-sum/spring-cloud-feign-upload/

Feign implements Form form submission

Add dependencies:

Io.github.openfeign.form feign-form 3.2.2 io.github.openfeign.form feign-form-spring 3.2.2

Feign Client example:

@ FeignClient (name = "xxx", url = "http://www.itmuch.com/", configuration = TestFeignClient.FormSupportConfig.class) public interface TestFeignClient {@ PostMapping (value =" / test ", consumes = {MediaType.APPLICATION_FORM_URLENCODED_VALUE}, produces = {MediaType.APPLICATION_JSON_UTF8_VALUE}) void post (Map queryParam); class FormSupportConfig {@ Autowired private ObjectFactory messageConverters / / new a form encoder to support form form submission @ Bean public Encoder feignFormEncoder () {return new SpringFormEncoder (new SpringEncoder (messageConverters));} / / enable Feign log @ Bean public Logger.Level logger () {return Logger.Level.FULL;}

Call example:

@ GetMapping ("/ user/ {id}") public User findById (@ PathVariable Long id) {HashMap param = Maps.newHashMap (); param.put ("username", "zhangsan"); param.put ("password", "pwd"); this.testFeignClient.post (param); return new User ();}

Log:

... > POST http://www.baidu.com/test HTTP/1.1... [TestFeignClient#post] Accept: application/json;charset=UTF-8... [TestFeignClient#post] Content-Type: application/x-www-form-urlencoded; charset=UTF-8... [TestFeignClient#post] Content-Length: 30... [TestFeignClient#post]... [TestFeignClient#post] password=pwd&username=zhangsan... [TestFeignClient#post]-> END HTTP (30-byte body)

As you can see from the log, Feign is now able to submit data using Form forms.

Original link: http://www.itmuch.com/spring-cloud-sum/feign-form-params/

How to construct multiple parameters for Feign GET requests

Assuming that the URL to be requested contains multiple parameters, such as http://microservice-provider-user/get?id=1&username= Zhang San, how do you use Feign construction? We know that Spring Cloud has added Spring MVC annotation support to Feign, so we might as well try it in the way Spring MVC is written:

FeignClient ("microservice-provider-user") public interface UserFeignClient {@ RequestMapping (value = "/ get", method = RequestMethod.GET) public User get0 (User user);}

However, this is not correct, and the console will output an exception similar to the following.

Feign.FeignException: status 405 reading UserFeignClient#get0 (User); content: {"timestamp": 1482676142940, "status": 405, "error": "MethodNot Allowed", "exception": "org.springframework.web.HttpRequestMethodNotSupportedException", "message": "Request method 'POST' not supported", "path": "/ get"}

From the exception, even though we specified the GET method, Feign still uses the POST method to send the request. Which leads to an exception. Write it correctly as follows

Method 1 [recommended] Note: Fegin's inheritance mode cannot be used with this method

@ FeignClient ("microservice-provider-user") public interface UserFeignClient {@ GetMapping ("/ get") public User get0 (@ SpringQueryMap User user);}

Method 2 [recommended]

@ FeignClient (name = "microservice-provider-user") public interface UserFeignClient {@ RequestMapping (value = "/ get", method = RequestMethod.GET) public User get1 (@ RequestParam ("id") Long id, @ RequestParam ("username") String username);}

This is the most intuitive way, URL has several parameters, the method in the Feign interface has several parameters. Use the @ RequestParam annotation to specify what the requested parameters are.

Method 3 [not recommended] Multi-parameter URL can also be built using Map. When the target URL parameters are very large, you can use this way to simplify the writing of the Feign interface.

FeignClient (name = "microservice-provider-user") public interface UserFeignClient {@ RequestMapping (value = "/ get", method = RequestMethod.GET) public User get2 (@ RequestParam Map map);}

When calling, you can use code similar to the following.

Public User get (String username, String password) {HashMap map = Maps.newHashMap (); map.put ("id", "1"); map.put ("username", "Zhang San"); return this.userFeignClient.get2 (map);}

* * Note: * * this method is not recommended. This is mainly because of poor readability, and there will be some problems if the parameter is empty, such as map.put ("username", null); it will cause the service caller (consumer service) to receive a username of "" instead of null.

Original link: http://www.itmuch.com/spring-cloud-sum/feign-multiple-params-2/

Switch to Okhttp3 to improve QPS performance optimization

Add dependency to introduce okhttp3

Io.github.openfeign feign-okhttp ${version}

Write configuration

Feign: # feign enable hystrix In order to fuse, Downgrade # hystrix: # enabled: true # enable okhttp turn off default httpclient httpclient: enabled: false # close httpclient # configure connection pool max-connections: 200 # feign maximum number of connections max-connections-per-route: 50 # fegin maximum number of connections per path okhttp: enabled: true # compression of requests and responses to improve communication efficiency compression: request: enabled: True min-request-size: 2048 mime-types: text/xml Application/xml,application/json response: enabled: true

Parameter configuration

/ * * configure okhttp and connection pool * ConnectionPool creates 5 threads by default and maintains a persistent connection for 5 minutes * / @ Configuration@ConditionalOnClass (Feign.class) @ AutoConfigureBefore (FeignAutoConfiguration.class) / / SpringBoot automatically configures public class OkHttpConfig {/ / default foreigners leave you egg Chinese garbled, plus it OK @ Bean public Encoder encoder () {return new FormEncoder () } @ Bean public okhttp3.OkHttpClient okHttpClient () {return new okhttp3.OkHttpClient.Builder () / / set connection timeout .connectTimeout (10, TimeUnit.SECONDS) / / set read timeout .readTimeout (10, TimeUnit.SECONDS) / / set write timeout .writeTimeout (10 TimeUnit.SECONDS) / / whether to automatically reconnect .retryOnConnectionFailure (true) .connectionPool (new ConnectionPool (10,5L, TimeUnit.MINUTES)) .build () }} at this point, I believe you have a deeper understanding of "what are the common problems with Spring Cloud Feign?" you might as well do it in practice. Here is the website, more related content can enter the relevant channels to inquire, follow us, continue to learn!

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