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This article mainly explains "how to customize the annotation translator for Feign". Interested friends may wish to have a look. The method introduced in this paper is simple, fast and practical. Let's let the editor take you to learn how to customize the annotation translator for Feign.

Feign Custom Note translator create a new custom note MyUrlpackage org.crazyit.cloud.contract; import java.lang.annotation.ElementType;import java.lang.annotation.Retention;import java.lang.annotation.RetentionPolicy;import java.lang.annotation.Target; / / this annotation can only define the method @ Target (ElementType.METHOD) @ Retention (RetentionPolicy.RUNTIME) public @ interface MyUrl {/ / configure two properties String url (); String method () for the annotation } create a new interface and annotate package org.crazyit.cloud.contract; public interface ContractClient {@ MyUrl (url = "/ hello", method = "GET") public String hello () using MyUrl; define the annotation translator package org.crazyit.cloud.contract; import java.lang.annotation.Annotation;import java.lang.reflect.Method; import feign.Contract.BaseContract;import feign.MethodMetadata Public class MyContract extends BaseContract {@ Override protected void processAnnotationOnClass (MethodMetadata data, Class clz) {/ / handles class-level annotations} @ Override protected void processAnnotationOnMethod (MethodMetadata data, Annotation annotation, Method method) {/ / annotations are of type MyUrl before processing if (MyUrl.class.isInstance (annotation)) {MyUrl myUrl = method.getAnnotation (MyUrl.class) String url = myUrl.url (); String httpMethod = myUrl.method (); data.template () .method (httpMethod); data.template () .append (url);} @ Override protected boolean processAnnotationsOnParameter (MethodMetadata data, Annotation [] annotations, int paramIndex) {/ / process parameter level annotation return false }} Test class package org.crazyit.cloud.contract; import org.crazyit.cloud.jaxrs.RsClient; import feign.Feign;import feign.jaxrs.JAXRSContract; public class ContractMain {public static void main (String [] args) {ContractClient client = Feign.builder () .contract (new MyContract ()) .target (ContractClient.class, "http://localhost:8080");" String result = client.hello (); System.out.println (result);}} start the service class

test

Hello World

Feign comment description

Feign is a commonly used micro-service rpc invocation framework. Here are some notes.

@ Target ({ElementType.TYPE}) @ Retention (RetentionPolicy.RUNTIME) @ Documented@Inheritedpublic @ interface FeignClient {/ * value works the same as name. If url is not configured, the configured value will be used as the service name for service discovery. On the contrary, it is just a name. * * / @ AliasFor ("name") String value () default ""; / * serviceId is obsolete and can be used directly with name. * / * * @ deprecated * / @ Deprecated String serviceId () default "; / * the interface provided by a service is defined in more than one class, so the name conflict of Bean will be reported when startup. * solution: * 1: add * spring.main.allow-bean-definition-overriding=true * * 2: specify contextid * * / String contextId () default "" for each client; / * * you need a name when registering Feign Client Configuration, which is obtained through the getClientName method. * looking at the source code, we can see that if contextId is configured, contextId will be used. * if it is not configured, it will go to value, then name, and finally serviceId. * it is not configured by default, and an error will be reported when a service has multiple Feign Client. * * the second role is that in registering FeignClient, contextId will be used as part of the Client alias. If qualifier is configured, qualifier will be used as the alias first. * * / / * see value * / @ AliasFor ("value") String name () default "; / * * in the registration FeignClient, specify the client alias * * / String qualifier () default" / * * url is used to configure the address of the specified service, which is equivalent to requesting the service directly without going through the service selection of Ribbon. Scenarios such as debugging can be used. * * / String url () default ""; / * when a 404 error occurs in the call request, the value of decode404 is true, then decoder decoding will be performed, otherwise an exception will be thrown. * * / boolean decode404 () default false; / * * configuration is the configuration Feign configuration class, in which you can customize Feign's Encoder, Decoder, LogLevel, Contract, and so on. * see the FeignConfiguration class * * / Class [] configuration () default {}; / * * define the fault-tolerant handling class, that is, fallback logic. The fallback class must implement the Feign Client interface and cannot know the exception information of the circuit breaker. * example: * / / implement calling API method * @ Component * public class UserRemoteClientFallback implements UserRemoteClient {* @ Override * public User getUser (int id) {* return new User (0, "default fallback") * user Service * @ FeignClient (value = "user", fallback = UserRemoteClientFallback.class) * public interface UserRemoteClient {* @ GetMapping ("/ user/get") * public User getUser (@ RequestParam ("id") int id); *} * / Class fallback () default void.class / * * is also a fault-tolerant processing, and you can know the abnormal information of the fuse. Another way to deal with fuses. * * / / Service class is passed into FallbackFactory template parameter * @ Component * public class UserRemoteClientFallbackFactory implements FallbackFactory {* private Logger logger = LoggerFactory.getLogger (UserRemoteClientFallbackFactory.class) as a parameter * * @ Override * public UserRemoteClient create (Throwable cause) {* return new UserRemoteClient () {* @ Override * public User getUser (int id) {* logger.error ("UserRemoteClient.getUser exception", cause) * return new User (0, "default"); * Class fallbackFactory () default void.class / * * path defines a unified prefix for the current FeignClient access interface * for example, the interface address is / user/get. If you define the prefix as user, you only need to write / get for the path on the specific method. * * @ FeignClient (name = "user", path= "user") * public interface UserRemoteClient {* @ GetMapping ("/ get") * public User getUser (@ RequestParam ("id") int id); *} * * / String path () default "; / * * primary corresponds to the @ Primary annotation and defaults to true. * there is also a reason for officials to set it this way. When our Feign implements fallback, it means that Feign Client has multiple identical Bean in the Spring container. * when we use @ Autowired (@ Resource injection object is recommended) for injection, we don't know which one to inject, so we need to set a high priority, @ Primary annotation does this. * * / boolean primary () default true;} at this point, I believe you have a better understanding of "how to customize the annotation translator for 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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