feign-plus
mock feign client without spring-cloud feign dependency
study from crossoverJie/feign-plus repository
Feign-Plus is a mock Spring-cloud Feign application
feign-plus，It is a clone for learning from crossover:feign-plus. The purpose is to learn how to start an annotation to inject a factorybean and get familiar with the injection process.
How To Use
The use method is the same as the original feign client.
1. using FeignPlusClient annotation on the defined third-party client
@FeignPlusClient(name = "client-service",url = "http://localhost:8080")
public interface HelloClient {
@RequestLine("GET /hello-world")
String hello();
@RequestLine("POST /bug-maker")
String bugMaker();
}2. Enable@EnableFeignPlusClientsannotation
@RunWith(SpringRunner.class)
@ActiveProfiles("test")
@SpringBootTest
@EnableFeignPlusClients(basePackages = "com.example.feignplus.test")
@EnableAutoConfiguration
class FeignPlusApplicationTests {
@Autowired
private HelloClient helloClient;
@Test
void should() {
System.out.println(helloClient.hello());
System.out.println(helloClient.bugMaker());
}
}In this way, you can build HTTP requests to call third-party interfaces, and avoid writing a lot of HTTP client code yourself.
code analysis
3. Definition of FeignPlusClient annotation
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface FeignPlusClient {
String name() default "";
/**
* @return Target url
*/
String url() default "";
}4. Definition of@EnableFeignPlusClientsannotation，Enables spring to scan the interface FeignPlusClient used by client，then construct client factory，inject into the container。
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
@Documented
@Import(FeignPlusClientsRegister.class)
public @interface EnableFeignPlusClients {
String[] value() default {};
/**
* Base packages to scan for annotated components.
*
* @return
*/
String[] basePackages() default {};
}@importis used to import configuration classes or some classes that need to be preloaded. It supports three methods。
- Configuration class with @ configuration.
- Implementation of ImportSelector.
- Implementation of ImportBeanDefinitionRegistrar.
By implementing importbeandefinitionregistrar, it can scan the client interface defined by yourself, and then define 'factorybean' to inject into the container
5. Implementation of FeignPlusBeanFactory，inject into the container
public class FeignPlusBeanFactory<T> implements FactoryBean<T>, ApplicationContextAware{
....
@Override
public T getObject() throws Exception {
FeignPlusConfigurationProperties conf = applicationContext.getBean(FeignPlusConfigurationProperties.class);
Client client;
try {
client = applicationContext.getBean("client", Client.class);
} catch (NoSuchBeanDefinitionException e) {
throw new NullPointerException("Without one of [okhttp3, Http2Client] client.");
}
T target = Feign.builder()
.client(client)
.retryer(new Retryer.Default(100, SECONDS.toMillis(1), 0))
.options(new Request.Options(conf.getConnectTimeout(), conf.getReadTimeout(), true))
.target(proxyInterface, url);
return target;
}
...
}The internal implementation is to return a feignplus factorybean object, that is, wrap a layer of third-party feign, so that each time you define HTTP client, you can reuse it and build factory beans. By calling the client interface, you can call the factoryBean class
6. Implementation of ImportBeanDefinitionRegistrar
public class FeignPlusClientsRegister implements ImportBeanDefinitionRegistrar, ResourceLoaderAware {
...
@Override
public void registerBeanDefinitions(AnnotationMetadata metadata, BeanDefinitionRegistry registry) {
AnnotationAttributes attributes = AnnotationAttributes.fromMap(metadata.getAnnotationAttributes(EnableFeignPlusClients.class.getName()));
List<String> basePackages = new ArrayList<>();
for (String pkg : attributes.getStringArray("basePackages")) {
if (StringUtils.hasText(pkg)) {
basePackages.add(pkg);
}
}
FeignPlusClientScanner scanner = new FeignPlusClientScanner(registry);
scanner.doScan(StringUtils.toStringArray(basePackages));
}
}Get the value defined in the @EnableFeignPlusClients annotation, that is, get the package address using the annotation @FeignPlusClient, and then inject it into the container through doscan function.
7. Implementation of FeignPlusClientScanner
public class FeignPlusClientScanner extends ClassPathBeanDefinitionScanner {
public FeignPlusClientScanner(BeanDefinitionRegistry registry) {
super(registry, true);
registerFilters();
}
/**
* @param basePackages
* @return
*/
@Override
public Set<BeanDefinitionHolder> doScan(String... basePackages) {
Set<BeanDefinitionHolder> beanDefinitions = super.doScan(basePackages);
if (beanDefinitions.isEmpty()) {
logger.warn("No feign plus client is found in package '" + Arrays.toString(basePackages) + "'.");
}
GenericBeanDefinition definition;
Set<String> classNames = new HashSet<>();
classNames.add("com.example.feignplus.register.FeignPlusClient");
classNames.add("com.example.feignplus.register.EnableFeignPlusClients");
List<BeanDefinitionHolder> holders = beanDefinitions.stream().filter((item) ->
!classNames.contains(item.getBeanDefinition().getBeanClassName()))
.collect(Collectors.toList());
for (BeanDefinitionHolder holder : holders) {
definition = (GenericBeanDefinition) holder.getBeanDefinition();
String beanClassName = definition.getBeanClassName();
MergedAnnotation<FeignPlusClient> feignPlus = ((ScannedGenericBeanDefinition) definition).getMetadata().getAnnotations().get(FeignPlusClient.class);
definition.setBeanClass(FeignPlusBeanFactory.class);
definition.getPropertyValues().add("proxyInterface", beanClassName);
definition.getPropertyValues().add("url", feignPlus.getValue("url").get());
}
return beanDefinitions;
}
// 只有该注解使用在interface上，才能进行FactoryBean构建和注入的候选人
@Override
protected boolean isCandidateComponent(AnnotatedBeanDefinition beanDefinition) {
return beanDefinition.getMetadata().isInterface();
}
}The implementation of Scanner is very important. It is to obtain the client interface annotated with @FeignPlusClient, build FeignPlusBeanFactory, and set the proxyInterface and url required by feign client; In this way, when the interface is called, the factory is actually called.
8. feign-client的动态指定
Feign can supports multiple clients, the clients here can be dynamically specified through the configuration file.
@Bean(value = "client")
@ConditionalOnExpression("'okhttp3'.equals('${feign.httpclient:okhttp3}')")
public Client okHttpClient(ConnectionPool connectionPool) {
OkHttpClient delegate = new OkHttpClient().newBuilder()
.connectionPool(connectionPool)
.connectTimeout(feignPlusConfigurationProperties.getConnectTimeout(), TimeUnit.MILLISECONDS)
.readTimeout(feignPlusConfigurationProperties.getReadTimeout(), TimeUnit.MILLISECONDS)
.writeTimeout(feignPlusConfigurationProperties.getWriteTimeout(), TimeUnit.MILLISECONDS)
.build();
return new feign.okhttp.OkHttpClient(delegate);
}
@Bean(value = "client")
@ConditionalOnExpression("'http2Client'.equals('${feign.httpclient:okhttp3}')")
public Client client() {
HttpClient httpClient = HttpClient.newBuilder()
.followRedirects(HttpClient.Redirect.ALWAYS)
.version(HttpClient.Version.HTTP_2)
.connectTimeout(Duration.ofMillis(feignPlusConfigurationProperties.getConnectTimeout()))
.build();
return new Http2Client(httpClient);
}