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本文主要研究一下 spring cloud openfeign 的 Targeter
Targeter
spring-cloud-openfeign-core-2.2.0.M1-sources.jar!/org/springframework/cloud/openfeign/Targeter.java
interface Targeter {
<T> T target(FeignClientFactoryBean factory, Feign.Builder feign,
FeignContext context, Target.HardCodedTarget<T> target);
}
- Targeter 定义了 target 方法,它接收 FeignClientFactoryBean、Feign.Builder、FeignContext、Target.HardCodedTarget 类型的参数
DefaultTargeter
spring-cloud-openfeign-core-2.2.0.M1-sources.jar!/org/springframework/cloud/openfeign/DefaultTargeter.java
class DefaultTargeter implements Targeter {
@Override
public <T> T target(FeignClientFactoryBean factory, Feign.Builder feign,
FeignContext context, Target.HardCodedTarget<T> target) {return feign.target(target);
}
}
- DefaultTargeter 实现了 Targeter 接口,它的 target 方法直接使用的是 Feign.Builder.target 方法
Target
feign-core-10.2.3-sources.jar!/feign/Target.java
public interface Target<T> {/* The type of the interface this target applies to. ex. {@code Route53}. */
Class<T> type();
/* configuration key associated with this target. For example, {@code route53}. */
String name();
/* base HTTP URL of the target. For example, {@code https://api/v2}. */
String url();
public Request apply(RequestTemplate input);
//......
}
- Target 接口定义了 type、name、url、apply 方法
HardCodedTarget
feign-core-10.2.3-sources.jar!/feign/Target.java
public static class HardCodedTarget<T> implements Target<T> {
private final Class<T> type;
private final String name;
private final String url;
public HardCodedTarget(Class<T> type, String url) {this(type, url, url);
}
public HardCodedTarget(Class<T> type, String name, String url) {this.type = checkNotNull(type, "type");
this.name = checkNotNull(emptyToNull(name), "name");
this.url = checkNotNull(emptyToNull(url), "url");
}
@Override
public Class<T> type() {return type;}
@Override
public String name() {return name;}
@Override
public String url() {return url;}
/* no authentication or other special activity. just insert the url. */
@Override
public Request apply(RequestTemplate input) {if (input.url().indexOf("http") != 0) {input.target(url());
}
return input.request();}
@Override
public boolean equals(Object obj) {if (obj instanceof HardCodedTarget) {HardCodedTarget<?> other = (HardCodedTarget) obj;
return type.equals(other.type)
&& name.equals(other.name)
&& url.equals(other.url);
}
return false;
}
@Override
public int hashCode() {
int result = 17;
result = 31 * result + type.hashCode();
result = 31 * result + name.hashCode();
result = 31 * result + url.hashCode();
return result;
}
@Override
public String toString() {if (name.equals(url)) {return "HardCodedTarget(type=" + type.getSimpleName() + ", url=" + url + ")";
}
return "HardCodedTarget(type=" + type.getSimpleName() + ", name=" + name + ", url=" + url
+ ")";
}
}
- HardCodedTarget 实现了 Target 接口,其构造器接收 type、name、url 参数,其 apply 方法对于 url 是 http 开头的则设置 RequestTemplate 的 target 为 url,然后构造 request 返回
HystrixTargeter
spring-cloud-openfeign-core-2.2.0.M1-sources.jar!/org/springframework/cloud/openfeign/HystrixTargeter.java
class HystrixTargeter implements Targeter {
@Override
public <T> T target(FeignClientFactoryBean factory, Feign.Builder feign,
FeignContext context, Target.HardCodedTarget<T> target) {if (!(feign instanceof feign.hystrix.HystrixFeign.Builder)) {return feign.target(target);
}
feign.hystrix.HystrixFeign.Builder builder = (feign.hystrix.HystrixFeign.Builder) feign;
SetterFactory setterFactory = getOptional(factory.getName(), context,
SetterFactory.class);
if (setterFactory != null) {builder.setterFactory(setterFactory);
}
Class<?> fallback = factory.getFallback();
if (fallback != void.class) {return targetWithFallback(factory.getName(), context, target, builder,
fallback);
}
Class<?> fallbackFactory = factory.getFallbackFactory();
if (fallbackFactory != void.class) {return targetWithFallbackFactory(factory.getName(), context, target, builder,
fallbackFactory);
}
return feign.target(target);
}
private <T> T targetWithFallbackFactory(String feignClientName, FeignContext context,
Target.HardCodedTarget<T> target, HystrixFeign.Builder builder,
Class<?> fallbackFactoryClass) {FallbackFactory<? extends T> fallbackFactory = (FallbackFactory<? extends T>) getFromContext(
"fallbackFactory", feignClientName, context, fallbackFactoryClass,
FallbackFactory.class);
return builder.target(target, fallbackFactory);
}
private <T> T targetWithFallback(String feignClientName, FeignContext context,
Target.HardCodedTarget<T> target, HystrixFeign.Builder builder,
Class<?> fallback) {
T fallbackInstance = getFromContext("fallback", feignClientName, context,
fallback, target.type());
return builder.target(target, fallbackInstance);
}
private <T> T getFromContext(String fallbackMechanism, String feignClientName,
FeignContext context, Class<?> beanType, Class<T> targetType) {Object fallbackInstance = context.getInstance(feignClientName, beanType);
if (fallbackInstance == null) {
throw new IllegalStateException(String.format(
"No" + fallbackMechanism
+ "instance of type %s found for feign client %s",
beanType, feignClientName));
}
if (!targetType.isAssignableFrom(beanType)) {
throw new IllegalStateException(String.format("Incompatible"
+ fallbackMechanism
+ "instance. Fallback/fallbackFactory of type %s is not assignable to %s for feign client %s",
beanType, targetType, feignClientName));
}
return (T) fallbackInstance;
}
private <T> T getOptional(String feignClientName, FeignContext context,
Class<T> beanType) {return context.getInstance(feignClientName, beanType);
}
}
- HystrixTargeter 实现了 Targeter 接口,其 target 方法首先判断 Feign.Builder 类型是否是 feign.hystrix.HystrixFeign.Builder,不是的话直接执行 feign.target(target) 返回
- 对于 fallback 不为 void.class 的使用 targetWithFallback 进行构造;对于 fallbackFactory 不为 void.class 的使用 targetWithFallbackFactory 进行构造;都不是的话则执行 feign.target(target) 返回
- targetWithFallbackFactory 方法使用 HystrixFeign.Builder 的 target 进行构造时使用的是 fallbackFactory;而 targetWithFallback 方法使用的是 fallbackInstance
FeignAutoConfiguration
spring-cloud-openfeign-core-2.2.0.M1-sources.jar!/org/springframework/cloud/openfeign/FeignAutoConfiguration.java
@Configuration
@ConditionalOnClass(Feign.class)
@EnableConfigurationProperties({ FeignClientProperties.class,
FeignHttpClientProperties.class })
public class FeignAutoConfiguration {
//......
@Configuration
@ConditionalOnClass(name = "feign.hystrix.HystrixFeign")
protected static class HystrixFeignTargeterConfiguration {
@Bean
@ConditionalOnMissingBean
public Targeter feignTargeter() {return new HystrixTargeter();
}
}
@Configuration
@ConditionalOnMissingClass("feign.hystrix.HystrixFeign")
protected static class DefaultFeignTargeterConfiguration {
@Bean
@ConditionalOnMissingBean
public Targeter feignTargeter() {return new DefaultTargeter();
}
}
//......
}
- FeignAutoConfiguration 在有 feign.hystrix.HystrixFeign 时创建的是 HystrixTargeter,否则创建的是 DefaultTargeter
小结
- Targeter 定义了 target 方法,它接收 FeignClientFactoryBean、Feign.Builder、FeignContext、Target.HardCodedTarget 类型的参数
- DefaultTargeter 实现了 Targeter 接口,它的 target 方法直接使用的是 Feign.Builder.target 方法
- HystrixTargeter 实现了 Targeter 接口,其 target 方法首先判断 Feign.Builder 类型是否是 feign.hystrix.HystrixFeign.Builder,不是的话直接执行 feign.target(target) 返回;否则对于 fallback 不为 void.class 的使用 targetWithFallback 进行构造;对于 fallbackFactory 不为 void.class 的使用 targetWithFallbackFactory 进行构造;都不是的话则执行 feign.target(target) 返回
doc
- Targeter