spring cloud openfeign 源码实例解析

2023-08-11 18:41:04 148

一、读取注解信息

入口

importorg.springframework.boot.SpringApplication;
importorg.springframework.boot.autoconfigure.SpringBootApplication;
importorg.springframework.cloud.openfeign.EnableFeignClients;


@SpringBootApplication
@EnableFeignClients
publicclassCjsPriceServiceApplication{

publicstaticvoidmain(String[]args){
SpringApplication.run(CjsPriceServiceApplication.class,args);
}

}

springboot项目启动后会自动扫描application上面的注解，@EnableFeignClients的注解如下

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
@Documented
@Import(FeignClientsRegistrar.class)
public@interfaceEnableFeignClients{
。。。。
}

在注解中导入了FeignClientsRegistrar类，用来像spring注册，EnableFeignClients和FeignClient上面开发人员添加的注解信息

@Override
publicvoidregisterBeanDefinitions(AnnotationMetadatametadata,
BeanDefinitionRegistryregistry){
registerDefaultConfiguration(metadata,registry);
registerFeignClients(metadata,registry);
}

二、当项目启动，读取@Autowired时会调用，实现了FactoryBean接口的FeignClientFactoryBean.getObject()方法

@Override
publicObjectgetObject()throwsException{
returngetTarget();
}

TgetTarget(){
FeignContextcontext=this.applicationContext.getBean(FeignContext.class);
Feign.Builderbuilder=feign(context);

if(!StringUtils.hasText(this.url)){
if(!this.name.startsWith("http")){
this.url="http://"+this.name;
}
else{
this.url=this.name;
}
this.url+=cleanPath();
return(T)loadBalance(builder,context,
newHardCodedTarget<>(this.type,this.name,this.url));
}
if(StringUtils.hasText(this.url)&&!this.url.startsWith("http")){
this.url="http://"+this.url;
}
Stringurl=this.url+cleanPath();
Clientclient=getOptional(context,Client.class);
if(client!=null){
if(clientinstanceofLoadBalancerFeignClient){
//notloadbalancingbecausewehaveaurl,
//butribbonisontheclasspath,sounwrap
client=((LoadBalancerFeignClient)client).getDelegate();
}
builder.client(client);
}
Targetertargeter=get(context,Targeter.class);
return(T)targeter.target(this,builder,context,
newHardCodedTarget<>(this.type,this.name,url));
}

可以看到getTarget（）有两种返回结果的情况，其原理都一样后来调用了targeter.target（）方法

packageorg.springframework.cloud.openfeign;

importfeign.Feign;
importfeign.Target;

/**
*@authorSpencerGibb
*/
interfaceTargeter{

Ttarget(FeignClientFactoryBeanfactory,Feign.Builderfeign,
FeignContextcontext,Target.HardCodedTargettarget);

}

默认实现类

packageorg.springframework.cloud.openfeign;

importfeign.Feign;
importfeign.Target;

/**
*@authorSpencerGibb
*/
classDefaultTargeterimplementsTargeter{

@Override
publicTtarget(FeignClientFactoryBeanfactory,Feign.Builderfeign,
FeignContextcontext,Target.HardCodedTargettarget){
returnfeign.target(target);
}

}

然后再看feign.target(target);方法

publicTtarget(Targettarget){
returnbuild().newInstance(target);
}

publicFeignbuild(){
SynchronousMethodHandler.FactorysynchronousMethodHandlerFactory=
newSynchronousMethodHandler.Factory(client,retryer,requestInterceptors,logger,
logLevel,decode404,closeAfterDecode,propagationPolicy);
ParseHandlersByNamehandlersByName=
newParseHandlersByName(contract,options,encoder,decoder,queryMapEncoder,
errorDecoder,synchronousMethodHandlerFactory);
returnnewReflectiveFeign(handlersByName,invocationHandlerFactory,queryMapEncoder);
}
}

build（）方法返回了创建代理类的对象，然后调用了创建代理的newInstance方法

publicTnewInstance(Targettarget){
MapnameToHandler=targetToHandlersByName.apply(target);
MapmethodToHandler=newLinkedHashMap();
ListdefaultMethodHandlers=newLinkedList();

for(Methodmethod:target.type().getMethods()){
if(method.getDeclaringClass()==Object.class){
continue;
}elseif(Util.isDefault(method)){
DefaultMethodHandlerhandler=newDefaultMethodHandler(method);
defaultMethodHandlers.add(handler);
methodToHandler.put(method,handler);
}else{
methodToHandler.put(method,nameToHandler.get(Feign.configKey(target.type(),method)));
}
}
InvocationHandlerhandler=factory.create(target,methodToHandler);
Tproxy=(T)Proxy.newProxyInstance(target.type().getClassLoader(),
newClass[]{target.type()},handler);

for(DefaultMethodHandlerdefaultMethodHandler:defaultMethodHandlers){
defaultMethodHandler.bindTo(proxy);
}
returnproxy;
}

最后，当我们项目中使用@Autowired注入时，就回调用工厂类FeignClientFactoryBean方法的getObject()方法返回我们的代理对象

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持毛票票。

spring cloud openfeign 源码实例解析

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