spring.factories
按照以往的慣例，在研究源碼的時候，我們先看一下spring.factories文件下自動裝配的類FeignAutoConfiguration，其中比較重要的東西有這么幾個
@Autowired(required = false)
private List<FeignClientSpecification> configurations = new ArrayList<>();
@Bean
public FeignContext feignContext() {
FeignContext context = new FeignContext();
context.setConfigurations(this.configurations);
return context;
}
@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();
}
}
- 屬性
configurations代表的是各個Feign客戶端的配置類，這個稍后會再次提到 FeignContext這個bean看名字就知道，Feign的上下文環境，包含了所有feign客戶端的配置- 接下來是兩個
Targeter是看當前是否存在hystrix環境，接下來也會提到 - 除此之外這個類還包含了HttpClient相關的配置就不展開了
@EnableFeignClients注解解析
查看完自動裝配的類，接着看@EnableFeignClients注解
進入這個注解發現，它引入了配置類 FeignClientsRegistrar，由於這個類實現了ImportBeanDefinitionRegistrar接口，所以按照我們以往的經歷直接看一下registerBeanDefinitions方法吧
public void registerBeanDefinitions(AnnotationMetadata metadata,
BeanDefinitionRegistry registry) {
registerDefaultConfiguration(metadata, registry);
registerFeignClients(metadata, registry);
}
這里分為了2步
注冊缺省配置
private void registerDefaultConfiguration(AnnotationMetadata metadata,BeanDefinitionRegistry registry) {
// 獲取注解@EnableFeignClients的注解屬性
Map<String, Object> defaultAttrs = metadata
.getAnnotationAttributes(EnableFeignClients.class.getName(), true);
if (defaultAttrs != null && defaultAttrs.containsKey("defaultConfiguration")) {
String name;
if (metadata.hasEnclosingClass()) {
name = "default." + metadata.getEnclosingClassName();
}
else {
name = "default." + metadata.getClassName();
}
// 各種信息准備就緒，現在執行注冊
registerClientConfiguration(registry, name,
defaultAttrs.get("defaultConfiguration"));
}
}
private void registerClientConfiguration(BeanDefinitionRegistry registry, Object name,
Object configuration) {
BeanDefinitionBuilder builder = BeanDefinitionBuilder
.genericBeanDefinition(FeignClientSpecification.class);
builder.addConstructorArgValue(name);
builder.addConstructorArgValue(configuration);
registry.registerBeanDefinition(
name + "." + FeignClientSpecification.class.getSimpleName(),
builder.getBeanDefinition());
}
可以看到這里就是處理注冊@EnableFeignClients上defaultConfiguration屬性所指定的客戶端的缺省配置，注意這里配置都是注冊為了FeignClientSpecification類型的bean，這個類型的bean也是本文剛開始提到的被Feign上下文持有的各個Feign客戶端持有的
注冊各個Feign客戶端
public void registerFeignClients(AnnotationMetadata metadata,
BeanDefinitionRegistry registry) {
ClassPathScanningCandidateComponentProvider scanner = getScanner();
scanner.setResourceLoader(this.resourceLoader);
Set<String> basePackages;
Map<String, Object> attrs = metadata
.getAnnotationAttributes(EnableFeignClients.class.getName());
AnnotationTypeFilter annotationTypeFilter = new AnnotationTypeFilter(
FeignClient.class);
final Class<?>[] clients = attrs == null ? null
: (Class<?>[]) attrs.get("clients");
if (clients == null || clients.length == 0) {
scanner.addIncludeFilter(annotationTypeFilter);
basePackages = getBasePackages(metadata);
}
else {
final Set<String> clientClasses = new HashSet<>();
basePackages = new HashSet<>();
for (Class<?> clazz : clients) {
basePackages.add(ClassUtils.getPackageName(clazz));
clientClasses.add(clazz.getCanonicalName());
}
AbstractClassTestingTypeFilter filter = new AbstractClassTestingTypeFilter() {
@Override
protected boolean match(ClassMetadata metadata) {
String cleaned = metadata.getClassName().replaceAll("\\$", ".");
return clientClasses.contains(cleaned);
}
};
scanner.addIncludeFilter(
new AllTypeFilter(Arrays.asList(filter, annotationTypeFilter)));
}
for (String basePackage : basePackages) {
Set<BeanDefinition> candidateComponents = scanner
.findCandidateComponents(basePackage);
for (BeanDefinition candidateComponent : candidateComponents) {
if (candidateComponent instanceof AnnotatedBeanDefinition) {
AnnotatedBeanDefinition beanDefinition = (AnnotatedBeanDefinition) candidateComponent;
AnnotationMetadata annotationMetadata = beanDefinition.getMetadata();
Assert.isTrue(annotationMetadata.isInterface(),
"@FeignClient can only be specified on an interface");
Map<String, Object> attributes = annotationMetadata
.getAnnotationAttributes(
FeignClient.class.getCanonicalName());
String name = getClientName(attributes);
registerClientConfiguration(registry, name,
attributes.get("configuration"));
registerFeignClient(registry, annotationMetadata, attributes);
}
}
}
這里一共分為3個步驟：
- 使用
ClassPathScanningCandidateComponentProvider掃描所有的標注了@FeignClient注解的接口 - 將注解上包含的屬性作為bean注冊，這些屬性也就是每個Feign客戶端端的配置
- 將
@Feign客戶端注冊
private void registerFeignClient(BeanDefinitionRegistry registry,
AnnotationMetadata annotationMetadata, Map<String, Object> attributes) {
// 1.獲取標注@Feign注解的接口名稱
String className = annotationMetadata.getClassName();
// 2.使用BeanDefinitionBuilder構造bean：FeignClientFactoryBean
BeanDefinitionBuilder definition = BeanDefinitionBuilder
.genericBeanDefinition(FeignClientFactoryBean.class);
validate(attributes);
// 3.添加FeignClientFactoryBean的各個屬性
definition.addPropertyValue("url", getUrl(attributes));
definition.addPropertyValue("path", getPath(attributes));
String name = getName(attributes);
definition.addPropertyValue("name", name);
definition.addPropertyValue("type", className);
definition.addPropertyValue("decode404", attributes.get("decode404"));
definition.addPropertyValue("fallback", attributes.get("fallback"));
definition.addPropertyValue("fallbackFactory", attributes.get("fallbackFactory"));
definition.setAutowireMode(AbstractBeanDefinition.AUTOWIRE_BY_TYPE);
// 4.設置別名
String alias = name + "FeignClient";
AbstractBeanDefinition beanDefinition = definition.getBeanDefinition();
boolean primary = (Boolean)attributes.get("primary"); // has a default, won't be null
beanDefinition.setPrimary(primary);
String qualifier = getQualifier(attributes);
if (StringUtils.hasText(qualifier)) {
alias = qualifier;
}
// 5.注冊FeignClientFactoryBean
BeanDefinitionHolder holder = new BeanDefinitionHolder(beanDefinition, className,
new String[] { alias });
BeanDefinitionReaderUtils.registerBeanDefinition(holder, registry);
}
上方這個方法通過了5步把各個FeignClient都注冊成了bean：FeignClientFactoryBean，相信看過之前文章的同學都知道FactoryBean系列的bean是干什么的了。而Feign整合Ribbon和Hystrix的核心應該也在這個類里面了