@Configuration
@EnableApolloConfig
public class AppConfig {
@Bean
public TestJavaConfigBean javaConfigBean() {
return new TestJavaConfigBean();
}
}
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先說最關鍵的兩個類，以前的Spring Boot系列也屢次提到過BeanFactoryPostProcessor（allows for custom modification of an application context's bean definitions，A BeanFactoryPostProcessor may interact with and modify bean definitions, but never bean instances）和BeanPostProcessor（Factory hook that allows for custom modification of new bean instances,e.g. checking for marker interfaces or wrapping them with proxies）。app
在上文提到的AnnotationConfigServletWebServerApplicationContext（即Spring Boot默認的ApplicationContext）裏面有個AnnotatedBeanDefinitionReader屬性， AnnotatedBeanDefinitionReader會向BeanFactory註冊各類BeanFactoryPostProcessor和BeanPostProcessor，其中的ConfigurationClassPostProcessor主要負責ConfigurationClass的解析（used for bootstrapping processing of{@link Configuration @Configuration} classes），此處爲Bean加載的入口，在後續的處理過程當中會陸續加入各類BeanFactoryProcessor和BeanPostProcessor用於擴展（若有須要，咱們都可以自定義），以下：
if (!registry.containsBeanDefinition(CONFIGURATION_ANNOTATION_PROCESSOR_BEAN_NAME)) {
RootBeanDefinition def = new RootBeanDefinition(`ConfigurationClassPostProcessor.class`);
def.setSource(source);
beanDefs.add(registerPostProcessor(registry, def, CONFIGURATION_ANNOTATION_PROCESSOR_BEAN_NAME));
}
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protected final SourceClass doProcessConfigurationClass(ConfigurationClass configClass, SourceClass sourceClass) throws IOException {
// Recursively process any member (nested) classes first
processMemberClasses(configClass, sourceClass);
// Process any @PropertySource annotations
...
// Process any @ComponentScan annotations
Set<AnnotationAttributes> componentScans = AnnotationConfigUtils.attributesForRepeatable(
sourceClass.getMetadata(), ComponentScans.class, ComponentScan.class);
if (!componentScans.isEmpty() &&
!this.conditionEvaluator.shouldSkip(sourceClass.getMetadata(), ConfigurationPhase.REGISTER_BEAN)) {
for (AnnotationAttributes componentScan : componentScans) {
// The config class is annotated with @ComponentScan -> perform the scan immediately
Set<BeanDefinitionHolder> scannedBeanDefinitions =
this.componentScanParser.parse(componentScan, sourceClass.getMetadata().getClassName());
// Check the set of scanned definitions for any further config classes and parse recursively if needed
for (BeanDefinitionHolder holder : scannedBeanDefinitions) {
BeanDefinition bdCand = holder.getBeanDefinition().getOriginatingBeanDefinition();
if (bdCand == null) {
bdCand = holder.getBeanDefinition();
}
if (ConfigurationClassUtils.checkConfigurationClassCandidate(bdCand, this.metadataReaderFactory)) {
parse(bdCand.getBeanClassName(), holder.getBeanName());
}
}
}
}
// Process any @Import annotations
processImports(configClass, sourceClass, getImports(sourceClass), true);
// Process any @ImportResource annotations
...
// Process individual @Bean methods
Set<MethodMetadata> beanMethods = retrieveBeanMethodMetadata(sourceClass);
for (MethodMetadata methodMetadata : beanMethods) {
configClass.addBeanMethod(new BeanMethod(methodMetadata, configClass));
}
// Process default methods on interfaces
processInterfaces(configClass, sourceClass);
// Process superclass, if any
...
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private void initializePropertySources() {
...
CompositePropertySource composite = new CompositePropertySource(PropertySourcesConstants.APOLLO_PROPERTY_SOURCE_NAME);
//sort by order asc
ImmutableSortedSet<Integer> orders = ImmutableSortedSet.copyOf(NAMESPACE_NAMES.keySet());
Iterator<Integer> iterator = orders.iterator();
while (iterator.hasNext()) {
int order = iterator.next();
for (String namespace : NAMESPACE_NAMES.get(order)) {
Config config = ConfigService.getConfig(namespace);
composite.addPropertySource(configPropertySourceFactory.getConfigPropertySource(namespace, config));
}
}
// add after the bootstrap property source or to the first
if (environment.getPropertySources()
.contains(PropertySourcesConstants.APOLLO_BOOTSTRAP_PROPERTY_SOURCE_NAME)) {
environment.getPropertySources()
.addAfter(PropertySourcesConstants.APOLLO_BOOTSTRAP_PROPERTY_SOURCE_NAME, composite);
} else {
environment.getPropertySources().addFirst(composite);
}
}
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@Override
public void onChange(ConfigChangeEvent changeEvent) {
...
for (String key : keys) {
// 1. check whether the changed key is relevant
Collection<SpringValue> targetValues = `springValueRegistry`.get(key);
if (targetValues == null || targetValues.isEmpty()) {
continue;
}
// 2. check whether the value is really changed or not (since spring property sources have hierarchies)
if (!shouldTriggerAutoUpdate(changeEvent, key)) {
continue;
}
// 3. update the value
for (SpringValue val : targetValues) {
updateSpringValue(val);
}
}
}
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