【全网首发】Spring集成apollo源码分析原创
引言
为了在项目中用好框架,以及出现问题时候能够快速定位、分析、优化,文章尝试从源码角度分析Spring集成apollo的过程。期望文章能够把以下几个事情描述清楚:
- apollo通过使用Spring哪些扩展点,完成了与Spring的集成;
- apollo中的配置如何融入到Spring Environment;
- apollo中的配置项如何赋值给Spring Bean相关字段、方法;
- 在应用运行过程中,当修改apollo中的配置,配置如何在Spring Bean相关字段、方法上生效的
由于Spring Framework和Spring Boot集成apollo的方式有些许不同,分别进行分析。
Spring Framework
示例
Spring XML配置
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:apollo="http://www.ctrip.com/schema/apollo"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context.xsd
http://www.ctrip.com/schema/apollo
http://www.ctrip.com/schema/apollo.xsd"
>
<apollo:config namespaces="application,public_namespace"/>
<context:component-scan base-package="test.springframework"/>
<bean id="test" class="test.springframework.Test">
<property name="test1" value="${test1}"/>
</bean>
</beans>
- apollo:config配置的是apollo app.id中的命令空间(app.id、app.meta配置可以参考apollo官方文档);
- context:component-scan配置的是Spring component注解的扫描路径;
- 另一个重要的配置是xmlns:apollo="http://www.ctrip.com/schema/apollo",后面内容会有分析。
Spring Bean
package test.springframework;
public class Test {
@ApolloConfig
private Config config;
@Value("${test2:}")
private String test2;
private String test1;
public String getTest1() {
return test1;
}
public void setTest1(String test1) {
this.test1 = test1;
}
@ApolloConfigChangeListener
public void onChange(ConfigChangeEvent changeEvent){
System.out.println(changeEvent);
}
}
集成分析
图中概括地描述了refresh过程,其中标识黄颜色的地方是这次分析的重点,下面分别进行描述。
解析apollo:config
当解析xml文件apollo:config标记的时候调用BeanDefinitionParserDelegate.parseCustomElement(…),主要流程如下:
图中流程主要完成了两件事:
- 将xml中配置的apollo命名空间存储到了PropertySourcesProcessor(属于apollo jar包)类中的NAMESPACE_NAMES字段;
- 将ConfigPropertySourcesProcessor(属于apollo jar包)作为BeanDefinition注册到了Spring容器中;ConfigPropertySourcesProcessor实现了Spring接口BeanDefinitionRegistryPostProcessor、BeanFactoryPostProcessor。
调用BeanFactoryPostProcessor
apollo中ConfigPropertySourcesProcessor实现了Spring接口BeanDefinitionRegistryPostProcessor、BeanFactoryPostProcessor,ConfigPropertySourcesProcessor实现如下:
public class ConfigPropertySourcesProcessor extends PropertySourcesProcessor
implements BeanDefinitionRegistryPostProcessor {
//使用java SPI机制,ConfigPropertySourcesProcessorHelper对应的实现类是DefaultConfigPropertySourcesProcessorHelper,这段代码完成了apollo client初始化
private ConfigPropertySourcesProcessorHelper helper = ServiceBootstrap.loadPrimary(ConfigPropertySourcesProcessorHelper.class);
@Override
public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {
helper.postProcessBeanDefinitionRegistry(registry);
}
}
调用BeanDefinitionRegistryPostProcessor.postProcessBeanDefinitionRegistry
实际调用的是DefaultConfigPropertySourcesProcessorHelper.postProcessBeanDefinitionRegistry方法,该方法主要完成以下几件事:
- 将PropertySourcesPlaceholderConfigurer注册到spring容器中,该类实现了接口BeanFactoryPostProcessor,用于占位符的转换处理;
- 将ApolloAnnotationProcessor注册到spring容器中,该类实现了接口BeanPostProcessor;
- 将SpringValueProcessor注册到spring容器中,该类实现了接口BeanFactoryPostProcessor和BeanPostProcessor;
- 将ApolloJsonValueProcessor注册到spring容器中,该类实现了接口BeanPostProcessor;
- 将BeanDefinition中带有占位符的所有属性存储到Map<BeanDefinitionRegistry, Multimap<String, SpringValueDefinition>>结构中
调用BeanFactoryPostProcessor.postProcessBeanFactory
PropertySourcesProcessor
CompositePropertySource composite = new CompositePropertySource(PropertySourcesConstants.APOLLO_PROPERTY_SOURCE_NAME);
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));
}
}
NAMESPACE_NAMES.clear();
environment.getPropertySources().addFirst(composite);
- NAMESPACE_NAMES中存储的是应用配置的apollo命名空间;
- 通过Config config = ConfigService.getConfig(namespace)获取每个命名空间的配置对象,将Config对象封装成ConfigPropertySource,接着将所有ConfigPropertySource放入CompositePropertySource,最后将CompositePropertySource加入到spring ConfigurableEnvironment中,此时spring容器的ConfigurableEnvironment已经拥有了apollo命令空间的配置;
AutoUpdateConfigChangeListener autoUpdateConfigChangeListener = new AutoUpdateConfigChangeListener(environment, beanFactory);
List<ConfigPropertySource> configPropertySources = configPropertySourceFactory.getAllConfigPropertySources();
for (ConfigPropertySource configPropertySource : configPropertySources) {
configPropertySource.addChangeListener(autoUpdateConfigChangeListener);
}
- 为apollo命名空间对象添加监听AutoUpdateConfigChangeListener,当改变命名空间中配置的时候,该监听完成Bean对象属性值得更新,及方法的调用。
PropertySourcesPlaceholderConfigurer
- 将ConfigurableEnvironment构造成自身的PropertySource;
new PropertySource<Environment>(ENVIRONMENT_PROPERTIES_PROPERTY_SOURCE_NAME, this.environment) {
public String getProperty(String key) {
return this.source.getProperty(key);
}
}
- 通过自身的PropertySource构造PropertySourcesPropertyResolver,PropertySourcesPropertyResolver中完成解析的类是PropertyPlaceholderHelper;
new PropertySourcesPropertyResolver(this.propertySources)
- 构造StringValueResolver,然后调用PropertySourcesPropertyResolver来进行解析;
StringValueResolver valueResolver = strVal -> {
String resolved = (ignoreUnresolvablePlaceholders ?
propertyResolver.resolvePlaceholders(strVal) :
propertyResolver.resolveRequiredPlaceholders(strVal));
if (trimValues) {
resolved = resolved.trim();
}
return (resolved.equals(nullValue) ? null : resolved);
};
- 构造BeanDefinitionVisitor,用于解析BeanDefinition包含的所有String值(属性、构造方法参数、元数据),解析找到的任何占位符。
BeanDefinitionVisitor visitor = new BeanDefinitionVisitor(valueResolver);
public void visitBeanDefinition(BeanDefinition beanDefinition) {
visitParentName(beanDefinition);
visitBeanClassName(beanDefinition);
visitFactoryBeanName(beanDefinition);
visitFactoryMethodName(beanDefinition);
visitScope(beanDefinition);
if (beanDefinition.hasPropertyValues()) {
visitPropertyValues(beanDefinition.getPropertyValues());
}
if (beanDefinition.hasConstructorArgumentValues()) {
ConstructorArgumentValues cas = beanDefinition.getConstructorArgumentValues();
visitIndexedArgumentValues(cas.getIndexedArgumentValues());
visitGenericArgumentValues(cas.getGenericArgumentValues());
}
}
@Nullable
protected String resolveStringValue(String strVal) {
if (this.valueResolver == null) {
throw new IllegalStateException("No StringValueResolver specified - xxx");
}
// 最终调用的是PropertySourcesPropertyResolver中的resolveXXX方法
String resolvedValue = this.valueResolver.resolveStringValue(strVal);
return (strVal.equals(resolvedValue) ? strVal : resolvedValue);
}
调用BeanPostProcessor
ApolloAnnotationProcessor
用于解析apollo注解ApolloConfig、ApolloConfigChangeListener。
ApolloConfig
为注解为ApolloConfig的字段赋值对应的namespace Config对象。
protected void processField(Object bean, String beanName, Field field) {
ApolloConfig annotation = AnnotationUtils.getAnnotation(field, ApolloConfig.class);
if (annotation == null) {
return;
}
Preconditions.checkArgument(Config.class.isAssignableFrom(field.getType()),
"Invalid type: %s for field: %s, should be Config", field.getType(), field);
String namespace = annotation.value();
Config config = ConfigService.getConfig(namespace);
ReflectionUtils.makeAccessible(field);
ReflectionUtils.setField(field, bean, config);
}
ApolloConfigChangeListener
为注解为ApolloConfigChangeListener的方法添加namespace的监听。
ApolloConfigChangeListener annotation = AnnotationUtils
.findAnnotation(method, ApolloConfigChangeListener.class);
String[] namespaces = annotation.value();
ConfigChangeListener configChangeListener = new ConfigChangeListener() {
@Override
public void onChange(ConfigChangeEvent changeEvent) {
ReflectionUtils.invokeMethod(method, bean, changeEvent);
}
};
for (String namespace : namespaces) {
Config config = ConfigService.getConfig(namespace);
config.addChangeListener(configChangeListener);
}
SpringValueProcessor
- 将Bean中含有Value注解的字段、方法注册到SpringValueRegistry(Map<BeanFactory, Multimap<String, SpringValue>>)中,SpringValue保存了Bean实例,对应的key,Field或Method;
protected void processField(Object bean, String beanName, Field field) {
Value value = field.getAnnotation(Value.class);
Set<String> keys = placeholderHelper.extractPlaceholderKeys(value.value());
for (String key : keys) {
SpringValue springValue = new SpringValue(key, value.value(), bean, beanName, field, false);
springValueRegistry.register(beanFactory, key, springValue);
}
}
protected void processMethod(Object bean, String beanName, Method method) {
Value value = method.getAnnotation(Value.class);
Set<String> keys = placeholderHelper.extractPlaceholderKeys(value.value());
for (String key : keys) {
SpringValue springValue = new SpringValue(key, value.value(), bean, beanName, method, false);
springValueRegistry.register(beanFactory, key, springValue);
}
}
- 将DefaultConfigPropertySourcesProcessorHelper中解析的Map<BeanDefinitionRegistry, Multimap<String, SpringValueDefinition>>转换为SpringValue保存在SpringValueRegistry中;
- 前面在PropertySourcesProcessor类中对每个namespace Config对象注册了监听AutoUpdateConfigChangeListener,AutoUpdateConfigChangeListener类含有SpringValueRegistry的引用;
- 当namespace Config配置改变的时候会通知到AutoUpdateConfigChangeListener,AutoUpdateConfigChangeListener通过配置key找到对应的SpringValue对象,通过SpringValue改变Bean对应的属性,或调用Bean对应的方法。
ApolloJsonValueProcessor
- 将Bean中含有ApolloJsonValue注解的字段、方法注册到SpringValueRegistry(Map<BeanFactory, Multimap<String, SpringValue>>)中,SpringValue保存了Bean实例,对应的key,Field或Method;
- 对于注解在Field的情况,获取ApolloJsonValue key的配置,将配置转换为Field对应类型的对象并完成对Field的赋值;
protected void processField(Object bean, String beanName, Field field) {
ApolloJsonValue apolloJsonValue = AnnotationUtils.getAnnotation(field, ApolloJsonValue.class);
String placeholder = apolloJsonValue.value();
Object propertyValue = placeholderHelper
.resolvePropertyValue(beanFactory, beanName, placeholder);
boolean accessible = field.isAccessible();
field.setAccessible(true);
ReflectionUtils
.setField(field, bean, parseJsonValue((String)propertyValue, field.getGenericType()));
field.setAccessible(accessible);
if (configUtil.isAutoUpdateInjectedSpringPropertiesEnabled()) {
Set<String> keys = placeholderHelper.extractPlaceholderKeys(placeholder);
for (String key : keys) {
SpringValue springValue = new SpringValue(key, placeholder, bean, beanName, field, true);
springValueRegistry.register(beanFactory, key, springValue);
}
}
}
- 对于注解在Method的情况,获取ApolloJsonValue key的配置,将配置转换为Method入参对应类型的对象并完成对Method的调用
protected void processMethod(Object bean, String beanName, Method method) {
ApolloJsonValue apolloJsonValue = AnnotationUtils.getAnnotation(method, ApolloJsonValue.class);
String placeHolder = apolloJsonValue.value();
Object propertyValue = placeholderHelper
.resolvePropertyValue(beanFactory, beanName, placeHolder);
boolean accessible = method.isAccessible();
method.setAccessible(true);
ReflectionUtils.invokeMethod(method, bean, parseJsonValue((String)propertyValue, types[0]));
method.setAccessible(accessible);
if (configUtil.isAutoUpdateInjectedSpringPropertiesEnabled()) {
Set<String> keys = placeholderHelper.extractPlaceholderKeys(placeHolder);
for (String key : keys) {
SpringValue springValue = new SpringValue(key, apolloJsonValue.value(), bean, beanName,method, true);
springValueRegistry.register(beanFactory, key, springValue);
}
}
}
Spring Boot
示例
// Spring Boot启动类
@SpringBootApplication
@EnableApolloConfig
public class Application {
public static void main(String[] args) {
SpringApplication.run(Application.class, args);
}
}
//测试Bean见Spring Framework部分示例
上面代码中的@EnableApolloConfig是一个接入点,后面会分析到。
集成分析
图中概括地描述了SpringApplication启动过程(其中会将启动类加入到spring容器中),其中标识黄颜色的地方是这次分析的重点,下面分别进行描述。
加载apollo ApplicationContextInitializer
- 通过SpringFactoriesLoader加载apollo jar包中META-INF/spring.factories文件,解析ApplicationContextInitializer实现类ApolloApplicationContextInitializer。
setInitializers((Collection) getSpringFactoriesInstances(
ApplicationContextInitializer.class));
// 通过SpringFactoriesLoader加载、解析META-INF/spring.factories
private <T> Collection<T> getSpringFactoriesInstances(Class<T> type,
Class<?>[] parameterTypes, Object... args) {
ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
Set<String> names = new LinkedHashSet<>(
SpringFactoriesLoader.loadFactoryNames(type, classLoader));
List<T> instances = createSpringFactoriesInstances(type, parameterTypes,
classLoader, args, names);
AnnotationAwareOrderComparator.sort(instances);
return instances;
}
apollo ApplicationContextInitializer initialize
- ApolloApplicationContextInitializer解析apollo.bootstrap.namespaces配置的命名空间名称,然后通过Config config = ConfigService.getConfig(namespace)获取每个命名空间的配置对象,将Config对象封装成ConfigPropertySource,接着将所有ConfigPropertySource放入CompositePropertySource,最后将CompositePropertySource加入到spring ConfigurableEnvironment中,此时spring容器的ConfigurableEnvironment已经拥有了apollo命令空间的配置。
protected void initialize(ConfigurableEnvironment environment) {
String namespaces = environment.getProperty(PropertySourcesConstants.APOLLO_BOOTSTRAP_NAMESPACES, ConfigConsts.NAMESPACE_APPLICATION);
List<String> namespaceList = NAMESPACE_SPLITTER.splitToList(namespaces);
CompositePropertySource composite = new CompositePropertySource(PropertySourcesConstants.APOLLO_BOOTSTRAP_PROPERTY_SOURCE_NAME);
for (String namespace : namespaceList) {
Config config = ConfigService.getConfig(namespace);
composite.addPropertySource(configPropertySourceFactory.getConfigPropertySource(namespace, config));
}
environment.getPropertySources().addFirst(composite);
}
初始化BeanDefinitionLoader
我们关注BeanDefinitionLoader类中属性annotatedReader=new AnnotatedBeanDefinitionReader(registry),AnnotatedBeanDefinitionReader构造方法如下:
public AnnotatedBeanDefinitionReader(BeanDefinitionRegistry registry, Environment environment) {
this.registry = registry;
this.conditionEvaluator = new ConditionEvaluator(registry, environment, null);
// 将Annotation相关的处理类注册到Spring容器中,如:
// ConfigurationClassPostProcessor : 处理Configuration注解
// AutowiredAnnotationBeanPostProcessor : 处理Value注解
// RequiredAnnotationBeanPostProcessor : 处理Required注解
// CommonAnnotationBeanPostProcessor : 处理PostConstruct/PreDestroy/Resource/Lazy注解
// ... ...
AnnotationConfigUtils.registerAnnotationConfigProcessors(this.registry);
}
与我们这次分析相关的类是:ConfigurationClassPostProcessor,该类实现了BeanDefinitionRegistryPostProcessor、BeanFactoryPostProcessor接口。
ConfigurationClassPostProcessor.postProcessBeanDefinitionRegistry
- 判断spring容器中BeanDefinition是否含有Configuration、Component、ComponentScan、Import
ImportResource、Bean注解,没有则直接返回;
- 构造ConfigurationClassParser(Parses a Configuration class definition, populating a collection of ConfigurationClass objects (parsing a single Configuration class may result in any number of ConfigurationClass objects because one Configuration class may import another using the Import annotation)),接着对BeanDefinition上的Configuration、Component、ComponentScan、Import
ImportResource、Bean注解进行解析。
- 解析完成后,通过ConfigurationClassBeanDefinitionReader.loadBeanDefinitions(ConfigurationClass)进行apollo相关BeanDefinition的加载:
- apollo EnableApolloConfig注解的定义如下
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
@Documented
// 在上面parse阶段会将Import封装在ConfigurationClass中
@Import(ApolloConfigRegistrar.class)
public @interface EnableApolloConfig {
String[] value() default {ConfigConsts.NAMESPACE_APPLICATION};
int order() default Ordered.LOWEST_PRECEDENCE;
}
- ConfigurationClassBeanDefinitionReader.loadBeanDefinitionsFromRegistrars会调用到ApolloConfigRegistrar类的registerBeanDefinitions方法
private void loadBeanDefinitionsFromRegistrars(Map<ImportBeanDefinitionRegistrar, AnnotationMetadata> registrars) {
registrars.forEach((registrar, metadata) ->
registrar.registerBeanDefinitions(metadata, this.registry));
}
- ApolloConfigRegistrar最终将apollo中BeanDefinitionRegistryPostProcessor、BeanFactoryPostProcessor、BeanPostProcessor实现类的注册到spring容器中(具体实现类与Spring Framework部分基本是一致的),后续的逻辑与Spring Framework部分分析的是一致的了。
public class ApolloConfigRegistrar implements ImportBeanDefinitionRegistrar {
private ApolloConfigRegistrarHelper helper = ServiceBootstrap.loadPrimary(ApolloConfigRegistrarHelper.class);
@Override
public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {
// 该方法中将apollo相关类注册到spring容器中,如:
// PropertySourcesProcessor
// ApolloAnnotationProcessor
// SpringValueProcessor
// SpringValueDefinitionProcessor
// ApolloJsonValueProcessor
helper.registerBeanDefinitions(importingClassMetadata, registry);
}
}
总结
文章主要介绍了apollo借助Spring扩展点完成了与Spring的集成:
Spring Framework集成方式使用到了loadBeanDefinitions阶段中apollo:config NamespaceHandler,BeanDefinitionRegistryPostProcessor,BeanFactoryPostProcessor,BeanPostProcessor;
Spring Boot集成方式使用到了ApplicationContextInitializer,BeanDefinitionRegistryPostProcessor,BeanFactoryPostProcessor,BeanPostProcessor。