这篇文档主要关注下配置修改后对应的 Java 对象是如何更新，并不关注整体的配置改动流程
所有代码都来自 apollo-client 项目
更新流程
在 Apollo 控制台进行配置修改并发布后，对应的 client 端拉取到更新后，会调用到 com.ctrip.framework.apollo.spring.property.AutoUpdateConfigChangeListener#onChange 方法
在调用 onChange 会收到对应的修改的配置信息 ConfigChangeEvent， 其中包含改动的 key 和 value, 则改动流程如下：
- 根据改动的配置的 key 从 springValueRegistry 找到对应的关联到这个 key 的 Spring Bean 信息，如果找不到则不处理
- 根据找到的 Spring Bean 信息，进行对应关联配置的更新
在第二步中会判断关联配置是用过属性关联还是方法进行关联的，代码如下
public void update(Object newVal) throws IllegalAccessException, InvocationTargetException {
if (isField()) {
injectField(newVal);
} else {
injectMethod(newVal);
}
}
在上面的问题中，还有两个问题存疑
- 如何通过 key 找到对应的 Spring Bean 信息
- 如何将 Apollo 的配置值转换为 Spring 的识别的值
public class AutoUpdateConfigChangeListener implements ConfigChangeListener{
private static final Logger logger = LoggerFactory.getLogger(AutoUpdateConfigChangeListener.class);
private final boolean typeConverterHasConvertIfNecessaryWithFieldParameter;
private final Environment environment;
private final ConfigurableBeanFactory beanFactory;
private final TypeConverter typeConverter;
private final PlaceholderHelper placeholderHelper;
private final SpringValueRegistry springValueRegistry;
private final Gson gson;
public AutoUpdateConfigChangeListener(Environment environment, ConfigurableListableBeanFactory beanFactory){
this.typeConverterHasConvertIfNecessaryWithFieldP<mark style="color:transparent">本文来源gaodaimacom搞#^代%!码&网*</mark>arameter = testTypeConverterHasConvertIfNecessaryWithFieldParameter();
this.beanFactory = beanFactory;
this.typeConverter = this.beanFactory.getTypeConverter();
this.environment = environment;
this.placeholderHelper = SpringInjector.getInstance(PlaceholderHelper.class);
this.springValueRegistry = SpringInjector.getInstance(SpringValueRegistry.class);
this.gson = new Gson();
}
@Override
public void onChange(ConfigChangeEvent changeEvent) {
Set<String> keys = changeEvent.changedKeys();
if (CollectionUtils.isEmpty(keys)) {
return;
}
for (String key : keys) {
// 1. check whether the changed key is relevant
Collection<SpringValue> targetValues = springValueRegistry.get(beanFactory, key);
if (targetValues == null || targetValues.isEmpty()) {
continue;
}
// 2. update the value
for (SpringValue val : targetValues) {
updateSpringValue(val);
}
}
}
private void updateSpringValue(SpringValue springValue) {
try {
Object value = resolvePropertyValue(springValue);
springValue.update(value);
logger.info("Auto update apollo changed value successfully, new value: {}, {}", value,
springValue);
} catch (Throwable ex) {
logger.error("Auto update apollo changed value failed, {}", springValue.toString(), ex);
}
}
/**
* Logic transplanted from DefaultListableBeanFactory
* @see org.springframework.beans.factory.support.DefaultListableBeanFactory#doResolveDependency(org.springframework.beans.factory.config.DependencyDescriptor, java.lang.String, java.util.Set, org.springframework.beans.TypeConverter)
*/
private Object resolvePropertyValue(SpringValue springValue) {
// value will never be null, as @Value and @ApolloJsonValue will not allow that
Object value = placeholderHelper
.resolvePropertyValue(beanFactory, springValue.getBeanName(), springValue.getPlaceholder());
if (springValue.isJson()) {
value = parseJsonValue((String)value, springValue.getGenericType());
} else {
if (springValue.isField()) {
// org.springframework.beans.TypeConverter#convertIfNecessary(java.lang.Object, java.lang.Class, java.lang.reflect.Field) is available from Spring 3.2.0+
if (typeConverterHasConvertIfNecessaryWithFieldParameter) {
value = this.typeConverter
.convertIfNecessary(value, springValue.getTargetType(), springValue.getField());
} else {
value = this.typeConverter.convertIfNecessary(value, springValue.getTargetType());
}
} else {
value = this.typeConverter.convertIfNecessary(value, springValue.getTargetType(),
springValue.getMethodParameter());
}
}
return value;
}
private Object parseJsonValue(String json, Type targetType) {
try {
return gson.fromJson(json, targetType);
} catch (Throwable ex) {
logger.error("Parsing json '{}' to type {} failed!", json, targetType, ex);
throw ex;
}
}
private boolean testTypeConverterHasConvertIfNecessaryWithFieldParameter() {
try {
TypeConverter.class.getMethod("convertIfNecessary", Object.class, Class.class, Field.class);
} catch (Throwable ex) {
return false;
}
return true;
}
}
如何将配置 key 和 Spring Bean 关联起来
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转载请注明原文链接：Java Apollo是如何实现配置更新的
转载请注明原文链接：Java Apollo是如何实现配置更新的
