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前言
前阵子和敌人聊天，他手头上有个 spring 单体我的项目，每次数据库配置变更，他都要重启我的项目，让配置失效。他就想说有没有什么方法，不重启我的项目，又能够让配置失效。过后我就跟他说，能够用配置核心，他的意思是因为是保护类我的项目，不想再额定引入一个配置核心，减少运维老本。后边跟他探讨了一个计划，能够实现一个监听配置文件变动的程序，当监听到文件变动，进行相应的变更操作。具体流程如下
在这些步骤，比拟麻烦就是如何动静刷新 bean，因为敌人是 spring 我的项目，明天就来聊下在 spring 我的项目中如何实现 bean 的动静刷新
实现思路
理解 spring 的敌人，应该晓得 spring 的单例 bean 是缓存在 singletonObjects 这个 map 外面，所以能够通过变更 singletonObjects 来实现 bean 的刷新。咱们能够通过调用 removeSingleton 和 addSingleton 这两个办法来实现，然而这种实现形式的毛病就是会扭转 bean 的生命周期，会导致原来的一些加强性能生效，比方 AOP。但 spring 作为一个极其优良的框架，他提供了让咱们本人治理 bean 的扩大点。这个扩大点就是通过指定 scope，来达到本人治理 bean 的成果
实现步骤
1、自定义 scope
public class RefreshBeanScope implements Scope {private final Map<String,Object> beanMap = new ConcurrentHashMap<>(256);
@Override
public Object get(String name, ObjectFactory<?> objectFactory) {if(beanMap.containsKey(name)){return beanMap.get(name);
}
Object bean = objectFactory.getObject();
beanMap.put(name,bean);
return bean;
}
@Override
public Object remove(String name) {return beanMap.remove(name);
}
@Override
public void registerDestructionCallback(String name, Runnable callback) { }
@Override
public Object resolveContextualObject(String key) {return null;}
@Override
public String getConversationId() {return null;}
}
2、自定义 scope 注册
public class RefreshBeanScopeDefinitionRegistryPostProcessor implements BeanDefinitionRegistryPostProcessor {
@Override
public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException { }
@Override
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {beanFactory.registerScope(SCOPE_NAME,new RefreshBeanScope());
}
}
3、自定义 scope 注解（可选）
@Target({ElementType.TYPE, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Scope("refreshBean")
@Documented
public @interface RefreshBeanScope {
/**
* @see Scope#proxyMode()
* @return proxy mode
*/
ScopedProxyMode proxyMode() default ScopedProxyMode.TARGET_CLASS;}4、编写自定义 scope bean 刷新逻辑
@RequiredArgsConstructor
public class RefreshBeanScopeHolder implements ApplicationContextAware {
private final DefaultListableBeanFactory beanFactory;
private ApplicationContext applicationContext;
public List<String> refreshBean(){String[] beanDefinitionNames = beanFactory.getBeanDefinitionNames();
List<String> refreshBeanDefinitionNames = new ArrayList<>();
for (String beanDefinitionName : beanDefinitionNames) {BeanDefinition beanDefinition = beanFactory.getBeanDefinition(beanDefinitionName);
if(SCOPE_NAME.equals(beanDefinition.getScope())){beanFactory.destroyScopedBean(beanDefinitionName);
beanFactory.getBean(beanDefinitionName);
refreshBeanDefinitionNames.add(beanDefinitionName);
applicationContext.publishEvent(new RefreshBeanEvent(beanDefinitionName));
}
}
return Collections.unmodifiableList(refreshBeanDefinitionNames);
}
@Override
public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {this.applicationContext = applicationContext;}
}
以上步骤就是实现自定义 scope 治理 bean 的过程，上面咱们以一个配置变更实现 bean 刷新例子，来演示以上步骤
示例
1、在我的项目 src/main/rescoures 目录下创立属性配置文件 config/config.properties
并填入测试内容
test:
name: zhangsan22222、将 config.yml 装载进 spring
public static void setConfig() {String configLocation = getProjectPath() + "/src/main/resources/config/config.yml";
System.setProperty("spring.config.additional-location",configLocation);
}
public static String getProjectPath() {String basePath = ConfigFileUtil.class.getResource("").getPath();
return basePath.substring(0, basePath.indexOf("/target"));
}3、实现配置监听
注： 利用 hutool 的 WatchMonitor 或者 apache common io 的文件监听即可实现
以 apache common io 为例
a、 业务 pom 文件引入 common-io gav
<dependency>
<groupId>commons-io</groupId>
<artifactId>commons-io</artifactId>
<version>${common-io.version}</version>
</dependency>b、 自定义文件变动监听器
@Slf4j
public class ConfigPropertyFileAlterationListener extends FileAlterationListenerAdaptor {
private ApplicationContext applicationContext;
public ConfigPropertyFileAlterationListener(ApplicationContext applicationContext) {this.applicationContext = applicationContext;}
@Override
public void onStart(FileAlterationObserver observer) {super.onStart(observer);
}
@Override
public void onDirectoryCreate(File directory) {super.onDirectoryCreate(directory);
}
@Override
public void onDirectoryChange(File directory) {super.onDirectoryChange(directory);
}
@Override
public void onDirectoryDelete(File directory) {super.onDirectoryDelete(directory);
}
@Override
public void onFileCreate(File file) {super.onFileCreate(file);
}
@Override
public void onFileChange(File file) {log.info(">>>>>>>>>>>>>>>>>>>>>>>>> Monitor PropertyFile with path --> {}",file.getName());
refreshConfig(file);
}
@Override
public void onFileDelete(File file) {super.onFileDelete(file);
}
@Override
public void onStop(FileAlterationObserver observer) {super.onStop(observer);
}
}c、 启动文件监听器
@SneakyThrows
private static void monitorPropertyChange(FileMonitor fileMonitor, File file,ApplicationContext context){if(fileMonitor.isFileScanEnabled()) {String ext = "." + FilenameUtils.getExtension(file.getName());
String monitorDir = file.getParent();
// 轮询间隔时间
long interval = TimeUnit.SECONDS.toMillis(fileMonitor.getFileScanInterval());
// 创立文件观察器
FileAlterationObserver observer = new FileAlterationObserver(
monitorDir, FileFilterUtils.and(FileFilterUtils.fileFileFilter(),
FileFilterUtils.suffixFileFilter(ext)));
observer.addListener(new ConfigPropertyFileAlterationListener(context));
// 创立文件变动监听器
FileAlterationMonitor monitor = new FileAlterationMonitor(interval, observer);
// 开始监听
monitor.start();}
}
4、监听文件变动，并实现 PropertySource 以及 bean 的刷新
@SneakyThrows
private void refreshConfig(File file){ConfigurableEnvironment environment = applicationContext.getBean(ConfigurableEnvironment.class);
MutablePropertySources propertySources = environment.getPropertySources();
PropertySourceLoader propertySourceLoader = new YamlPropertySourceLoader();
List<PropertySource<?>> propertySourceList = propertySourceLoader.load(file.getAbsolutePath(), applicationContext.getResource("file:"+file.getAbsolutePath()));
for (PropertySource<?> propertySource : propertySources) {if(propertySource.getName().contains(file.getName())){propertySources.replace(propertySource.getName(),propertySourceList.get(0));
}
}
RefreshBeanScopeHolder refreshBeanScopeHolder = applicationContext.getBean(RefreshBeanScopeHolder.class);
List<String> strings = refreshBeanScopeHolder.refreshBean();
log.info(">>>>>>>>>>>>>>> refresh Bean :{}",strings);
}5、测试
a、 编写 controller 并将 controller scope 设置为咱们自定义的 scope
@RestController
@RequestMapping("test")
@RefreshBeanScope
public class TestController {@Value("${test.name:}")
private String name;
@GetMapping("print")
public String print(){return name;}
}
原来的 test.name 内容如下
test:
name: zhangsan2222咱们通过浏览器拜访
b、 此时咱们不重启服务器，并将 test.name 改为如下
test:
name: zhangsan3333此时发现控制台会输入咱们的日志信息
通过浏览器再拜访
发现内容曾经发生变化
附录：自定义 scope 办法触发机会
1、scope get 办法
// Create bean instance.
if (mbd.isSingleton()) {sharedInstance = getSingleton(beanName, () -> {
try {return createBean(beanName, mbd, args);
}
catch (BeansException ex) {
// Explicitly remove instance from singleton cache: It might have been put there
// eagerly by the creation process, to allow for circular reference resolution.
// Also remove any beans that received a temporary reference to the bean.
destroySingleton(beanName);
throw ex;
}
});
bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd);
}
else if (mbd.isPrototype()) {
// It's a prototype -> create a new instance.
Object prototypeInstance = null;
try {beforePrototypeCreation(beanName);
prototypeInstance = createBean(beanName, mbd, args);
}
finally {afterPrototypeCreation(beanName);
}
bean = getObjectForBeanInstance(prototypeInstance, name, beanName, mbd);
}
else {String scopeName = mbd.getScope();
final Scope scope = this.scopes.get(scopeName);
if (scope == null) {throw new IllegalStateException("No Scope registered for scope name'" + scopeName + "'");
}
try {Object scopedInstance = scope.get(beanName, () -> {beforePrototypeCreation(beanName);
try {return createBean(beanName, mbd, args);
}
finally {afterPrototypeCreation(beanName);
}
});
bean = getObjectForBeanInstance(scopedInstance, name, beanName, mbd);
}
catch (IllegalStateException ex) {
throw new BeanCreationException(beanName,
"Scope'" + scopeName + "'is not active for the current thread; consider" +
"defining a scoped proxy for this bean if you intend to refer to it from a singleton",
ex);
}
}
}
catch (BeansException ex) {cleanupAfterBeanCreationFailure(beanName);
throw ex;
}触发机会就是在调用 getBean 时触发
2、scope remove 办法
@Override
public void destroyScopedBean(String beanName) {RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);
if (mbd.isSingleton() || mbd.isPrototype()) {
throw new IllegalArgumentException("Bean name'" + beanName + "'does not correspond to an object in a mutable scope");
}
String scopeName = mbd.getScope();
Scope scope = this.scopes.get(scopeName);
if (scope == null) {throw new IllegalStateException("No Scope SPI registered for scope name'" + scopeName + "'");
}
Object bean = scope.remove(beanName);
if (bean != null) {destroyBean(beanName, bean, mbd);
}
}
触发机会切实调用 destroyScopedBean 办法
总结
如果对 spring cloud RefreshScope 有钻研的话，就会发现上述的实现形式，就是 RefreshScope 的毛糙版本实现
demo 链接
https://github.com/lyb-geek/springboot-learning/tree/master/springboot-bean-refresh
正文完
