SpringBoot自動(dòng)裝配的套路，直接看 spring.factories 文件，當(dāng)我們使用的時(shí)候只需要引入如下依賴

<dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-actuator</artifactId></dependency>

然后在 org.springframework.boot.spring-boot-actuator-autoconfigure 包下去就可以找到這個(gè)文件

自動(dòng)裝配

查看這個(gè)文件發(fā)現(xiàn)引入了很多的配置類，這里先關(guān)注一下 XXXHealthIndicatorAutoConfiguration 系列的類，這里咱們拿第一個(gè) RabbitHealthIndicatorAutoConfiguration 為例來(lái)解析一下。看名字就知道這個(gè)是RabbitMQ的健康檢查的自動(dòng)配置類

@Configuration@ConditionalOnClass(RabbitTemplate.class)@ConditionalOnBean(RabbitTemplate.class)@ConditionalOnEnabledHealthIndicator('rabbit')@AutoConfigureBefore(HealthIndicatorAutoConfiguration.class)@AutoConfigureAfter(RabbitAutoConfiguration.class)public class RabbitHealthIndicatorAutoConfiguration extends CompositeHealthIndicatorConfiguration<RabbitHealthIndicator, RabbitTemplate> { private final Map<String, RabbitTemplate> rabbitTemplates; public RabbitHealthIndicatorAutoConfiguration( Map<String, RabbitTemplate> rabbitTemplates) { this.rabbitTemplates = rabbitTemplates; } @Bean @ConditionalOnMissingBean(name = 'rabbitHealthIndicator') public HealthIndicator rabbitHealthIndicator() { return createHealthIndicator(this.rabbitTemplates); }}

按照以往的慣例，先解析注解

@ConditionalOnXXX 系列又出現(xiàn)了，前兩個(gè)就是說(shuō)如果當(dāng)前存在 RabbitTemplate 這個(gè)bean也就是說(shuō)我們的項(xiàng)目中使用到了RabbitMQ才能進(jìn)行下去 @ConditionalOnEnabledHealthIndicator 這個(gè)注解很明顯是SpringBoot actuator自定義的注解，看一下吧

@Conditional(OnEnabledHealthIndicatorCondition.class)public @interface ConditionalOnEnabledHealthIndicator { String value();}class OnEnabledHealthIndicatorCondition extends OnEndpointElementCondition { OnEnabledHealthIndicatorCondition() { super('management.health.', ConditionalOnEnabledHealthIndicator.class); }}public abstract class OnEndpointElementCondition extends SpringBootCondition { private final String prefix; private final Class<? extends Annotation> annotationType; protected OnEndpointElementCondition(String prefix, Class<? extends Annotation> annotationType) { this.prefix = prefix; this.annotationType = annotationType; } @Override public ConditionOutcome getMatchOutcome(ConditionContext context, AnnotatedTypeMetadata metadata) { AnnotationAttributes annotationAttributes = AnnotationAttributes .fromMap(metadata.getAnnotationAttributes(this.annotationType.getName())); String endpointName = annotationAttributes.getString('value'); ConditionOutcome outcome = getEndpointOutcome(context, endpointName); if (outcome != null) { return outcome; } return getDefaultEndpointsOutcome(context); } protected ConditionOutcome getEndpointOutcome(ConditionContext context, String endpointName) { Environment environment = context.getEnvironment(); String enabledProperty = this.prefix + endpointName + '.enabled'; if (environment.containsProperty(enabledProperty)) { boolean match = environment.getProperty(enabledProperty, Boolean.class, true); return new ConditionOutcome(match, ConditionMessage.forCondition(this.annotationType).because( this.prefix + endpointName + '.enabled is ' + match)); } return null; } protected ConditionOutcome getDefaultEndpointsOutcome(ConditionContext context) { boolean match = Boolean.valueOf(context.getEnvironment() .getProperty(this.prefix + 'defaults.enabled', 'true')); return new ConditionOutcome(match, ConditionMessage.forCondition(this.annotationType).because( this.prefix + 'defaults.enabled is considered ' + match)); }}public abstract class SpringBootCondition implements Condition { private final Log logger = LogFactory.getLog(getClass()); @Override public final boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) { String classOrMethodName = getClassOrMethodName(metadata); try { ConditionOutcome outcome = getMatchOutcome(context, metadata); logOutcome(classOrMethodName, outcome); recordEvaluation(context, classOrMethodName, outcome); return outcome.isMatch(); } catch (NoClassDefFoundError ex) { throw new IllegalStateException( 'Could not evaluate condition on ' + classOrMethodName + ' due to ' + ex.getMessage() + ' not ' + 'found. Make sure your own configuration does not rely on ' + 'that class. This can also happen if you are ' + '@ComponentScanning a springframework package (e.g. if you ' + 'put a @ComponentScan in the default package by mistake)', ex); } catch (RuntimeException ex) { throw new IllegalStateException( 'Error processing condition on ' + getName(metadata), ex); } } private void recordEvaluation(ConditionContext context, String classOrMethodName, ConditionOutcome outcome) { if (context.getBeanFactory() != null) { ConditionEvaluationReport.get(context.getBeanFactory()) .recordConditionEvaluation(classOrMethodName, this, outcome); } }}

上方的入口方法是 SpringBootCondition 類的 matches 方法， getMatchOutcome 這個(gè)方法則是子類 OnEndpointElementCondition 的，這個(gè)方法首先會(huì)去環(huán)境變量中查找是否存在 management.health.rabbit.enabled 屬性，如果沒有的話則去查找 management.health.defaults.enabled 屬性，如果這個(gè)屬性還沒有的話則設(shè)置默認(rèn)值為true

當(dāng)這里返回true時(shí)整個(gè) RabbitHealthIndicatorAutoConfiguration 類的自動(dòng)配置才能繼續(xù)下去

@AutoConfigureBefore 既然這樣那就先看看類 HealthIndicatorAutoConfiguration 都是干了啥再回來(lái)吧

@Configuration@EnableConfigurationProperties({ HealthIndicatorProperties.class })public class HealthIndicatorAutoConfiguration { private final HealthIndicatorProperties properties; public HealthIndicatorAutoConfiguration(HealthIndicatorProperties properties) { this.properties = properties; } @Bean @ConditionalOnMissingBean({ HealthIndicator.class, ReactiveHealthIndicator.class }) public ApplicationHealthIndicator applicationHealthIndicator() { return new ApplicationHealthIndicator(); } @Bean @ConditionalOnMissingBean(HealthAggregator.class) public OrderedHealthAggregator healthAggregator() { OrderedHealthAggregator healthAggregator = new OrderedHealthAggregator(); if (this.properties.getOrder() != null) { healthAggregator.setStatusOrder(this.properties.getOrder()); } return healthAggregator; }}

首先這個(gè)類引入了配置文件 HealthIndicatorProperties 這個(gè)配置類是系統(tǒng)狀態(tài)相關(guān)的配置

@ConfigurationProperties(prefix = 'management.health.status')public class HealthIndicatorProperties { private List<String> order = null; private final Map<String, Integer> httpMapping = new HashMap<>();}

接著就是注冊(cè)了2個(gè)bean ApplicationHealthIndicator 和 OrderedHealthAggregator 這兩個(gè)bean的作用稍后再說(shuō)，現(xiàn)在回到 RabbitHealthIndicatorAutoConfiguration 類

@AutoConfigureAfterHealthIndicatorpublic abstract class CompositeHealthIndicatorConfiguration<H extends HealthIndicator, S> { @Autowired private HealthAggregator healthAggregator; protected HealthIndicator createHealthIndicator(Map<String, S> beans) { if (beans.size() == 1) { return createHealthIndicator(beans.values().iterator().next()); } CompositeHealthIndicator composite = new CompositeHealthIndicator( this.healthAggregator); for (Map.Entry<String, S> entry : beans.entrySet()) { composite.addHealthIndicator(entry.getKey(), createHealthIndicator(entry.getValue())); } return composite; } @SuppressWarnings('unchecked') protected H createHealthIndicator(S source) { Class<?>[] generics = ResolvableType .forClass(CompositeHealthIndicatorConfiguration.class, getClass()) .resolveGenerics(); Class<H> indicatorClass = (Class<H>) generics[0]; Class<S> sourceClass = (Class<S>) generics[1]; try { return indicatorClass.getConstructor(sourceClass).newInstance(source); } catch (Exception ex) { throw new IllegalStateException('Unable to create indicator ' + indicatorClass + ' for source ' + sourceClass, ex); } }} 首先這里注入了一個(gè)對(duì)象 HealthAggregator ，這個(gè)對(duì)象就是剛才注冊(cè)的 OrderedHealthAggregator 第一個(gè) createHealthIndicator 方法執(zhí)行邏輯為：如果傳入的beans的size 為1,則調(diào)用 createHealthIndicator 創(chuàng)建 HealthIndicator 否則創(chuàng)建 CompositeHealthIndicator ,遍歷傳入的beans,依次創(chuàng)建 HealthIndicator ,加入到 CompositeHealthIndicator 中 第二個(gè) createHealthIndicator 的執(zhí)行邏輯為：獲得 CompositeHealthIndicatorConfiguration 中的泛型參數(shù)根據(jù)泛型參數(shù)H對(duì)應(yīng)的class和S對(duì)應(yīng)的class,在H對(duì)應(yīng)的class中找到聲明了參數(shù)為S類型的構(gòu)造器進(jìn)行實(shí)例化 最后這里創(chuàng)建出來(lái)的bean為 RabbitHealthIndicator 回憶起之前學(xué)習(xí)健康檢查的使用時(shí)，如果我們需要自定義健康檢查項(xiàng)時(shí)一般的操作都是實(shí)現(xiàn) HealthIndicator 接口，由此可以猜測(cè) RabbitHealthIndicator 應(yīng)該也是這樣做的。觀察這個(gè)類的繼承關(guān)系可以發(fā)現(xiàn)這個(gè)類繼承了一個(gè)實(shí)現(xiàn)實(shí)現(xiàn)此接口的類 AbstractHealthIndicator ，而RabbitMQ的監(jiān)控檢查流程則如下代碼所示

//這個(gè)方法是AbstractHealthIndicator的public final Health health() { Health.Builder builder = new Health.Builder(); try { doHealthCheck(builder); } catch (Exception ex) { if (this.logger.isWarnEnabled()) { String message = this.healthCheckFailedMessage.apply(ex); this.logger.warn(StringUtils.hasText(message) ? message : DEFAULT_MESSAGE, ex); } builder.down(ex); } return builder.build(); }//下方兩個(gè)方法是由類RabbitHealthIndicator實(shí)現(xiàn)的protected void doHealthCheck(Health.Builder builder) throws Exception { builder.up().withDetail('version', getVersion()); } private String getVersion() { return this.rabbitTemplate.execute((channel) -> channel.getConnection() .getServerProperties().get('version').toString()); }健康檢查

上方一系列的操作之后，其實(shí)就是搞出了一個(gè)RabbitMQ的 HealthIndicator 實(shí)現(xiàn)類，而負(fù)責(zé)檢查RabbitMQ健康不健康也是這個(gè)類來(lái)負(fù)責(zé)的。由此我們可以想象到如果當(dāng)前環(huán)境存在MySQL、Redis、ES等情況應(yīng)該也是這么個(gè)操作

那么接下來(lái)無(wú)非就是當(dāng)有調(diào)用方訪問如下地址時(shí)，分別調(diào)用整個(gè)系統(tǒng)的所有的 HealthIndicator 的實(shí)現(xiàn)類的 health 方法即可了

http://ip:port/actuator/health

HealthEndpointAutoConfiguration

上邊說(shuō)的這個(gè)操作過程就在類 HealthEndpointAutoConfiguration 中，這個(gè)配置類同樣也是在 spring.factories 文件中引入的

@Configuration@EnableConfigurationProperties({HealthEndpointProperties.class, HealthIndicatorProperties.class})@AutoConfigureAfter({HealthIndicatorAutoConfiguration.class})@Import({HealthEndpointConfiguration.class, HealthEndpointWebExtensionConfiguration.class})public class HealthEndpointAutoConfiguration { public HealthEndpointAutoConfiguration() { }}

這里重點(diǎn)的地方在于引入的 HealthEndpointConfiguration 這個(gè)類

@Configurationclass HealthEndpointConfiguration { @Bean @ConditionalOnMissingBean @ConditionalOnEnabledEndpoint public HealthEndpoint healthEndpoint(ApplicationContext applicationContext) { return new HealthEndpoint(HealthIndicatorBeansComposite.get(applicationContext)); }}

這個(gè)類只是構(gòu)建了一個(gè)類 HealthEndpoint ，這個(gè)類我們可以理解為一個(gè)SpringMVC的Controller，也就是處理如下請(qǐng)求的

http://ip:port/actuator/health

那么首先看一下它的構(gòu)造方法傳入的是個(gè)啥對(duì)象吧

public static HealthIndicator get(ApplicationContext applicationContext) { HealthAggregator healthAggregator = getHealthAggregator(applicationContext); Map<String, HealthIndicator> indicators = new LinkedHashMap<>(); indicators.putAll(applicationContext.getBeansOfType(HealthIndicator.class)); if (ClassUtils.isPresent('reactor.core.publisher.Flux', null)) { new ReactiveHealthIndicators().get(applicationContext) .forEach(indicators::putIfAbsent); } CompositeHealthIndicatorFactory factory = new CompositeHealthIndicatorFactory(); return factory.createHealthIndicator(healthAggregator, indicators); }

跟我們想象中的一樣，就是通過Spring容器獲取所有的 HealthIndicator 接口的實(shí)現(xiàn)類，我這里只有幾個(gè)默認(rèn)的和RabbitMQ

然后都放入了其中一個(gè)聚合的實(shí)現(xiàn)類 CompositeHealthIndicator 中

既然 HealthEndpoint構(gòu)建好了，那么只剩下最后一步處理請(qǐng)求了

@Endpoint(id = 'health')public class HealthEndpoint { private final HealthIndicator healthIndicator; @ReadOperation public Health health() { return this.healthIndicator.health(); }}

剛剛我們知道，這個(gè)類是通過 CompositeHealthIndicator 構(gòu)建的，所以 health 方法的實(shí)現(xiàn)就在這個(gè)類中

public Health health() { Map<String, Health> healths = new LinkedHashMap<>(); for (Map.Entry<String, HealthIndicator> entry : this.indicators.entrySet()) { //循環(huán)調(diào)用 healths.put(entry.getKey(), entry.getValue().health()); } //對(duì)結(jié)果集排序 return this.healthAggregator.aggregate(healths); }

至此SpringBoot的健康檢查實(shí)現(xiàn)原理全部解析完成

以上就是詳解SpringBoot健康檢查的實(shí)現(xiàn)原理的詳細(xì)內(nèi)容，更多關(guān)于SpringBoot健康檢查實(shí)現(xiàn)原理的資料請(qǐng)關(guān)注好吧啦網(wǎng)其它相關(guān)文章！