前言

spring boot 中有个很诱人的组件–actuator,可以对spring boot应用做监控,只需在pom文件中加入如下配置即可:

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

此时我们便可以访问/env,获得spring boot 应用的环境变量.关于如何使用,可以参考如下链接:
Spring Boot Actuator监控端点小结

actuator项目如图:

actuator项目架构图

actuator中的端点类型有3种:

应用配置类：获取应用程序中加载的应用配置、环境变量、自动化配置报告等与Spring Boot应用密切相关的配置类信息。实现一般在org.springframework.boot.actuate.endpoint中.
度量指标类：获取应用程序运行过程中用于监控的度量指标，比如：内存信息、线程池信息、HTTP请求统计等。
操作控制类：提供了对应用的关闭等操作类功能。

我们这里详细说明org.springframework.boot.actuate.endpoint中的实现.通过如下几点来进行分析:

xxxEndpoint的作用
xxxEndpoint的字段,构造器
xxxEndpoint核心方法invoke 实现分析
xxxEndpoint如何进行配置
xxxEndpoint如何自动化装配

解析

在org.springframework.boot.actuate.endpoint 中还有2个子包-jmx(可通过jmx协议访问),mvc(通过spring mvc 暴露,可通过接口进行访问,在下篇文章进行分析).这里我们不关注这些,这看org.springframework.boot.actuate.endpoint 包下的类,类比较多,先看个类图吧,如下:

endpoint类图

Endpoint

Endpoint接口–>一个端点可以用于暴露操作的实用信息.通常暴露信息是通过spring mvc 但是其他一些技术也能实现,可以通过继承AbstractEndpoint的方式实现自己的endpoint.代码如下:

public interface Endpoint<T> {// 端点的逻辑标识(字母、数字和下划线('_') 组成)String getId();// 端点是否启用boolean isEnabled();// 端点是否输出敏感数据boolean isSensitive();// 调用端点，并返回调用结果T invoke();
}

其中泛型参数T为暴露的数据类型.方法的作用已经注释,就不再赘述了.

AbstractEndpoint

Endpoint有一个子类–> AbstractEndpoint(Endpoint接口实现的抽象基类),该类实现了EnvironmentAware,因此, AbstractEndpoint也就持有了Environment.

AbstractEndpoint 有如下属性:

// 匹配包括下划线的任何单词字符。类似但不等价于“[A-Za-z0-9_]”
private static final Pattern ID_PATTERN = Pattern.compile("\\w+");
// 通过EnvironmentAware接口注入
private Environment environment;
// 端点标识符
private String id;
// 是否默认敏感
private final boolean sensitiveDefault;
// 标识该端点是否暴露敏感信息
private Boolean sensitive;
// 是否端点可用
private Boolean enabled;

AbstractEndpoint方法实现了Endpoint接口中的getId, isEnabled, isSensitive,其中, getId只需返回AbstractEndpoint中的id属性即可,我们分别来看下其他方法的实现:

isEnabled,代码如下:

public boolean isEnabled() {return EndpointProperties.isEnabled(this.environment, this.enabled);
}

调用

public static boolean isEnabled(Environment environment, Boolean enabled) {if (enabled != null) {return enabled;}if (environment != null&& environment.containsProperty(ENDPOINTS_ENABLED_PROPERTY)) {return environment.getProperty(ENDPOINTS_ENABLED_PROPERTY, Boolean.class);}return true;
}

3件事:

如果AbstractEndpoint#enabled属性有值,则使用AbstractEndpoint的配置
如果Environment 不等于null 并且Environment 配置有endpoints.enabled的属性,则返回其配置的值
默认为true

isSensitive和isEnabled实现差不多,如下:

public boolean isSensitive() {return EndpointProperties.isSensitive(this.environment, this.sensitive,this.sensitiveDefault);
}

调用:

public static boolean isSensitive(Environment environment, Boolean sensitive,boolean sensitiveDefault) {if (sensitive != null) {return sensitive;}if (environment != null&& environment.containsProperty(ENDPOINTS_SENSITIVE_PROPERTY)) {return environment.getProperty(ENDPOINTS_SENSITIVE_PROPERTY, Boolean.class);}return sensitiveDefault;
}

如果AbstractEndpoint#enabled属性有值,则使用sensitive的配置
如果environment 不等于null 并且 environment中配置有endpoints.sensitive的属性,则返回其配置值
返回指定的默认值(默认为false)

EnvironmentEndpoint

EnvironmentEndpoint–>暴露ConfigurableEnvironment 中的信息,继承了AbstractEndpoint.其默认构造器如下:
```
public EnvironmentEndpoint() {// 设置 id 为 envsuper("env");
}
```
调用
```
public AbstractEndpoint(String id) {this(id, true);
}
```
最终,设置id为env,标识为敏感数据

其实现了invoke方法,代码如下:

public Map<String, Object> invoke() {// 1. 返回值Map<String, Object> result = new LinkedHashMap<String, Object>();// 2. 将spring boot 中激活的profile 放入result中,key --> profileresult.put("profiles", getEnvironment().getActiveProfiles());// 3. 获得PlaceholderSanitizingPropertyResolver --> 处理占位符,处理敏感数据PropertyResolver resolver = getResolver();// 4. 遍历environment 配置的PropertySource,依次处理之for (Entry<String, PropertySource<?>> entry : getPropertySourcesAsMap().entrySet()) {PropertySource<?> source = entry.getValue();String sourceName = entry.getKey();if (source instanceof EnumerablePropertySource) {// 4.1 只针对EnumerablePropertySource 类型的PropertySource 进行处理--> 依次将属性添加到properties中,// 如果属性值为string,则在添加前进行占位符,数据脱敏的处理EnumerablePropertySource<?> enumerable = (EnumerablePropertySource<?>) source;Map<String, Object> properties = new LinkedHashMap<String, Object>();for (String name : enumerable.getPropertyNames()) {Object property = source.getProperty(name);Object resolved = property instanceof String? resolver.resolvePlaceholders((String) property) : property;properties.put(name, sanitize(name, resolved));}// 4.2 后置处理,该方法的实现是直接返回原始值,可以通过覆写的方式进行扩展properties = postProcessSourceProperties(sourceName, properties);if (properties != null) {// 4.3 如果不为空,则添加到result中result.put(sourceName, properties);}}}return result;
}

将spring boot 中激活的profile 放入result中,key –> profile

获得PlaceholderSanitizingPropertyResolver –> 处理占位符,处理敏感数据.代码如下:

public PropertyResolver getResolver() {
// 1. 实例化PlaceholderSanitizingPropertyResolver --> 处理占位符,处理敏感数据
PlaceholderSanitizingPropertyResolver resolver = new PlaceholderSanitizingPropertyResolver(getPropertySources(), this.sanitizer);
// 2. 设置ignoreUnresolvableNestedPlaceholders 为true
resolver.setIgnoreUnresolvableNestedPlaceholders(true);
return resolver;
}

实例化PlaceholderSanitizingPropertyResolver –> 处理占位符,处理敏感数据
设置ignoreUnresolvableNestedPlaceholders 为true

PlaceholderSanitizingPropertyResolver继承了PropertySourcesPropertyResolver,这样就能对占位符进行处理了,又因为其内部持有Sanitizer(用于敏感数据脱敏),复写了getPropertyAsRawString,这样就能处理占位符,敏感数据了.代码如下:

protected String getPropertyAsRawString(String key) {String value = super.getPropertyAsRawString(key);return (String) this.sanitizer.sanitize(key, value);
}

遍历environment 配置的PropertySource,依次处理之
1. 只针对EnumerablePropertySource 类型的PropertySource 进行处理–> 依次将属性添加到properties中,如果属性值为string,则在添加前进行占位符,数据脱敏的处理
2. 后置处理(postProcessSourceProperties),该方法的实现是直接返回原始值,可以通过覆写的方式进行扩展
3. 如果不为空,则添加到result中

属性配置,由于EnvironmentEndpoint被@ConfigurationProperties(prefix = “endpoints.env”)注解,因此可通过如下配置进行个性化配置:
```
endpoints.env.id=env  
endpoints.env.sensitive=true  
endpoints.env.enabled=true
```
同时,又因为其声明了如下方法:
```
public void setKeysToSanitize(String... keysToSanitize) {this.sanitizer.setKeysToSanitize(keysToSanitize);
}
```
因此可以通过endpoints.env.keys-to-sanitize=xx,xx 来配置对指定的数据进行脱敏
自动化装配:

EnvironmentEndpoint的自动化装配是在EndpointAutoConfiguration中,代码如下:
```
@Bean
@ConditionalOnMissingBean
public EnvironmentEndpoint environmentEndpoint() {return new EnvironmentEndpoint();
}
```
- @Bean –> 注册1个id为environmentEndpoint,类型为EnvironmentEndpoint的bean
- @ConditionalOnMissingBean –> 当beanFactory中不存在EnvironmentEndpoint类型的bean时注册

InfoEndpoint

InfoEndpoint–>暴露应用信息，继承自AbstractEndpoint.

其字段和构造器如下:

private final List<InfoContributor> infoContributors;
public InfoEndpoint(List<InfoContributor> infoContributors) {super("info", false);Assert.notNull(infoContributors, "Info contributors must not be null");this.infoContributors = infoContributors;
}

其内部持有了BeanFactory中所有InfoContributor类型的bean,其通过构造器注入

invoke 实现如下:
```
public Map<String, Object> invoke() {Info.Builder builder = new Info.Builder();for (InfoContributor contributor : this.infoContributors) {contributor.contribute(builder);}Info build = builder.build();return build.getDetails();
}
```
通过遍历其内部的持有infoContributors,因此调用其contribute将info的数据添加到Info.Builder中,最后通过Info.Builder构建出Info,返回Info持有的details(建造者模式). Info中的details为Map. 这里的代码比较简单,读者可自行阅读.

InfoContributor接口用于向Info$Builder添加信息,关于这部分的内容,我们后续文章有分析.这里就不在赘述了.
属性配置:

InfoEndpoint由于有@ConfigurationProperties(prefix = “endpoints.info”)注解,因此可通过如下进行配置:
```
endpoints.info.id=info  
endpoints.info.sensitive=true  
endpoints.info.enabled=true 
```
自动化装配–>在EndpointAutoConfiguration中,代码如下:
```
@Bean
@ConditionalOnMissingBean
public InfoEndpoint infoEndpoint() throws Exception {return new InfoEndpoint(this.infoContributors == null? Collections.<InfoContributor>emptyList() : this.infoContributors);
}
```
- @Bean –> 注册1个id为infoEndpoint,类型为InfoEndpoint的bean
- @ConditionalOnMissingBean –> 当beanFactory中不存在InfoEndpoint类型的bean时注册

RequestMappingEndpoint

RequestMappingEndpoint 实现了ApplicationContextAware接口,因此,在初始化该类时会注入applicationContext.
RequestMappingEndpoint,构造器如下:
```
public RequestMappingEndpoint() {super("mappings");
}
```
因此, RequestMappingEndpoint的id为 mappings,默认为敏感

invoke 实现如下:

public Map<String, Object> invoke() {Map<String, Object> result = new LinkedHashMap<String, Object>();// 1. 从handlerMappings中获取HandlerMapping,默认情况下handlerMappings是不存在数据的extractHandlerMappings(this.handlerMappings, result);// 2. 从applicationContext中获取AbstractUrlHandlerMapping类型的bean,依次将其注册的handler 添加进去.extractHandlerMappings(this.applicationContext, result);// 3. 从methodMappings中获取HandlerMapping,默认情况下methodMappings是不存在数据的extractMethodMappings(this.methodMappings, result);// 3. 从applicationContext中获取AbstractUrlHandlerMapping类型的bean,依次获得其持有的HandlerMethods,进行处理.extractMethodMappings(this.applicationContext, result);return result;
}

从handlerMappings中获取HandlerMapping,默认情况下handlerMappings是不存在数据的
从applicationContext中获取AbstractUrlHandlerMapping类型的bean,依次将其注册的handler 添加进去.代码如下:
```
protected void extractHandlerMappings(ApplicationContext applicationContext,Map<String, Object> result) {
if (applicationContext != null) {Map<String, AbstractUrlHandlerMapping> mappings = applicationContext.getBeansOfType(AbstractUrlHandlerMapping.class);for (Entry<String, AbstractUrlHandlerMapping> mapping : mappings.entrySet()) {Map<String, Object> handlers = getHandlerMap(mapping.getValue());for (Entry<String, Object> handler : handlers.entrySet()) {result.put(handler.getKey(),Collections.singletonMap("bean", mapping.getKey()));}}
}
}
```
1. 获得AbstractUrlHandlerMapping类型的bean,此时有4个:
  1. beanNameHandlerMapping=org.springframework.web.servlet.handler.BeanNameUrlHandlerMapping
  2. resourceHandlerMapping=org.springframework.web.servlet.handler.SimpleUrlHandlerMapping
  3. faviconHandlerMapping=org.springframework.web.servlet.handler.SimpleUrlHandlerMapping
  4. welcomePageHandlerMapping=org.springframework.boot.autoconfigure.web.WebMvcAutoConfiguration$WelcomePageHandlerMapping
2. 依次遍历mappings:
  1. 获得AbstractUrlHandlerMapping中注册的handler,key–> path,value–>handler
  2. 依次遍历handlerss,存入结果集中,存入的key–>AbstractUrlHandlerMapping的id,value={bean=AbstractUrlHandlerMapping中注册的handler的路径}
从methodMappings中获取HandlerMapping,默认情况下methodMappings是不存在数据的

从applicationContext中获取AbstractUrlHandlerMapping类型的bean,依次获得其持有的HandlerMethods,进行处理.代码如下:

protected void extractMethodMappings(ApplicationContext applicationContext,Map<String, Object> result) {
if (applicationContext != null) {for (Entry<String, AbstractHandlerMethodMapping> bean : applicationContext.getBeansOfType(AbstractHandlerMethodMapping.class).entrySet()) {@SuppressWarnings("unchecked")Map<?, HandlerMethod> methods = bean.getValue().getHandlerMethods();for (Entry<?, HandlerMethod> method : methods.entrySet()) {Map<String, String> map = new LinkedHashMap<String, String>();map.put("bean", bean.getKey());map.put("method", method.getValue().toString());result.put(method.getKey().toString(), map);}}
}
}

获得AbstractUrlHandlerMapping类型的bean
依次遍历AbstractUrlHandlerMapping中注册的handler,添加至结果集中,key–> Handler 映射路径 ,value = {bean = AbstractHandlerMethodMapping的id,method=HandlerMethod}

属性配置–>可通过如下属性配置(因为有@ConfigurationProperties(prefix = “endpoints.mappings”)注解):

endpoints.mappings.enabled= # Enable the endpoint.
endpoints.mappings.id= # Endpoint identifier.
endpoints.mappings.sensitive= # Mark if the endpoint exposes sensitive information.

自动装配–>在EndpointAutoConfiguration$RequestMappingEndpointConfiguration中:

代码如下:
```
@Configuration
@ConditionalOnClass(AbstractHandlerMethodMapping.class)
protected static class RequestMappingEndpointConfiguration {@Bean@ConditionalOnMissingBeanpublic RequestMappingEndpoint requestMappingEndpoint() {RequestMappingEndpoint endpoint = new RequestMappingEndpoint();return endpoint;}}
```
当满足如下条件时生效,注册1个id为requestMappingEndpoint,类型为RequestMappingEndpoint的bean:
1. @ConditionalOnClass(AbstractHandlerMethodMapping.class) –> 在beanFactory中存在AbstractHandlerMethodMapping类型的bean时生效
2. @ConditionalOnMissingBean–>在beanFactory中不存在RequestMappingEndpoint类型的bean时生效

DumpEndpoint

DumpEndpoint–> 打印出线程的堆栈信息.id为dump,默认为敏感
invoke 实现:
```
@Override
public List<ThreadInfo> invoke() {return Arrays.asList(ManagementFactory.getThreadMXBean().dumpAllThreads(true, true));
}
```
调用了ThreadMXBean的dumpAllThreads来返回所有活动线程的线程信息，并带有堆栈跟踪和同步信息。当此方法返回时，返回数组中包含的一些线程可能已经终止。其中两个参数指的意义如下:
1. 第1个–>如果为 true，则转储所有锁定的监视器。
2. 第2个–>如果为 true，则转储所有锁定的可拥有同步器。
可参考如下链接:
接口 ThreadMXBean 一个很好用的线程管理接口类

可通过如下属性进行配置(因为有@ConfigurationProperties(prefix = “endpoints.dump”)注解):

endpoints.dump.enabled= # Enable the endpoint.
endpoints.dump.id= # Endpoint identifier.
endpoints.dump.sensitive= # Mark if the endpoint exposes sensitive information.

自动化装配:

在EndpointAutoConfiguration中声明,代码如下:
```
@Bean
@ConditionalOnMissingBean
public DumpEndpoint dumpEndpoint() {return new DumpEndpoint();
}
```
- @Bean –> 注册1个id为dumpEndpoint,类型为DumpEndpoint的bean
- @ConditionalOnMissingBean –> 当beanFactory中不存在DumpEndpoint类型的Bean时生效

FlywayEndpoint

没有启用,列在这里是为了做个提示

ShutdownEndpoint

ShutdownEndpoint 实现了ApplicationContextAware.其构造器如下:
```
public ShutdownEndpoint() {super("shutdown", true, false);
}
```
调用:
```
public AbstractEndpoint(String id, boolean sensitive, boolean enabled) {setId(id);this.sensitiveDefault = sensitive;this.enabled = enabled;
}
```
因此,其id为shutdown,默认敏感,默认不启用.

如何启用ShutdownEndpoint呢?

因为ShutdownEndpoint在类上声明了@ConfigurationProperties(prefix = “endpoints.shutdown”)的注解,因此可以通过endpoints.shutdown.enabled = true的方式来在ShutdownEndpoint 实例化后进行配置(在AbstractAutowireCapableBeanFactory#applyBeanPostProcessorsBeforeInitialization方法中,会调用ConfigurationPropertiesBindingPostProcessor实现属性注入).关于这部分的原理我们在 spring boot 源码解析13-@ConfigurationProperties是如何生效的中有详解.

invoke 实现:

public Map<String, Object> invoke() {if (this.context == null) {return NO_CONTEXT_MESSAGE;}try {return SHUTDOWN_MESSAGE;}finally {Thread thread = new Thread(new Runnable() {@Overridepublic void run() {try {Thread.sleep(500L);}catch (InterruptedException ex) {Thread.currentThread().interrupt();}ShutdownEndpoint.this.context.close();}});thread.setContextClassLoader(getClass().getClassLoader());thread.start();}
}

如果context 等于null,则返回{message=No context to shutdown.}, 2. 否则,返回{message=Shutting down, bye…},然后启动一个线程,在该线程中,先sleep 5秒后,然后调用了ShutdownEndpoint中持有的context的close方法进行关闭.

属性配置(因为有@ConfigurationProperties(prefix = “endpoints.shutdown”)注解):

endpoints.shutdown.enabled= # Enable the endpoint.
endpoints.shutdown.id= # Endpoint identifier.
endpoints.shutdown.sensitive= # Mark if the endpoint exposes sensitive information.

自动装配:

在EndpointAutoConfiguration中配置,代码如下:
```
@Bean
@ConditionalOnMissingBean
public ShutdownEndpoint shutdownEndpoint() {return new ShutdownEndpoint();
}
```
- @Bean –> 注册1个id为shutdownEndpoint,类型为ShutdownEndpoint的bean
- @ConditionalOnMissingBean –> 当beanFactory中不存在ShutdownEndpoint类型的Bean时生效

AutoConfigurationReportEndpoint

AutoConfigurationReportEndpoint 构造器如下:
```
public AutoConfigurationReportEndpoint() {super("autoconfig");
}
```
因此其id为autoconfig,默认为敏感

其内部持有ConditionEvaluationReport,会在实例化的时候进行注入.

invoke 实现:

public Report invoke() {return new Report(this.autoConfigurationReport);
}

Report类上声明了如下注解:
```
@JsonPropertyOrder({ "positiveMatches", "negativeMatches", "exclusions" })
@JsonInclude(Include.NON_EMPTY)
```
- @JsonPropertyOrder–>作用在类上，被用来指明当序列化时需要对属性做排序，它有2个属性:一个是alphabetic：布尔类型，表示是否采用字母拼音顺序排序，默认是为false，即不排序
- @JsonInclude–> Report中的属性值为空集合则不进行展示

Report 有如下字段:


// 匹配的
private final MultiValueMap<String, MessageAndCondition> positiveMatches;// 不匹配的
private final Map<String, MessageAndConditions> negativeMatches;// 去除的
private final List<String> exclusions;// 一般为null
private final Report parent;

其中MessageAndCondition封装了ConditionAndOutcome中的condition,message以进行更好的展示(json友好).其类上声明了如下注解:

@JsonPropertyOrder({ "condition", "message" })

因此在进行输出的时候,先输出condition,再输出message.

构造器如下:

public MessageAndCondition(ConditionAndOutcome conditionAndOutcome) {Condition condition = conditionAndOutcome.getCondition();ConditionOutcome outcome = conditionAndOutcome.getOutcome();this.condition = ClassUtils.getShortName(condition.getClass());if (StringUtils.hasLength(outcome.getMessage())) {this.message = outcome.getMessage();}else {this.message = (outcome.isMatch() ? "matched" : "did not match");}
}

赋值condition为ConditionAndOutcome中的Condition的短类名.
赋值message:如果ConditionAndOutcome中的Message有值则直接赋值,否则,如果对应的Condition匹配,则赋值为matched,否则赋值为did not match。

构造器如下:

public Report(ConditionEvaluationReport report) {this.positiveMatches = new LinkedMultiValueMap<String, MessageAndCondition>();this.negativeMatches = new LinkedHashMap<String, MessageAndConditions>();// 1. 通过report#getExclusions 获得不进行加载的beanthis.exclusions = report.getExclusions();// 2. for (Map.Entry<String, ConditionAndOutcomes> entry : report.getConditionAndOutcomesBySource().entrySet()) {// 2.1 如果该配置生效条件都匹配,则加入到positiveMatches,否则,加入到negativeMatchesif (entry.getValue().isFullMatch()) {add(this.positiveMatches, entry.getKey(), entry.getValue());}else {add(this.negativeMatches, entry.getKey(), entry.getValue());}}// 3. 如果report存在父report,则进行初始化Report 赋值为当前类的parent 属性boolean hasParent = report.getParent() != null;this.parent = (hasParent ? new Report(report.getParent()) : null);
}

通过ConditionEvaluationReport#getExclusions 获得不进行加载的bean,赋值为exclusions
调用ConditionEvaluationReport#getConditionAndOutcomesBySource 获得ConditionEvaluationReport中持有匹配信息,返回的map中,key–> 匹配类名,ConditionAndOutcomes–> 匹配结果.

依次遍历第2步的返回值–>如果该配置生效条件都匹配,则加入到positiveMatches,否则,加入到negativeMatches.其中add 代码如下:

private void add(MultiValueMap<String, MessageAndCondition> map, String source,ConditionAndOutcomes conditionAndOutcomes) {
String name = ClassUtils.getShortName(source);
for (ConditionAndOutcome conditionAndOutcome : conditionAndOutcomes) {map.add(name, new MessageAndCondition(conditionAndOutcome));
}
}

因此positiveMatches,negativeMatches 中的key为配置类的简单类名.

如果report存在父report,则进行初始化Report 赋值为当前类的parent 属性.一般来说，是不存在父report的

属性配置(因为有@ConfigurationProperties(prefix = “endpoints.autoconfig”) 注解):

endpoints.autoconfig.enabled= # Enable the endpoint.
endpoints.autoconfig.id= # Endpoint identifier.
endpoints.autoconfig.sensitive= # Mark if the endpoint exposes sensitive information.

自动装配:

同样还是在EndpointAutoConfiguration中,代码如下:
```
@Bean
@ConditionalOnBean(ConditionEvaluationReport.class)
@ConditionalOnMissingBean(search = SearchStrategy.CURRENT)
public AutoConfigurationReportEndpoint autoConfigurationReportEndpoint() {return new AutoConfigurationReportEndpoint();
}
```
- @Bean –> 注册1个id为autoConfigurationReportEndpoint,类型为AutoConfigurationReportEndpoint的bean
- @ConditionalOnBean(ConditionEvaluationReport.class)–>beanFactory中存在ConditionEvaluationReport类型的bean时生效
- @ConditionalOnMissingBean(search = SearchStrategy.CURRENT)–> 在当前上下文中不存在AutoConfigurationReportEndpoint类型的bean时生效

ConditionEvaluationReport

AutoConfigurationReportEndpoint 是通过ConditionEvaluationReport 来进行暴露信息.

ConditionEvaluationReport 字段如下:

private static final String BEAN_NAME = "autoConfigurationReport";// 如果一个配置类中内部配置类不匹配,则在其外部类的所对应的ConditionAndOutcomes中添加1个AncestorsMatchedCondition
private static final AncestorsMatchedCondition ANCESTOR_CONDITION = new AncestorsMatchedCondition();// key-->配置类类名,ConditionAndOutcomes-->匹配条件结果的封装
private final SortedMap<String, ConditionAndOutcomes> outcomes = new TreeMap<String, ConditionAndOutcomes>();// 是否添加AncestorsMatchedCondition,默认为false
private boolean addedAncestorOutcomes;// 父ConditionEvaluationReport,一般为null
private ConditionEvaluationReport parent;// 去除加载的配置
private List<String> exclusions = Collections.emptyList();// 在ConditionEvaluationReportAutoConfigurationImportListener#onAutoConfigurationImportEvent 添加,用于保存还没有
// 执行判断的class
private Set<String> unconditionalClasses = new HashSet<String>();

ConditionEvaluationReport 实例化过程如下:

在SpringApplication#run中会调用AbstractApplicationContext#refresh,在refresh会调用PostProcessorRegistrationDelegate#invokeBeanFactoryPostProcessors,在该方法中最终会调用到AutoConfigurationImportSelector#selectImports方法.在该方法中会调用fireAutoConfigurationImportEvents,代码如下:

private void fireAutoConfigurationImportEvents(List<String> configurations,Set<String> exclusions) {List<AutoConfigurationImportListener> listeners = getAutoConfigurationImportListeners();if (!listeners.isEmpty()) {AutoConfigurationImportEvent event = new AutoConfigurationImportEvent(this,configurations, exclusions);for (AutoConfigurationImportListener listener : listeners) {invokeAwareMethods(listener);listener.onAutoConfigurationImportEvent(event);}}
}

会加载/META-INF/spring.factories 中配置的org.springframework.boot.autoconfigure.AutoConfigurationImportListener,实例化后,依次调用其onAutoConfigurationImportEvent 方法. spring.factories 配置如下:

org.springframework.boot.autoconfigure.AutoConfigurationImportListener=\
org.springframework.boot.autoconfigure.condition.ConditionEvaluationReportAutoConfigurationImportListener

因此此处会调用ConditionEvaluationReportAutoConfigurationImportListener#onAutoConfigurationImportEvent.代码如下:

public void onAutoConfigurationImportEvent(AutoConfigurationImportEvent event) {if (this.beanFactory != null) {ConditionEvaluationReport report = ConditionEvaluationReport.get(this.beanFactory);report.recordEvaluationCandidates(event.getCandidateConfigurations());report.recordExclusions(event.getExclusions());}
}

实例化ConditionEvaluationReport,代码如下:

public static ConditionEvaluationReport get(ConfigurableListableBeanFactory beanFactory) {
synchronized (beanFactory) {ConditionEvaluationReport report;// 1. 如果当前beanFactory包含autoConfigurationReport定义的话,就从beanFactory中获取,if (beanFactory.containsSingleton(BEAN_NAME)) {report = beanFactory.getBean(BEAN_NAME, ConditionEvaluationReport.class);}else {// 否则就实例化一个,然后进行注册report = new ConditionEvaluationReport();beanFactory.registerSingleton(BEAN_NAME, report);}// 2. 如果存在父容器的话,就从父容器中获取。locateParent(beanFactory.getParentBeanFactory(), report);return report;
}
}

如果当前beanFactory包含autoConfigurationReport定义的话,就从beanFactory中获取,否则就实例化一个,然后进行注册

如果存在父容器的话,就从父容器中获取,并将其赋值为当前context中获得的ConditionEvaluationReport的父ConditionEvaluationReport.代码如下:

private static void locateParent(BeanFactory beanFactory,
ConditionEvaluationReport report) {
if (beanFactory != null && report.parent == null&& beanFactory.containsBean(BEAN_NAME)) {
report.parent = beanFactory.getBean(BEAN_NAME,ConditionEvaluationReport.class);
}
}

一般都是null,不会执行的

设置unconditionalClasses为event#getCandidateConfigurations的返回值
设置exclusions为event#getExclusions的返回值

在AutoConfigurationReportEndpoint中是通过Report来进行暴露信息的,而在其构造器中,调用了ConditionEvaluationReport#getConditionAndOutcomesBySource方法,代码如下:

    public Map<String, ConditionAndOutcomes> getConditionAndOutcomesBySource() {if (!this.addedAncestorOutcomes) {// 1. 如果addedAncestorOutcomes 设为false,则依次遍历outcomes,如果一个配置类中内部配置类不匹配,则在其外部类的所对应的ConditionAndOutcomes中添加1个AncestorsMatchedConditionfor (Map.Entry<String, ConditionAndOutcomes> entry : this.outcomes.entrySet()) {if (!entry.getValue().isFullMatch()) {addNoMatchOutcomeToAncestors(entry.getKey());}}this.addedAncestorOutcomes = true;}return Collections.unmodifiableMap(this.outcomes);
}

如果addedAncestorOutcomes 设为false,则依次遍历outcomes,如果一个配置类中内部配置类不匹配,则在其外部类的所对应的ConditionAndOutcomes中添加1个AncestorsMatchedCondition
返回outcomes.

问题来了, outcomes 中的数据是如何添加的?

答案: 有2处.

还是在AutoConfigurationImportSelector#selectImports中,会调用其filter方法.代码如下

private List<String> filter(List<String> configurations,AutoConfigurationMetadata autoConfigurationMetadata) {
long startTime = System.nanoTime();
String[] candidates = configurations.toArray(new String[configurations.size()]);
boolean[] skip = new boolean[candidates.length];
boolean skipped = false;
// 1. 获取META-INFspring.factories/中配置的org.springframework.boot.autoconfigure.AutoConfigurationImportFilter,.OnClassCondition.依次进行遍历之
// 此时获得的是org.springframework.boot.autoconfigure.condition
for (AutoConfigurationImportFilter filter : getAutoConfigurationImportFilters()) {// 1.1 进行属性注入invokeAwareMethods(filter);// 1.2 调用AutoConfigurationImportFilter#match 进行判断,依次遍历其返回值,如果返回的是false,则说明该配置为跳过,并将skipped设置为true// 获得AutoConfigurationMetadata中配置的ConditionalOnClass,如果不会空,则依次遍历之,看是否在当前类路径下存在// 如果不匹配的话,则调用ConditionEvaluationReport.#ecordConditionEvaluation 进行记录// 由于此时AutoConfigurationMetadata 什么都没有配置,因此此步骤相当于空操作,最终会在第2步返回boolean[] match = filter.match(candidates, autoConfigurationMetadata);for (int i = 0; i < match.length; i++) {if (!match[i]) {skip[i] = true;skipped = true;}}
}
// 2. 如果skipped 等于false,则直接返回configurations,说明没有配置是需要跳过的
if (!skipped) {return configurations;
}
// 3. 依次遍历candidates,如果该配置是不进行跳过的,则添加至result中进行返回
List<String> result = new ArrayList<String>(candidates.length);
for (int i = 0; i < candidates.length; i++) {if (!skip[i]) {result.add(candidates[i]);}
}
return new ArrayList<String>(result);
}

获取META-INFspring.factories/中配置的org.springframework.boot.autoconfigure.AutoConfigurationImportFilter,.OnClassCondition.依次进行遍历之.此时获得的是org.springframework.boot.autoconfigure.condition
1. 进行属性注入
2. 调用AutoConfigurationImportFilter#match 进行判断,依次遍历其返回值,如果返回的是false,则说明该配置为跳过,并将skipped设置为true.由于此时调用的是OnClassCondition,其判断逻辑为获得AutoConfigurationMetadata中配置的ConditionalOnClass,如果不会空,则依次遍历之,看是否在当前类路径下存在.如果不匹配的话,则调用ConditionEvaluationReport#ecordConditionEvaluation 进行记录.由于此时AutoConfigurationMetadata 什么都没有配置,因此此步骤相当于空操作,最终会在第2步返回
如果skipped 等于false,则直接返回configurations,说明没有配置是需要跳过的
依次遍历candidates,如果该配置是不进行跳过的,则添加至result中进行返回

在ConfigurationClassParser#processConfigurationClass进行解析加载配置类时,会调用ConditionEvaluator#shouldSkip,在该方法中,会因此遍历配置类配置的@Conditional所对应的处理类.此时,如果处理类是SpringBootCondition的子类的话,就会调用ConditionEvaluationReport进行记录匹配结果. 代码如下:
```
private void recordEvaluation(ConditionContext context, String classOrMethodName,ConditionOutcome outcome) {
if (context.getBeanFactory() != null) {ConditionEvaluationReport.get(context.getBeanFactory()).recordConditionEvaluation(classOrMethodName, this, outcome);
}
}
```

LiquibaseEndpoint

默认不生效,这里就不进行分析了

BeansEndpoint

BeansEndpoint的作用 –> 暴露关于beans的json视图.如果Environment 中设置了spring.liveBeansView.mbeanDomain,则所有spring 上下文的bean都会展示.否则只会展示当前的上下文中的bean.默认是没有配置的
BeansEndpoint,构造器如下：
```
public BeansEndpoint() {super("beans");
}
```
id为beans,默认为敏感

BeansEndpoint的字段如下:

// 继承自LiveBeansView,用于生成json格式的数据
private final HierarchyAwareLiveBeansView liveBeansView = new HierarchyAwareLiveBeansView();// json 解析器对象
private final JsonParser parser = JsonParserFactory.getJsonParser();

由于BeansEndpoint实现了ApplicationContextAware接口,因此当前初始化时,会调用其setApplicationContext方法,代码如下:

    public void setApplicationContext(ApplicationContext context) throws BeansException {if (context.getEnvironment().getProperty(LiveBeansView.MBEAN_DOMAIN_PROPERTY_NAME) == null) {this.liveBeansView.setLeafContext(context);}
}

如果没有设置spring.liveBeansView.mbeanDomain的属性,则将HierarchyAwareLiveBeansView中的leafContext设置为传入的ApplicationContext(通常是当前应用所对应的上下文)

invoke实现如下:

public List<Object> invoke() {return this.parser.parseList(this.liveBeansView.getSnapshotAsJson());
}

调用HierarchyAwareLiveBeansView#getSnapshotAsJson 生成json串.代码如下：

public String getSnapshotAsJson() {if (this.leafContext == null) {return super.getSnapshotAsJson();}// 2. 将leafContext的整个继承关系都添加到contexts中,即:如果给定的leafContext 存在父context,则一直递归的添加至contexts// 直至顶级容器,然后调用LiveBeansView#generateJson 来生成json串return generateJson(getContextHierarchy());
}

如果leafContext 等于null,则调用LiveBeansView#getSnapshotAsJson来生成json串.一般都会执行第2步

将leafContext的整个继承关系都添加到contexts中,即:如果给定的leafContext 存在父context,则一直递归的添加至contexts.代码如下:

private Set<ConfigurableApplicationContext> getContextHierarchy() {
Set<ConfigurableApplicationContext> contexts = new LinkedHashSet<ConfigurableApplicationContext>();
ApplicationContext context = this.leafContext;
while (context != null) {contexts.add(asConfigurableContext(context));context = context.getParent();
}
return contexts;
}

将leafContext的整个继承关系都添加到contexts中,即:如果给定的leafContext 存在父context,则一直递归的添加至contexts直至顶级容器

调用LiveBeansView#generateJson 来生成json串.在该方法中没有使用第3方的json解析库的目的是为了避免对其进行依赖.返回的格式为数组格式.代码如下:

protected String generateJson(Set<ConfigurableApplicationContext> contexts) {
StringBuilder result = new StringBuilder("[\n");
for (Iterator<ConfigurableApplicationContext> it = contexts.iterator(); it.hasNext();) {
// 1. context和parent属性来标识该数据是属于哪个context的
ConfigurableApplicationContext context = it.next();
result.append("{\n\"context\": \"").append(context.getId()).append("\",\n");
if (context.getParent() != null) {result.append("\"parent\": \"").append(context.getParent().getId()).append("\",\n");
}
else {result.append("\"parent\": null,\n");
}
// 2.构造beans的数组格式的字符串,含有bean,aliases,scope,type,resource,dependencies 属性
result.append("\"beans\": [\n");
ConfigurableListableBeanFactory bf = context.getBeanFactory();
String[] beanNames = bf.getBeanDefinitionNames();
boolean elementAppended = false;
for (String beanName : beanNames) {BeanDefinition bd = bf.getBeanDefinition(beanName);if (isBeanEligible(beanName, bd, bf)) {// 如果该BeanDefinition的角色不是ROLE_INFRASTRUCTURE 并且(不是延迟初始化|| 该bean是1个单例)if (elementAppended) {result.append(",\n");}result.append("{\n\"bean\": \"").append(beanName).append("\",\n");result.append("\"aliases\": ");appendArray(result, bf.getAliases(beanName));result.append(",\n");String scope = bd.getScope();if (!StringUtils.hasText(scope)) {scope = BeanDefinition.SCOPE_SINGLETON;}result.append("\"scope\": \"").append(scope).append("\",\n");Class<?> beanType = bf.getType(beanName);if (beanType != null) {result.append("\"type\": \"").append(beanType.getName()).append("\",\n");}else {result.append("\"type\": null,\n");}result.append("\"resource\": \"").append(getEscapedResourceDescription(bd)).append("\",\n");result.append("\"dependencies\": ");appendArray(result, bf.getDependenciesForBean(beanName));result.append("\n}");elementAppended = true;}
}
result.append("]\n");
result.append("}");
if (it.hasNext()) {result.append(",\n");
}
}
result.append("]");
return result.toString();
}

依次遍历给定的contexts
1. 构建context和parent属性来标识该数据是属于哪个context的和继承关系
2. 构造beans的数组格式的字符串,依次遍历该上下文中注册的bean的id,如果该id所对应的BeanDefinition的角色不是ROLE_INFRASTRUCTURE 并且(不是延迟初始化|| 该bean是1个单例),则进行拼接json串

进行json串的反序列化

由于BeansEndpoint声明了@ConfigurationProperties(prefix = “endpoints.beans”),因此可以通过如下属性来配置:
```
endpoints.beans.id
endpoints.beans.sensitive
endpoints.beans.enabled
```
自动化配置:

beansEndpoint 是在EndpointAutoConfiguration 中进行配置的,代码如下:
```
@Bean
@ConditionalOnMissingBean
public BeansEndpoint beansEndpoint() {return new BeansEndpoint();
}
```
- @Bean –> 注册1个id为 beansEndpoint,类型为BeansEndpoint的bean
- @ConditionalOnMissingBean–> 当beanFactory中不存在BeansEndpoint类型的bean时生效

ConfigurationPropertiesReportEndpoint

作用:–>暴露被@ConfigurationProperties 注解的bean的属性.为了保护数据,将敏感数据进行了脱敏

字段:

private static final String CONFIGURATION_PROPERTIES_FILTER_ID = "configurationPropertiesFilter";// 数据脱敏
private final Sanitizer sanitizer = new Sanitizer();// 通过实现ApplicationContextAware 进行自动注入
private ApplicationContext context;public ConfigurationPropertiesReportEndpoint() {super("configprops");
}

invoke 实现:

public Map<String, Object> invoke() {return extract(this.context);
}

调用:

protected Map<String, Object> extract(ApplicationContext context) {// Serialize beans into map structure and sanitize valuesObjectMapper mapper = new ObjectMapper();// 1. 配置ObjectMapper的属性configureObjectMapper(mapper);// 2. 抽取数据return extract(context, mapper);
}

对ObjectMapper 进行配置:

代码如下:

protected void configureObjectMapper(ObjectMapper mapper) {
mapper.configure(SerializationFeature.FAIL_ON_EMPTY_BEANS, false);
mapper.configure(SerializationFeature.WRITE_NULL_MAP_VALUES, false);
applyConfigurationPropertiesFilter(mapper);
applySerializationModifier(mapper);
}

SerializationFeature.FAIL_ON_EMPTY_BEANS –> 设置当对于给定的类型无法访问时如何处理,true–> 抛出异常,false–> 返回null
SerializationFeature.WRITE_NULL_MAP_VALUES –> 设置当map对于的value为null时如何处理,treu–>序列化,false–> 跳过

applyConfigurationPropertiesFilter 代码如下:

private void applyConfigurationPropertiesFilter(ObjectMapper mapper) {
mapper.setAnnotationIntrospector(new ConfigurationPropertiesAnnotationIntrospector());
mapper.setFilterProvider(new SimpleFilterProvider().setDefaultFilter(new ConfigurationPropertiesPropertyFilter()));
}

设置AnnotationIntrospector为ConfigurationPropertiesAnnotationIntrospector.该类的作用是:获得@JsonFilter注解的值,如果获取不到,则返回configurationPropertiesFilter.代码如下:

private static class ConfigurationPropertiesAnnotationIntrospector
extends JacksonAnnotationIntrospector {
@Override
public Object findFilterId(Annotated a) {
// 1. 获得@JsonFilter注解的值,如果获取不到,则返回configurationPropertiesFilter
Object id = super.findFilterId(a);
if (id == null) {
id = CONFIGURATION_PROPERTIES_FILTER_ID;
}
return id;
}
}

设置默认的过滤器为ConfigurationPropertiesPropertyFilter,该类的作用是进行如下规则的过滤:

类名以$$开头的被过滤掉
自我引用的字段被过滤掉
当在序列化时抛出异常时过滤掉

代码如下:

public void serializeAsField(Object pojo, JsonGenerator jgen,
SerializerProvider provider, PropertyWriter writer) throws Exception {
if (writer instanceof BeanPropertyWriter) {
try {// 1. 自我引用的字段被过滤掉if (pojo == ((BeanPropertyWriter) writer).get(pojo)) {if (logger.isDebugEnabled()) {logger.debug("Skipping '" + writer.getFullName() + "' on '"+ pojo.getClass().getName()+ "' as it is self-referential");}return;}
}
catch (Exception ex) {// 2. 当在序列化时抛出异常时过滤掉if (logger.isDebugEnabled()) {logger.debug("Skipping '" + writer.getFullName() + "' on '"+ pojo.getClass().getName() + "' as an exception "+ "was thrown when retrieving its value", ex);}return;
}
}
// 3. 序列化字段
super.serializeAsField(pojo, jgen, provider, writer);
}

设置序列化工厂中的方法序列化器为GenericSerializerModifier.代码如下:

    public List<BeanPropertyWriter> changeProperties(SerializationConfig config,BeanDescription beanDesc, List<BeanPropertyWriter> beanProperties) {
List<BeanPropertyWriter> result = new ArrayList<BeanPropertyWriter>();
for (BeanPropertyWriter writer : beanProperties) {boolean readable = isReadable(beanDesc, writer);if (readable) {result.add(writer);}
}
return result;
}

依次遍历beanProperties,如果可读的话,则添加至result中.可读的判断逻辑如下:

根据bean 的类型和属性的类型找出对应的set方法
如果set方法存在或者是同一包下的类或者是map或者集合的子类,则返回true

调用extract方法抽取数据.代码如下:

private Map<String, Object> extract(ApplicationContext context, ObjectMapper mapper) {
Map<String, Object> result = new HashMap<String, Object>();
// 1. 获得beanFactory中ConfigurationBeanFactoryMetaData类型的bean
ConfigurationBeanFactoryMetaData beanFactoryMetaData = getBeanFactoryMetaData(context);
// 2. 获得被@ConfigurationProperties注解的bean，key--> bean的id,value --> bean
Map<String, Object> beans = getConfigurationPropertiesBeans(context,beanFactoryMetaData);
// 3. 依次遍历beans
for (Map.Entry<String, Object> entry : beans.entrySet()) {String beanName = entry.getKey();Object bean = entry.getValue();Map<String, Object> root = new HashMap<String, Object>();String prefix = extractPrefix(context, beanFactoryMetaData, beanName, bean);// 3.1 获得@ConfigurationProperties注解的前缀,添加至root中,key-->prefix,value-->@ConfigurationProperties注解的前缀root.put("prefix", prefix);// 3.2 root.put("properties", sanitize(prefix, safeSerialize(mapper, bean, prefix)));// 3.3 添加至result中,key--> bean id,value-->map{prefix=xx,properties=xx}result.put(beanName, root);
}
// 4. 如果ApplicationContext存在父容器的,则递归调用extract提取数据,key为parent.
if (context.getParent() != null) {result.put("parent", extract(context.getParent(), mapper));
}
return result;
}

获得beanFactory中ConfigurationBeanFactoryMetaData类型的bean
获得被@ConfigurationProperties注解的bean，key–> bean的id,value –> bean

依次遍历beans

获得@ConfigurationProperties注解的前缀,添加至root中,key–>prefix,value–>@ConfigurationProperties注解的前缀

对数据进行脱敏.代码如下:

private Map<String, Object> sanitize(String prefix, Map<String, Object> map) {
for (Map.Entry<String, Object> entry : map.entrySet()) {
String key = entry.getKey();
String qualifiedKey = (prefix.isEmpty() ? prefix : prefix + ".") + key;
Object value = entry.getValue();
if (value instanceof Map) {
// 1. 如果对应的属性值为Map,List 则递归调用sanitize 进行数据脱敏
map.put(key, sanitize(qualifiedKey, (Map<String, Object>) value));
}
else if (value instanceof List) {
map.put(key, sanitize(qualifiedKey, (List<Object>) value));
}
else {
// 2. 如果属性名包含password", "secret", "key", "token", ".*credentials.*", "vcap_services,则将其替换为******
value = this.sanitizer.sanitize(key, value);
value = this.sanitizer.sanitize(qualifiedKey, value);
map.put(key, value);
}
}
return map;
}

如果对应的属性值为Map,List 则递归调用sanitize 进行数据脱敏
否则如果属性名包含password, secret, key, token, .*credentials.*, vcap_services,则将其替换为**

添加至result中,key–> bean id,value–>map{prefix=xx,properties=xx}

如果ApplicationContext存在父容器的,则递归调用extract提取数据,key为parent.

由于ConfigurationPropertiesReportEndpoint 被@ConfigurationProperties(prefix = “endpoints.configprops”)注解,因此可通过如下属性配置:
```
endpoints.configprops.id=configprops  
endpoints.configprops.sensitive=true  
endpoints.configprops.enabled=true  
endpoints.configprops.keys-to-sanitize=password,secret
```
之所以可以通过 endpoints.configprops.keys-to-sanitize 进行配置,是因为ConfigurationPropertiesReportEndpoint声明了如下方法:
```
public void setKeysToSanitize(String... keysToSanitize) {this.sanitizer.setKeysToSanitize(keysToSanitize);
}
```
自动化配置(在EndpointAutoConfiguration中配置):

代码如下:
```
@Bean
@ConditionalOnMissingBean
public ConfigurationPropertiesReportEndpoint configurationPropertiesReportEndpoint() {return new ConfigurationPropertiesReportEndpoint();
}
```
- @Bean –> 注册1个id为configurationPropertiesReportEndpoint,类型为ConfigurationPropertiesReportEndpoint的Bean
- @ConditionalOnMissingBean –> beanFactory中不存在ConfigurationPropertiesReportEndpoint类型的bean时生效

TraceEndpoint

作用:–> 该端点用来返回基本的HTTP跟踪信息。默认情况下，跟踪信息的存储采用org.springframework.boot.actuate.trace.InMemoryTraceRepository实现的内存方式，始终保留最近的100条请求记录.其中,返回的Trace定义如下:

public final class Trace {// 时间戳
private final Date timestamp;// 保存用于分析上下文信息，例如HTTP头
private final Map<String, Object> info;public Trace(Date timestamp, Map<String, Object> info) {super();Assert.notNull(timestamp, "Timestamp must not be null");Assert.notNull(info, "Info must not be null");this.timestamp = timestamp;this.info = info;
}public Date getTimestamp() {return this.timestamp;
}public Map<String, Object> getInfo() {return this.info;
}
}

字段:

private final TraceRepository repository;

这里我们有必要说明一下TraceRepository:

TraceRepository 是用来保存Trace的. 接口定义如下:

public interface TraceRepository {// 返回保存的Trace
List<Trace> findAll();// 进行添加
void add(Map<String, Object> traceInfo);
}

TraceRepository 只要1个实现–>InMemoryTraceRepository.其字段如下:

// 容量为100
private int capacity = 100;
// 是否倒序展示,默认为false
private boolean reverse = true;
// 容器,用于保存Trace
private final List<Trace> traces = new LinkedList<Trace>();

findAll只需简单的返回保存的traces即可.实现如下:

public List<Trace> findAll() {
synchronized (this.traces) {return Collections.unmodifiableList(new ArrayList<Trace>(this.traces));
}
}

add,代码如下:

public void add(Map<String, Object> map) {
// 1. 实例化Trace,时间戳为当前时间
Trace trace = new Trace(new Date(), map);
synchronized (this.traces) {// 2. 如果traces中的容量大于等于了阈值,则进行删除.如果reverse等于true 则删除最后1个,否则,删除第1个while (this.traces.size() >= this.capacity) {this.traces.remove(this.reverse ? this.capacity - 1 : 0);}// 3. 进行添加,如果reverse等于true 则添加至第1个,否则,添加至最后if (this.reverse) {this.traces.add(0, trace);}else {this.traces.add(trace);}
}
}

实例化Trace,时间戳为当前时间
如果traces中的容量大于等于了阈值,则进行删除.如果reverse等于true 则删除最后1个,否则,删除第1个
进行添加,如果reverse等于true 则添加至第1个,否则,添加至最后

TraceRepository 是在何处配置的呢?

在TraceRepositoryAutoConfiguration中,代码如下:
```
@ConditionalOnMissingBean(TraceRepository.class)
@Bean
public InMemoryTraceRepository traceRepository() {
return new InMemoryTraceRepository();
}
```
- @Bean –> 注册1个id为traceRepository,类型为InMemoryTraceRepository的bean
- @ConditionalOnMissingBean(TraceRepository.class)–> 当beanFactory中不存在TraceRepository类型的bean时生效

invoke 实现:

@Override
public List<Trace> invoke() {return this.repository.findAll();
}

只需调用TraceRepository# findAll,返回保存的Trace即可.

属性配置,因此其被@ConfigurationProperties(prefix = “endpoints.trace”)注解,因此可以通过如下属性进行配置:
```
endpoints.trace.id=trace  
endpoints.trace.sensitive=true  
endpoints.trace.enabled=true 
```
自动装配:

在EndpointAutoConfiguration中进行了装配,代码如下:
```
@Bean
@ConditionalOnMissingBean
public TraceEndpoint traceEndpoint() {return new TraceEndpoint(this.traceRepository == null? new InMemoryTraceRepository() : this.traceRepository);
}
```
- @Bean–> 注册1个id为traceEndpoint,类型为TraceEndpoint的bean
- @ConditionalOnMissingBean–> 当beanFactory中不存在TraceEndpoint类型的bean时生效

这里提1个问题,TraceEndpoint 是通过TraceRepository获取Trace,那么TraceRepository中的Trace是如何保存的呢?

答案:

通过WebRequestTraceFilter(Filter)来实现. WebRequestTraceFilter实现了Ordered接口,指定了其在过滤器链中的顺序,代码如下:

private int order = Ordered.LOWEST_PRECEDENCE - 10;public int getOrder() {return this.order;
}

WebRequestTraceFilter中的字段如下:

    private static final Log logger = LogFactory.getLog(WebRequestTraceFilter.class);// debug时使用.如果启用的话,并且log的trace级别可用的话,则打印请求头信息,默认为false
private boolean dumpRequests = false;// Not LOWEST_PRECEDENCE, but near the end, so it has a good chance of catching all
// enriched headers, but users can add stuff after this if they want to
private int order = Ordered.LOWEST_PRECEDENCE - 10;private final TraceRepository repository;private ErrorAttributes errorAttributes;private final TraceProperties properties;

其中TraceProperties的定义如下:

@ConfigurationProperties(prefix = "management.trace")
public class TraceProperties {private static final Set<Include> DEFAULT_INCLUDES;static {Set<Include> defaultIncludes = new LinkedHashSet<Include>();defaultIncludes.add(Include.REQUEST_HEADERS);defaultIncludes.add(Include.RESPONSE_HEADERS);defaultIncludes.add(Include.COOKIES);defaultIncludes.add(Include.ERRORS);defaultIncludes.add(Include.TIME_TAKEN);DEFAULT_INCLUDES = Collections.unmodifiableSet(defaultIncludes);}private Set<Include> include = new HashSet<Include>(DEFAULT_INCLUDES);public Set<Include> getInclude() {return this.include;}public void setInclude(Set<Include> include) {this.include = include;}
}

默认配置的是Include.REQUEST_HEADERS, Include.RESPONSE_HEADERS, Include.COOKIES ,Include.ERRORS, Include.TIME_TAKEN. 可以通过如下进行配置

management.trace.include=REQUEST_HEADERS,RESPONSE_HEADERS

可选值为org.springframework.boot.actuate.trace.TraceProperties.Include.这里就不在贴出了

WebRequestTraceFilter 继承了OncePerRequestFilter,因此只需实现doFilterInternal即可,代码如下：

protected void doFilterInternal(HttpServletRequest request,HttpServletResponse response, FilterChain filterChain)throws ServletException, IOException {long startTime = System.nanoTime();// 1. 获得traceMap<String, Object> trace = getTrace(request);// 2. 打印日志-->如果log的trace级别可用的话并且dumpRequests等于true,则打印请求头信息,默认为falselogTrace(request, trace);int status = HttpStatus.INTERNAL_SERVER_ERROR.value();try {// 3. 继续过滤器链的过滤,最后获得响应状态filterChain.doFilter(request, response);status = response.getStatus();}finally {// 4. 添加Http请求耗时统计-->如果TraceProperties中配置了Include#TIME_TAKEN(默认配置了),则添加到trace中,key为timeTaken，value-->当前时间-开始时间的毫秒值addTimeTaken(trace, startTime);// 5. 添加响应头信息enhanceTrace(trace, status == response.getStatus() ? response: new CustomStatusResponseWrapper(response, status));// 6. 添加至TraceRepository 中this.repository.add(trace);}
}

记录开始时间

获得trace.代码如下:

protected Map<String, Object> getTrace(HttpServletRequest request) {
// 1. 获得HttpSession
HttpSession session = request.getSession(false);
// 2. 获得javax.servlet.error.exception,所对应的异常--> 当spring mvc 出现异常时,会加入到javax.servlet.error.exception中
Throwable exception = (Throwable) request.getAttribute("javax.servlet.error.exception");
// 3. 获得Principal,如果返回null,说明没有该请求没有进行验证
Principal userPrincipal = request.getUserPrincipal();
Map<String, Object> trace = new LinkedHashMap<String, Object>();
Map<String, Object> headers = new LinkedHashMap<String, Object>();
// 4. 添加请求方法,请求路径,请求头到trace中
trace.put("method", request.getMethod());
trace.put("path", request.getRequestURI());
trace.put("headers", headers);
if (isIncluded(Include.REQUEST_HEADERS)) {headers.put("request", getRequestHeaders(request));
}
// 省略掉默认不执行的代码....
// 5. 如果有异常并且errorAttributes不等于null,则记录error
if (isIncluded(Include.ERRORS) && exception != null&& this.errorAttributes != null) {trace.put("error", this.errorAttributes.getErrorAttributes(new ServletRequestAttributes(request), true));
}
return trace;
}

继续过滤器链的过滤,最后获得响应状态

添加Http请求耗时统计–>如果TraceProperties中配置了Include#TIME_TAKEN(默认配置了),则添加到trace中,key为timeTaken，value–>当前时间-开始时间的毫秒值.代码如下:

private void addTimeTaken(Map<String, Object> trace, long startTime) {
long timeTaken = System.nanoTime() - startTime;
add(trace, Include.TIME_TAKEN, "timeTaken","" + TimeUnit.NANOSECONDS.toMillis(timeTaken));
}

添加响应头信息.代码如下:

protected void enhanceTrace(Map<String, Object> trace, HttpServletResponse response) {
if (isIncluded(Include.RESPONSE_HEADERS)) {Map<String, Object> headers = (Map<String, Object>) trace.get("headers");headers.put("response", getResponseHeaders(response));
}
}

getResponseHeaders 代码如下:

private Map<String, String> getResponseHeaders(HttpServletResponse response) {
Map<String, String> headers = new LinkedHashMap<String, String>();
// 1. 依次遍历响应头,添加至headers 中,key--> 响应头名,value-->响应头对应的值
for (String header : response.getHeaderNames()) {String value = response.getHeader(header);headers.put(header, value);
}
// 2. 如果TraceProperties中没有配置Include#COOKIES,则在headers中删除key为Set-Cookie的值.默认是配置了的,因此不会删除
if (!isIncluded(Include.COOKIES)) {headers.remove("Set-Cookie");
}
// 3. 向headers 中添加 key--> status,value-->响应状态码
headers.put("status", "" + response.getStatus());
return headers;
}

遍历响应头,添加至headers 中,key–> 响应头名,value–>响应头对应的值
如果TraceProperties中没有配置Include#COOKIES,则在headers中删除key为Set-Cookie的值.默认是配置了的,因此不会删除
向headers 中添加 key–> status,value–>响应状态码

添加至TraceRepository中

WebRequestTraceFilter 是如何配置的呢?

答案: 在TraceWebFilterAutoConfiguration中.代码如下:

@Bean
@ConditionalOnMissingBean
public WebRequestTraceFilter webRequestLoggingFilter(BeanFactory beanFactory) {WebRequestTraceFilter filter = new WebRequestTraceFilter(this.traceRepository,this.traceProperties);if (this.errorAttributes != null) {filter.setErrorAttributes(this.errorAttributes);}return filter;
}

@Bean–> 注册1个id为webRequestLoggingFilter,类型为WebRequestTraceFilter的bean
@ConditionalOnMissingBean–> 当beanFactory中不存在WebRequestTraceFilter类型的bean时生效

同时由于TraceWebFilterAutoConfiguration声明了如下注解:

@Configuration
@ConditionalOnClass({ Servlet.class, DispatcherServlet.class, ServletRegistration.class })
@AutoConfigureAfter(TraceRepositoryAutoConfiguration.class)
@ConditionalOnProperty(prefix = "endpoints.trace.filter", name = "enabled", matchIfMissing = true)
@EnableConfigurationProperties(TraceProperties.class)

@Configuration–> 配置类
@ConditionalOnClass({ Servlet.class, DispatcherServlet.class, ServletRegistration.class })–> 在当前的类路径下存在Servlet.class, DispatcherServlet.class, ServletRegistration.class时生效
@AutoConfigureAfter(TraceRepositoryAutoConfiguration.class)–> 在TraceRepositoryAutoConfiguration之后进行自动装配,这样就可以自动注入TraceRepository
@ConditionalOnProperty(prefix = “endpoints.trace.filter”, name = “enabled”, matchIfMissing = true)–> 当配置有endpoints.trace.filter.enabled 等于true时生效,如果没有配置,默认生效
@EnableConfigurationProperties(TraceProperties.class)–> 可以通过management.trace.include 进行配置.