前往小程序,Get更优阅读体验!
立即前往
首页
学习
活动
专区
工具
TVP
发布
社区首页 >专栏 >SpringApplication_一个阶段结束

SpringApplication_一个阶段结束

作者头像
全栈程序员站长
发布2022-09-30 09:14:47
1680
发布2022-09-30 09:14:47
举报
文章被收录于专栏:全栈程序员必看

大家好,又见面了,我是你们的朋友全栈君。

1、SpringApplication正常结束

Spring Boot2.0为SpringApplication正常结束新引入了SpringApplicationRunListener的生命周期,即running(ConfigurableApplicationContext),该方法在Spring应用上下文中已准备,并且CommandLineRunner和ApplicationRunner Bean均已执行完毕。EventPublishingRunListener作为Spring ApplicationRunner 唯一内建实现,本方法中仅简单地广播ApplicationReadyEvent事件:

代码语言:javascript
复制
	@Override
	public void running(ConfigurableApplicationContext context) { 
   
		context.publishEvent(new ApplicationReadyEvent(this.application, this.args, context));
	}

不难看出当ApplicationReadyEvent事件触发后,SpringApplication的生命周期进入尾声,除非SpringApplicationRunListeners#running方法执行异常:

代码语言:javascript
复制
	public ConfigurableApplicationContext run(String... args) { 
   
		...
		try { 
   
			listeners.running(context);
		}
		catch (Throwable ex) { 
   
			handleRunFailure(context, ex, exceptionReporters, null);
			throw new IllegalStateException(ex);
		}
		return context;
	}

换言之,开发人员有两种技术手段实现完成阶段的监听,一种为实现SpringApplicationRunListeners#running方法,另一种为实现ApplicationReadyEvent事件的SpringApplicationListener。

2、SpringApplication异常结束

SpringApplication异常结束就宣告Spring Boot应用运行失败。与正常流程类似,异常流程同样作为SpringApplication生命周期的一个环节,将在SpringApplicationRunListener#failed(ConfigurableApplicationContext, Throwable)方法。

2.1、Spring Boot异常处理

代码语言:javascript
复制
	private void handleRunFailure(ConfigurableApplicationContext context, Throwable exception,
Collection<SpringBootExceptionReporter> exceptionReporters, SpringApplicationRunListeners listeners) { 

try { 

try { 

handleExitCode(context, exception);
if (listeners != null) { 

listeners.failed(context, exception);
}
}
finally { 

reportFailure(exceptionReporters, exception);
if (context != null) { 

context.close();
}
}
}
catch (Exception ex) { 

logger.warn("Unable to close ApplicationContext", ex);
}
ReflectionUtils.rethrowRuntimeException(exception);
}

Spring Boot异常处理主要包含两部分:一是退出码处理,二是异常报告。退出码处理放在《Spring Boot应用退出》中讲解,这里这要分析异常报告。 在Spring Boot2.0中新增了一个SpringBootExceptionReporter接口,用于支持SpringApplication启动错误的自定义报告的回调接口。

代码语言:javascript
复制
public interface SpringBootExceptionReporter { 

boolean reportException(Throwable failure);
}

由于SpringBootExceptionReporter 集合在初始化过程中,明确地执行了getSpringFactoriesInstances(SpringBootExceptionReporter.class,new Class[] { ConfigurableApplicationContext.class }, context);语句,所以当自定义SpringBootExceptionReporter 时,必须用一个ConfigurableApplicationContext参数声明一个公共构造函数,比如Spring Boot2.x内建唯一实现FailureAnalyzers:

代码语言:javascript
复制
final class FailureAnalyzers implements SpringBootExceptionReporter { 

private static final Log logger = LogFactory.getLog(FailureAnalyzers.class);
private final ClassLoader classLoader;
private final List<FailureAnalyzer> analyzers;
FailureAnalyzers(ConfigurableApplicationContext context) { 

this(context, null);
}
FailureAnalyzers(ConfigurableApplicationContext context, ClassLoader classLoader) { 

Assert.notNull(context, "Context must not be null");
this.classLoader = (classLoader != null) ? classLoader : context.getClassLoader();
this.analyzers = loadFailureAnalyzers(this.classLoader);
prepareFailureAnalyzers(this.analyzers, context);
}
...
}

可简单地认为FailureAnalyzers 是FailureAnalyzer的组合类,在其构造阶段通过Spring工厂加载机制初始化并排序FailureAnalyzer列表:

代码语言:javascript
复制
	private List<FailureAnalyzer> loadFailureAnalyzers(ClassLoader classLoader) { 

List<String> analyzerNames = SpringFactoriesLoader.loadFactoryNames(FailureAnalyzer.class, classLoader);
List<FailureAnalyzer> analyzers = new ArrayList<>();
for (String analyzerName : analyzerNames) { 

try { 

Constructor<?> constructor = ClassUtils.forName(analyzerName, classLoader).getDeclaredConstructor();
ReflectionUtils.makeAccessible(constructor);
analyzers.add((FailureAnalyzer) constructor.newInstance());
}
catch (Throwable ex) { 

logger.trace(LogMessage.format("Failed to load %s", analyzerName), ex);
}
}
AnnotationAwareOrderComparator.sort(analyzers);
return analyzers;
}
private void prepareFailureAnalyzers(List<FailureAnalyzer> analyzers, ConfigurableApplicationContext context) { 

for (FailureAnalyzer analyzer : analyzers) { 

prepareAnalyzer(context, analyzer);
}
}
private void prepareAnalyzer(ConfigurableApplicationContext context, FailureAnalyzer analyzer) { 

if (analyzer instanceof BeanFactoryAware) { 

((BeanFactoryAware) analyzer).setBeanFactory(context.getBeanFactory());
}
if (analyzer instanceof EnvironmentAware) { 

((EnvironmentAware) analyzer).setEnvironment(context.getEnvironment());
}
}

加载后的FailureAnalyzer列表作为FailureAnalyzers#(Throwable, List<FailureAnalyzer>)方法的参数,随着SpringApplication#(Collection<SpringBootExceptionReporter>, Throwable)方法调用执行:

代码语言:javascript
复制
	@Override
public boolean reportException(Throwable failure) { 

FailureAnalysis analysis = analyze(failure, this.analyzers);
return report(analysis, this.classLoader);
}
private FailureAnalysis analyze(Throwable failure, List<FailureAnalyzer> analyzers) { 

for (FailureAnalyzer analyzer : analyzers) { 

try { 

FailureAnalysis analysis = analyzer.analyze(failure);
if (analysis != null) { 

return analysis;
}
}
catch (Throwable ex) { 

logger.debug(LogMessage.format("FailureAnalyzer %s failed", analyzer), ex);
}
}
return null;
}
private boolean report(FailureAnalysis analysis, ClassLoader classLoader) { 

List<FailureAnalysisReporter> reporters = SpringFactoriesLoader.loadFactories(FailureAnalysisReporter.class,
classLoader);
if (analysis == null || reporters.isEmpty()) { 

return false;
}
for (FailureAnalysisReporter reporter : reporters) { 

reporter.report(analysis);
}
return true;
}

不难看出FailureAnalyzer仅分析故障,而故障报告则由FailureAnalysisReporter 对象负责。

2.2、错误分析报告器——FailureAnalysisReporter

同样地FailureAnalysisReporter也由Spring工厂加载机制初始化并排序。在Spring Boot框架中仅存在一个内建FailureAnalysisReporter的实现LoggingFailureAnalysisReporter。

代码语言:javascript
复制
public final class LoggingFailureAnalysisReporter implements FailureAnalysisReporter { 

private static final Log logger = LogFactory.getLog(LoggingFailureAnalysisReporter.class);
@Override
public void report(FailureAnalysis failureAnalysis) { 

if (logger.isDebugEnabled()) { 

logger.debug("Application failed to start due to an exception", failureAnalysis.getCause());
}
if (logger.isErrorEnabled()) { 

logger.error(buildMessage(failureAnalysis));
}
}
private String buildMessage(FailureAnalysis failureAnalysis) { 

StringBuilder builder = new StringBuilder();
builder.append(String.format("%n%n"));
builder.append(String.format("***************************%n"));
builder.append(String.format("APPLICATION FAILED TO START%n"));
builder.append(String.format("***************************%n%n"));
builder.append(String.format("Description:%n%n"));
builder.append(String.format("%s%n", failureAnalysis.getDescription()));
if (StringUtils.hasText(failureAnalysis.getAction())) { 

builder.append(String.format("%nAction:%n%n"));
builder.append(String.format("%s%n", failureAnalysis.getAction()));
}
return builder.toString();
}
}

与FailureAnalysisReporter不同的是,FailureAnalyzer的内建实现相当丰富,下面是org.springframework.boot:spring-boot-autoconfigure:2.3.0中的META-INF/spring.factories:

代码语言:javascript
复制
# Failure analyzers
org.springframework.boot.diagnostics.FailureAnalyzer=\
org.springframework.boot.autoconfigure.diagnostics.analyzer.NoSuchBeanDefinitionFailureAnalyzer,\
org.springframework.boot.autoconfigure.flyway.FlywayMigrationScriptMissingFailureAnalyzer,\
org.springframework.boot.autoconfigure.jdbc.DataSourceBeanCreationFailureAnalyzer,\
org.springframework.boot.autoconfigure.jdbc.HikariDriverConfigurationFailureAnalyzer,\
org.springframework.boot.autoconfigure.session.NonUniqueSessionRepositoryFailureAnalyzer

其中NoSuchBeanDefinitionFailureAnalyzer和DataSourceBeanCreationFailureAnalyzer在Spring Boot中经常出现。

版权声明:本文内容由互联网用户自发贡献,该文观点仅代表作者本人。本站仅提供信息存储空间服务,不拥有所有权,不承担相关法律责任。如发现本站有涉嫌侵权/违法违规的内容, 请发送邮件至 举报,一经查实,本站将立刻删除。

本文参与 腾讯云自媒体同步曝光计划,分享自作者个人站点/博客。
原始发表:2022年9月8日 下,如有侵权请联系 cloudcommunity@tencent.com 删除

本文分享自 作者个人站点/博客 前往查看

如有侵权,请联系 cloudcommunity@tencent.com 删除。

本文参与 腾讯云自媒体同步曝光计划  ,欢迎热爱写作的你一起参与!

评论
登录后参与评论
0 条评论
热度
最新
推荐阅读
目录
  • 1、SpringApplication正常结束
  • 2、SpringApplication异常结束
    • 2.1、Spring Boot异常处理
      • 2.2、错误分析报告器——FailureAnalysisReporter
      领券
      问题归档专栏文章快讯文章归档关键词归档开发者手册归档开发者手册 Section 归档