死磕源码系列【ConfigurationWarningsApplicationContextInitializer源码解析】

﹏ヽ暗。殇╰゛Y 2022-11-21 03:34 245阅读 0赞

> ConfigurationWarningsApplicationContextInitializer是ApplicationContextInitializer初始化器接口的实现类，用作报告常见错误配置的警告（通过分析源码实际情况是如果系统配置包扫描（@ComponentScan）到了org或者org.springframework包就会发出警告并停止系统启动）

##### ConfigurationWarningsApplicationContextInitializer初始化器源码： #####

public class ConfigurationWarningsApplicationContextInitializer
    		implements ApplicationContextInitializer<ConfigurableApplicationContext> { 
    
    	private static final Log logger = LogFactory.getLog(ConfigurationWarningsApplicationContextInitializer.class);
    	//初始化方法会在容器启动时调用，并将ConfigurationWarningsPostProcessor后置处理器注入到应用上下文中
    	@Override
    	public void initialize(ConfigurableApplicationContext context) { 
    		context.addBeanFactoryPostProcessor(new ConfigurationWarningsPostProcessor(getChecks()));
    	}
    
    	/** * 返回有问题的扫描包（@ComponentScan）Check对象 * @return the checks to apply */
    	protected Check[] getChecks() { 
    		return new Check[] {  new ComponentScanPackageCheck() };
    	}
    	}

##### ComponentScanPackageCheck是ConfigurationWarningsApplicationContextInitializer的一个内部类，源码分析 #####

/** * 可以应用的单一检查 */
    	@FunctionalInterface
    	protected interface Check { 
    
    		/** * 返回检查结果，如果检查失败，则返回警告，如果没有问题，则返回null * @param registry the {@link BeanDefinitionRegistry} * @return a warning message or {@code null} */
    		String getWarning(BeanDefinitionRegistry registry);
    
    	}
    
    	/** * 检查@ComponentScan注解扫描有问题的包 */
    	protected static class ComponentScanPackageCheck implements Check { 
    
    		private static final Set<String> PROBLEM_PACKAGES;
    		//定义扫描有问题的包
    		static { 
    			Set<String> packages = new HashSet<>();
    			packages.add("org.springframework");
    			packages.add("org");
    			PROBLEM_PACKAGES = Collections.unmodifiableSet(packages);
    		}
    		//检查@ComponentScan注解扫描的包是否有问题，如果有，则返回警告，否则返回null
    		@Override
    		public String getWarning(BeanDefinitionRegistry registry) { 
          //获取@ComponentScan注解扫描的包集合
    			Set<String> scannedPackages = getComponentScanningPackages(registry);
          //获取有问题的扫描包集合
    			List<String> problematicPackages = getProblematicPackages(scannedPackages);
    			if (problematicPackages.isEmpty()) { 
    				return null;
    			}
    			return "Your ApplicationContext is unlikely to start due to a @ComponentScan of "
    					+ StringUtils.collectionToDelimitedString(problematicPackages, ", ") + ".";
    		}
    		//获取@ComponentScan注解扫描的包
    		protected Set<String> getComponentScanningPackages(BeanDefinitionRegistry registry) { 
    			Set<String> packages = new LinkedHashSet<>();
          //获取容器中所有bean定义名称
    			String[] names = registry.getBeanDefinitionNames();
    			for (String name : names) { 
            //获取name对应的bean定义对象
    				BeanDefinition definition = registry.getBeanDefinition(name);
    				if (definition instanceof AnnotatedBeanDefinition) { 
    					AnnotatedBeanDefinition annotatedDefinition = (AnnotatedBeanDefinition) definition;
    					addComponentScanningPackages(packages, annotatedDefinition.getMetadata());
    				}
    			}
    			return packages;
    		}
    		//将bean实例上注解@ComponentScan扫描包
    		private void addComponentScanningPackages(Set<String> packages, AnnotationMetadata metadata) { 
    			AnnotationAttributes attributes = AnnotationAttributes
    					.fromMap(metadata.getAnnotationAttributes(ComponentScan.class.getName(), true));
    			if (attributes != null) { 
    				addPackages(packages, attributes.getStringArray("value"));
    				addPackages(packages, attributes.getStringArray("basePackages"));
    				addClasses(packages, attributes.getStringArray("basePackageClasses"));
    				if (packages.isEmpty()) { 
    					packages.add(ClassUtils.getPackageName(metadata.getClassName()));
    				}
    			}
    		}
    
    		private void addPackages(Set<String> packages, String[] values) { 
    			if (values != null) { 
    				Collections.addAll(packages, values);
    			}
    		}
    
    		private void addClasses(Set<String> packages, String[] values) { 
    			if (values != null) { 
    				for (String value : values) { 
    					packages.add(ClassUtils.getPackageName(value));
    				}
    			}
    		}
    		//获取有问题的扫描包集合，即包名是：org或org.springframework
    		private List<String> getProblematicPackages(Set<String> scannedPackages) { 
    			List<String> problematicPackages = new ArrayList<>();
    			for (String scannedPackage : scannedPackages) { 
            //判定包名是否有问题，即包名是：org或org.springframework
    				if (isProblematicPackage(scannedPackage)) { 
    					problematicPackages.add(getDisplayName(scannedPackage));
    				}
    			}
    			return problematicPackages;
    		}
    		//判定包名是否有问题，即包名是：org或org.springframework
    		private boolean isProblematicPackage(String scannedPackage) { 
    			if (scannedPackage == null || scannedPackage.isEmpty()) { 
    				return true;
    			}
    			return PROBLEM_PACKAGES.contains(scannedPackage);
    		}
    
    		private String getDisplayName(String scannedPackage) { 
    			if (scannedPackage == null || scannedPackage.isEmpty()) { 
    				return "the default package";
    			}
    			return "'" + scannedPackage + "'";
    		}
    
    	}

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GitHub地址：[https://github.com/mingyang66/spring-parent][https_github.com_mingyang66_spring-parent]

[https_github.com_mingyang66_spring-parent]: https://github.com/mingyang66/spring-parent