2023-09-14
原文作者:王伟王胖胖 原文地址: https://blog.csdn.net/wangwei19871103/article/details/105458217

refresh和自动配置大致流程

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DeferredImportSelectorHandler的process处理

前面说道这里:

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其实第一次进去的时候是放进集合里的:

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因为这个deferredImportSelectors成员变量初始化的时候就创建了:

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放进去之后就执行其他,最后都解析完到这里,就是前面说的DeferredImportSelector类型的会等其他解析完,最后处理:

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这里就是处理逻辑,其实就是创建DeferredImportSelectorGroupingHandler,然后把前面放进去的DeferredImportSelectorHolder都拿出来,都注册到里面去,就是前面讲的分组注册,最后处理,处理完之后还要创建deferredImportSelectors,这里就是避免迭代器在迭代的时候还要新的元素添加进来,会出问题。

    	public void process() {
    			List<DeferredImportSelectorHolder> deferredImports = this.deferredImportSelectors;
    			this.deferredImportSelectors = null;//设置为空,如果有新的就会直接注册处理
    			try {
    				if (deferredImports != null) {//如果有存在DeferredImportSelector
    					DeferredImportSelectorGroupingHandler handler = new DeferredImportSelectorGroupingHandler();
    					deferredImports.sort(DEFERRED_IMPORT_COMPARATOR);
    					deferredImports.forEach(handler::register);//迭代注册到DeferredImportSelectorGroupingHandler
    					handler.processGroupImports();//处理
    				}
    			}
    			finally {
    				this.deferredImportSelectors = new ArrayList<>();//处理完了再创建
    			}
    		}

processGroupImports处理

为什么要这么分组,这里就体现出来了,看他怎么处理的,遍历所有的ImportSelector组,获取所有import的实体Entry,其实这个时候已经把要自动配置的类找到了,然后迭代去进行递归processImports处理。

    public void processGroupImports() {
    			for (DeferredImportSelectorGrouping grouping : this.groupings.values()) {
    				Predicate<String> exclusionFilter = grouping.getCandidateFilter();
    				grouping.getImports().forEach(entry -> {//每一个自动配置类都要进行processImports处理
    					ConfigurationClass configurationClass = this.configurationClasses.get(entry.getMetadata());
    					try {
    						processImports(configurationClass, asSourceClass(configurationClass, exclusionFilter),
    								Collections.singleton(asSourceClass(entry.getImportClassName(), exclusionFilter)),
    								exclusionFilter, false);
    					}
    					catch (BeanDefinitionStoreException ex) {
    						throw ex;
    					}
    					catch (Throwable ex) {
    						throw new BeanDefinitionStoreException(
    								"Failed to process import candidates for configuration class [" +
    										configurationClass.getMetadata().getClassName() + "]", ex);
    					}
    				});
    			}
    		}

DeferredImportSelectorGrouping的处理getImports

这里要开始处理了,其实是要组group对象来处理对应的DeferredImportSelector集合,最后在返回Iterable<Group.Entry>实体迭代器,就是已经把自动配置的类名集合封装成迭代器了。

    		public Iterable<Group.Entry> getImports() {
    			for (DeferredImportSelectorHolder deferredImport : this.deferredImports) {
    				this.group.process(deferredImport.getConfigurationClass().getMetadata(),
    						deferredImport.getImportSelector());
    			}
    			return this.group.selectImports();
    		}

AutoConfigurationGroup的处理getImports

其实这里关键的是AutoConfigurationImportSelectorgetAutoConfigurationEntry获取AutoConfigurationEntry,这里面封装着自动配置类名字集合,后面只是放到对应的映射里,方便用。

    	@Override
    		public void process(AnnotationMetadata annotationMetadata, DeferredImportSelector deferredImportSelector) {
    			...
    			AutoConfigurationEntry autoConfigurationEntry = ((AutoConfigurationImportSelector) deferredImportSelector)
    					.getAutoConfigurationEntry(getAutoConfigurationMetadata(), annotationMetadata);//获取自动装配实体
    			this.autoConfigurationEntries.add(autoConfigurationEntry);
    			for (String importClassName : autoConfigurationEntry.getConfigurations()) {
    				this.entries.putIfAbsent(importClassName, annotationMetadata);
    			}//建立配置类名和注解属性的映射
    		}

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接下去我们主要要看AutoConfigurationImportSelector这个类啦。

好了,今天就到这里了,希望对学习理解有帮助,大神看见勿喷,仅为自己的学习理解,能力有限,请多包涵。

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