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springboot应用，启动spring容器大致有如下几个过程：
对应的Spring应用的启动器的监听器可以监听以上的过程，接口如下：
1 public interface SpringApplicationRunListener { 2 3 /** 4 * Called immediately when the run method has first started. Can be used for very 5 * early initialization. 6 */ 7 void started(); 8 9 /** 10 * Called once the environment has been prepared, but before the 11 * {@link ApplicationContext} has been created. 12 * @param environment the environment 13 */ 14 void environmentPrepared(ConfigurableEnvironment environment); 15 16 /** 17 * Called once the {@link ApplicationContext} has been created and prepared, but 18 * before sources have been loaded. 19 * @param context the application context 20 */ 21 void contextPrepared(ConfigurableApplicationContext context); 22 23 /** 24 * Called once the application context has been loaded but before it has been 25 * refreshed. 26 * @param context the application context 27 */ 28 void contextLoaded(ConfigurableApplicationContext context); 29 30 /** 31 * Called immediately before the run method finishes. 32 * @param context the application context or null if a failure occurred before the 33 * context was created 34 * @param exception any run exception or null if run completed successfully. 35 */ 36 void finished(ConfigurableApplicationContext context, Throwable exception); 37 38 }
对应几个关键事件
监听器接口中的每个方法代表容器启动过程一个阶段，每一个阶段可以自定义执行一系列任务。可以将SpringApplicationRunListener理解成一个命令模式（传入一个对象，至于当前这个时间点，如何调用，不关心）。SpringApplicationRunListener有一个特殊的实现EventPublishingRunListener，他的主要功能就是，在特定时间点出发特殊事件。
@Override public void started() { this.initialMulticaster.multicastEvent(new ApplicationStartedEvent( this.application, this.args)); } @Override public void environmentPrepared(ConfigurableEnvironment environment) { this.initialMulticaster.multicastEvent(new ApplicationEnvironmentPreparedEvent( this.application, this.args, environment)); }
SpringApplicationRunListeners是对多个SpringApplicationRunListener做了一次代理，聚合多个SpringApplicationRunListener,在任一个过程完成，会依次调用对应方法。
private final List<SpringApplicationRunListener> listeners; SpringApplicationRunListeners(Log log, Collection<? extends SpringApplicationRunListener> listeners) { this.log = log; this.listeners = new ArrayList<SpringApplicationRunListener>(listeners); } public void started() { for (SpringApplicationRunListener listener : this.listeners) { listener.started(); } } public void environmentPrepared(ConfigurableEnvironment environment) { for (SpringApplicationRunListener listener : this.listeners) { listener.environmentPrepared(environment); } }
事件发布采用观察者模式
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原文地址：http://www.cnblogs.com/dragonfei/p/5911259.html
