spring容器初始化执行某个方法

在做web项目开发中，尤其是企业级应用开发的时候，往往会在工程启动的时候做许多的前置检查。

比如检查是否使用了我们组禁止使用的Mysql的group_concat函数，如果使用了项目就不能启动，并指出哪个文件的xml文件使用了这个函数。

而在Spring的web项目中，我们可以介入Spring的启动过程。我们希望在Spring容器将所有的Bean都初始化完成之后，做一些操作，这个时候我们就可以实现一个接口：

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package com.yk.test.executor.processor public class InstantiationTracingBeanPostProcessor implements ApplicationListener<ContextRefreshedEvent> { @Override public void onApplicationEvent(ContextRefreshedEvent event) { //需要执行的逻辑代码，当spring容器初始化完成后就会执行该方法。 } }

　　

　　同时在Spring的配置文件中，添加注入：

1 2	<!-- 当Spring容器启动完成后执行下面的这个Bean --> <bean class="com.yk.test.executor.processor.InstantiationTracingBeanPostProcessor"/>

　　

　　

但是这个时候，会存在一个问题，在web 项目中（spring mvc），系统会存在两个容器，一个是root application context ,另一个就是我们自己的 projectName-servlet context（作为root application context的子容器）。

这种情况下，就会造成onApplicationEvent方法被执行两次。为了避免上面提到的问题，我们可以只在root application context初始化完成后调用逻辑代码，其他的容器的初始化完成，则不做任何处理，修改后代码

如下：

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@Override public void onApplicationEvent(ContextRefreshedEvent event) { if(event.getApplicationContext().getParent() == null){//root application context 没有parent，他就是老大. //需要执行的逻辑代码，当spring容器初始化完成后就会执行该方法。 } }

　　

其实更简单的方法是使用注解：`@PostConstruct`，只需要在需要启动的时候执行的方法上标注这个注解就搞定了。

注解描述如下：

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/*  * Copyright (c) 2005, 2013, Oracle and/or its affiliates. All rights reserved.  * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.  *  *  *  *  *  *  *  *  *  *  *  *  *  *  *  *  *  *  *  *  */   package javax.annotation;   import java.lang.annotation.*; import static java.lang.annotation.ElementType.*; import static java.lang.annotation.RetentionPolicy.*;   /**  * The PostConstruct annotation is used on a method that needs to be executed  * after dependency injection is done to perform any initialization. This  * method MUST be invoked before the class is put into service. This  * annotation MUST be supported on all classes that support dependency  * injection. The method annotated with PostConstruct MUST be invoked even  * if the class does not request any resources to be injected. Only one  * method can be annotated with this annotation. The method on which the  * PostConstruct annotation is applied MUST fulfill all of the following  * criteria:  * <p>  * <ul>  * <li>The method MUST NOT have any parameters except in the case of  * interceptors in which case it takes an InvocationContext object as  * defined by the Interceptors specification.</li>  * <li>The method defined on an interceptor class MUST HAVE one of the  * following signatures:  * <p>  * void <METHOD>(InvocationContext)  * <p>  * Object <METHOD>(InvocationContext) throws Exception  * <p>  * <i>Note: A PostConstruct interceptor method must not throw application  * exceptions, but it may be declared to throw checked exceptions including  * the java.lang.Exception if the same interceptor method interposes on  * business or timeout methods in addition to lifecycle events. If a  * PostConstruct interceptor method returns a value, it is ignored by  * the container.</i>  * </li>  * <li>The method defined on a non-interceptor class MUST HAVE the  * following signature:  * <p>  * void <METHOD>()  * </li>  * <li>The method on which PostConstruct is applied MAY be public, protected,  * package private or private.</li>  * <li>The method MUST NOT be static except for the application client.</li>  * <li>The method MAY be final.</li>  * <li>If the method throws an unchecked exception the class MUST NOT be put into  * service except in the case of EJBs where the EJB can handle exceptions and  * even recover from them.</li></ul>  * @since Common Annotations 1.0  * @see javax.annotation.PreDestroy  * @see javax.annotation.Resource  */ @Documented @Retention (RUNTIME) @Target(METHOD) public @interface PostConstruct { }