启动tomcat 运行某一程序

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：

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：

<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：

@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：

/*

* 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:

* 

* <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:

* 

* void <METHOD>(InvocationContext)

* 

* Object <METHOD>(InvocationContext) throws Exception

* 

* 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.

* </li>

* <li>The method defined on a non-interceptor class MUST HAVE the

* following signature:

* 

* 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 {

}

转载：https://www.cnblogs.com/rollenholt/p/3612440.html

启动tomcat 运行某一程序

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