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首页 / 《这是知识点》之ApplicationContextInitializer源码和简单使用

《这是知识点》之ApplicationContextInitializer源码和简单使用

开发者的花花世界 2020-09-19
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一、 ApplicationContextInitializer 介绍

首先看下spring官方说明

源码

package org.springframework.context;


/**
 * Callback interface for initializing a Spring {@link ConfigurableApplicationContext}
 * prior to being {@linkplain ConfigurableApplicationContext#refresh() refreshed}.
 *
 * <p>Typically used within web applications that require some programmatic initialization
 * of the application context. For example, registering property sources or activating
 * profiles against the {@linkplain ConfigurableApplicationContext#getEnvironment()
 * context's environment}. See {@code ContextLoader} and {@code FrameworkServlet} support
 * for declaring a "contextInitializerClasses" context-param and init-param, respectively.
 *
 * <p>{@code ApplicationContextInitializer} processors are encouraged to detect
 * whether Spring's {@link org.springframework.core.Ordered Ordered} interface has been
 * implemented or if the @{@link org.springframework.core.annotation.Order Order}
 * annotation is present and to sort instances accordingly if so prior to invocation.
 *
 * @author Chris Beams
 * @since 3.1
 * @param <C> the application context type
 * @see org.springframework.web.context.ContextLoader#customizeContext
 * @see org.springframework.web.context.ContextLoader#CONTEXT_INITIALIZER_CLASSES_PARAM
 * @see org.springframework.web.servlet.FrameworkServlet#setContextInitializerClasses
 * @see org.springframework.web.servlet.FrameworkServlet#applyInitializers
 */
public interface ApplicationContextInitializer<C extends ConfigurableApplicationContext> {


    /**
     * Initialize the given application context.
     * @param applicationContext the application to configure
     */
    void initialize(C applicationContext);


}


简单说明一下：

•用于spring上下文初始化的回调函数在上下文（ConfigurableApplicationContext）刷新（refresh）之前调用。•通常被用作web应用，在一些程序设计在spring容器初始化使用。比如说注册一些熟悉配置或者激活一些配置文件针对（ConfigurableApplicationContext的getEnvironment()方法）。参考ContextLoader和FrameworkServlet支持定义一个"contextInitializerClasses"上下文参数或者初始化参数。•可排序的（实现Ordered接口，或者添加@Order注解）

二、 ApplicationContextInitializer实现方式

首先新建一个类 MyApplicationContextInitializer 并实现 ApplicationContextInitializer 接口

•SpringBoot的main方法添加

@SpringBootApplication
public class Application {
    public static void main(String[] args) {
        SpringApplication application = new SpringApplication(Application.class);
        application.addInitializers(new MyApplicationContextInitializer());
        application.run(args);
    }
}

•在application.properties中配置

context.initializer.classes=org.springframework.boot.demo.common.MyApplicationContextInitializer

•SpringBoot的SPI扩展---META-INF/spring.factories中配置

org.springframework.context.ApplicationContextInitializer=org.springframework.boot.demo.common.MyApplicationContextInitializer

关注Github：1/2极客[1]

关注博客：御前提笔小书童[2]

关注网站：HuMingfeng[3]

关注公众号：开发者的花花世界

References

[1]
 1/2极客: https://github.com/humingfeng
[2]
 御前提笔小书童: https://blog.csdn.net/qq_22260641
[3]
 HuMingfeng: https://royalscholar.cn

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