ApplicationContextInitializer接口是在spring容器刷新之前执行的一个回调函数。
发现这个接口是定义在org.springframework.context包下的。看看其javadoc：
Callback interface for initializing a Spring ConfigurableApplicationContext
prior to being ConfigurableApplicationContext#refresh() refreshed.
spring上下文初始化的回调函数在上下文（ConfigurableApplicationContext）刷新（refresh）之前调用。
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 ContextLoader and FrameworkServlet support for declaring a "contextInitializerClasses" context-param and init-param, respectively.
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。
ApplicationContextInitializer processors are encouraged to detect whether Spring's org.springframework.core.Ordered Ordered} interface has been implemented or if the org.springframework.core.annotation.Order Order annotation is present and to sort instances accordingly if so prior to invocation.
支持Order注解。并且代表着执行顺序。
demo
定义MyApplicationContextInitializer继承ApplicationContextInitializer接口
package com.zhihao.miao;
import org.springframework.context.ApplicationContextInitializer;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.core.annotation.Order;
@Order(2)
public class MyApplicationContextInitializer implements ApplicationContextInitializer{
@Override
public void initialize(ConfigurableApplicationContext applicationContext) {
System.out.println("bean count====="+applicationContext.getBeanDefinitionCount());
}
}
定义另外一个MyApplicationContextInitializer2继承ApplicationContextInitializer接口：
package com.zhihao.miao;
import org.springframework.context.ApplicationContextInitializer;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.core.annotation.Order;
@Order(1)
public class MyApplicationContextInitializer2 implements ApplicationContextInitializer {
@Override
public void initialize(ConfigurableApplicationContext applicationContext) {
System.out.println("app name : " + applicationContext.getDisplayName());
}
}
主类测试：
package com.zhihao.miao;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ConfigurableApplicationContext;
@SpringBootApplication
public class Application {
public static void main(String[] args) {
SpringApplication application = new SpringApplication(Application.class);
application.addInitializers(new MyApplicationContextInitializer());
application.addInitializers(new MyApplicationContextInitializer2());
ConfigurableApplicationContext context =application.run(args);
context.close();
}
}
执行顺序和@Order注解的顺序相反，Order的value值越小表示越早执行。
上面是关于自定义ApplicationContextInitializer的一种注册方法，还有二种注册方法,
第二种方式
在application.properties中定义：
context.initializer.classes=com.zhihao.miao.MyApplicationContextInitializer,com.zhihao.miao.MyApplicationContextInitializer2
主类测试：
package com.zhihao.miao;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
public class Application {
public static void main(String[] args) {
SpringApplication.run(Application.class,args);
}
}
第三种方式
新建core-baen（名字自己定义）项目，新建一个MyApplicationContextInitializer实现ApplicationContextInitializer接口
package core.bean;
import org.springframework.context.ApplicationContextInitializer;
import org.springframework.context.ConfigurableApplicationContext;
public class MyApplicationContextInitializer implements ApplicationContextInitializer<ConfigurableApplicationContext>{
@Override
public void initialize(ConfigurableApplicationContext applicationContext) {
System.out.println("========initialize=======");
}
}
然后在core-bean项目下的resources下新建META-INF文件夹，文件夹下新建spring.factories文件
org.springframework.context.ApplicationContextInitializer=core.bean.MyApplicationContextInitializer
在项目中引入
<dependency>
<groupId>com.zhihao.miao</groupId>
<artifactId>core-bean</artifactId>
<version>1.0-SNAPSHOT</version>
</dependency>
启动类：
package com.zhihao.miao;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
public class Application {
public static void main(String[] args) {
SpringApplication.run(Application.class,args);
}
}
启动启动类并执行：
总结
自定义ApplicationContextInitializer接口的方式：
1)写一个类，实现ApplicationContextInitializer接口
2)注册ApplicationContextInitializer
