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pull merged 2 commits into Mu-L:master from ipipman:master
Sep 21, 2021
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100 changes: 100 additions & 0 deletions springboot-source-code-analysis/(8)自定义监听器实战.md
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### 自定义监听器实战

#### 实现方式一

- 实现ApplicationListener接口,ApplicationListener<ApplicationStartedEvent>声明感兴趣的事件

```java
@Order(1)
public class FirstListener implements ApplicationListener<ApplicationStartedEvent> {

private final static Logger logger = LoggerFactory.getLogger(FirstListener.class);

@Override
public void onApplicationEvent(ApplicationStartedEvent event) {
logger.info("设置框架事件监听器【ApplicationListener】成功 : run firstListener");

}
}

```

- 在spring.factories 配置文件中配置FirstListener事件监听器,key值为org.springframework.context.ApplicationListener

```java
# 通过系统事件监听器,设置自定义事件监听器
org.springframework.context.ApplicationListener=\
com.example.springboot.source.code.analysis.listener.FirstListener
```



#### 实现方式三

- 实现ApplicationListener接口,声明感兴趣的事件ApplicationListener<ApplicationStartedEvent>

```java
@Order(3)
public class ThirdListener implements ApplicationListener<ApplicationStartedEvent> {

private final static Logger logger = LoggerFactory.getLogger(ThirdListener.class);

@Override
public void onApplicationEvent(ApplicationStartedEvent event) {
logger.info("设置框架事件监听器【ApplicationListener】成功 : run thirdListener");
}
}
```

- 在application.properties 内配置事件监听器,key值为context.listener.classes

```java
# 通过系统事件监听器,监听事件
context.listener.classes=\
com.example.springboot.source.code.analysis.listener.ThirdListener,\
```

> application.properties 内配置的 conext.listener.classes 事件监听器执行优先级最高
>
> ```java
> // context.listener.classes 是通过 DelegatingApplicationListener 委派给 ApplicationListener
> public class DelegatingApplicationListener implements ApplicationListener<ApplicationEvent>, Ordered {
> private static final String PROPERTY_NAME = "context.listener.classes";
> // 在委派过程中,DelegatingApplicationListener 会将 order 优先级设置为最高
> private int order = 0;
> private SimpleApplicationEventMulticaster multicaster;
>
> ```



#### 实现方式四

- 实现SmartApplicationListener接口

```java
@Order(4)
public class FourthListener implements SmartApplicationListener {

private final static Logger logger = LoggerFactory.getLogger(FourthListener.class);

// 通过重写 supportEventType()方法 判断该监听器对哪些事件感兴趣
@Override
public boolean supportsEventType(Class<? extends ApplicationEvent> eventType) {
return ApplicationStartedEvent.class.isAssignableFrom(eventType)
|| ApplicationPreparedEvent.class.isAssignableFrom(eventType);
}

// 编写事件触发逻辑
@Override
public void onApplicationEvent(ApplicationEvent event) {
logger.info("设置框架事件监听器【SmartApplicationListener】成功 : run fourthListener");
}
}

```

- 可以通过spring.factories 或 application.properties 或 new SpringApplication().addListeners() 三种方式注入该事件



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@@ -1,6 +1,7 @@
package com.example.springboot.source.code.analysis;

import com.example.springboot.source.code.analysis.initializer.SecondInitializer;
import com.example.springboot.source.code.analysis.listener.SecondListener;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

Expand All @@ -14,6 +15,9 @@ public static void main(String[] args) {
// 手动添加一个框架的初始化器
springApplication.addInitializers(new SecondInitializer());

// 手动添加一个框架事件监听器
springApplication.addListeners(new SecondListener());

springApplication.run();

}
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@@ -0,0 +1,28 @@
package com.example.springboot.source.code.analysis.listener;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.boot.context.event.ApplicationStartedEvent;
import org.springframework.context.ApplicationListener;
import org.springframework.core.annotation.Order;

/**
* Created by ipipman on 2021年9月21日.
*
* @version V1.0
* @Package com.example.springboot.source.code.analysis.listener
* @Description: (用一句话描述该文件做什么)
* @date 2021年9月21日 4:12 下午
*/

@Order(1)
public class FirstListener implements ApplicationListener<ApplicationStartedEvent> {

private final static Logger logger = LoggerFactory.getLogger(FirstListener.class);

@Override
public void onApplicationEvent(ApplicationStartedEvent event) {
logger.info("设置框架事件监听器【ApplicationListener】成功 : run firstListener");

}
}
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@@ -0,0 +1,34 @@
package com.example.springboot.source.code.analysis.listener;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.boot.context.event.ApplicationPreparedEvent;
import org.springframework.boot.context.event.ApplicationStartedEvent;
import org.springframework.context.ApplicationEvent;
import org.springframework.context.event.SmartApplicationListener;
import org.springframework.core.annotation.Order;

/**
* Created by ipipman on 2021年9月21日.
*
* @version V1.0
* @Package com.example.springboot.source.code.analysis.listener
* @Description: (用一句话描述该文件做什么)
* @date 2021年9月21日 4:26 下午
*/
@Order(4)
public class FourthListener implements SmartApplicationListener {

private final static Logger logger = LoggerFactory.getLogger(FourthListener.class);

@Override
public boolean supportsEventType(Class<? extends ApplicationEvent> eventType) {
return ApplicationStartedEvent.class.isAssignableFrom(eventType)
|| ApplicationPreparedEvent.class.isAssignableFrom(eventType);
}

@Override
public void onApplicationEvent(ApplicationEvent event) {
logger.info("设置框架事件监听器【SmartApplicationListener】成功 : run fourthListener");
}
}
Original file line number Diff line number Diff line change
@@ -0,0 +1,26 @@
package com.example.springboot.source.code.analysis.listener;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.boot.context.event.ApplicationStartedEvent;
import org.springframework.context.ApplicationListener;
import org.springframework.core.annotation.Order;

/**
* Created by ipipman on 2021年9月21日.
*
* @version V1.0
* @Package com.example.springboot.source.code.analysis.listener
* @Description: (用一句话描述该文件做什么)
* @date 2021年9月21日 4:19 下午
*/
@Order(2)
public class SecondListener implements ApplicationListener<ApplicationStartedEvent> {

private static final Logger logger = LoggerFactory.getLogger(SecondListener.class);

@Override
public void onApplicationEvent(ApplicationStartedEvent event) {
logger.info("设置框架事件监听器【ApplicationListener】成功 : run secondListener");
}
}
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@@ -0,0 +1,27 @@
package com.example.springboot.source.code.analysis.listener;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.boot.context.event.ApplicationStartedEvent;
import org.springframework.context.ApplicationListener;
import org.springframework.core.annotation.Order;


/**
* Created by ipipman on 2021年9月21日.
*
* @version V1.0
* @Package com.example.springboot.source.code.analysis.listener
* @Description: (用一句话描述该文件做什么)
* @date 2021年9月21日 4:21 下午
*/
@Order(3)
public class ThirdListener implements ApplicationListener<ApplicationStartedEvent> {

private final static Logger logger = LoggerFactory.getLogger(ThirdListener.class);

@Override
public void onApplicationEvent(ApplicationStartedEvent event) {
logger.info("设置框架事件监听器【ApplicationListener】成功 : run thirdListener");
}
}
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Expand Up @@ -2,3 +2,7 @@
org.springframework.context.ApplicationContextInitializer=\
com.example.springboot.source.code.analysis.initializer.FirstInitializer


# 通过系统事件监听器,设置自定义事件监听器
org.springframework.context.ApplicationListener=\
com.example.springboot.source.code.analysis.listener.FirstListener
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@@ -1,3 +1,8 @@
# 通过系统初始化器,设置环境属性
context.initializer.classes=\
com.example.springboot.source.code.analysis.initializer.ThirdInitializer

# 通过系统事件监听器,监听事件
context.listener.classes=\
com.example.springboot.source.code.analysis.listener.ThirdListener,\
com.example.springboot.source.code.analysis.listener.FourthListener

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