1、ApplicationContext
Spring的核心，Context我們通常解釋為上下文環境。ApplicationContext則是應用的容器。 Spring把Bean（object）放在容器中，需要用就通過get方法取出來。在ApplicationContext接口的眾多實現類中，有3個是我們經常用到的（見表1-1），并且使用這3個實現類也基本能滿足我們Java EE應用開發中的絕大部分需求。
表1-1 ApplicationContext接口的常用實現類介紹
2、ApplicationEvent
是個抽象類，里面只有一個構造函數和一個長整型的timestamp。其源碼如下
public abstract class ApplicationEvent extends EventObject {
/** use serialVersionUID from Spring 1.2 for interoperability */
private static final long serialVersionUID = 7099057708183571937L;
/** System time when the event happened */
private final long timestamp;
/**
* Create a new ApplicationEvent.
* @param source the object on which the event initially occurred (never {@code null})
*/
public ApplicationEvent(Object source) {
super(source);
this.timestamp = System.currentTimeMillis();
}
/**
* Return the system time in milliseconds when the event happened.
*/
public final long getTimestamp() {
return this.timestamp;
}
}
3、ApplicationListener是一個接口，里面只有一個onApplicationEvent方法。如果在上下文中部署一個實現了ApplicationListener接口的bean,那么每當在一個ApplicationEvent發布到 ApplicationContext時，調用ApplicationContext.publishEvent()方法，這個bean得到通知。類似于Oberver設計模式。
其源碼如下：
public interface ApplicationListener<E extends ApplicationEvent> extends EventListener {
/**
* Handle an application event.
* @param event the event to respond to
*/
void onApplicationEvent(E event);
}
下面舉個例子
自定義事件NotifyEvent:
import org.springframework.context.ApplicationEvent;
public class NotifyEvent extends ApplicationEvent {
private String email;
private String content;
public NotifyEvent(Object source){
super(source);
}
public NotifyEvent(Object source,String email,String content){
super(source);
this.email = email;
this.content = content;
}
public String getEmail() {
return email;
}
public void setEmail(String email) {
this.email = email;
}
public String getContent() {
return content;
}
public void setContent(String content) {
this.content = content;
}
}
定義監聽器NotifyListener:
import org.springframework.context.ApplicationListener;
import org.springframework.context.annotation.Configuration;
@Configuration
public class NotifyListener implements ApplicationListener<NotifyEvent>{
@Override
public void onApplicationEvent(NotifyEvent event) {
System.out.println("郵件地址：" + event.getEmail());
System.out.println("郵件內容：" + event.getContent());
}
}
單元測試類ListenerTest： import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;
import org.springframework.web.context.WebApplicationContext;
@RunWith(SpringRunner.class)
@SpringBootTest(classes = ServerLauncher.class, webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
public class ListenerTest {
@Autowired
private WebApplicationContext webApplicationContext;
@Test
public void testListener(){
NotifyEvent event = new NotifyEvent("object","abc@qq.com","This is the content");
webApplicationContext.publishEvent(event);
}
}
posted on 2020-04-09 14:47
Terry Zou 閱讀(1293)
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