Spring Boot学习记3

2023-01-31 01:01:46 spring 学习 Boot
  1. 点睛

    在我们实际开发的时候,经常会遇到在Bean在使用之前或者止呕做一些必要的操作,spring对Bean的生命周期的操作提供了支持。在使用Java配置和注解配置下提供如下两种方式:

  2. Java配置方式:使用@Bean的initMethod和destroyMethod(相当于XML配置init-method和destory-method)。

  3. 注解方式:利用jsR-250的@PostConstruct和@PreDestroy。

  4. 示例

  5. 被注入Bean

package hightlight_spirng4.ch2.prepost;

 

 

public class BeanWayService {

        public BeanWayService() {

                System.out.println("初始化構造函数-BeanWayService");

        }

        public void init() {

                System.out.println("@Bean-init-Method");

               

        }

        public void destroy() {

                System.out.println("@Bean-destory-Method");

        }

 

}

 

package hightlight_spirng4.ch2.prepost;

 

import javax.annotation.PostConstruct;

import javax.annotation.PreDestroy;

 

public class JSR250WayService {

        public JSR250WayService() {

                System.out.println("初始化構造函数-JSR250WayService");

        }

        @PostConstruct //1 在构造函数执行完之后执行

        public void init() {

                System.out.println("JSR250-init-Method");

        }

        @PreDestroy //2 在Bean销毁之前执行

        public void destroy() {

                System.out.println("JSR250-destory-Method");

        }

 

}

 

 

  1. 配置类

package hightlight_spirng4.ch2.prepost;

 

import org.springframework.context.annotation.Bean;

import org.springframework.context.annotation.ComponentScan;

import org.springframework.context.annotation.Configuration;

 

@Configuration

@ComponentScan("hightlight_spirng4.ch2.prepost")

public class PrePostConfig {

        // initMethod 和destroyMethod 指定BeanWayService 类的init 和destroy

    // 方法在构造之后、Bean 销毁之前执行。

        @Bean(initMethod="init",destroyMethod="destroy")

        public BeanWayService beanWayService() {

                return new BeanWayService();

        }

       

        @Bean

        public JSR250WayService   jsr250WayService() {

                return new JSR250WayService();

        }

}

 

 

  1. 运行

package hightlight_spirng4.ch2.prepost;

 

import   org.springframework.context.annotation.AnnotationConfigApplicationContext;

 

public class Main {

    public static void main(String[] args) {

        AnnotationConfigApplicationContext context =

                new   AnnotationConfigApplicationContext(PrePostConfig.class);

 

        BeanWayService beanWayService = context.getBean(BeanWayService.class);

        JSR250WayService JSR250WayService = context.getBean(JSR250WayService.class);

 

 

        context.close();

    }

}

结果

r6.png                                           

  1. 点睛

Profile为在不同环境下使用不同的配置提供了支持(开发环境下的配置和生产环境下的配置肯定是不同的,例如数据库配置)

  1. 通过设定Environment的ActiveProfile来设定当前context需要使用的配置环境。在开发中使用@Profile注解类或者方法,达到在不同情况下选择实例化不同的Bean。

  2. 通过设定JVM的spring.profiles.active参数来设置配置环境。

  3. WEB项目设置在Servlet的context parameter中。

  4. 示例

package hightlight_spirng4.ch2.profile;

 

public class DemoBean {

       

        public DemoBean(String content) {

                super();

                this.content=content;

        }

       

        private String content;

       

        public String getContent() {

                return content;

        }

        public void setContent(String content) {

                this.content = content;

        }

       

}

 

package hightlight_spirng4.ch2.profile;

 

import org.springframework.context.annotation.Bean;

import org.springframework.context.annotation.Configuration;

import org.springframework.context.annotation.Profile;

@Configuration

public class ProfileConfig {

        @Bean

        @Profile("dev") //1

        public DemoBean deveDemoBean() {

                return new DemoBean("from development profile");

        }

       

        @Bean

        @Profile("prod") //2

        public DemoBean proDemoBean() {

                return new DemoBean("from production profile");

        }

}

 

 

  1. 结果

r5.png

  1. 点睛

    Spring的事件(Application Event)为Bean与Bean之间的消息通信提供了支持。当一个Bean处理完一个任务之后,希望另一个Bean知道并能做相应的处理,这时外面见需要让另外一个Bean监听当前Bean所发送的事件。

    Spring的事件需要遵循如下流程:

  2. 自定义事件,继承ApplicationEvent。

  3. 定义事件监听器,实现ApplicationListener。

  4. 使用容器发布事件。

  5. 示例

package hightlight_spirng4.ch2.event;

 

import org.springframework.context.ApplicationEvent;

 

public class DemoEvent extends ApplicationEvent {

 

       

        private static final long serialVersionUID = 1L;

       

        private String msg;

       

       

 

        public DemoEvent(Object source,String msg) {

                super(source);

                this.msg=msg;

        }

 

 

 

        public String getMsg() {

                return msg;

        }

 

 

 

        public void setMsg(String msg) {

                this.msg = msg;

        }

       

       

       

 

}

 

package hightlight_spirng4.ch2.event;

 

import org.springframework.context.ApplicationListener;

import org.springframework.stereotype.Component;

 

@Component

public class DemoListener implements   ApplicationListener<DemoEvent> { //1

 

        @Override

        public void onApplicationEvent(DemoEvent event) { //2

                String msg=event.getMsg();

                System.out.println("我(bean-demoListener)接受到了bean-demoPublisher发布的消息:" + msg);

                System.out.println("发生事件的对象是:" + event.getSource());

 

        }

 

}

 

package hightlight_spirng4.ch2.event;

 

import   org.springframework.beans.factory.annotation.Autowired;

import org.springframework.context.ApplicationContext;

import org.springframework.stereotype.Component;

 

@Component

public class DemoPublisher {

        @Autowired //1

        ApplicationContext context;

       

        public void publish(String msg) {

                context.publishEvent(new DemoEvent(this, msg)); //2

        }

}

 

package hightlight_spirng4.ch2.event;

 

import org.springframework.context.annotation.ComponentScan;

import org.springframework.context.annotation.Configuration;

 

@Configuration

@ComponentScan("hightlight_spirng4.ch2.event")

public class EventConfig {

 

}

 

package hightlight_spirng4.ch2.event;

 

import   org.springframework.context.annotation.AnnotationConfigApplicationContext;

 

public class Main {

 

        public static void main(String[] args) {

                AnnotationConfigApplicationContext   context = new AnnotationConfigApplicationContext(EventConfig.class);

                DemoPublisher publisher = context.getBean(DemoPublisher.class);

                publisher.publish("Hello application event");

                context.close();

 

        }

 

}

 

  1. 结果

r4.png

  1. 点睛

    Spring的依赖注入最大的亮点就是所有的Bean对Spring容器的存在是没有意识的。即你可以将你的容器替换成别的容器,如Google Guice,只是Bean之间的耦合度很低。

    但是在实际项目中,你不可避免的要用到Spring容器本身的功能资源,这时你的Bean必须要意识到Spring容器的存在,才能调用Spring所提供的资源,着就是所谓的Spring Aware。其实Spring Aware本来就是Spring设计用来框架内部使用的,若使用了Spring Aware,你的Bean将会和Spring框架耦合。

    Spring提供的Aware接口如下所示:

BeanNameAware

获得到容器中Bean名称

BeanFactoryAware

获得当前Bean   Factory,这样可以调用容器的服务

ApplicationContextAware*

当前ApplicationContext,这样可以调用容器的服务

MessageSourceAware

获得messagesource,这样可以获得文本信息

ApplicationEventPublisherAware

应用事件发布器,可以发布事件

ResourceLoaderAware

获得资源加载器,可以获得外部资源文件

Spring Aware的目的是为了让Bean获得Spring容器的服务。因为ApplicationContext接口集成了MessageSource接口、ApplicationEventPublisher接口和ResourceLoader接口,所以Bean继承ApplicationContextAware可以获得Spring容器的所有服务,但原则上我们还是用到什么接口,就实现什么接口。

  1. 示例

  2. 准备。新建test.txt,内容随意,给下面的外部资源加载使用。

  3. Spring Aware演示Bean。

package hightlight_spirng4.ch3.aware;

 

import org.apache.commons.io.IOUtils;

import org.springframework.beans.factory.BeanNameAware;

import org.springframework.context.ResourceLoaderAware;

import org.springframework.core.io.Resource;

import org.springframework.core.io.ResourceLoader;

import org.springframework.stereotype.Service;

@Service

public class BeanService implements BeanNameAware,   ResourceLoaderAware {//1

        private String BeanName;

        private ResourceLoader resourceLoader;

 

        @Override

        public void setResourceLoader(ResourceLoader resourceLoader) {//2

                this.resourceLoader=resourceLoader;

 

        }

 

        @Override

        public void setBeanName(String name) {//3

                this.BeanName=name;

        }

       

        public void outputResult() {

                System.out.println("BeanName is "+BeanName);

                Resource resource = resourceLoader.getResource("classpath:hightlight_spirng4/ch3/aware/test.txt");

                try {

                        System.out.println("resource info :"+IOUtils.toString(resource.getInputStream(), "utf-8"));

                } catch (Exception e) {

                        e.printStackTrace();

                }

        }

 

}

 

package hightlight_spirng4.ch3.aware;

 

import org.springframework.context.annotation.ComponentScan;

import org.springframework.context.annotation.Configuration;

 

@Configuration

@ComponentScan("hightlight_spirng4.ch3.aware")

public class AwareConfig {

 

}

 

package hightlight_spirng4.ch3.aware;

 

import   org.springframework.context.annotation.AnnotationConfigApplicationContext;

 

public class Main {

 

        public static void main(String[] args) {

                AnnotationConfigApplicationContext   context = new AnnotationConfigApplicationContext(AwareConfig.class);

                BeanService bean=context.getBean(BeanService.class);

                bean.outputResult();

                context.close();

 

        }

 

}

 

 

  1. 结果

r3.png

  1. 点睛

    Spring通过任务执行器(TaskExecutor)来实现多线程并发编程。使用RhreadPoolTaskExecutor可实现一个基于线程池的TaskExecutor。而实际开发中人物一般式非阻碍的,即异步的,所以我们要在配置类中通过@EnableAsync开始起对一部人物的支持,并通过在实际执行的Bean的方法中使用@Async注解来声明其是一个异步任务。

  2. 示例

package hightlight_spirng4.ch3.taskexecutor;

 

import java.util.concurrent.Executor;

 

import   org.springframework.aop.interceptor.AsyncUncaughtExceptionHandler;

import org.springframework.context.annotation.ComponentScan;

import org.springframework.context.annotation.Configuration;

import   org.springframework.scheduling.annotation.AsyncConfigurer;

import org.springframework.scheduling.annotation.EnableAsync;

import org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor;

@Configuration

@ComponentScan("hightlight_spirng4.ch3.taskexecutor")

@EnableAsync //1 开启异步任务支持

//2配置类实现AsyncConfigurer 接口并重写getAsyncExecutor 方法,并返回一个ThreadPoolTaskExecutor ,这样我们就获得了一个基于线程池TaskExecutor。

public class TaskExecutorConfig implements AsyncConfigurer {

 

 

        @Override

        public Executor getAsyncExecutor() {

                ThreadPoolTaskExecutor taskExecutor = new   ThreadPoolTaskExecutor();

                taskExecutor.setCorePoolSize(5);

                taskExecutor.setMaxPoolSize(10);

                taskExecutor.setQueueCapacity(25);

                taskExecutor.initialize();

                return taskExecutor;

        }

 

        @Override

        public AsyncUncaughtExceptionHandler   getAsyncUncaughtExceptionHandler() {

                // TODO Auto-generated method stub

                return null;

        }

 

       

 

}

 

package hightlight_spirng4.ch3.taskexecutor;

 

import org.springframework.scheduling.annotation.Async;

import org.springframework.stereotype.Service;

 

@Service

public class AsyncTaskService {

        @Async

        public void executeAsyncTask(Integer i) {

                System.out.println("Async task: "+i);

        }

        @Async

        public void executeAsyncTaskPlus(Integer i) {

                System.out.println("Async task i+1: "+(i+1));

        }

}

 

package hightlight_spirng4.ch3.taskexecutor;

 

import   org.springframework.context.annotation.AnnotationConfigApplicationContext;

 

public class Main {

        public static void main(String[] args) {

                AnnotationConfigApplicationContext   context = new AnnotationConfigApplicationContext(TaskExecutorConfig.class);

                AsyncTaskService bean=context.getBean(AsyncTaskService.class);

                for(int i=0;i<10;i++) {

                        bean.executeAsyncTask(i);

                        bean.executeAsyncTaskPlus(i);

                }

                context.close();

        }

}

 

结果并发执行并不是顺序的

r2.png

  1. 点睛

    从Spring3.1开始,计划任务在Spring中的实现变得异常的简单。首先通过在配置类注解@EnableScheduling来开启对计划任务的支持,然后在执行计划任务的方法上注解@Scheduled,声明这是一个计划任务。

    Sring通过@Scheduled支持多种类型的任务计划,包含cron、fixDelay、fixRate等。

  2. 示例

package hightlight_spirng4.ch3.taskscheduler;

 

import java.text.SimpleDateFORMat;

import java.util.Date;

 

import org.springframework.scheduling.annotation.Scheduled;

import org.springframework.stereotype.Service;

 

@Service

public class ScheduledTaskService {

        private static final SimpleDateFormat dateformat = new SimpleDateFormat("HH:mm:ss");

       

        //声明该方法是计划任务,使用fixedRate属性每隔固定时间执行

        @Scheduled(fixedRate=5000)

        public void reportCurrentTime() {

                System.out.println("每隔5秒执行一次:"+dateformat.format(new Date()));

        }

        //可按照指定时间执行,每天11点28分执行。cron是UNIX和类UNIX系统下的定时任务

        @Scheduled(cron="0 28 11 ? * *")

        public void fixTimeExecut() {

                System.out.println("指定时间执行:"+dateformat.format(new Date()));

        }

                       

 

}

 

package hightlight_spirng4.ch3.taskscheduler;

 

import org.springframework.context.annotation.ComponentScan;

import org.springframework.context.annotation.Configuration;

import   org.springframework.scheduling.annotation.EnableScheduling;

 

@Configuration

@ComponentScan("hightlight_spirng4.ch3.taskscheduler")

@EnableScheduling  //开启对计划任务的支持

public class TaskScheduledConfig {

 

}

package hightlight_spirng4.ch3.taskscheduler;

 

import   org.springframework.context.annotation.AnnotationConfigApplicationContext;

 

public class Main {

        public    static void main(String[] args) {

                AnnotationConfigApplicationContext   context = new AnnotationConfigApplicationContext(TaskScheduledConfig.class);

                ScheduledTaskService bean=context.getBean(ScheduledTaskService.class);

                bean.reportCurrentTime();

                bean.fixTimeExecut();

                context.close();

        }

}

 

 

  1. 结果

r.png

 

相关文章