Spring高级话题

Posted 2020-12-31 bigfly277

所有代码示例必须配置好Spring Spring项目的快速搭建.

1、Apring Aware

1.1、理论

Spring Aware的目的就是为了让Bean获得Spring容器的服务。
Spring 提供的Aware接口：

• BeanNameAware：获得容器中的Bean的名称；
  
• BeanFactoryAware：获得当前bean factory，这样容易调用容器服务；
  
• ApplicationContextAware*：获得当前application context，这样容易调用容器服务；
  
• MessageSourceAware： 获得message source，这样可以获得文本信息；
  
• ApplicationEventPublisher Aware：应用实践发布器，可以发布事件；
  
• ResourceLoaderAware： 获得资源加载器，可以获得外部资源文件；

1.2、示例

1）准备
新建一个text.tex，内容随意，用于测试资源加载

2）演示Bean

package com.wisely.highlight_spring4.ch3.aware;

import java.io.IOException;

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 AwareService implements BeanNameAware,ResourceLoaderAware{//实现接口，分别获得Bean名称和资源加载的服务
    
    private String beanName;
    private ResourceLoader loader;
    
    @Override
    public void setResourceLoader(ResourceLoader resourceLoader) {//重写ResourceLoaderAware的setResourceLoader方法
        this.loader = resourceLoader;
    }

    @Override
    public void setBeanName(String name) {//重写BeanNameAware的setBeanName方法
        this.beanName = name;
    }
    
    public void outputResult(){
        System.out.println("Bean的名称是：" + beanName);
        
        Resource resource = 
                loader.getResource("classpath:com/wisely/highlight_spring4/ch3/aware/test.txt");
        try{
            
            System.out.println("ResourceLoader加载的文件的内容为: " + IOUtils.toString(resource.getInputStream()));
            
           }catch(IOException e){
            e.printStackTrace();
           }
    
    }

}

3）配置类

package com.wisely.highlight_spring4.ch3.aware;

import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
@Configuration
@ComponentScan("com.wisely.highlight_spring4.ch2.aware")
public class AwareConfig {

}

4）测试

package com.wisely.highlight_spring4.ch3.aware;

import org.springframework.context.annotation.AnnotationConfigApplicationContext;

public class Main {
    public static void main(String[] args) {
        
        AnnotationConfigApplicationContext context =
                new AnnotationConfigApplicationContext(AwareConfig.class);
        
        AwareService awareService = context.getBean(AwareService.class);
        awareService.outputResult();
        
        context.close();
    }
}

2、多线程

2.1、理论

Spring通过任务执行器（TaskExecutor）来实现多线程和并发编程。使用TreadPoolTaskExecutor可以实现一个基于线程池的TaskExecutor。而实际开发中任务一般是非常阻碍的，即异步的，所以我们要在配置类中通过@EnableAsync开启对异步任务的支持，并通过在实际执行的Bean方法中使用@Asynv注解来声明其实一个异步任务。

2.2、示例

1）配置类

package com.wisely.highlight_spring4.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("com.wisely.highlight_spring4.ch3.taskexecutor")
@EnableAsync //开启异步任务支持
public class TaskExecutorConfig implements AsyncConfigurer{//实现AsyncConfigurer接口

    @Override
    public Executor getAsyncExecutor() {//重写getAsyncExecutor返回一个ThreadPoolTaskExecutor,这样我们就获得了一个基于线程池的TaskExecutor
         ThreadPoolTaskExecutor taskExecutor = new ThreadPoolTaskExecutor();
            taskExecutor.setCorePoolSize(5);
            taskExecutor.setMaxPoolSize(10);
            taskExecutor.setQueueCapacity(25);
            taskExecutor.initialize();
            return taskExecutor;
    }

    @Override
    public AsyncUncaughtExceptionHandler getAsyncUncaughtExceptionHandler() {
        return null;
    }

}

2）业务执行类

package com.wisely.highlight_spring4.ch3.taskexecutor;

import org.springframework.scheduling.annotation.Async;
import org.springframework.stereotype.Service;
@Service
public class AsyncTaskService {
    
    @Async //表明这个方法是个异步方法，如果注解在类级别，则表明该类所有的方法都是异步方法，而这里的方法自动被注入使用ThreadPoolTaskExecutor作为TaskExecutor
    public void executeAsyncTask(Integer i){
        System.out.println("执行异步任务： "+i);
    }

    @Async
    public void executeAsyncTaskPlus(Integer i){
        System.out.println("执行异步任务+1: "+(i+1));
    }

}

4）测试

package com.wisely.highlight_spring4.ch3.taskexecutor;

import org.springframework.context.annotation.AnnotationConfigApplicationContext;

public class Main {
    
    public static void main(String[] args) {
         AnnotationConfigApplicationContext context =
                    new AnnotationConfigApplicationContext(TaskExecutorConfig.class);
         
         AsyncTaskService asyncTaskService = context.getBean(AsyncTaskService.class);
         
         for(int i =0 ;i<5;i++){
             asyncTaskService.executeAsyncTask(i);
             asyncTaskService.executeAsyncTaskPlus(i);
            }
            context.close();
    }
}