SpringBoot支持Crontab任务改造的方法

package com.github.zhgxun.learn.common.task;

import com.github.zhgxun.learn.common.task.annotation.ScheduleTask;
import lombok.extern.slf4j.Slf4j;
import org.springframework.boot.SpringApplication;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationListener;
import org.springframework.context.event.ContextRefreshedEvent;

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.Stream;

/**
 * 不自动加入容器, 用于区分是否属于任务启动, 否则放入容器中, Spring 无法选择性执行
 * 需要根据特殊参数在启动时注入
 * 该监听器本身不能访问容器变量, 如果需要访问, 需要从上下文中获取对象实例后方可继续访问实例信息
 * 如果其它类中启动了多线程, 是无法接管异常抛出的, 需要子线程中正确处理退出操作
 * 该监听器最好不用直接做线程操作, 子类的实现不干预
 */
@Slf4j
public class TaskApplicationListener implements ApplicationListener {
  /**
   * 任务启动监听类标识, 启动时注入
   * 即是 java -Dspring.task.class=com.github.zhgxun.learn.task.TestTask -jar learn.jar
   */
  private static final String SPRING_TASK_CLASS = "spring.task.class";

  /**
   * 支持该注解的方法个数, 目前仅一个
   * 可以理解为控制台一次执行一个类, 依赖的任务应该通过其它方式控制依赖
   */
  private static final int SUPPORT_METHOD_COUNT = 1;

  /**
   * 保存当前容器运行上下文
   */
  private ApplicationContext context;

  /**
   * 监听容器刷新事件
   *
   * @param event 容器刷新事件
   */
  @Override
  @SuppressWarnings("unchecked")
  public void onApplicationEvent(ContextRefreshedEvent event) {
    cOntext= event.getApplicationContext();
    // 不存在时可能为正常的容器启动运行, 无需关心
    String taskClass = System.getProperty(SPRING_TASK_CLASS);
    log.info("ScheduleTask spring task Class: {}", taskClass);
    if (taskClass != null) {
      try {
        // 获取类字节码文件
        Class clazz = findClass(taskClass);

        // 尝试从内容上下文中获取已加载的目标类对象实例, 这个类实例是已经加载到容器内的对象实例, 即可以获取类的信息
        Object object = context.getBean(clazz);

        Method method = findMethod(object);

        log.info("start to run task Class: {}, Method: {}", taskClass, method.getName());
        invoke(method, object);
      } catch (ClassNotFoundException | IllegalAccessException | InvocationTargetException e) {
        e.printStackTrace();
      } finally {
        // 需要确保容器正常出发停止事件, 否则容器会僵尸卡死
        shutdown();
      }
    }
  }

  /**
   * 根据class路径名称查找类文件
   *
   * @param clazz 类名称
   * @return 类对象
   * @throws ClassNotFoundException ClassNotFoundException
   */
  private Class findClass(String clazz) throws ClassNotFoundException {
    return Class.forName(clazz);
  }

  /**
   * 获取目标对象中符合条件的方法
   *
   * @param object 目标对象实例
   * @return 符合条件的方法
   */
  private Method findMethod(Object object) {
    Method[] methods = object.getClass().getDeclaredMethods();
    List schedules = Stream.of(methods)
        .filter(method -> method.isAnnotationPresent(ScheduleTask.class))
        .collect(Collectors.toList());
    if (schedules.size() != SUPPORT_METHOD_COUNT) {
      throw new IllegalStateException("only one method should be annotated with @ScheduleTask, but found "
          + schedules.size());
    }
    return schedules.get(0);
  }

  /**
   * 执行目标对象方法
   *
   * @param method 目标方法
   * @param object 目标对象实例
   * @throws IllegalAccessException  IllegalAccessException
   * @throws InvocationTargetException InvocationTargetException
   */
  private void invoke(Method method, Object object) throws IllegalAccessException, InvocationTargetException {
    method.invoke(object);
  }

  /**
   * 执行完毕退出运行容器, 并将返回值交给执行环节, 比如控制台等
   */
  private void shutdown() {
    log.info("shutdown ...");
    System.exit(SpringApplication.exit(context));
  }
}

package com.github.zhgxun.learn.common.task.annotation;

import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
@Documented
public @interface ScheduleTask {
}

package com.github.zhgxun.learn.task;

import com.github.zhgxun.learn.common.task.annotation.ScheduleTask;
import com.github.zhgxun.learn.service.first.LaunchInfoService;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.util.concurrent.TimeUnit;

@Service
@Slf4j
public class TestTask {

  @Autowired
  private LaunchInfoService launchInfoService;

  @ScheduleTask
  public void test() {
    log.info("Start task ...");
    log.info("LaunchInfoList: {}", launchInfoService.findAll());

    log.info("模拟启动线程操作");
    for (int i = 0; i <5; i++) {
      new MyTask(i).start();
    }

    try {
      TimeUnit.SECONDS.sleep(3);
    } catch (InterruptedException e) {
      e.printStackTrace();
    }
  }
}

class MyTask extends Thread {
  private int i;
  private int j;
  private String s;

  public MyTask(int i) {
    this.i = i;
  }

  @Override
  public void run() {
    super.run();
    System.out.println("第 " + i + " 个线程启动..." + Thread.currentThread().getName());
    if (i == 2) {
      throw new RuntimeException("模拟运行时异常");
    }
    if (i == 3) {
      // 除数不为0
      int a = i / j;
    }
    // 未对字符串对象赋值, 获取长度报空指针错误
    if (i == 4) {
      System.out.println(s.length());
    }
  }
}

package com.github.zhgxun.learn;

import com.github.zhgxun.learn.common.task.TaskApplicationListener;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.builder.SpringApplicationBuilder;

@SpringBootApplication
public class LearnApplication {

  public static void main(String[] args) {
    SpringApplicationBuilder builder = new SpringApplicationBuilder(LearnApplication.class);
    // 根据启动注入参数判断是否为任务动作即可, 否则不干预启动
    if (System.getProperty("spring.task.class") != null) {
      builder.listeners(new TaskApplicationListener()).run(args);
    } else {
      builder.run(args);
    }
  }
}

java -Dspring.task.class=com.github.zhgxun.learn.task.TestTask -jar target/learn.jar