Java异常处理UncaughtExceptionHandler使用实例代码详解

异常处理

线程未捕获异常 UncaughtException 需要UncaughtZExceptionHandler 来进行处理

那么为什么非要用UncaughtZExceptionHandler呢？

• 主线程可以轻松捕获线程，子线程不可以
• 从下面代码可知，即使子线程抛出异常，主线程丝毫不受影响

public class ChildException implements Runnable{
  public static void main(String[] args) {
      new Thread(new ChildException()).start();
      for (int i = 0; i < 10; i++) {
          System.out.println(i);
      }
  }
  @Override
  public void run() {
      throw new RuntimeException();
  }
}
/*
* Exception in thread "Thread-0" java.lang.RuntimeException
 at com.jx.JavaTest.Thread.Exception.ChildException.run(ChildException.java:14)
 at java.lang.Thread.run(Thread.java:748)
0
1
2
3
4
5
6
7
8
9
* */

• 从下面代码可知，即使想用catch捕获子线程异常，时没有用的
• try catch 是针对主线程的，没有办法捕获子线程的异常

public class CantCatch implements Runnable {
  public static void main(String[] args) throws InterruptedException {
      try {
          new Thread(new CantCatch(), "thread0").start();
          Thread.sleep(300);
          new Thread(new CantCatch(), "thread1").start();
          Thread.sleep(300);
          new Thread(new CantCatch(), "thread2").start();
          Thread.sleep(300);
          new Thread(new CantCatch(), "thread3").start();
          Thread.sleep(300);
      } catch (RuntimeException e) {
          System.out.println("catch");
      }
  }
  @Override
  public void run() {
      throw new RuntimeException();
  }
}
/*
* Exception in thread "thread0" java.lang.RuntimeException
 at com.jx.JavaTest.Thread.Exception.CantCatch.run(CantCatch.java:22)
 at java.lang.Thread.run(Thread.java:748)
Exception in thread "thread1" java.lang.RuntimeException
 at com.jx.JavaTest.Thread.Exception.CantCatch.run(CantCatch.java:22)
 at java.lang.Thread.run(Thread.java:748)
Exception in thread "thread2" java.lang.RuntimeException
 at com.jx.JavaTest.Thread.Exception.CantCatch.run(CantCatch.java:22)
 at java.lang.Thread.run(Thread.java:748)
Exception in thread "thread3" java.lang.RuntimeException
 at com.jx.JavaTest.Thread.Exception.CantCatch.run(CantCatch.java:22)
 at java.lang.Thread.run(Thread.java:748)
Process finished with exit code 0
* */

在run方法中进行try catch可以捕获到异常，但是特别麻烦，因为需要手动地在每个run方法中都进行try catch

UncaughtExceptionHandler

自定义UncaughtExceptionHandler

public class MyUncaughtHandler implements Thread.UncaughtExceptionHandler{
  private String name;
  public MyUncaughtHandler(String name) {
      this.name = name;
  }
  @Override
  public void uncaughtException(Thread t, Throwable e) {
      Logger logger = Logger.getAnonymousLogger();
      logger.log(Level.WARNING, "线程异常" + t.getName(), e);
      System.out.println(name + "捕获" + t.getName()+ e);
  }
}

使用自定义的类来捕获异常

public class UseOwnExceptionHandler implements Runnable {
  public static void main(String[] args) throws InterruptedException {
      Thread.setDefaultUncaughtExceptionHandler(new MyUncaughtHandler("MyHandler"));
//        try {
      new Thread(new UseOwnExceptionHandler(), "thread0").start();
      Thread.sleep(300);
      new Thread(new UseOwnExceptionHandler(), "thread1").start();
      Thread.sleep(300);
      new Thread(new UseOwnExceptionHandler(), "thread2").start();
      Thread.sleep(300);
      new Thread(new UseOwnExceptionHandler(), "thread3").start();
      Thread.sleep(300);
//        } catch (RuntimeException e) {
//            System.out.println("catch");
//        }
  }
  @Override
  public void run() {
//        try {
      throw new RuntimeException();
//        } catch (RuntimeException e) {
//            System.out.println("e");
//        }
  }
}
/*
* 一月 29, 2023 11:22:01 上午 com.jx.JavaTest.Thread.Exception.MyUncaughtHandler uncaughtException
警告: 线程异常thread0
java.lang.RuntimeException
 at com.jx.JavaTest.Thread.Exception.UseOwnExceptionHandler.run(UseOwnExceptionHandler.java:24)
 at java.lang.Thread.run(Thread.java:748)
MyHandler捕获thread0java.lang.RuntimeException
一月 29, 2023 11:22:01 上午 com.jx.JavaTest.Thread.Exception.MyUncaughtHandler uncaughtException
警告: 线程异常thread1
java.lang.RuntimeException
 at com.jx.JavaTest.Thread.Exception.UseOwnExceptionHandler.run(UseOwnExceptionHandler.java:24)
 at java.lang.Thread.run(Thread.java:748)
MyHandler捕获thread1java.lang.RuntimeException
一月 29, 2023 11:22:02 上午 com.jx.JavaTest.Thread.Exception.MyUncaughtHandler uncaughtException
警告: 线程异常thread2
java.lang.RuntimeException
 at com.jx.JavaTest.Thread.Exception.UseOwnExceptionHandler.run(UseOwnExceptionHandler.java:24)
 at java.lang.Thread.run(Thread.java:748)
MyHandler捕获thread2java.lang.RuntimeException
一月 29, 2023 11:22:02 上午 com.jx.JavaTest.Thread.Exception.MyUncaughtHandler uncaughtException
警告: 线程异常thread3
java.lang.RuntimeException
 at com.jx.JavaTest.Thread.Exception.UseOwnExceptionHandler.run(UseOwnExceptionHandler.java:24)
 at java.lang.Thread.run(Thread.java:748)
MyHandler捕获thread3java.lang.RuntimeException
Process finished with exit code 0
* */

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