UncaughtExceptionHandler

Author: CodePrometheus

README.md

@@ -9,6 +9,7 @@ Java并发编程
      线程六大生命周期
      Thread和Object中的重要方法
      线程的属性
+     未捕获异常的处理
      ThreadPool
      ThreadLocal
 

Thread/src/uncaughtexception/CantCatchDirectly.java

@@ -0,0 +1,46 @@
+package uncaughtexception;
+
+/**
+ * 说明线程的异常不能用传统方法捕获
+ *
+ * @Author: zzStar
+ * @Date: 10-18-2020 16:15
+ */
+public class CantCatchDirectly implements Runnable {
+
+    public static void main(String[] args) throws InterruptedException {
+
+        // 失效的原因 -> try语句里只能捕获对应线程内的异常，是针对主线程的，没有办法捕获到子线程中的异常
+        try {
+            new Thread(new CantCatchDirectly(), "th1").start();
+            Thread.sleep(300);
+            new Thread(new CantCatchDirectly(), "th2").start();
+            Thread.sleep(300);
+            new Thread(new CantCatchDirectly(), "th3").start();
+            Thread.sleep(300);
+            new Thread(new CantCatchDirectly(), "th4").start();
+            Thread.sleep(300);
+        } catch (RuntimeException e) {
+            // 并未执行到
+            System.out.println("Caught Exception");
+        }
+
+    }
+
+/*
+    @Override
+    public void run() {
+        throw new RuntimeException();
+    }
+*/
+
+    // 方案一，手动在每个run方法里进行try catch
+    @Override
+    public void run() {
+        try {
+            throw new RuntimeException();
+        } catch (RuntimeException e) {
+            System.out.println("Caught Exception");
+        }
+    }
+}

Thread/src/uncaughtexception/ExceptionInChildThread.java

@@ -0,0 +1,24 @@
+package uncaughtexception;
+
+/**
+ * 单线程 -> 抛出，处理，有异常堆栈
+ * 多线程 -> 子线程异常无法用传统方法捕获
+ *
+ * @Author: zzStar
+ * @Date: 10-18-2020 16:11
+ */
+public class ExceptionInChildThread implements Runnable {
+
+    public static void main(String[] args) {
+        new Thread(new ExceptionInChildThread()).start();
+        // 主线程并未受到任何影响
+        for (int i = 0; i < 100; i++) {
+            System.out.println(i);
+        }
+    }
+
+    @Override
+    public void run() {
+        throw new RuntimeException();
+    }
+}

Thread/src/uncaughtexception/MyUncaughtExceptionHandler.java

@@ -0,0 +1,49 @@
+package uncaughtexception;
+
+import java.util.logging.Level;
+import java.util.logging.Logger;
+
+/**
+ * 方案二 -> UncaughtExceptionHandler
+ *
+ * @Author: zzStar
+ * @Date: 10-18-2020 16:33
+ */
+public class MyUncaughtExceptionHandler implements Thread.UncaughtExceptionHandler {
+
+    private String name;
+
+    public MyUncaughtExceptionHandler(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，终止" + t.getName(), e);
+        System.out.println(name + "捕获了异常" + t.getName() + "异常" + e);
+    }
+
+
+}
+
+/*
+    public void uncaughtException(Thread t, Throwable e) {
+        if (parent != null) {
+            // 递归，一直向上找
+            parent.uncaughtException(t, e);
+        } else {
+            // 调用setDefaultUncaughtExceptionHandler方法设置的全局handler进行处理
+            Thread.UncaughtExceptionHandler ueh =
+                    Thread.getDefaultUncaughtExceptionHandler();
+            if (ueh != null) {
+                ueh.uncaughtException(t, e);
+            } else if (!(e instanceof ThreadDeath)) {
+                // 全局handler不存在就输出异常栈
+                System.err.print("Exception in thread \""
+                        + t.getName() + "\" ");
+                e.printStackTrace(System.err);
+            }
+        }
+    }
+*/

Thread/src/uncaughtexception/UncaughtException.png

@@ -0,0 +1,32 @@
+package uncaughtexception;
+
+/**
+ * @Author: zzStar
+ * @Date: 10-18-2020 16:45
+ */
+public class UserOwnUncaughtExceptionHandler implements Runnable {
+
+    public static void main(String[] args) throws InterruptedException {
+
+        Thread.setDefaultUncaughtExceptionHandler(new MyUncaughtExceptionHandler("MyHandler"));
+
+        new Thread(new UserOwnUncaughtExceptionHandler(), "th1").start();
+        Thread.sleep(300);
+        new Thread(new UserOwnUncaughtExceptionHandler(), "th2").start();
+        Thread.sleep(300);
+        new Thread(new UserOwnUncaughtExceptionHandler(), "th3").start();
+        Thread.sleep(300);
+        new Thread(new UserOwnUncaughtExceptionHandler(), "th4").start();
+        Thread.sleep(300);
+
+        System.out.println("Caught Exception");
+
+
+    }
+
+
+    @Override
+    public void run() {
+        throw new RuntimeException();
+    }
+}