4.异常捕获后再次抛出

• 4.异常捕获后再次抛出

• 情况一：捕获后抛出原来的异常，希望保留最新的异常抛出点－－fillStackTrace

• 情况二：捕获后抛出新的异常，希望抛出完整的异常链－－initCause

• 1.捕获后重新抛出捕获的异常
• 在函数中捕获了异常，在catch模块中不做进一步的处理，而是向上一级进行传递
• catch(Exception e){
•      throw e;
• }

public class ReThrow {
    public static void f()throws Exception{
        throw new Exception("Exception: f()");
    }

    public static void g() throws Exception{
        try{
            f();
        }catch(Exception e){
            System.out.println("inside g()");
            throw e;
        }
    }
    public static void main(String[] args){
        try{
            g();
        }
        catch(Exception e){
            System.out.println("inside main() function");
            e.printStackTrace(System.out);
        }
    }
}

 运行结果如下：

inside g()

inside main() function

java.lang.Exception: Exception: f()

    at ReThrow.f(ReThrow.java:6)   //异常的抛出点还是最初抛出异常的函数f()

    at ReThrow.g(ReThrow.java:11)

    at ReThrow.main(ReThrow.java:19)

    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)

    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)

    at java.lang.reflect.Method.invoke(Method.java:606)

    at com.intellij.rt.execution.application.AppMain.main(AppMain.java:144)

 

• 2.fillStackTrace——覆盖前边的异常抛出点(获取最新的异常抛出点)
• 在此抛出异常的时候进行设置
• catch(Exception e){
•      (Exception)e.fillInStackTrace();
• }

public static void g() throws Exception{
    try{
        f();
    }catch(Exception e){
        System.out.println("inside g()");
        throw (Exception)e.fillInStackTrace();
    }
}

 运行结果如下：

inside g()

inside main() function

java.lang.Exception: Exception: f()

    at ReThrow.g(ReThrow.java:14)         //显示的就是最新的抛出点

    at ReThrow.main(ReThrow.java:19)

    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)

    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)

    at java.lang.reflect.Method.invoke(Method.java:606)

    at com.intellij.rt.execution.application.AppMain.main(AppMain.java:144)

 

• 3.捕获异常后抛出新的异常（ 区别于捕获异常之后重新抛出）
• 方式1:Exception e＝new Exception();－－－－important
• e.initCause(ex);
• 方式2:
• Exception e =new Exception(ex);

• public void f(){
      try{
           g();//throws NullPointException 
       }catch(NullPointException ex){
           ex.printStasckTrace();
           Exception e=new Exception();
           e.initCause(ex);//就可以看到原始的异常保留下来
           throw e;
       }
  }

• 运行结果：
• java.lang.Exception
•     at Main.g(Main.java:14)
•     at Main.main(Main.java:22)
•     at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
•     at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
•     at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
•     at java.lang.reflect.Method.invoke(Method.java:606)
•     at com.intellij.rt.execution.application.AppMain.main(AppMain.java:144)
• Caused by: java.lang.NullPointerException
•     at Main.f(Main.java:6)
•     at Main.g(Main.java:11)
•     ... 6 more