本文概览：介绍了异常种类、异常堆栈和自定义异常。

1 异常种类

异常层次结构为：

对于Erro类【未检查异常】，描述的是系统内部错误类和资源耗尽错误。在代码中不抛出这种类型的对象,只需要关注Exception层次结构。
RuntimeExcetion【未检查异常】，程序运行过程中才可能发生的异常。一般为代码的逻辑错误，例如：数组下标越界，空指针、类型转换错误等。我们在代码中自定义的异常都属于该类型。
IOException【已检查异常】,编译期间可以检查到的异常。显式的进行处理，比如捕获或者直接通过throws向上抛出，比如 FileNotFoundException等。

2 堆栈

1、堆栈信息理解

打印最上面的就是最底层抛出异常的地方。举例如

main(){
   f1();
} 
 f1(){
   f2()；
}
f2(){
  f3()
}

main(){

f1();

}

f1(){

f2()；

}

f2(){

f3()

}

如果执行main()时f3()有异常，则此时打印堆栈信息如下：

f3()异常

f2()位置

f1()位置

main()位置

2、堆栈信息的传递

public class TestExcetpion {

    private void f1() {
        throw new RuntimeException("f1");
    }


    private void f2() {
        try {
            f1();
        } catch (Exception e) {
            throw new RuntimeException("f2");
        }
    }

    public void f3() {
        try{
            f2();
        }catch (Exception e){
        throw new RuntimeException("f3",e);}
    }

    public static void main(String[] args){
        TestExcetpion e = new TestExcetpion();
        e.f3();
    }
}

public class TestExcetpion {

private void f1() {

throw new RuntimeException("f1");

}

private void f2() {

try {

f1();

} catch (Exception e) {

throw new RuntimeException("f2");

}

public void f3() {

try{

f2();

}catch (Exception e){

throw new RuntimeException("f3",e);}

}

public static void main(String[] args){

TestExcetpion e = new TestExcetpion();

e.f3();

}

如下f3的堆栈信息只能到f2，不能延续到f1了。

Exception in thread “main” java.lang.RuntimeException: f3

at exception.TestExcetpion.f3(TestExcetpion.java:25)

at exception.TestExcetpion.main(TestExcetpion.java:31)

……..

Caused by: java.lang.RuntimeException: f2

at exception.TestExcetpion.f2(TestExcetpion.java:17)

at exception.TestExcetpion.f3(TestExcetpion.java:23)

… 6 more

（2）如果修改f3

 public void f2() {
        try{
            f1();
        }catch (Exception e){
        throw new RuntimeException("f2"，e);}
}

public void f2() {

try{

f1();

}catch (Exception e){

throw new RuntimeException("f2"，e);}

}

f3的堆栈信息才能向下延续到f1`

Exception in thread “main” java.lang.RuntimeException: f3

at exception.TestExcetpion.f3(TestExcetpion.java:23)

at exception.TestExcetpion.main(TestExcetpion.java:29)

……

Caused by: java.lang.RuntimeException: f2

at exception.TestExcetpion.f2(TestExcetpion.java:15)

at exception.TestExcetpion.f3(TestExcetpion.java:21)

… 6 more

Caused by: java.lang.RuntimeException: f1

at exception.TestExcetpion.f1(TestExcetpion.java:9)

at exception.TestExcetpion.f2(TestExcetpion.java:13)

… 7 more

3 自定义异常

1、自定义异常作用

是为了对于每一种异常都设置一个错误码。

2、自定义异常

public class MonitorException extends RuntimeException {
    private String errorCode;
    private String errorMsg;
    private MonitorErrorEnum errorEnum;

    public MonitorException() {
        super();
    }

    public MonitorException(String errorCode, String errorMsg) {
        super(errorCode);
        this.errorCode = errorCode;
        this.errorMsg = errorMsg;
    }

    public String getErrorCode() {
        return errorCode;
    }

    public void setErrorCode(String errorCode) {
        this.errorCode = errorCode;
    }

    public String getErrorMsg() {
        return errorMsg;
    }

    public void setErrorMsg(String errorMsg) {
        this.errorMsg = errorMsg;
    }

    public MonitorErrorEnum getErrorEnum() {
        return errorEnum;
    }

    public void setErrorEnum(MonitorErrorEnum errorEnum) {
        this.errorEnum = errorEnum;
    }
}

public class MonitorException extends RuntimeException {

private String errorCode;

private String errorMsg;

private MonitorErrorEnum errorEnum;

public MonitorException() {

super();

}

public MonitorException(String errorCode, String errorMsg) {

super(errorCode);

this.errorCode = errorCode;

this.errorMsg = errorMsg;

}

public String getErrorCode() {

return errorCode;

}

public void setErrorCode(String errorCode) {

this.errorCode = errorCode;

}

public String getErrorMsg() {

return errorMsg;

}

public void setErrorMsg(String errorMsg) {

this.errorMsg = errorMsg;

}

public MonitorErrorEnum getErrorEnum() {

return errorEnum;

}

public void setErrorEnum(MonitorErrorEnum errorEnum) {

this.errorEnum = errorEnum;

}

3、自定义错误码

public enum MonitorErrorEnum {
    SUCESS("0", "成功"),
    FAIL("9999", "失败");


    private String errCode;
    private String errMessage;

    MonitorErrorEnum(String errCode, String errMessage) {
        this.errCode = errCode;
        this.errMessage = errMessage;
    }

    public String getErrCode() {
        return errCode;
    }

    public void setErrCode(String errCode) {
        this.errCode = errCode;
    }

    public String getErrMessage() {
        return errMessage;
    }

    public void setErrMessage(String errMessage) {
        this.errMessage = errMessage;
    }
}

public enum MonitorErrorEnum {

SUCESS("0", "成功"),

FAIL("9999", "失败");

private String errCode;

private String errMessage;

MonitorErrorEnum(String errCode, String errMessage) {

this.errCode = errCode;

this.errMessage = errMessage;

}

public String getErrCode() {

return errCode;

}

public void setErrCode(String errCode) {

this.errCode = errCode;

}

public String getErrMessage() {

return errMessage;

}

public void setErrMessage(String errMessage) {

this.errMessage = errMessage;

}

参考

https://www.cnblogs.com/aspirant/p/10790803.html

（全文完）

Heart.Think.Do

Java异常体系和自定义类

1 异常种类

2 堆栈

3 自定义异常

参考

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