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】，就是运行时刻异常。我们在代码中自定义的异常都属于该类型。

IOException【已检查异常】。Throws只声明检查类型异常，即IOException类型；对于RuntimeException类型不声明。

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()

}

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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();

}

}

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publicclassTestExcetpion{

privatevoidf1(){

thrownewRuntimeException("f1");

}

privatevoidf2(){

try{

f1();

}catch(Exceptione){

thrownewRuntimeException("f2");

}

}

publicvoidf3(){

try{

f2();

}catch(Exceptione){

thrownewRuntimeException("f3",e);}

}

publicstaticvoidmain(String[]args){

TestExcetpione=newTestExcetpion();

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);}

}

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publicvoidf2(){

try{

f1();

}catch(Exceptione){

thrownewRuntimeException("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;

}

}

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publicclassMonitorExceptionextendsRuntimeException{

privateStringerrorCode;

privateStringerrorMsg;

privateMonitorErrorEnumerrorEnum;

publicMonitorException(){

super();

}

publicMonitorException(StringerrorCode,StringerrorMsg){

super(errorCode);

this.errorCode=errorCode;

this.errorMsg=errorMsg;

}

publicStringgetErrorCode(){

returnerrorCode;

}

publicvoidsetErrorCode(StringerrorCode){

this.errorCode=errorCode;

}

publicStringgetErrorMsg(){

returnerrorMsg;

}

publicvoidsetErrorMsg(StringerrorMsg){

this.errorMsg=errorMsg;

}

publicMonitorErrorEnumgetErrorEnum(){

returnerrorEnum;

}

publicvoidsetErrorEnum(MonitorErrorEnumerrorEnum){

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;

}

}

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publicenumMonitorErrorEnum{

SUCESS("0","成功"),

FAIL("9999","失败");

privateStringerrCode;

privateStringerrMessage;

MonitorErrorEnum(StringerrCode,StringerrMessage){

this.errCode=errCode;

this.errMessage=errMessage;

}

publicStringgetErrCode(){

returnerrCode;

}

publicvoidsetErrCode(StringerrCode){

this.errCode=errCode;

}

publicStringgetErrMessage(){

returnerrMessage;

}

publicvoidsetErrMessage(StringerrMessage){

this.errMessage=errMessage;

}

}

(全文完)