Java异常框架设计2
}else
{
//checked exception such as xxxBusinessException
//将这样的异常暴露给客户显示
}
}
}
我们可以这样设计xxxBusinessException
public class xxxBusinessException extends ApplicationException
{
public xxxBusinessException(String s){
super(s);
};
import java.io.PrintStream;
import java.io.PrintWriter;
public class ApplicationException extends Exception {
/** A wrapped Throwable */
protected Throwable cause;
public ApplicationException() {
super("Error occurred in application.");
}
public ApplicationException(String message) {
super(message);
}
public ApplicationException(String message, Throwable cause) {
super(message);
this.cause = cause;
}
// Created to match the JDK 1.4 Throwable method.
public Throwable initCause(Throwable cause) {
this.cause = cause;
return cause;
}
public String getMessage() {
// Get this exception's message.
String msg = super.getMessage();
Throwable parent = this;
Throwable child;
// Look for nested exceptions.
while((child = getNestedException(parent)) != null) {
// Get the child's message.
String msg2 = child.getMessage();
// If we found a message for the child exception,
// we append it.
if (msg2 != null) {
if (msg != null) {
msg += ": " + msg2;
} else {
msg = msg2;
}
}
// Any nested ApplicationException will append its own
// children, so we need to break out of here.
if (child instanceof ApplicationException) {
break;
}
parent = child;
}
// Return the completed message.
return msg;
}
public void printStackTrace() {
// Print the stack trace for this exception.
super.printStackTrace();
Throwable parent = this;
Throwable child;
// Print the stack trace for each nested exception.
while((child = getNestedException(parent)) != null) {
if (child != null) {
System.err.print("Caused by: ");
child.printStackTrace();
if (child instanceof ApplicationException) {
break;
}
parent = child;
}
}
}
public void printStackTrace(PrintStream s) {
// Print the stack trace for this exception.
super.printStackTrace(s);
Throwable parent = this;
Throwable child;
// Print the stack trace for each nested exception.
while((child = getNestedException(parent)) != null) {
if (child != null) {
s.print("Caused by: ");
child.printStackTrace(s);
if (child instanceof ApplicationException) {
break;
}
parent = child;
}
}
}
public void printStackTrace(PrintWriter w) {
// Print the stack trace for this exception.
super.printStackTrace(w);
Throwable parent = this;
Throwable child;
// Print the stack trace for each nested exception.
while((child = getNestedException(parent)) != null) {
if (child != null) {
w.print("Caused by: ");
child.printStackTrace(w);
if (child instanceof ApplicationException) {
break;
}
parent = child;
}
}
}
public Throwable getCause() {
return cause;
}
}
而"聪明"的读者肯定要问我那doBusiness()这个业务方法该如何包装异常呢？
public void doBusiness() throw xxxBusinessException
{
try
{
execute1(); // if it throw exception1
exexute2(); // if it throw exception 2
.... .....
}
catch (exception1 e1)
{
throw new xxxBusinessException(e1);
}
catch(exception2 e2)
{
throw new xxxBusinessException(e2);
}
........
}
也可以这样
public void doBusiness() throw xxxBusinessException
{
try
{
execute1(); // if it throw exception1
exexute2(); // if it throw exception 2
.... .....
}
catch (Exception e)
{
// 注意很多应用在这里根本不判断异常的类型而一股脑的采用
// throw new xxxBusinessException(e);
// 而这样带来的问题就是xxxBusinessException"吞掉了"RuntimeException
// 从而将checked excption 与unchecked exception混在了一起！
// 其实xxxBusinessException属于checked excpetion ，它根本不应该也不能够理睬RuntimeException
if(! e instanceof RuntimeException) throw new xxxBusinessException(e);
}
}
总结
1。JAVA的异常分为两类: checked exception & unchecked excpetion
2。应用开发中产生的异常都应该集成自Exception 但都属于checked excpetion类型
3。应用中的每一层在包装并传递异常的时候要过滤掉RuntimeException！
4。从责任这个角度看Error属于JVM需要负担的责任;RuntimeException是程序应该负担的责任;checked exception 是具体应用负担的责任
5。无论如何我们都不希望或者确切的说是不应该将RuntimeException这样的异常暴露给客户的，因为他们没有解决这个问题的责任！
{
//checked exception such as xxxBusinessException
//将这样的异常暴露给客户显示
}
}
}
我们可以这样设计xxxBusinessException
public class xxxBusinessException extends ApplicationException
{
public xxxBusinessException(String s){
super(s);
};
import java.io.PrintStream;
import java.io.PrintWriter;
public class ApplicationException extends Exception {
/** A wrapped Throwable */
protected Throwable cause;
public ApplicationException() {
super("Error occurred in application.");
}
public ApplicationException(String message) {
super(message);
}
public ApplicationException(String message, Throwable cause) {
super(message);
this.cause = cause;
}
// Created to match the JDK 1.4 Throwable method.
public Throwable initCause(Throwable cause) {
this.cause = cause;
return cause;
}
public String getMessage() {
// Get this exception's message.
String msg = super.getMessage();
Throwable parent = this;
Throwable child;
// Look for nested exceptions.
while((child = getNestedException(parent)) != null) {
// Get the child's message.
String msg2 = child.getMessage();
// If we found a message for the child exception,
// we append it.
if (msg2 != null) {
if (msg != null) {
msg += ": " + msg2;
} else {
msg = msg2;
}
}
// Any nested ApplicationException will append its own
// children, so we need to break out of here.
if (child instanceof ApplicationException) {
break;
}
parent = child;
}
// Return the completed message.
return msg;
}
public void printStackTrace() {
// Print the stack trace for this exception.
super.printStackTrace();
Throwable parent = this;
Throwable child;
// Print the stack trace for each nested exception.
while((child = getNestedException(parent)) != null) {
if (child != null) {
System.err.print("Caused by: ");
child.printStackTrace();
if (child instanceof ApplicationException) {
break;
}
parent = child;
}
}
}
public void printStackTrace(PrintStream s) {
// Print the stack trace for this exception.
super.printStackTrace(s);
Throwable parent = this;
Throwable child;
// Print the stack trace for each nested exception.
while((child = getNestedException(parent)) != null) {
if (child != null) {
s.print("Caused by: ");
child.printStackTrace(s);
if (child instanceof ApplicationException) {
break;
}
parent = child;
}
}
}
public void printStackTrace(PrintWriter w) {
// Print the stack trace for this exception.
super.printStackTrace(w);
Throwable parent = this;
Throwable child;
// Print the stack trace for each nested exception.
while((child = getNestedException(parent)) != null) {
if (child != null) {
w.print("Caused by: ");
child.printStackTrace(w);
if (child instanceof ApplicationException) {
break;
}
parent = child;
}
}
}
public Throwable getCause() {
return cause;
}
}
而"聪明"的读者肯定要问我那doBusiness()这个业务方法该如何包装异常呢？
public void doBusiness() throw xxxBusinessException
{
try
{
execute1(); // if it throw exception1
exexute2(); // if it throw exception 2
.... .....
}
catch (exception1 e1)
{
throw new xxxBusinessException(e1);
}
catch(exception2 e2)
{
throw new xxxBusinessException(e2);
}
........
}
也可以这样
public void doBusiness() throw xxxBusinessException
{
try
{
execute1(); // if it throw exception1
exexute2(); // if it throw exception 2
.... .....
}
catch (Exception e)
{
// 注意很多应用在这里根本不判断异常的类型而一股脑的采用
// throw new xxxBusinessException(e);
// 而这样带来的问题就是xxxBusinessException"吞掉了"RuntimeException
// 从而将checked excption 与unchecked exception混在了一起！
// 其实xxxBusinessException属于checked excpetion ，它根本不应该也不能够理睬RuntimeException
if(! e instanceof RuntimeException) throw new xxxBusinessException(e);
}
}
总结
1。JAVA的异常分为两类: checked exception & unchecked excpetion
2。应用开发中产生的异常都应该集成自Exception 但都属于checked excpetion类型
3。应用中的每一层在包装并传递异常的时候要过滤掉RuntimeException！
4。从责任这个角度看Error属于JVM需要负担的责任;RuntimeException是程序应该负担的责任;checked exception 是具体应用负担的责任
5。无论如何我们都不希望或者确切的说是不应该将RuntimeException这样的异常暴露给客户的，因为他们没有解决这个问题的责任！