Java-高效地使用Exception-实践

package com.me.mypackage;
public class ResourceLoadException extends Exception {
public ResourceLoadException(String message) {
super(message);
}
}
...
public class ResourceLoader {
public getResource(String name) throws ResourceLoadException {
...
}

public class ResourceLoader {
public getResource(String name) throws ResourceLoadException {
try {
// try to load the resource from the database
...
}
catch (SQLException e) {
throw new ResourceLoadException(e.toString()):
}
}

public class ResourceLoader {
public loadResource(String resourceName) throws ResourceLoadException {
Resource r;
try {
r = loadResourceFromDB(resourceName);
}
catch (SQLException e) {
throw new ResourceLoadException("SQL Exception loading resource "
+ resourceName: " + e.toString());
}
}
}

public class ChainedException extends Exception {
private Throwable cause = null;
public ChainedException() {
super();
}
public ChainedException(String message) {
super(message);
}
public ChainedException(String message, Throwable cause) {
super(message);
this.cause = cause;
}
public Throwable getCause() {
return cause;
}
public void printStackTrace() {
super.printStackTrace();
if (cause != null) {
System.err.println("Caused by:");
cause.printStackTrace();
}
}
public void printStackTrace(java.io.PrintStream ps) {
super.printStackTrace(ps);
if (cause != null) {
ps.println("Caused by:");
cause.printStackTrace(ps);
}
}
public void printStackTrace(java.io.PrintWriter pw) {
super.printStackTrace(pw);
if (cause != null) {
pw.println("Caused by:");
cause.printStackTrace(pw);
}
}
}

public class ResourceLoadException extends ChainedException {
public ResourceLoadException(String message) {
super(message);
}
public ResourceLoadException(String message, Throwable cause) {
super(message, cause);
}
}

public class ResourceLoader {
public loadResource(String resourceName) throws ResourceLoadException {
Resource r;
try {
r = loadResourceFromDB(resourceName);
}
catch (SQLException e) {
throw new ResourceLoadException("Unable to load resource "
+ resourceName, e);
}
}
}

if (!file.exists()) {
throw new ResourceException("Cannot find file " + file.getName());
}

public static final String MSG_FILE_NOT_FOUND = "Cannot find file {1}";
...
public static String formatMessage(String messageString, Object arg0) {
MessageFormat mf = new MessageFormat(messageString);
Object[] args = new Object[1];
args[0] = arg0;
return mf.format(args);
}
...
if (!file.exists()) {
throw new ResourceException(formatMessage(MSG_FILE_NOT_FOUND,
file.getName()));
}

public interface FooResourcesKeys {
public static String MSG_FILE_NOT_FOUND = "MSG_FILE_NOT_FOUND";
public static String MSG_CANT_OPEN_FILE = "MSG_CANT_OPEN_FILE";
}
public class FooResources extends ListResourceBundle
implements FooResourcesKeys {
public Object[][] getContents() {
return contents;
} static final Object[][] contents = {
// Localize from here
{MSG_FILE_NOT_FOUND, "Cannot find file {1}"},
{MSG_CANT_OPEN_FILE, "Cannot open file {1}"},
// Localize to here
};
}
public class MessageUtil {
private static ResourceBundle myResources =
ResourceBundle.getBundle("com.foo.FooResources");
private static String getMessageString(String messageKey) {
return myResources.getString(messageKey);
}
public static String formatMessage(String messageKey) {
MessageFormat mf = new MessageFormat(getMessageString(messageKey));
return mf.format(new Object[0]);
}
public static String formatMessage(String messageKey,
Object arg0) {
MessageFormat mf = new MessageFormat(getMessageString(messageKey));
Object[] args = new Object[1];
args[0] = arg0;
return mf.format(args);
}
public static String formatMessage(String messageKey,
Object arg0,
Object arg1) {
MessageFormat mf = new MessageFormat(getMessageString(messageKey));
Object[] args = new Object[2];
args[0] = arg0;
args[1] = arg1;
return mf.format(args);
}
// Include implementations of formatMessage() for as many arguments
// as you need
}
public class SomeClass implements FooResourcesKeys {
...
if (!file.exists()) {
throw new ResourceException(
MessageUtil.formatMessage(MSG_FILE_NOT_FOUND,
file.getName()));
}
}

package ResourceBundleDemo;import java.io.File;
import java.io.FileNotFoundException;/*
* 工程信息
* @源码地址： http://www.javaworld.com/article/2075897/testing-debugging/exceptional-practices--part-3.html
* @功能：演示使用ResourceBundle构造错误消息以及本地化的过程
* @结构：ResourceBundleDemoStart[起始点]，MessageUtil,ExceptionMsgResourcesKeys,ExceptionMsgResources_ZN,ExceptionMsgResources_EN
* @版本：20150816
*//*
* 类信息
* @功能：项目起始点
* @版本：20150816
*/public class ResourceBundleDemoStart implements ExceptionMsgResourcesKeys { public void run() {
try {
loadResource();
} catch (ResourceLoadException e) {
// TODO Auto-generated catch block System.out.println("error occured when loadResource : "+ e.getMessage());
e.printStackTrace();
if (e.getCause() instanceof FileNotFoundException) {
FileNotFoundException exception = (FileNotFoundException) e
.getCause();
System.out.println("FileNotFoundException message : " + exception.getMessage());
}
}
} public void loadResource() throws ResourceLoadException {
File file = new File("config.txt");
try {
loadFile(file);
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
//e.printStackTrace();
throw new ResourceLoadException("Unable to load resource "
+ file.getName(), e);
}
} private void loadFile(File file) throws FileNotFoundException {
String exceptionMsg = MessageUtil.formatMessage(MSG_FILE_NOT_FOUND,
file.getName());
throw new FileNotFoundException(exceptionMsg);
} public static void main(String[] args) {
// TODO Auto-generated method stub
ResourceBundleDemoStart resourceBundleDemoStart = new ResourceBundleDemoStart();
resourceBundleDemoStart.run();
}
}

package ResourceBundleDemo;public class ResourceLoadException extends Exception { private Throwable cause = null; public ResourceLoadException() {
super();
} public ResourceLoadException(String message) {
super(message);
} public ResourceLoadException(String message, Throwable cause) {
super(message);
this.cause = cause;
} public Throwable getCause() {
return cause;
}
}

package ResourceBundleDemo;import java.text.MessageFormat;
import java.util.ResourceBundle;
/*
* 类信息
* @功能：读取资源包并进行本地化，最终生成正确的错误消息
* @版本：20150816
*/
public class MessageUtil { //private static ResourceBundle myResources = ResourceBundle.getBundle("ResourceBundleDemo.ExceptionMsgResources_EN");
private static ResourceBundle myResources = ResourceBundle.getBundle("ResourceBundleDemo.ExceptionMsgResources_ZN"); private static String getMessageString(String messageKey) {
return myResources.getString(messageKey);
} public static String formatMessage(String messageKey) {
MessageFormat mf = new MessageFormat(getMessageString(messageKey));
return mf.format(new Object[0]);
} public static String formatMessage(String messageKey, Object arg0) {
MessageFormat mf = new MessageFormat(getMessageString(messageKey));
Object[] args = new Object[1];
args[0] = arg0;
return mf.format(args);
} public static String formatMessage(String messageKey, Object arg0,
Object arg1) {
MessageFormat mf = new MessageFormat(getMessageString(messageKey));
Object[] args = new Object[2];
args[0] = arg0;
args[1] = arg1;
return mf.format(args);
}
// Include implementations of formatMessage() for as many arguments
// as you need
}

package ResourceBundleDemo;/*
* 类信息
* @功能：本接口规定错误消息的键名称以及结构
* @版本：20150816
*/public interface ExceptionMsgResourcesKeys {
public static String MSG_FILE_NOT_FOUND = "MSG_FILE_NOT_FOUND";
public static String MSG_CANT_OPEN_FILE = "MSG_CANT_OPEN_FILE";
}

package ResourceBundleDemo;import java.util.ListResourceBundle;/*
* 类信息
* @功能：错误消息的中文资源包
* @版本：20150816
*/public class ExceptionMsgResources_ZN extends ListResourceBundle implements ExceptionMsgResourcesKeys{ @Override
protected Object[][] getContents() {
// TODO Auto-generated method stub
return contents;
} static final Object[][] contents = {
// Localize from here
{MSG_FILE_NOT_FOUND, "找不到文件 {0}"},//原文这里有误
{MSG_CANT_OPEN_FILE, "打不开文件 {0}"},//原文这里有误
// Localize to here
};
}

package ResourceBundleDemo;import java.util.ListResourceBundle;/*
* 类信息
* @功能：错误消息的英文资源包
* @版本：20150816
*/public class ExceptionMsgResources_EN extends ListResourceBundle implements ExceptionMsgResourcesKeys{ @Override
protected Object[][] getContents() {
// TODO Auto-generated method stub
return contents;
} static final Object[][] contents = {
// Localize from here
{MSG_FILE_NOT_FOUND, "Cannot find file {0}"},//原文这里有误
{MSG_CANT_OPEN_FILE, "Cannot open file {0}"},//原文这里有误
// Localize to here
};
}

error occured when loadResource : Unable to load resource config.txt
ResourceBundleDemo.ResourceLoadException: Unable to load resource config.txt
at ResourceBundleDemo.ResourceBundleDemoStart.loadResource(ResourceBundleDemoStart.java:45)
at ResourceBundleDemo.ResourceBundleDemoStart.run(ResourceBundleDemoStart.java:24)
at ResourceBundleDemo.ResourceBundleDemoStart.main(ResourceBundleDemoStart.java:59)
Caused by: java.io.FileNotFoundException: 找不到文件 : config.txt
at ResourceBundleDemo.ResourceBundleDemoStart.loadFile(ResourceBundleDemoStart.java:53)
at ResourceBundleDemo.ResourceBundleDemoStart.loadResource(ResourceBundleDemoStart.java:41)
... 2 more
FileNotFoundException message : 找不到文件 : config.txt

error occured when loadResource : Unable to load resource config.txt
ResourceBundleDemo.ResourceLoadException: Unable to load resource config.txt
at ResourceBundleDemo.ResourceBundleDemoStart.loadResource(ResourceBundleDemoStart.java:45)
at ResourceBundleDemo.ResourceBundleDemoStart.run(ResourceBundleDemoStart.java:24)
at ResourceBundleDemo.ResourceBundleDemoStart.main(ResourceBundleDemoStart.java:59)
Caused by: java.io.FileNotFoundException: Cannot find file : config.txt
at ResourceBundleDemo.ResourceBundleDemoStart.loadFile(ResourceBundleDemoStart.java:53)
at ResourceBundleDemo.ResourceBundleDemoStart.loadResource(ResourceBundleDemoStart.java:41)
... 2 more
detailed error message : Cannot find file : config.txt