org.zkoss.lang

Class Exceptions

java.lang.Object

org.zkoss.lang.Exceptions

public class Exceptions
extends Object

Utilities for Exceptions.

Author:

tomyeh

Constructor Summary

Constructors

Constructor and Description
Exceptions()

Method Summary

Methods

Modifier and Type	Method and Description
static Throwable	findCause(Throwable ex, Class<?> cause) Finds the causes of an exception, ex, to see whether any of them is the given type.
static StringBuffer	formatStackTrace(StringBuffer sb, Throwable t, String prefix) Formats the stack trace and appends it to the specified string buffer.
static StringBuffer	formatStackTrace(StringBuffer sb, Throwable t, String prefix, int maxcnt) Formats the stack trace and appends it to the specified string buffer, but only display at most maxcnt lines.
static String	formatStackTrace(Throwable t, String prefix) Formats the stack trace and returns the result.
static String	getBriefStackTrace(Throwable t) Returns the first few lines of the stack trace.
static Throwable	getCause(Throwable ex) Returns the cause of the given throwable.
static String	getExtraMessage(Throwable ex) Returns the extra message, or null if no extra.
static String	getMessage(int code) Gets the message for an exception without format-argument.
static String	getMessage(int code, Object fmtArg) Gets the message for an exception with one format-argument.
static String	getMessage(int code, Object[] fmtArgs) Gets the message for an exception's getMessage method.
static String	getMessage(Throwable ex) Returns a message of the exception.
static Throwable	getRealCause(Throwable ex) Unveils the real cause.
static Throwable	unwrap(Throwable ex) Unwraps an exception if the enclosing one is InvocationTargetException or UndeclaredThrowableException.
static Throwable	wrap(Throwable ex, Class<? extends Throwable> targetExceptCls) Converts an exception to the specified class.
static Throwable	wrap(Throwable ex, Class<? extends Throwable> targetExceptCls, int code) Converts an exception to the specified class plus a message.
static Throwable	wrap(Throwable ex, Class<? extends Throwable> targetExceptCls, int code, Object fmtArg) Converts an exception to the specified class plus a message.
static Throwable	wrap(Throwable ex, Class<? extends Throwable> targetExceptCls, int code, Object[] fmtArgs) Converts an exception to the specified class plus a message.
static Throwable	wrap(Throwable ex, Class<? extends Throwable> targetExceptCls, String msg) Converts an exception to the specified class plus a message.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Exceptions

public Exceptions()

Method Detail

findCause

public static final Throwable findCause(Throwable ex,
                  Class<?> cause)

Finds the causes of an exception, ex, to see whether any of them is the given type.

Returns:

the cause if found; null if not found

getCause

public static final Throwable getCause(Throwable ex)

Returns the cause of the given throwable. It is the same as t.getCause, but it solves the compatibility of J2EE that might not support JDK 1.4.

getRealCause

public static final Throwable getRealCause(Throwable ex)

Unveils the real cause. A throwable object is called a real cause, if it doesn't have any cause (or called chained throwable).

Parameters:

ex - the throwable

Returns:

the real cause; ex itself if it is already the real cause

See Also:

wrap(java.lang.Throwable, java.lang.Class<? extends java.lang.Throwable>)

wrap

public static final Throwable wrap(Throwable ex,
             Class<? extends Throwable> targetExceptCls)

Converts an exception to the specified class. If any of causes is the specified class, the cause is returned. If the giving exception is RuntimeException or error, it is re-thrown directly. In other words, Unlike findCause(java.lang.Throwable, java.lang.Class<?>), it is designed to be used in the throw statement as follows.

Usage 1: one kind of exception is examined.

 try {
   ...
 } catch (Exception ex) {
   throw (MyException)Exceptions.wrap(ex, MyException.class);
 }

Usage 2: two kinds of exceptions are examined.

 try {
   ...
 } catch (Exception ex) {
   Throwable t = Exceptions.findCause(ex, AnotherException.class);
   if (t != null)
      throw (AnotherException)t;
   throw (MyException)Exceptions.wrap(ex, MyException.class);
 }

Usage 3: two kinds of exceptions are examined.

 try {
   ...
 } catch (AnotherException ex) {
   throw ex;
 } catch (Exception ex) {
   throw (MyException)Exceptions.wrap(ex, MyException.class);
 }

If you already know the exception, you don't need this method -- AnotherException won't never be RuntimeException or MyException.

 try {
   ...
 } catch (AnotherException ex) {
   throw new MyException(ex);
 }

Note: It assumes the exception has the constructor: MyException(Throwable cause);

Parameters:

targetExceptCls - the class of exception to be converted to

ex - the exception being caught (and to be converted)

See Also:

getRealCause(java.lang.Throwable), SystemException.Aide.wrap(java.lang.Throwable)

wrap

public static final Throwable wrap(Throwable ex,
             Class<? extends Throwable> targetExceptCls,
             String msg)

Converts an exception to the specified class plus a message. It is similar to wrap(Throwable, Class) but with an additional message. Thus, the target exception class must has the constructor: MyException(String msg, Throwable cause);

wrap

public static final Throwable wrap(Throwable ex,
             Class<? extends Throwable> targetExceptCls,
             int code,
             Object[] fmtArgs)

Converts an exception to the specified class plus a message. It is similar to wrap(Throwable, Class) but with an additional message code. Thus, the target exception class must has the constructor: MyException(int code, Object[] fmtArgs, Throwable cause);

wrap

public static final Throwable wrap(Throwable ex,
             Class<? extends Throwable> targetExceptCls,
             int code,
             Object fmtArg)

Converts an exception to the specified class plus a message. It is similar to wrap(Throwable, Class) but with an additional message code. Thus, the target exception class must has the constructor: MyException(int code, Object fmtArgs, Throwable cause);

wrap

public static final Throwable wrap(Throwable ex,
             Class<? extends Throwable> targetExceptCls,
             int code)

Converts an exception to the specified class plus a message. It is similar to wrap(Throwable, Class) but with an additional message code. Thus, the target exception class must has the constructor: MyException(int code, Throwable cause);

unwrap

public static final Throwable unwrap(Throwable ex)

Unwraps an exception if the enclosing one is InvocationTargetException or UndeclaredThrowableException.

Use it if you are catching exceptions thrown by Method.invoke().

getExtraMessage

public static final String getExtraMessage(Throwable ex)

Returns the extra message, or null if no extra.

Currently, it handles only SQLException

getMessage

public static final String getMessage(Throwable ex)

Returns a message of the exception.

getMessage

public static final String getMessage(int code,
                Object[] fmtArgs)

Gets the message for an exception's getMessage method.

It actually delegates to Messages, and then appends an error code.

getMessage

public static final String getMessage(int code,
                Object fmtArg)

Gets the message for an exception with one format-argument.

getMessage

public static final String getMessage(int code)

Gets the message for an exception without format-argument.

getBriefStackTrace

public static final String getBriefStackTrace(Throwable t)

Returns the first few lines of the stack trace. It is useful to make the cause exception's stack trace to be part of the message of the exception thrown to the user.

formatStackTrace

public static final String formatStackTrace(Throwable t,
                      String prefix)

Formats the stack trace and returns the result. Currently, it only adds the prefix to each line.

Parameters:

prefix - the prefix shown in front of each line of the stack trace; null to denote empty

See Also:

Log.realCause(java.lang.Throwable)

formatStackTrace

public static final StringBuffer formatStackTrace(StringBuffer sb,
                            Throwable t,
                            String prefix)

Formats the stack trace and appends it to the specified string buffer.

Parameters:

sb - the string buffer to append the stack trace. A string buffer will be created if null.

prefix - the prefix shown in front of each line of the stack trace; null to denote empty

formatStackTrace

public static final StringBuffer formatStackTrace(StringBuffer sb,
                            Throwable t,
                            String prefix,
                            int maxcnt)

Formats the stack trace and appends it to the specified string buffer, but only display at most maxcnt lines.

The maximal allowed number of lines is controlled by maxcnt. Note: a stack frame is not counted, if it belongs to java.*, javax.* or sun.*.

Parameters:

sb - the string buffer to append the stack trace. A string buffer will be created if null.

prefix - the prefix shown in front of each line of the stack trace; null to denote empty

maxcnt - the maximal allowed number of lines to dump (<=0: no limit)