Package org.apache.commons.lang3.exception

Class ExceptionUtils

java.lang.Object
org.apache.commons.lang3.exception.ExceptionUtils
public class ExceptionUtils extends Object
Provides utilities for manipulating and examining Throwable objects.
Since:
1.0

  • Constructor Details

    • ExceptionUtils

      @Deprecated public ExceptionUtils()
      Deprecated.
      TODO Make private in 4.0.
      Public constructor allows an instance of ExceptionUtils to be created, although that is not normally necessary.

  • Method Details

    • asRuntimeException

      public static <T extends RuntimeException> T asRuntimeException(Throwable throwable)
      Throws the given (usually checked) exception without adding the exception to the throws clause of the calling method. This method prevents throws clause inflation and reduces the clutter of "Caused by" exceptions in the stack trace.

      The use of this technique may be controversial, but useful. 

        // There is no throws clause in the method signature.
  public int propagateExample {
      try {
          // Throws IOException
          invocation();
      } catch (Exception e) {
          // Propagates a checked exception.
          throw ExceptionUtils.asRuntimeException(e);
      }
      // more processing
      ...
      return value;
  }

      This is an alternative to the more conservative approach of wrapping the checked exception in a RuntimeException: 

        // There is no throws clause in the method signature.
  public int wrapExample() {
      try {
          // throws IOException.
          invocation();
      } catch (Error e) {
          throw e;
      } catch (RuntimeException e) {
          // Throws an unchecked exception.
          throw e;
      } catch (Exception e) {
          // Wraps a checked exception.
          throw new UndeclaredThrowableException(e);
      }
      // more processing
      ...
      return value;
  }

      One downside to using this approach is that the Java compiler will not allow invoking code to specify a checked exception in a catch clause unless there is some code path within the try block that has invoked a method declared with that checked exception. If the invoking site wishes to catch the shaded checked exception, it must either invoke the shaded code through a method re-declaring the desired checked exception, or catch Exception and use the instanceof operator. Either of these techniques are required when interacting with non-Java JVM code such as Jython, Scala, or Groovy, since these languages do not consider any exceptions as checked.

      Type Parameters:
      T - The type of the returned value.
      Parameters:
      throwable - The throwable to rethrow.
      Returns:
      Never actually returned, this generic type matches any type which the calling site requires. "Returning" the results of this method, as done in the propagateExample above, will satisfy the Java compiler requirement that all code paths return a value.
      Since:
      3.14.0
      See Also:

    • forEach

      public static void forEach(Throwable throwable, Consumer<Throwable> consumer)
      Performs an action for each Throwable causes of the given Throwable.

      A throwable without cause will return a stream containing one element - the input throwable. A throwable with one cause will return a stream containing two elements. - the input throwable and the cause throwable. A null throwable will return a stream of count zero.

      This method handles recursive cause structures that might otherwise cause infinite loops. The cause chain is processed until the end is reached, or until the next item in the chain is already in the result set.

      Parameters:
      throwable - The Throwable to traverse.
      consumer - a non-interfering action to perform on the elements.
      Since:
      3.13.0

    • getCause

      @Deprecated public static Throwable getCause(Throwable throwable)
      Deprecated.
      This feature will be removed in Lang 4, use Throwable.getCause() instead
      Introspects the Throwable to obtain the cause.

      The method searches for methods with specific names that return a Throwable object. This will pick up most wrapping exceptions, including those from JDK 1.4.

      The default list searched for are:

      • getCause()
      • getNextException()
      • getTargetException()
      • getException()
      • getSourceException()
      • getRootCause()
      • getCausedByException()
      • getNested()

      If none of the above is found, returns null.

      Parameters:
      throwable - the throwable to introspect for a cause, may be null
      Returns:
      the cause of the Throwable, null if none found or null throwable input
      Since:
      1.0

    • getCause

      @Deprecated public static Throwable getCause(Throwable throwable, String[] methodNames)
      Deprecated.
      This feature will be removed in Lang 4, use Throwable.getCause() instead
      Introspects the Throwable to obtain the cause.

      A null set of method names means use the default set. A null in the set of method names will be ignored.

      Parameters:
      throwable - the throwable to introspect for a cause, may be null
      methodNames - the method names, null treated as default set
      Returns:
      the cause of the Throwable, null if none found or null throwable input
      Since:
      1.0

    • getDefaultCauseMethodNames

      @Deprecated public static String[] getDefaultCauseMethodNames()
      Deprecated.
      This feature will be removed in Lang 4
      Gets the default names used when searching for the cause of an exception.

      This may be modified and used in the overloaded getCause(Throwable, String[]) method.

      Returns:
      cloned array of the default method names
      Since:
      3.0

    • getMessage

      public static String getMessage(Throwable th)
      Gets a short message summarizing the exception.

      The message returned is of the form {ClassNameWithoutPackage}: {ThrowableMessage}

      Parameters:
      th - the throwable to get a message for, null returns empty string
      Returns:
      the message, non-null
      Since:
      2.2

    • getRootCause

      public static Throwable getRootCause(Throwable throwable)
      Walks the Throwable to obtain its root cause.

      This method walks through the exception chain until the last element, the root cause of the chain, using Throwable.getCause(), and returns that exception.

      This method handles recursive cause chains that might otherwise cause infinite loops. The cause chain is processed until the end, or until the next item in the chain is already processed. If we detect a loop, then return the element before the loop.

      Parameters:
      throwable - the throwable to get the root cause for, may be null
      Returns:
      the root cause of the Throwable, null if null throwable input

    • getRootCauseMessage

      public static String getRootCauseMessage(Throwable throwable)
      Gets a short message summarizing the root cause exception.

      The message returned is of the form {ClassNameWithoutPackage}: {ThrowableMessage}

      Parameters:
      throwable - the throwable to get a message for, null returns empty string
      Returns:
      the message, non-null
      Since:
      2.2

    • getRootCauseStackTrace

      public static String[] getRootCauseStackTrace(Throwable throwable)
      Gets a compact stack trace for the root cause of the supplied Throwable.

      The output of this method is consistent across JDK versions. It consists of the root exception followed by each of its wrapping exceptions separated by '[wrapped]'. Note that this is the opposite order to the JDK1.4 display.

      Parameters:
      throwable - the throwable to examine, may be null
      Returns:
      an array of stack trace frames, never null
      Since:
      2.0

    • getRootCauseStackTraceList

      public static List<String> getRootCauseStackTraceList(Throwable throwable)
      Gets a compact stack trace for the root cause of the supplied Throwable.

      The output of this method is consistent across JDK versions. It consists of the root exception followed by each of its wrapping exceptions separated by '[wrapped]'. Note that this is the opposite order to the JDK1.4 display.

      Parameters:
      throwable - the throwable to examine, may be null
      Returns:
      a list of stack trace frames, never null
      Since:
      3.13.0

    • getStackFrames

      public static String[] getStackFrames(Throwable throwable)
      Gets the stack trace associated with the specified Throwable object, decomposing it into a list of stack frames.

      The result of this method vary by JDK version as this method uses Throwable.printStackTrace(java.io.PrintWriter). On JDK1.3 and earlier, the cause exception will not be shown unless the specified throwable alters printStackTrace.

      Parameters:
      throwable - the Throwable to examine, may be null
      Returns:
      an array of strings describing each stack frame, never null

    • getStackTrace

      public static String getStackTrace(Throwable throwable)
      Gets the stack trace from a Throwable as a String.

      The result of this method vary by JDK version as this method uses Throwable.printStackTrace(java.io.PrintWriter). On JDK1.3 and earlier, the cause exception will not be shown unless the specified throwable alters printStackTrace.

      Parameters:
      throwable - the Throwable to be examined, may be null
      Returns:
      the stack trace as generated by the exception's printStackTrace(PrintWriter) method, or an empty String if null input

    • getThrowableCount

      public static int getThrowableCount(Throwable throwable)
      Gets a count of the number of Throwable objects in the exception chain.

      A throwable without cause will return 1. A throwable with one cause will return 2 and so on. A null throwable will return 0.

      This method handles recursive cause chains that might otherwise cause infinite loops. The cause chain is processed until the end, or until the next item in the chain is already in the result.

      Parameters:
      throwable - the throwable to inspect, may be null
      Returns:
      the count of throwables, zero on null input

    • getThrowableList

      public static List<Throwable> getThrowableList(Throwable throwable)
      Gets the list of Throwable objects in the exception chain.

      A throwable without cause will return a list containing one element - the input throwable. A throwable with one cause will return a list containing two elements. - the input throwable and the cause throwable. A null throwable will return a list of size zero.

      This method handles recursive cause chains that might otherwise cause infinite loops. The cause chain is processed until the end, or until the next item in the chain is already in the result list.

      Parameters:
      throwable - the throwable to inspect, may be null
      Returns:
      the list of throwables, never null
      Since:
      2.2

    • getThrowables

      public static Throwable[] getThrowables(Throwable throwable)
      Gets the list of Throwable objects in the exception chain.

      A throwable without cause will return an array containing one element - the input throwable. A throwable with one cause will return an array containing two elements. - the input throwable and the cause throwable. A null throwable will return an array of size zero.

      This method handles recursive cause chains that might otherwise cause infinite loops. The cause chain is processed until the end, or until the next item in the chain is already in the result array.

      Parameters:
      throwable - the throwable to inspect, may be null
      Returns:
      the array of throwables, never null
      See Also:

    • hasCause

      public static boolean hasCause(Throwable chain, Class<? extends Throwable> type)
      Tests if the throwable's causal chain have an immediate or wrapped exception of the given type?
      Parameters:
      chain - The root of a Throwable causal chain.
      type - The exception type to test.
      Returns:
      true, if chain is an instance of type or is an UndeclaredThrowableException wrapping a cause.
      Since:
      3.5
      See Also:

    • indexOfThrowable

      public static int indexOfThrowable(Throwable throwable, Class<? extends Throwable> clazz)
      Returns the (zero-based) index of the first Throwable that matches the specified class (exactly) in the exception chain. Subclasses of the specified class do not match - see indexOfType(Throwable, Class) for the opposite.

      A null throwable returns -1. A null type returns -1. No match in the chain returns -1.

      Parameters:
      throwable - the throwable to inspect, may be null
      clazz - the class to search for, subclasses do not match, null returns -1
      Returns:
      the index into the throwable chain, -1 if no match or null input

    • indexOfThrowable

      public static int indexOfThrowable(Throwable throwable, Class<? extends Throwable> clazz, int fromIndex)
      Returns the (zero-based) index of the first Throwable that matches the specified type in the exception chain from a specified index. Subclasses of the specified class do not match - see indexOfType(Throwable, Class, int) for the opposite.

      A null throwable returns -1. A null type returns -1. No match in the chain returns -1. A negative start index is treated as zero. A start index greater than the number of throwables returns -1.

      Parameters:
      throwable - the throwable to inspect, may be null
      clazz - the class to search for, subclasses do not match, null returns -1
      fromIndex - the (zero-based) index of the starting position, negative treated as zero, larger than chain size returns -1
      Returns:
      the index into the throwable chain, -1 if no match or null input

    • indexOfType

      public static int indexOfType(Throwable throwable, Class<? extends Throwable> type)
      Returns the (zero-based) index of the first Throwable that matches the specified class or subclass in the exception chain. Subclasses of the specified class do match - see indexOfThrowable(Throwable, Class) for the opposite.

      A null throwable returns -1. A null type returns -1. No match in the chain returns -1.

      Parameters:
      throwable - the throwable to inspect, may be null
      type - the type to search for, subclasses match, null returns -1
      Returns:
      the index into the throwable chain, -1 if no match or null input
      Since:
      2.1

    • indexOfType

      public static int indexOfType(Throwable throwable, Class<? extends Throwable> type, int fromIndex)
      Returns the (zero-based) index of the first Throwable that matches the specified type in the exception chain from a specified index. Subclasses of the specified class do match - see indexOfThrowable(Throwable, Class) for the opposite.

      A null throwable returns -1. A null type returns -1. No match in the chain returns -1. A negative start index is treated as zero. A start index greater than the number of throwables returns -1.

      Parameters:
      throwable - the throwable to inspect, may be null
      type - the type to search for, subclasses match, null returns -1
      fromIndex - the (zero-based) index of the starting position, negative treated as zero, larger than chain size returns -1
      Returns:
      the index into the throwable chain, -1 if no match or null input
      Since:
      2.1

    • isChecked

      public static boolean isChecked(Throwable throwable)
      Checks if a throwable represents a checked exception
      Parameters:
      throwable - The throwable to check.
      Returns:
      True if the given Throwable is a checked exception.
      Since:
      3.13.0

    • isUnchecked

      public static boolean isUnchecked(Throwable throwable)
      Checks if a throwable represents an unchecked exception
      Parameters:
      throwable - The throwable to check.
      Returns:
      True if the given Throwable is an unchecked exception.
      Since:
      3.13.0

    • printRootCauseStackTrace

      public static void printRootCauseStackTrace(Throwable throwable)
      Prints a compact stack trace for the root cause of a throwable to System.err.

      The compact stack trace starts with the root cause and prints stack frames up to the place where it was caught and wrapped. Then it prints the wrapped exception and continues with stack frames until the wrapper exception is caught and wrapped again, etc.

      The output of this method is consistent across JDK versions. Note that this is the opposite order to the JDK1.4 display.

      The method is equivalent to printStackTrace for throwables that don't have nested causes.

      Parameters:
      throwable - the throwable to output
      Since:
      2.0

    • printRootCauseStackTrace

      public static void printRootCauseStackTrace(Throwable throwable, PrintStream printStream)
      Prints a compact stack trace for the root cause of a throwable.

      The compact stack trace starts with the root cause and prints stack frames up to the place where it was caught and wrapped. Then it prints the wrapped exception and continues with stack frames until the wrapper exception is caught and wrapped again, etc.

      The output of this method is consistent across JDK versions. Note that this is the opposite order to the JDK1.4 display.

      The method is equivalent to printStackTrace for throwables that don't have nested causes.

      Parameters:
      throwable - the throwable to output, may be null
      printStream - the stream to output to, may not be null
      Throws:
      NullPointerException - if the printStream is null
      Since:
      2.0

    • printRootCauseStackTrace

      public static void printRootCauseStackTrace(Throwable throwable, PrintWriter printWriter)
      Prints a compact stack trace for the root cause of a throwable.

      The compact stack trace starts with the root cause and prints stack frames up to the place where it was caught and wrapped. Then it prints the wrapped exception and continues with stack frames until the wrapper exception is caught and wrapped again, etc.

      The output of this method is consistent across JDK versions. Note that this is the opposite order to the JDK1.4 display.

      The method is equivalent to printStackTrace for throwables that don't have nested causes.

      Parameters:
      throwable - the throwable to output, may be null
      printWriter - the writer to output to, may not be null
      Throws:
      NullPointerException - if the printWriter is null
      Since:
      2.0

    • removeCommonFrames

      public static void removeCommonFrames(List<String> causeFrames, List<String> wrapperFrames)
      Removes common frames from the cause trace given the two stack traces.
      Parameters:
      causeFrames - stack trace of a cause throwable
      wrapperFrames - stack trace of a wrapper throwable
      Throws:
      NullPointerException - if either argument is null
      Since:
      2.0

    • rethrow

      public static <T> T rethrow(Throwable throwable)
      Throws the given (usually checked) exception without adding the exception to the throws clause of the calling method. This method prevents throws clause inflation and reduces the clutter of "Caused by" exceptions in the stack trace.

      The use of this technique may be controversial, but useful. 

        // There is no throws clause in the method signature.
  public int propagateExample() {
      try {
          // throws SomeCheckedException.
          return invocation();
      } catch (SomeCheckedException e) {
          // Propagates a checked exception and compiles to return an int.
          return ExceptionUtils.rethrow(e);
      }
  }

      This is an alternative to the more conservative approach of wrapping the checked exception in a RuntimeException: 

        // There is no throws clause in the method signature.
  public int wrapExample() {
      try {
          // throws IOException.
          return invocation();
      } catch (Error e) {
          throw e;
      } catch (RuntimeException e) {
          // Throws an unchecked exception.
          throw e;
      } catch (Exception e) {
          // wraps a checked exception.
          throw new UndeclaredThrowableException(e);
      }
  }

      One downside to using this approach is that the Java compiler will not allow invoking code to specify a checked exception in a catch clause unless there is some code path within the try block that has invoked a method declared with that checked exception. If the invoking site wishes to catch the shaded checked exception, it must either invoke the shaded code through a method re-declaring the desired checked exception, or catch Exception and use the instanceof operator. Either of these techniques are required when interacting with non-Java JVM code such as Jython, Scala, or Groovy, since these languages do not consider any exceptions as checked.

      Type Parameters:
      T - The type of the return value.
      Parameters:
      throwable - The throwable to rethrow.
      Returns:
      Never actually returns, this generic type matches any type which the calling site requires. "Returning" the results of this method, as done in the propagateExample above, will satisfy the Java compiler requirement that all code paths return a value.
      Since:
      3.5
      See Also:

    • stream

      public static Stream<Throwable> stream(Throwable throwable)
      Streams causes of a Throwable.

      A throwable without cause will return a stream containing one element - the input throwable. A throwable with one cause will return a stream containing two elements. - the input throwable and the cause throwable. A null throwable will return a stream of count zero.

      This method handles recursive cause chains that might otherwise cause infinite loops. The cause chain is processed until the end, or until the next item in the chain is already in the result.

      Parameters:
      throwable - The Throwable to traverse
      Returns:
      A new Stream of Throwable causes.
      Since:
      3.13.0

    • throwableOfThrowable

      public static <T extends Throwable> T throwableOfThrowable(Throwable throwable, Class<T> clazz)
      Returns the first Throwable that matches the specified class (exactly) in the exception chain. Subclasses of the specified class do not match - see throwableOfType(Throwable, Class) for the opposite.

      A null throwable returns null. A null type returns null. No match in the chain returns null.

      Type Parameters:
      T - the type of Throwable you are searching.
      Parameters:
      throwable - the throwable to inspect, may be null
      clazz - the class to search for, subclasses do not match, null returns null
      Returns:
      the first matching throwable from the throwable chain, null if no match or null input
      Since:
      3.10

    • throwableOfThrowable

      public static <T extends Throwable> T throwableOfThrowable(Throwable throwable, Class<T> clazz, int fromIndex)
      Returns the first Throwable that matches the specified type in the exception chain from a specified index. Subclasses of the specified class do not match - see throwableOfType(Throwable, Class, int) for the opposite.

      A null throwable returns null. A null type returns null. No match in the chain returns null. A negative start index is treated as zero. A start index greater than the number of throwables returns null.

      Type Parameters:
      T - the type of Throwable you are searching.
      Parameters:
      throwable - the throwable to inspect, may be null
      clazz - the class to search for, subclasses do not match, null returns null
      fromIndex - the (zero-based) index of the starting position, negative treated as zero, larger than chain size returns null
      Returns:
      the first matching throwable from the throwable chain, null if no match or null input
      Since:
      3.10

    • throwableOfType

      public static <T extends Throwable> T throwableOfType(Throwable throwable, Class<T> type)
      Returns the throwable of the first Throwable that matches the specified class or subclass in the exception chain. Subclasses of the specified class do match - see throwableOfThrowable(Throwable, Class) for the opposite.

      A null throwable returns null. A null type returns null. No match in the chain returns null.

      Type Parameters:
      T - the type of Throwable you are searching.
      Parameters:
      throwable - the throwable to inspect, may be null
      type - the type to search for, subclasses match, null returns null
      Returns:
      the first matching throwable from the throwable chain, null if no match or null input
      Since:
      3.10

    • throwableOfType

      public static <T extends Throwable> T throwableOfType(Throwable throwable, Class<T> type, int fromIndex)
      Returns the first Throwable that matches the specified type in the exception chain from a specified index. Subclasses of the specified class do match - see throwableOfThrowable(Throwable, Class) for the opposite.

      A null throwable returns null. A null type returns null. No match in the chain returns null. A negative start index is treated as zero. A start index greater than the number of throwables returns null.

      Type Parameters:
      T - the type of Throwable you are searching.
      Parameters:
      throwable - the throwable to inspect, may be null
      type - the type to search for, subclasses match, null returns null
      fromIndex - the (zero-based) index of the starting position, negative treated as zero, larger than chain size returns null
      Returns:
      the first matching throwable from the throwable chain, null if no match or null input
      Since:
      3.10

    • throwUnchecked

      @Deprecated public static <T> T throwUnchecked(T throwable)
      Deprecated.
      Use throwUnchecked(Throwable).
      Tests whether the specified Throwable is unchecked and throws it if so.
      Type Parameters:
      T - The Throwable type.
      Parameters:
      throwable - the throwable to test and throw or return.
      Returns:
      the given throwable.
      Since:
      3.13.0

    • throwUnchecked

      public static <T extends Throwable> T throwUnchecked(T throwable)
      Tests whether the specified Throwable is unchecked and throws it if so.
      Type Parameters:
      T - The Throwable type.
      Parameters:
      throwable - the throwable to test and throw or return.
      Returns:
      the given throwable.
      Since:
      3.14.0

    • wrapAndThrow

      public static <R> R wrapAndThrow(Throwable throwable)
      Throws a checked exception without adding the exception to the throws clause of the calling method. For checked exceptions, this method throws an UndeclaredThrowableException wrapping the checked exception. For Errors and RuntimeExceptions, the original exception is rethrown.

      The downside to using this approach is that invoking code which needs to handle specific checked exceptions must sniff up the exception chain to determine if the caught exception was caused by the checked exception.

      Type Parameters:
      R - The type of the returned value.
      Parameters:
      throwable - The throwable to rethrow.
      Returns:
      Never actually returned, this generic type matches any type which the calling site requires. "Returning" the results of this method will satisfy the Java compiler requirement that all code paths return a value.
      Since:
      3.5
      See Also: