1592
votes

What is the easiest way to convert the result of Throwable.getStackTrace() to a string that depicts the stacktrace?

30
Because jqno's answer actually uses the Throwable.getStackTrace() method that you specified in your question, whereas Brian doesn't. He uses Throwable.printStackTrace() instead.Stijn de Witt
Just about every Java project should include Apache commons-lang. It includes many convenience methods implementing extremely common development needs.Russell Silva
@StijndeWitt Those three lines of code almost certainly need factoring out of the place you've called them. Since you don't know where to put them, they'll go in your utility toolbox with all the other useful snippets. Bingo! you've just reinvented guava / commons-lang / whatever... only not so well. Import a sensible utilities library instead, and save reinventing the wheel. The true sign of a novice is thinking you can do a better job than the library writers.Andrew Spencer
1. Guava has - Throwables.getStackTraceAsString(e) 2. Apache Commons Lang - ExceptionUtils.getFullStackTrace 3. Write our own custom methodsuser2323036
@AndrewSpencer I don't understand why you guys try so hard to bash StijndeWitt for wanting to achieve this with some small snippet. There is really not much danger in writing a tiny utility method (I don't see it as "SHEER ARROGANCE oh nooooo!! he thinks he's better than Apache!!"). There are tons of projects especially in non-Java JVM languages that really don't want to include Guava or Commons Lang just to log a stacktrace. I write Scala & Clojure libraries and certainly will not be making Apache Commons Lang a transitive dependency just for one method.jm0

30 Answers

1086
votes

One can use the following method to convert an Exception stack trace to String. This class is available in Apache commons-lang which is most common dependent library with many popular open sources

org.apache.commons.lang.exception.ExceptionUtils.getStackTrace(Throwable)

2284
votes

Use Throwable.printStackTrace(PrintWriter pw) to send the stack trace to an appropriate writer.

import java.io.StringWriter;
import java.io.PrintWriter;

// ...

StringWriter sw = new StringWriter();
PrintWriter pw = new PrintWriter(sw);
e.printStackTrace(pw);
String sStackTrace = sw.toString(); // stack trace as a string
System.out.println(sStackTrace);
481
votes

This should work:

StringWriter sw = new StringWriter();
e.printStackTrace(new PrintWriter(sw));
String exceptionAsString = sw.toString();
246
votes

If you are developing for Android, a far easier way is to use this:

import android.util.Log;

String stackTrace = Log.getStackTraceString(exception); 

The format is the same as getStacktrace, for e.g.

09-24 16:09:07.042: I/System.out(4844): java.lang.NullPointerException
09-24 16:09:07.042: I/System.out(4844):   at com.temp.ttscancel.MainActivity.onCreate(MainActivity.java:43)
09-24 16:09:07.042: I/System.out(4844):   at android.app.Activity.performCreate(Activity.java:5248)
09-24 16:09:07.043: I/System.out(4844):   at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1110)
09-24 16:09:07.043: I/System.out(4844):   at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2162)
09-24 16:09:07.043: I/System.out(4844):   at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2257)
09-24 16:09:07.043: I/System.out(4844):   at android.app.ActivityThread.access$800(ActivityThread.java:139)
09-24 16:09:07.043: I/System.out(4844):   at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1210)
09-24 16:09:07.043: I/System.out(4844):   at android.os.Handler.dispatchMessage(Handler.java:102)
09-24 16:09:07.043: I/System.out(4844):   at android.os.Looper.loop(Looper.java:136)
09-24 16:09:07.044: I/System.out(4844):   at android.app.ActivityThread.main(ActivityThread.java:5097)
09-24 16:09:07.044: I/System.out(4844):   at java.lang.reflect.Method.invokeNative(Native Method)
09-24 16:09:07.044: I/System.out(4844):   at java.lang.reflect.Method.invoke(Method.java:515)
09-24 16:09:07.044: I/System.out(4844):   at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
09-24 16:09:07.044: I/System.out(4844):   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
142
votes

Guava's Throwables class

If you have the actual Throwable instance, Google Guava provides Throwables.getStackTraceAsString().

Example:

String s = Throwables.getStackTraceAsString ( myException ) ;
113
votes

WARNING: Does not include cause (which is usually the useful bit!)

public String stackTraceToString(Throwable e) {
    StringBuilder sb = new StringBuilder();
    for (StackTraceElement element : e.getStackTrace()) {
        sb.append(element.toString());
        sb.append("\n");
    }
    return sb.toString();
}
103
votes

For me the cleanest and easiest way was:

import java.util.Arrays;
Arrays.toString(e.getStackTrace());
29
votes
public static String getStackTrace(Throwable t) {
    StringWriter sw = new StringWriter();
    t.printStackTrace(new PrintWriter(sw));
    return sw.toString();
}
26
votes

The following code allows you to get the entire stackTrace with a String format, without using APIs like log4J or even java.util.Logger:

catch (Exception e) {
    StackTraceElement[] stack = e.getStackTrace();
    String exception = "";
    for (StackTraceElement s : stack) {
        exception = exception + s.toString() + "\n\t\t";
    }
    System.out.println(exception);
    // then you can send the exception string to a external file.
}
20
votes

Here is a version that is copy-pastable directly into code:

import java.io.StringWriter; 
import java.io.PrintWriter;

//Two lines of code to get the exception into a StringWriter
StringWriter sw = new StringWriter();
new Throwable().printStackTrace(new PrintWriter(sw));

//And to actually print it
logger.info("Current stack trace is:\n" + sw.toString());

Or, in a catch block

} catch (Throwable t) {
    StringWriter sw = new StringWriter();
    t.printStackTrace(new PrintWriter(sw));
    logger.info("Current stack trace is:\n" + sw.toString());
}
20
votes

Print the stack trace to a PrintStream, then convert it to a String:

// ...

catch (Exception e)
{
    ByteArrayOutputStream out = new ByteArrayOutputStream(); 
    e.printStackTrace(new PrintStream(out));
    String str = new String(out.toByteArray());

    System.out.println(str);
}
19
votes
Arrays.toString(thrown.getStackTrace())

Is the easiest way to convert the result into String I am using this in my program to print the stack trace

LOGGER.log(Level.SEVERE, "Query Builder Issue Stack Trace : {0} ,Message : {1} objid {2}", new Object[]{Arrays.toString(e.getStackTrace()), e.getMessage(),objId});
14
votes

Kotlin >= 1.4

Use the built-in function stackTraceToString() on a Throwable.

Kotlin < 1.4

Extending the Throwable class will give you the String property error.stackTraceString:

val Throwable.stackTraceString: String
  get() {
    val sw = StringWriter()
    val pw = PrintWriter(sw)
    this.printStackTrace(pw)
    return sw.toString()
  }
12
votes

Printing stack trace to string

import java.io.PrintWriter;
import java.io.StringWriter;

public class StackTraceUtils {
    public static String stackTraceToString(StackTraceElement[] stackTrace) {
        StringWriter sw = new StringWriter();
        printStackTrace(stackTrace, new PrintWriter(sw));
        return sw.toString();
    }
    public static void printStackTrace(StackTraceElement[] stackTrace, PrintWriter pw) {
        for(StackTraceElement stackTraceEl : stackTrace) {
            pw.println(stackTraceEl);
        }
    }
}

It's useful when you want to print the current thread stack trace without creating instance of Throwable - but note that creating new Throwable and getting stack trace from there is actually faster and cheaper than calling Thread.getStackTrace.

11
votes
private String getCurrentStackTraceString() {
    StackTraceElement[] stackTrace = Thread.currentThread().getStackTrace();
    return Arrays.stream(stackTrace).map(StackTraceElement::toString)
            .collect(Collectors.joining("\n"));
}
10
votes

Code from Apache Commons Lang 3.4 (JavaDoc):

public static String getStackTrace(final Throwable throwable) {
    final StringWriter sw = new StringWriter();
    final PrintWriter pw = new PrintWriter(sw, true);
    throwable.printStackTrace(pw);
    return sw.getBuffer().toString();
}

The difference with the other answers is that it uses autoFlush on the PrintWriter.

9
votes

The clever sniping in the first set of comments was very amusing, but it really depends on what you are trying to do. If you don't already have the correct library, then 3 lines of code (as in D. Wroblewski's answer) is perfect. OTOH, if you already have the apache.commons library (as most large projects will), then Amar's answer is shorter. OK, it might take you ten minutes to get the library and install it correctly (less than one if you know what you're doing). But the clock is ticking, so you may not have the time to spare. Jarek Przygódzki had an interesting caveat--"If you don't need nested exceptions".

But what if I do need the full stack traces, nested and all? In that case, the secret is to use apache.common's getFullStackTrace (see http://commons.apache.org/proper/commons-lang/javadocs/api-2.6/org/apache/commons/lang/exception/ExceptionUtils.html#getFullStackTrace%28java.lang.Throwable%29)

It saved my bacon. Thanks, Amar, for the hint!

9
votes

if you are using Java 8, try this

Arrays.stream(e.getStackTrace())
                .map(s->s.toString())
                .collect(Collectors.joining("\n"));

you can find the code for getStackTrace() function provided by Throwable.java as :

public StackTraceElement[] getStackTrace() {
    return getOurStackTrace().clone();
}

and for StackTraceElement, it provides toString() as follows:

public String toString() {
    return getClassName() + "." + methodName +
        (isNativeMethod() ? "(Native Method)" :
         (fileName != null && lineNumber >= 0 ?
          "(" + fileName + ":" + lineNumber + ")" :
          (fileName != null ?  "("+fileName+")" : "(Unknown Source)")));
}

So just join the StackTraceElement with "\n".

8
votes

Without java.io.* it can be done like this.

String trace = e.toString() + "\n";                     

for (StackTraceElement e1 : e.getStackTrace()) {
    trace += "\t at " + e1.toString() + "\n";
}   

And then the trace variable holds your stack trace. Output also holds the initial cause, the output is identical to printStackTrace()

Example, printStackTrace() yields:

java.io.FileNotFoundException: / (Is a directory)
    at java.io.FileOutputStream.open0(Native Method)
    at java.io.FileOutputStream.open(FileOutputStream.java:270)
    at java.io.FileOutputStream.<init>(FileOutputStream.java:213)
    at java.io.FileOutputStream.<init>(FileOutputStream.java:101)
    at Test.main(Test.java:9)

The trace String holds, when printed to stdout

java.io.FileNotFoundException: / (Is a directory)
     at java.io.FileOutputStream.open0(Native Method)
     at java.io.FileOutputStream.open(FileOutputStream.java:270)
     at java.io.FileOutputStream.<init>(FileOutputStream.java:213)
     at java.io.FileOutputStream.<init>(FileOutputStream.java:101)
     at Test.main(Test.java:9)
7
votes

With Java 8 Stream API you can do something like this:

Stream
    .of(throwable.getStackTrace())
    .map(StackTraceElement::toString)
    .collect(Collectors.joining("\n"));

It will take array of stack trace elements, convert them to string and join into multiline string.

5
votes

an exapansion on Gala's answer that will also include the causes for the exception:

private String extrapolateStackTrace(Exception ex) {
    Throwable e = ex;
    String trace = e.toString() + "\n";
    for (StackTraceElement e1 : e.getStackTrace()) {
        trace += "\t at " + e1.toString() + "\n";
    }
    while (e.getCause() != null) {
        e = e.getCause();
        trace += "Cause by: " + e.toString() + "\n";
        for (StackTraceElement e1 : e.getStackTrace()) {
            trace += "\t at " + e1.toString() + "\n";
        }
    }
    return trace;
}
5
votes

Scala version

def stackTraceToString(e: Exception): String = {
  import java.io.PrintWriter
  val sw = new StringWriter()
  e.printStackTrace(new PrintWriter(sw))
  sw.toString
}
4
votes

The solution is to convert the stackTrace of array to string data type. See the following example:

import java.util.Arrays;

try{

}catch(Exception ex){
    String stack = Arrays.toString(ex.getStackTrace());
    System.out.println("stack "+ stack);
}
3
votes

If you don't want to use an external library and you're not developing for Android, you could create an 'extension' method like this:

public static String getStackTraceString(Throwable e) {
    return getStackTraceString(e, "");
}

private static String getStackTraceString(Throwable e, String indent) {
    StringBuilder sb = new StringBuilder();
    sb.append(e.toString());
    sb.append("\n");

    StackTraceElement[] stack = e.getStackTrace();
    if (stack != null) {
        for (StackTraceElement stackTraceElement : stack) {
            sb.append(indent);
            sb.append("\tat ");
            sb.append(stackTraceElement.toString());
            sb.append("\n");
        }
    }

    Throwable[] suppressedExceptions = e.getSuppressed();
    // Print suppressed exceptions indented one level deeper.
    if (suppressedExceptions != null) {
        for (Throwable throwable : suppressedExceptions) {
            sb.append(indent);
            sb.append("\tSuppressed: ");
            sb.append(getStackTraceString(throwable, indent + "\t"));
        }
    }

    Throwable cause = e.getCause();
    if (cause != null) {
        sb.append(indent);
        sb.append("Caused by: ");
        sb.append(getStackTraceString(cause, indent));
    }

    return sb.toString();
}
3
votes

My oneliner to convert stack trace to the enclosed multi-line string:

Stream.of(e.getStackTrace()).map((a) -> a.toString()).collect(Collectors.joining("\n", "[", "]"))

Easy to pass to the logger "as is".

3
votes
 import java.io.PrintWriter;
import java.io.StringWriter;

public class PrintStackTrace {

    public static void main(String[] args) {

        try {
            int division = 0 / 0;
        } catch (ArithmeticException e) {
            StringWriter sw = new StringWriter();
            e.printStackTrace(new PrintWriter(sw));
            String exceptionAsString = sw.toString();
            System.out.println(exceptionAsString);
        }
    }
}

When you run the program, the output will be something similar:

java.lang.ArithmeticException: / by zero
at PrintStackTrace.main(PrintStackTrace.java:9)
2
votes

Old question, but I would just like to add the special case where you don't want to print all the stack, by removing some parts you are not actually interested in, excluding certain classes or packages.

Instead of a PrintWriter use a SelectivePrintWriter:

// This filters out this package and up.
String packageNameToFilter = "org.springframework";

StringWriter sw = new StringWriter();
PrintWriter pw = new SelectivePrintWriter(sw, packageNameToFilter);
e.printStackTrace(pw);
String sStackTrace = sw.toString(); 
System.out.println(sStackTrace);

Where the SelectivePrintWriter class is given by:

public class SelectivePrintWriter extends PrintWriter {
    private boolean on = true;
    private static final String AT = "\tat";
    private String internal;

    public SelectivePrintWriter(Writer out, String packageOrClassName) {
        super(out);
        internal = "\tat " + packageOrClassName;
    }

    public void println(Object obj) {
        if (obj instanceof String) {
            String txt = (String) obj;
            if (!txt.startsWith(AT)) on = true;
            else if (txt.startsWith(internal)) on = false;
            if (on) super.println(txt);
        } else {
            super.println(obj);
        }
    }
}

Please note this class may be easily adapted to filter out by Regex, contains or other criteria. Also note it depends upon Throwable implementation details (not likely to change, but still).

2
votes

Warning: This may be a bit off topic, but oh well... ;)

I don't know what the original posters reason was for wanting the stack trace as string in the first place. When the stack trace should end up in an SLF4J/Logback LOG, but no exception was or should be thrown here's what I do:

public void remove(List<String> ids) {
    if(ids == null || ids.isEmpty()) {
        LOG.warn(
            "An empty list (or null) was passed to {}.remove(List). " +
            "Clearly, this call is unneccessary, the caller should " + 
            "avoid making it. A stacktrace follows.", 
            getClass().getName(),
            new Throwable ("Stacktrace")
        );

        return;
    }

    // actual work, remove stuff
}

I like it because it does not require an external library (other than your logging backend, which will be in place most of the time anyway, of course).

2
votes

Few options

  1. StringWriter sw = new StringWriter(); e.printStackTrace(new PrintWriter(sw)); String exceptionAsString = sw.toString();

  2. Using Google Guava lib String stackTrace = Throwables.getStackTraceAsString ( myException ) ;

  3. org.apache.commons.lang.exception.ExceptionUtils.getStackTrace(Throwable)

2
votes

I wrote a few methods for this a while ago, so I figured why not throw my two cents at this.

/** @param stackTraceElements The elements to convert
 * @return The resulting string */
public static final String stackTraceElementsToStr(StackTraceElement[] stackTraceElements) {
    return stackTraceElementsToStr(stackTraceElements, "\n");
}

/** @param stackTraceElements The elements to convert
 * @param lineSeparator The line separator to use
 * @return The resulting string */
public static final String stackTraceElementsToStr(StackTraceElement[] stackTraceElements, String lineSeparator) {
    return stackTraceElementsToStr(stackTraceElements, lineSeparator, "");
}

/** @param stackTraceElements The elements to convert
 * @param lineSeparator The line separator to use
 * @param padding The string to be used at the start of each line
 * @return The resulting string */
public static final String stackTraceElementsToStr(StackTraceElement[] stackTraceElements, String lineSeparator, String padding) {
    String str = "";
    if(stackTraceElements != null) {
        for(StackTraceElement stackTrace : stackTraceElements) {
            str += padding + (!stackTrace.toString().startsWith("Caused By") ? "\tat " : "") + stackTrace.toString() + lineSeparator;
        }
    }
    return str;
}

/** @param stackTraceElements The elements to convert
 * @return The resulting string */
public static final String stackTraceCausedByElementsOnlyToStr(StackTraceElement[] stackTraceElements) {
    return stackTraceCausedByElementsOnlyToStr(stackTraceElements, "\n");
}

/** @param stackTraceElements The elements to convert
 * @param lineSeparator The line separator to use
 * @return The resulting string */
public static final String stackTraceCausedByElementsOnlyToStr(StackTraceElement[] stackTraceElements, String lineSeparator) {
    return stackTraceCausedByElementsOnlyToStr(stackTraceElements, lineSeparator, "");
}

/** @param stackTraceElements The elements to convert
 * @param lineSeparator The line separator to use
 * @param padding The string to be used at the start of each line
 * @return The resulting string */
public static final String stackTraceCausedByElementsOnlyToStr(StackTraceElement[] stackTraceElements, String lineSeparator, String padding) {
    String str = "";
    if(stackTraceElements != null) {
        for(StackTraceElement stackTrace : stackTraceElements) {
            str += (!stackTrace.toString().startsWith("Caused By") ? "" : padding + stackTrace.toString() + lineSeparator);
        }
    }
    return str;
}

/** @param e The {@link Throwable} to convert
 * @return The resulting String */
public static final String throwableToStrNoStackTraces(Throwable e) {
    return throwableToStrNoStackTraces(e, "\n");
}

/** @param e The {@link Throwable} to convert
 * @param lineSeparator The line separator to use
 * @return The resulting String */
public static final String throwableToStrNoStackTraces(Throwable e, String lineSeparator) {
    return throwableToStrNoStackTraces(e, lineSeparator, "");
}

/** @param e The {@link Throwable} to convert
 * @param lineSeparator The line separator to use
 * @param padding The string to be used at the start of each line
 * @return The resulting String */
public static final String throwableToStrNoStackTraces(Throwable e, String lineSeparator, String padding) {
    if(e == null) {
        return "null";
    }
    String str = e.getClass().getName() + ": ";
    if((e.getMessage() != null) && !e.getMessage().isEmpty()) {
        str += e.getMessage() + lineSeparator;
    } else {
        str += lineSeparator;
    }
    str += padding + stackTraceCausedByElementsOnlyToStr(e.getStackTrace(), lineSeparator, padding);
    for(Throwable suppressed : e.getSuppressed()) {
        str += padding + throwableToStrNoStackTraces(suppressed, lineSeparator, padding + "\t");
    }
    Throwable cause = e.getCause();
    while(cause != null) {
        str += padding + "Caused by:" + lineSeparator + throwableToStrNoStackTraces(e.getCause(), lineSeparator, padding);
        cause = cause.getCause();
    }
    return str;
}

/** @param e The {@link Throwable} to convert
 * @return The resulting String */
public static final String throwableToStr(Throwable e) {
    return throwableToStr(e, "\n");
}

/** @param e The {@link Throwable} to convert
 * @param lineSeparator The line separator to use
 * @return The resulting String */
public static final String throwableToStr(Throwable e, String lineSeparator) {
    return throwableToStr(e, lineSeparator, "");
}

/** @param e The {@link Throwable} to convert
 * @param lineSeparator The line separator to use
 * @param padding The string to be used at the start of each line
 * @return The resulting String */
public static final String throwableToStr(Throwable e, String lineSeparator, String padding) {
    if(e == null) {
        return "null";
    }
    String str = padding + e.getClass().getName() + ": ";
    if((e.getMessage() != null) && !e.getMessage().isEmpty()) {
        str += e.getMessage() + lineSeparator;
    } else {
        str += lineSeparator;
    }
    str += padding + stackTraceElementsToStr(e.getStackTrace(), lineSeparator, padding);
    for(Throwable suppressed : e.getSuppressed()) {
        str += padding + "Suppressed: " + throwableToStr(suppressed, lineSeparator, padding + "\t");
    }
    Throwable cause = e.getCause();
    while(cause != null) {
        str += padding + "Caused by:" + lineSeparator + throwableToStr(e.getCause(), lineSeparator, padding);
        cause = cause.getCause();
    }
    return str;
}

Example:

try(InputStream in = new FileInputStream(file)) {
    ...
} catch(IOException e) {
    String exceptionToString = throwableToStr(e);
    someLoggingUtility.println(exceptionToString);
    ...
}

Prints:

java.io.FileNotFoundException: C:\test.txt (The system cannot find the file specified)
    at java.io.FileInputStream.open0(Native Method)
    at java.io.FileInputStream.open(Unknown Source)
    at java.io.FileInputStream.<init>(Unknown Source)
    at com.gmail.br45entei.Example.main(Example.java:32)