package org.junit.internal;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.PrintWriter;
import java.io.StringReader;
import java.io.StringWriter;
import java.lang.reflect.Method;
import java.util.AbstractList;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
/**
* Miscellaneous functions dealing with {@code Throwable}.
*
* @author kcooney@google.com (Kevin Cooney)
* @since 4.12
*/
public final class Throwables {
private Throwables() {
}
/**
* Rethrows the given {@code Throwable}, allowing the caller to
* declare that it throws {@code Exception}. This is useful when
* your callers have nothing reasonable they can do when a
* {@code Throwable} is thrown. This is declared to return {@code Exception}
* so it can be used in a {@code throw} clause:
* <pre>
* try {
* doSomething();
* } catch (Throwable e} {
* throw Throwables.rethrowAsException(e);
* }
* doSomethingLater();
* </pre>
*
* @param e exception to rethrow
* @return does not return anything
* @since 4.12
*/
public static Exception rethrowAsException(Throwable e) throws Exception {
Throwables.<Exception>rethrow(e);
return null; // we never get here
}
@SuppressWarnings("unchecked")
private static <T extends Throwable> void rethrow(Throwable e) throws T {
throw (T) e;
}
/**
* Returns the stacktrace of the given Throwable as a String.
*
* @since 4.13
*/
public static String getStacktrace(Throwable exception) {
StringWriter stringWriter = new StringWriter();
PrintWriter writer = new PrintWriter(stringWriter);
exception.printStackTrace(writer);
return stringWriter.toString();
}
/**
* Gets a trimmed version of the stack trace of the given exception. Stack trace
* elements that are below the test method are filtered out.
*
* @return a trimmed stack trace, or the original trace if trimming wasn't possible
*/
public static String getTrimmedStackTrace(Throwable exception) {
List<String> trimmedStackTraceLines = getTrimmedStackTraceLines(exception);
if (trimmedStackTraceLines.isEmpty()) {
return getFullStackTrace(exception);
}
StringBuilder result = new StringBuilder(exception.toString());
appendStackTraceLines(trimmedStackTraceLines, result);
appendStackTraceLines(getCauseStackTraceLines(exception), result);
return result.toString();
}
private static List<String> getTrimmedStackTraceLines(Throwable exception) {
List<StackTraceElement> stackTraceElements = Arrays.asList(exception.getStackTrace());
int linesToInclude = stackTraceElements.size();
State state = State.PROCESSING_OTHER_CODE;
for (StackTraceElement stackTraceElement : asReversedList(stackTraceElements)) {
state = state.processStackTraceElement(stackTraceElement);
if (state == State.DONE) {
List<String> trimmedLines = new ArrayList<String>(linesToInclude + 2);
trimmedLines.add("");
for (StackTraceElement each : stackTraceElements.subList(0, linesToInclude)) {
trimmedLines.add(" at " + each);
}
if (exception.getCause() != null) {
trimmedLines.add(" ... " + (stackTraceElements.size() - trimmedLines.size()) + " trimmed");
}
return trimmedLines;
}
linesToInclude--;
}
return Collections.emptyList();
}
private static final Method getSuppressed = initGetSuppressed();
private static Method initGetSuppressed() {
try {
return Throwable.class.getMethod("getSuppressed");
} catch (Throwable e) {
return null;
}
}
private static boolean hasSuppressed(Throwable exception) {
if (getSuppressed == null) {
return false;
}
try {
Throwable[] suppressed = (Throwable[]) getSuppressed.invoke(exception);
return suppressed.length != 0;
} catch (Throwable e) {
return false;
}
}
private static List<String> getCauseStackTraceLines(Throwable exception) {
if (exception.getCause() != null || hasSuppressed(exception)) {
String fullTrace = getFullStackTrace(exception);
BufferedReader reader = new BufferedReader(
new StringReader(fullTrace.substring(exception.toString().length())));
List<String> causedByLines = new ArrayList<String>();
try {
String line;
while ((line = reader.readLine()) != null) {
if (line.startsWith("Caused by: ") || line.trim().startsWith("Suppressed: ")) {
causedByLines.add(line);
while ((line = reader.readLine()) != null) {
causedByLines.add(line);
}
return causedByLines;
}
}
} catch (IOException e) {
// We should never get here, because we are reading from a StringReader
}
}
return Collections.emptyList();
}
private static String getFullStackTrace(Throwable exception) {
StringWriter stringWriter = new StringWriter();
PrintWriter writer = new PrintWriter(stringWriter);
exception.printStackTrace(writer);
return stringWriter.toString();
}
private static void appendStackTraceLines(
List<String> stackTraceLines, StringBuilder destBuilder) {
for (String stackTraceLine : stackTraceLines) {
destBuilder.append(String.format("%s%n", stackTraceLine));
}
}
private static <T> List<T> asReversedList(final List<T> list) {
return new AbstractList<T>() {
@Override
public T get(int index) {
return list.get(list.size() - index - 1);
}
@Override
public int size() {
return list.size();
}
};
}
private enum State {
PROCESSING_OTHER_CODE {
@Override public State processLine(String methodName) {
if (isTestFrameworkMethod(methodName)) {
return PROCESSING_TEST_FRAMEWORK_CODE;
}
return this;
}
},
PROCESSING_TEST_FRAMEWORK_CODE {
@Override public State processLine(String methodName) {
if (isReflectionMethod(methodName)) {
return PROCESSING_REFLECTION_CODE;
} else if (isTestFrameworkMethod(methodName)) {
return this;
}
return PROCESSING_OTHER_CODE;
}
},
PROCESSING_REFLECTION_CODE {
@Override public State processLine(String methodName) {
if (isReflectionMethod(methodName)) {
return this;
} else if (isTestFrameworkMethod(methodName)) {
// This is here to handle TestCase.runBare() calling TestCase.runTest().
return PROCESSING_TEST_FRAMEWORK_CODE;
}
return DONE;
}
},
DONE {
@Override public State processLine(String methodName) {
return this;
}
};
/** Processes a stack trace element method name, possibly moving to a new state. */
protected abstract State processLine(String methodName);
/** Processes a stack trace element, possibly moving to a new state. */
public final State processStackTraceElement(StackTraceElement element) {
return processLine(element.getClassName() + "." + element.getMethodName() + "()");
}
}
private static final String[] TEST_FRAMEWORK_METHOD_NAME_PREFIXES = {
"org.junit.runner.",
"org.junit.runners.",
"org.junit.experimental.runners.",
"org.junit.internal.",
"junit.extensions",
"junit.framework",
"junit.runner",
"junit.textui",
};
private static final String[] TEST_FRAMEWORK_TEST_METHOD_NAME_PREFIXES = {
"org.junit.internal.StackTracesTest",
};
private static boolean isTestFrameworkMethod(String methodName) {
return isMatchingMethod(methodName, TEST_FRAMEWORK_METHOD_NAME_PREFIXES) &&
!isMatchingMethod(methodName, TEST_FRAMEWORK_TEST_METHOD_NAME_PREFIXES);
}
private static final String[] REFLECTION_METHOD_NAME_PREFIXES = {
"sun.reflect.",
"java.lang.reflect.",
"jdk.internal.reflect.",
"org.junit.rules.RunRules.<init>(",
"org.junit.rules.RunRules.applyAll(", // calls TestRules
"org.junit.runners.RuleContainer.apply(", // calls MethodRules & TestRules
"junit.framework.TestCase.runBare(", // runBare() directly calls setUp() and tearDown()
};
private static boolean isReflectionMethod(String methodName) {
return isMatchingMethod(methodName, REFLECTION_METHOD_NAME_PREFIXES);
}
private static boolean isMatchingMethod(String methodName, String[] methodNamePrefixes) {
for (String methodNamePrefix : methodNamePrefixes) {
if (methodName.startsWith(methodNamePrefix)) {
return true;
}
}
return false;
}
}