001package org.junit.internal; 002 003import java.io.BufferedReader; 004import java.io.IOException; 005import java.io.PrintWriter; 006import java.io.StringReader; 007import java.io.StringWriter; 008import java.lang.reflect.Method; 009import java.util.AbstractList; 010import java.util.ArrayList; 011import java.util.Arrays; 012import java.util.Collections; 013import java.util.List; 014 015/** 016 * Miscellaneous functions dealing with {@code Throwable}. 017 * 018 * @author kcooney@google.com (Kevin Cooney) 019 * @since 4.12 020 */ 021public final class Throwables { 022 023 private Throwables() { 024 } 025 026 /** 027 * Rethrows the given {@code Throwable}, allowing the caller to 028 * declare that it throws {@code Exception}. This is useful when 029 * your callers have nothing reasonable they can do when a 030 * {@code Throwable} is thrown. This is declared to return {@code Exception} 031 * so it can be used in a {@code throw} clause: 032 * <pre> 033 * try { 034 * doSomething(); 035 * } catch (Throwable e} { 036 * throw Throwables.rethrowAsException(e); 037 * } 038 * doSomethingLater(); 039 * </pre> 040 * 041 * @param e exception to rethrow 042 * @return does not return anything 043 * @since 4.12 044 */ 045 public static Exception rethrowAsException(Throwable e) throws Exception { 046 Throwables.<Exception>rethrow(e); 047 return null; // we never get here 048 } 049 050 @SuppressWarnings("unchecked") 051 private static <T extends Throwable> void rethrow(Throwable e) throws T { 052 throw (T) e; 053 } 054 055 /** 056 * Returns the stacktrace of the given Throwable as a String. 057 * 058 * @since 4.13 059 */ 060 public static String getStacktrace(Throwable exception) { 061 StringWriter stringWriter = new StringWriter(); 062 PrintWriter writer = new PrintWriter(stringWriter); 063 exception.printStackTrace(writer); 064 return stringWriter.toString(); 065 } 066 067 /** 068 * Gets a trimmed version of the stack trace of the given exception. Stack trace 069 * elements that are below the test method are filtered out. 070 * 071 * @return a trimmed stack trace, or the original trace if trimming wasn't possible 072 */ 073 public static String getTrimmedStackTrace(Throwable exception) { 074 List<String> trimmedStackTraceLines = getTrimmedStackTraceLines(exception); 075 if (trimmedStackTraceLines.isEmpty()) { 076 return getFullStackTrace(exception); 077 } 078 079 StringBuilder result = new StringBuilder(exception.toString()); 080 appendStackTraceLines(trimmedStackTraceLines, result); 081 appendStackTraceLines(getCauseStackTraceLines(exception), result); 082 return result.toString(); 083 } 084 085 private static List<String> getTrimmedStackTraceLines(Throwable exception) { 086 List<StackTraceElement> stackTraceElements = Arrays.asList(exception.getStackTrace()); 087 int linesToInclude = stackTraceElements.size(); 088 089 State state = State.PROCESSING_OTHER_CODE; 090 for (StackTraceElement stackTraceElement : asReversedList(stackTraceElements)) { 091 state = state.processStackTraceElement(stackTraceElement); 092 if (state == State.DONE) { 093 List<String> trimmedLines = new ArrayList<String>(linesToInclude + 2); 094 trimmedLines.add(""); 095 for (StackTraceElement each : stackTraceElements.subList(0, linesToInclude)) { 096 trimmedLines.add("\tat " + each); 097 } 098 if (exception.getCause() != null) { 099 trimmedLines.add("\t... " + (stackTraceElements.size() - trimmedLines.size()) + " trimmed"); 100 } 101 return trimmedLines; 102 } 103 linesToInclude--; 104 } 105 return Collections.emptyList(); 106 } 107 108 private static final Method getSuppressed = initGetSuppressed(); 109 110 private static Method initGetSuppressed() { 111 try { 112 return Throwable.class.getMethod("getSuppressed"); 113 } catch (Throwable e) { 114 return null; 115 } 116 } 117 118 private static boolean hasSuppressed(Throwable exception) { 119 if (getSuppressed == null) { 120 return false; 121 } 122 try { 123 Throwable[] suppressed = (Throwable[]) getSuppressed.invoke(exception); 124 return suppressed.length != 0; 125 } catch (Throwable e) { 126 return false; 127 } 128 } 129 130 private static List<String> getCauseStackTraceLines(Throwable exception) { 131 if (exception.getCause() != null || hasSuppressed(exception)) { 132 String fullTrace = getFullStackTrace(exception); 133 BufferedReader reader = new BufferedReader( 134 new StringReader(fullTrace.substring(exception.toString().length()))); 135 List<String> causedByLines = new ArrayList<String>(); 136 137 try { 138 String line; 139 while ((line = reader.readLine()) != null) { 140 if (line.startsWith("Caused by: ") || line.trim().startsWith("Suppressed: ")) { 141 causedByLines.add(line); 142 while ((line = reader.readLine()) != null) { 143 causedByLines.add(line); 144 } 145 return causedByLines; 146 } 147 } 148 } catch (IOException e) { 149 // We should never get here, because we are reading from a StringReader 150 } 151 } 152 153 return Collections.emptyList(); 154 } 155 156 private static String getFullStackTrace(Throwable exception) { 157 StringWriter stringWriter = new StringWriter(); 158 PrintWriter writer = new PrintWriter(stringWriter); 159 exception.printStackTrace(writer); 160 return stringWriter.toString(); 161 } 162 163 private static void appendStackTraceLines( 164 List<String> stackTraceLines, StringBuilder destBuilder) { 165 for (String stackTraceLine : stackTraceLines) { 166 destBuilder.append(String.format("%s%n", stackTraceLine)); 167 } 168 } 169 170 private static <T> List<T> asReversedList(final List<T> list) { 171 return new AbstractList<T>() { 172 173 @Override 174 public T get(int index) { 175 return list.get(list.size() - index - 1); 176 } 177 178 @Override 179 public int size() { 180 return list.size(); 181 } 182 }; 183 } 184 185 private enum State { 186 PROCESSING_OTHER_CODE { 187 @Override public State processLine(String methodName) { 188 if (isTestFrameworkMethod(methodName)) { 189 return PROCESSING_TEST_FRAMEWORK_CODE; 190 } 191 return this; 192 } 193 }, 194 PROCESSING_TEST_FRAMEWORK_CODE { 195 @Override public State processLine(String methodName) { 196 if (isReflectionMethod(methodName)) { 197 return PROCESSING_REFLECTION_CODE; 198 } else if (isTestFrameworkMethod(methodName)) { 199 return this; 200 } 201 return PROCESSING_OTHER_CODE; 202 } 203 }, 204 PROCESSING_REFLECTION_CODE { 205 @Override public State processLine(String methodName) { 206 if (isReflectionMethod(methodName)) { 207 return this; 208 } else if (isTestFrameworkMethod(methodName)) { 209 // This is here to handle TestCase.runBare() calling TestCase.runTest(). 210 return PROCESSING_TEST_FRAMEWORK_CODE; 211 } 212 return DONE; 213 } 214 }, 215 DONE { 216 @Override public State processLine(String methodName) { 217 return this; 218 } 219 }; 220 221 /** Processes a stack trace element method name, possibly moving to a new state. */ 222 protected abstract State processLine(String methodName); 223 224 /** Processes a stack trace element, possibly moving to a new state. */ 225 public final State processStackTraceElement(StackTraceElement element) { 226 return processLine(element.getClassName() + "." + element.getMethodName() + "()"); 227 } 228 } 229 230 private static final String[] TEST_FRAMEWORK_METHOD_NAME_PREFIXES = { 231 "org.junit.runner.", 232 "org.junit.runners.", 233 "org.junit.experimental.runners.", 234 "org.junit.internal.", 235 "junit.extensions", 236 "junit.framework", 237 "junit.runner", 238 "junit.textui", 239 }; 240 241 private static final String[] TEST_FRAMEWORK_TEST_METHOD_NAME_PREFIXES = { 242 "org.junit.internal.StackTracesTest", 243 }; 244 245 private static boolean isTestFrameworkMethod(String methodName) { 246 return isMatchingMethod(methodName, TEST_FRAMEWORK_METHOD_NAME_PREFIXES) && 247 !isMatchingMethod(methodName, TEST_FRAMEWORK_TEST_METHOD_NAME_PREFIXES); 248 } 249 250 private static final String[] REFLECTION_METHOD_NAME_PREFIXES = { 251 "sun.reflect.", 252 "java.lang.reflect.", 253 "jdk.internal.reflect.", 254 "org.junit.rules.RunRules.<init>(", 255 "org.junit.rules.RunRules.applyAll(", // calls TestRules 256 "org.junit.runners.RuleContainer.apply(", // calls MethodRules & TestRules 257 "junit.framework.TestCase.runBare(", // runBare() directly calls setUp() and tearDown() 258 }; 259 260 private static boolean isReflectionMethod(String methodName) { 261 return isMatchingMethod(methodName, REFLECTION_METHOD_NAME_PREFIXES); 262 } 263 264 private static boolean isMatchingMethod(String methodName, String[] methodNamePrefixes) { 265 for (String methodNamePrefix : methodNamePrefixes) { 266 if (methodName.startsWith(methodNamePrefix)) { 267 return true; 268 } 269 } 270 271 return false; 272 } 273}