了解正在发生的事情的最佳方法是直接通过 OpenJDK 网站访问源代码。如果我们看com.sun.tools.javac.api.JavacTool
public JavacTask getTask(Writer out,
JavaFileManager fileManager,
DiagnosticListener<? super JavaFileObject> diagnosticListener,
Iterable<String> options,
Iterable<String> classes,
Iterable<? extends JavaFileObject> compilationUnits)
{
try {
Context context = new Context();
ClientCodeWrapper ccw = ClientCodeWrapper.instance(context);
final String kindMsg = "All compilation units must be of SOURCE kind";
if (options != null)
for (String option : options)
option.getClass(); // null check
if (classes != null) {
for (String cls : classes)
if (!SourceVersion.isName(cls)) // implicit null check
throw new IllegalArgumentException("Not a valid class name: " + cls);
}
if (compilationUnits != null) {
compilationUnits = ccw.wrapJavaFileObjects(compilationUnits); // implicit null check
for (JavaFileObject cu : compilationUnits) {
if (cu.getKind() != JavaFileObject.Kind.SOURCE)
throw new IllegalArgumentException(kindMsg);
}
}
if (diagnosticListener != null)
context.put(DiagnosticListener.class, ccw.wrap(diagnosticListener));
if (out == null)
context.put(Log.outKey, new PrintWriter(System.err, true));
else
context.put(Log.outKey, new PrintWriter(out, true));
if (fileManager == null)
fileManager = getStandardFileManager(diagnosticListener, null, null);
fileManager = ccw.wrap(fileManager);
context.put(JavaFileManager.class, fileManager);
processOptions(context, fileManager, options);
Main compiler = new Main("javacTask", context.get(Log.outKey));
return new JavacTaskImpl(compiler, options, context, classes, compilationUnits);
} catch (ClientCodeException ex) {
throw new RuntimeException(ex.getCause());
}
}
您可以看到有问题的行：
if (!SourceVersion.isName(cls)) // implicit null check
throw new IllegalArgumentException("Not a valid class name: " + cls);
所以现在让我们看看 javax.lang.model.SourceVersion
/**
* Returns whether or not {@code name} is a syntactically valid
* qualified name in the latest source version. Unlike {@link
* #isIdentifier isIdentifier}, this method returns {@code false}
* for keywords and literals.
*
* @param name the string to check
* @return {@code true} if this string is a
* syntactically valid name, {@code false} otherwise.
* @jls 6.2 Names and Identifiers
*/
public static boolean isName(CharSequence name) {
String id = name.toString();
for(String s : id.split("\\.", -1)) {
if (!isIdentifier(s) || isKeyword(s))
return false;
}
return true;
}
所以你可以看到我们期望返回true（但返回false）的方法是：
public static boolean isIdentifier(CharSequence name) {
String id = name.toString();
if (id.length() == 0) {
return false;
}
int cp = id.codePointAt(0);
if (!Character.isJavaIdentifierStart(cp)) {
return false;
}
for (int i = Character.charCount(cp);
i < id.length();
i += Character.charCount(cp)) {
cp = id.codePointAt(i);
if (!Character.isJavaIdentifierPart(cp)) {
return false;
}
}
return true;
}
问题是 !Character.isJavaIdentifierPart(cp)
现在如果我们看一下 1.6 版本：
public static boolean isJavaIdentifierPart(int codePoint) {
boolean bJavaPart = false;
if (codePoint >= MIN_CODE_POINT && codePoint <= FAST_PATH_MAX) {
bJavaPart = CharacterDataLatin1.isJavaIdentifierPart(codePoint);
} else {
int plane = getPlane(codePoint);
switch(plane) {
case(0):
bJavaPart = CharacterData00.isJavaIdentifierPart(codePoint);
break;
case(1):
bJavaPart = CharacterData01.isJavaIdentifierPart(codePoint);
break;
case(2):
bJavaPart = CharacterData02.isJavaIdentifierPart(codePoint);
break;
case(3): // Undefined
case(4): // Undefined
case(5): // Undefined
case(6): // Undefined
case(7): // Undefined
case(8): // Undefined
case(9): // Undefined
case(10): // Undefined
case(11): // Undefined
case(12): // Undefined
case(13): // Undefined
bJavaPart = CharacterDataUndefined.isJavaIdentifierPart(codePoint);
break;
case(14):
bJavaPart = CharacterData0E.isJavaIdentifierPart(codePoint);
break;
case(15): // Private Use
case(16): // Private Use
bJavaPart = CharacterDataPrivateUse.isJavaIdentifierPart(codePoint);
break;
default:
// the argument's plane is invalid, and thus is an invalid codepoint
// bJavaPart remains false;
break;
}
}
return bJavaPart;
}
和 1.7 版本：
public static boolean isJavaIdentifierPart(int codePoint) {
return CharacterData.of(codePoint).isJavaIdentifierPart(codePoint);
}
这里发生了一些重构，如果你查看 CharacterData，你会发现它返回了一些类，这些类是在/openjdk/make/tools/GenerateCharacter/CharacterData**.java.template构建 java 分发时从模板中动态生成的：
// Character <= 0xff (basic latin) is handled by internal fast-path
// to avoid initializing large tables.
// Note: performance of this "fast-path" code may be sub-optimal
// in negative cases for some accessors due to complicated ranges.
// Should revisit after optimization of table initialization.
static final CharacterData of(int ch) {
if (ch >>> 8 == 0) { // fast-path
return CharacterDataLatin1.instance;
} else {
switch(ch >>> 16) { //plane 00-16
case(0):
return CharacterData00.instance;
case(1):
return CharacterData01.instance;
case(2):
return CharacterData02.instance;
case(14):
return CharacterData0E.instance;
case(15): // Private Use
case(16): // Private Use
return CharacterDataPrivateUse.instance;
default:
return CharacterDataUndefined.instance;
}
}
}
我认为您可以尝试在调试模式下运行 javah 并查看在这两种情况下会发生什么，然后将准确的错误报告发送给 OpenJDK 人员，因为此重构显然已经引入了错误。