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Formatting exception message #16

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5211a23
Fixed class saving and formatting exception message
Chaarlesss Jan 13, 2017
539f90c
Verify the transformedClass is not null before using it
Chaarlesss Jan 14, 2017
b61e5a9
Removed NPE security
Chaarlesss Jan 14, 2017
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21 changes: 13 additions & 8 deletions src/main/java/net/minecraft/launchwrapper/LaunchClassLoader.java
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Original file line number Diff line number Diff line change
Expand Up @@ -168,22 +168,27 @@ public Class<?> findClass(final String name) throws ClassNotFoundException {
}

final byte[] transformedClass = runTransformers(untransformedName, transformedName, getClassBytes(untransformedName));
if (DEBUG_SAVE) {
saveTransformedClass(transformedClass, transformedName);
}

final CodeSource codeSource = urlConnection == null ? null : new CodeSource(urlConnection.getURL(), signers);
final Class<?> clazz = defineClass(transformedName, transformedClass, 0, transformedClass.length, codeSource);
cachedClasses.put(transformedName, clazz);
return clazz;
if (transformedClass != null) {
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@LexManos LexManos Jan 14, 2017

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Honestly I don't think there is anything wrong with skipping the null check here. If it is null then it throws an exception which is caught and logged below. Thus adding more detail to the stack trace. More details, the better. So I don't see a need for this protection.

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@thiakil thiakil May 10, 2018

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IMO it is worth checking it, as otherwise it will NPE when trying to save the transformed class (DEBUG_SAVE == true), and when not debug saving, the exception it does print points to the classloader itself NPEing, not that it couldn't find the class source.

There's also zero point going through the transformer list with null bytes, unless you're expecting one of them might provide the data?!

if(DEBUG_SAVE) {
saveTransformedClass(transformedClass, transformedName);
}

final CodeSource codeSource = urlConnection == null ? null : new CodeSource(urlConnection.getURL(), signers);
final Class<?> clazz = defineClass(transformedName, transformedClass, 0, transformedClass.length, codeSource);
cachedClasses.put(transformedName, clazz);
return clazz;
}
} catch (Throwable e) {
invalidClasses.add(name);
if (DEBUG) {
LogWrapper.log(Level.TRACE, e, "Exception encountered attempting classloading of %s", name);
LogManager.getLogger("LaunchWrapper").log(Level.ERROR, "Exception encountered attempting classloading of %s", e);
LogManager.getLogger("LaunchWrapper").log(Level.ERROR, String.format("Exception encountered attempting classloading of %s", name), e);
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@LexManos LexManos Jan 14, 2017

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This however, is fine, cuz derp.

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@jamierocks jamierocks Jan 23, 2018 •
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Why not use the proper log4j way of doing things - basically replace %s for {}, no String#format(String) needed.

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@thiakil thiakil May 10, 2018

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@jamierocks There does not appear to be an interface method that takes both a Throwable and params.

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@Pokechu22 Pokechu22 May 10, 2018

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I believe that log4j knows to use the last parameter as a Throwable when taking a series of other parameters; however, I cannot find a source.

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@mezz mezz May 12, 2018

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I would write it this way:

LogManager.getLogger("LaunchWrapper").error("Exception encountered attempting classloading of {}", name, e);

Internally the logger creates a FormattedMessage which can take a Throwable as the last argument:
https://logging.apache.org/log4j/log4j-2.1/log4j-api/apidocs/org/apache/logging/log4j/message/FormattedMessage.html

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@thiakil thiakil May 12, 2018

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Tracing through it doesn't use that constructor from the varargs method, but it does appear poke was correct as it seems to scan it at org.apache.logging.log4j.message.ParameterizedMessage#parseArguments

}
throw new ClassNotFoundException(name, e);
}

throw new ClassNotFoundException(name);
}

private void saveTransformedClass(final byte[] data, final String transformedName) {
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