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jdk-classfile-preview's Introduction

Unofficial JDK Classfile API Backport

Maven Central

This is a (very) unofficial backport to JDK 17 of the new classfile API found in JDK 21 and later. That API is non-public (not even preview) at the time of this writing, so this project gives no compatibility guarnatees and in fact may break compatibility at any time with no notice.

However, it should suffice to allow projects to test out the new API and give feedback which could then potentially even be relayed to the upstream project.

Bugs in this project should be reported to https://github.com/dmlloyd/jdk-classfile-preview/issues first. Bugs in this project are likely to be a result of backporting. Some bugs might be relayed upstream by the project maintainer(s), subject to testing and verification; in this case, the upstream bug will be linked for easier tracking.

Releases

There is, at present, no release schedule. The maintainer(s) may, at their discretion and at any time, update the upstream snapshot, and manually apply differences from the upstream project into the downstream backport.

If you encounter a bug which has been fixed in this project but not yet released, feel free to open an issue to request a release.

Getting started

After adding the appropriate Maven dependency (see the Maven release badge above), the easiest entry points are:

For parsing a class:

byte[] b = Files.readAllBytes(Path.of("some/file.class"));
ClassModel model = ClassFile.of().parse(b);
// now, do something with `model`...

Or for writing a class:

byte[] b = ClassFile.of().build(classDesc, classBuilder -> {
    // ... build the class here ...
});

jdk-classfile-preview's People

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Forkers

lwr84 scottmarlow

jdk-classfile-preview's Issues

Crash in signature parser, would like something easier to understand

Compiling and running the following code crash with

import io.github.dmlloyd.classfile.ClassSignature;

public class Crash {
    public static void main(String[] args) {
	String goodSignature = "Ljava/lang/Object;Ljava/lang/Iterable<LFoo;>;";
	String badSignature = "Ljava/lang/Object;Ljava/lang/Iterable<LFoo;>";

	System.out.println ("Trying to parse good signature");
	ClassSignature.parseFrom (goodSignature);
	System.out.println ("Trying to parse bad signature");
	ClassSignature.parseFrom (badSignature);
    }
}

The stack trace looks like:

Exception in thread "main" java.lang.StringIndexOutOfBoundsException: Index 44 out of bounds for length 44
	at java.base/jdk.internal.util.Preconditions$1.apply(Preconditions.java:55)
	at java.base/jdk.internal.util.Preconditions$1.apply(Preconditions.java:52)
	at java.base/jdk.internal.util.Preconditions$4.apply(Preconditions.java:213)
	at java.base/jdk.internal.util.Preconditions$4.apply(Preconditions.java:210)
	at java.base/jdk.internal.util.Preconditions.outOfBounds(Preconditions.java:98)
	at java.base/jdk.internal.util.Preconditions.outOfBoundsCheckIndex(Preconditions.java:106)
	at java.base/jdk.internal.util.Preconditions.checkIndex(Preconditions.java:302)
	at java.base/java.lang.String.checkIndex(String.java:4828)
	at java.base/java.lang.StringLatin1.charAt(StringLatin1.java:46)
	at java.base/java.lang.String.charAt(String.java:1555)
	at io.github.dmlloyd.classfile.impl.SignaturesImpl.referenceTypeSig(SignaturesImpl.java:137)
	at io.github.dmlloyd.classfile.impl.SignaturesImpl.parseClassSignature(SignaturesImpl.java:53)
	at io.github.dmlloyd.classfile.ClassSignature.parseFrom(ClassSignature.java:80)
	at Crash.main(Crash.java:12)

The SIOIBE is hard to understand!
I would be fine with a crash, if it was a bit more helpful, perhaps "IllegalArgumentException: invalid signature" and if it could also say "Missing ";" at position 44" then that would be great.

Documentation still uses Classfile, but the name was changed to ClassFile

Looking at the web page and we find "ClassModel model = Classfile.of().parse(b);" as one example of how to use the library.
This does not compile. The class name was changed in a recent merge to ClassFile.

This affects the README.md file, but possibly also other files in the project.

Expected:
Updates to the documentation/examples.

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