JD-Core

JD-Core is a Java decompiler written in Java.

This is a fork of the original JD-Core project, which is no longer maintained. I tried to fix and update dependencies to make it live longer and be useful for the community. If you have a good knowledge of Java and want to help, feel free to contribute. 😃

• Java Decompiler project home page: https://java-decompiler.github.io
• JD-Core source code: https://github.com/QuentiumYT/jd-core
• JD-GUI public releases: https://launchpad.net/~quentiumyt/+archive/ubuntu/jd-gui

Description

JD-Core is a standalone Java library containing the Java decompiler of "Java Decompiler project". It support Java 1.1.8 (not tested) to Java 17 (recently added), including Lambda expressions, method references and default methods. JD-Core is the engine of JD-GUI.

How to build JD-Core ?

> git clone https://github.com/QuentiumYT/jd-core.git
> cd jd-core/
> ./gradlew build

generate "build/libs/jd-core-x.y.z.jar"

How to use JD-Core ?

1. Implement the org.jd.core.loader.Loader interface,
2. Implement the org.jd.core.printer.Printer interface,
3. And call the method "decompile(loader, printer, internalTypeName);"

Example

1. Implement the Loader interface:

Loader loader = new Loader() {
    @Override
    public byte[] load(String internalName) throws LoaderException {
        InputStream is = this.getClass().getResourceAsStream("/" + internalName + ".class");

        if (is == null) {
            return null;
        } else {
            try (InputStream in=is; ByteArrayOutputStream out=new ByteArrayOutputStream()) {
                byte[] buffer = new byte[1024];
                int read = in.read(buffer);

                while (read > 0) {
                    out.write(buffer, 0, read);
                    read = in.read(buffer);
                }

                return out.toByteArray();
            } catch (IOException e) {
                throw new LoaderException(e);
            }
        }
    }

    @Override
    public boolean canLoad(String internalName) {
        return this.getClass().getResource("/" + internalName + ".class") != null;
    }
};

2. Implement the Printer interface

Printer printer = new Printer() {
    protected static final String TAB = "  ";
    protected static final String NEWLINE = "\n";

    protected int indentationCount = 0;
    protected StringBuilder sb = new StringBuilder();

    @Override public String toString() { return sb.toString(); }

    @Override public void start(int maxLineNumber, int majorVersion, int minorVersion) {}
    @Override public void end() {}

    @Override public void printText(String text) { sb.append(text); }
    @Override public void printNumericConstant(String constant) { sb.append(constant); }
    @Override public void printStringConstant(String constant, String ownerInternalName) { sb.append(constant); }
    @Override public void printKeyword(String keyword) { sb.append(keyword); }
    @Override public void printDeclaration(int type, String internalTypeName, String name, String descriptor) { sb.append(name); }
    @Override public void printReference(int type, String internalTypeName, String name, String descriptor, String ownerInternalName) { sb.append(name); }

    @Override public void indent() { this.indentationCount++; }
    @Override public void unindent() { this.indentationCount--; }

    @Override public void startLine(int lineNumber) { for (int i=0; i<indentationCount; i++) sb.append(TAB); }
    @Override public void endLine() { sb.append(NEWLINE); }
    @Override public void extraLine(int count) { while (count-- > 0) sb.append(NEWLINE); }

    @Override public void startMarker(int type) {}
    @Override public void endMarker(int type) {}
};

3. And call the method "decompile(loader, printer, internalTypeName);"

ClassFileToJavaSourceDecompiler decompiler = new ClassFileToJavaSourceDecompiler();

decompiler.decompile(loader, printer, "path/to/YourClass");

String source = printer.toString();

License

Released under the GNU GPL v3.