JCH
Java Community | Help. Code. Learn.•3w ago
asdru

Java classfile api example

https://openjdk.org/jeps/457 can anyone provide an example of using this to get the contents of a class method? its relatively new tech and couldn't find it anywhere
6 Replies
JavaBot
JavaBot•3w ago
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asdru
asdruOP•3w ago
import java.io.File;
import java.io.IOException;
import java.lang.classfile.ClassFile;
import java.lang.classfile.FieldModel;
import java.lang.classfile.MethodModel;
import java.nio.file.Files;


void main() {

    var classModel = ClassFile.of().parse(getGivenClassBytes("/src/main/java/Person"));
    for (var classElement : classModel) {
        switch (classElement) {
            case MethodModel mm ->
                    System.out.printf("Method name %s type %s%n", mm.methodName().stringValue(), mm.methodType().stringValue());
            case FieldModel fm ->
                    System.out.printf("Field name %s type %s%n", fm.fieldName().stringValue(), fm.fieldType().stringValue());

            default -> {
            }
        }
    }
}

private static byte[] getGivenClassBytes(final String className) {
    try {
        var path = System.getProperty("user.dir") + "/" + className + ".class";
        File file = new File(path);
        return Files.readAllBytes(file.toPath());
    } catch (IOException ioe) {
        throw new RuntimeException(ioe.getMessage());
    }
}
import java.io.File;
import java.io.IOException;
import java.lang.classfile.ClassFile;
import java.lang.classfile.FieldModel;
import java.lang.classfile.MethodModel;
import java.nio.file.Files;


void main() {

    var classModel = ClassFile.of().parse(getGivenClassBytes("/src/main/java/Person"));
    for (var classElement : classModel) {
        switch (classElement) {
            case MethodModel mm ->
                    System.out.printf("Method name %s type %s%n", mm.methodName().stringValue(), mm.methodType().stringValue());
            case FieldModel fm ->
                    System.out.printf("Field name %s type %s%n", fm.fieldName().stringValue(), fm.fieldType().stringValue());

            default -> {
            }
        }
    }
}

private static byte[] getGivenClassBytes(final String className) {
    try {
        var path = System.getProperty("user.dir") + "/" + className + ".class";
        File file = new File(path);
        return Files.readAllBytes(file.toPath());
    } catch (IOException ioe) {
        throw new RuntimeException(ioe.getMessage());
    }
}
i got this basic example but i still cant get it to print the contents of the function like 
func @"sub" @loc="19:5:file:/.../ExpressionGraphs.java" (%0 : double, %1 : double)double -> {
    %2 : Var<double> = var %0 @"a" @loc="19:5";
    %3 : Var<double> = var %1 @"b" @loc="19:5";
    %4 : double = var.load %2 @loc="21:16";
    %5 : double = var.load %3 @loc="21:20";
    %6 : double = sub %4 %5 @loc="21:16";
    return %6 @loc="21:9";
};
func @"sub" @loc="19:5:file:/.../ExpressionGraphs.java" (%0 : double, %1 : double)double -> {
    %2 : Var<double> = var %0 @"a" @loc="19:5";
    %3 : Var<double> = var %1 @"b" @loc="19:5";
    %4 : double = var.load %2 @loc="21:16";
    %5 : double = var.load %3 @loc="21:20";
    %6 : double = sub %4 %5 @loc="21:16";
    return %6 @loc="21:9";
};
dan1st
dan1st•3w ago
Just mm.code()? and then iterate icer it in a foreach loop and finally you can switch over that
JavaBot
JavaBot•3w ago
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nothing
nothing•3w ago
nice
JavaBot
JavaBot•3w ago
💤 Post marked as dormant
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