Examples with ClassWriter com.sun.tools.classfile.ClassWriter used on opensource projects

Example 1 with ClassWriter

use of com.sun.tools.classfile.ClassWriter in project jdk8u_jdk by JetBrains.

the class RemoveMethods method main.

public static void main(String[] args) throws Exception {
    if (args.length < 2) {
        System.err.println("Usage: java RemoveMethods classfile output [method...]");
        System.exit(-1);
    }
    // class file to read
    Path input = Paths.get(args[0]);
    // class file to write, if directory then use the name of the input
    Path output = Paths.get(args[1]);
    if (Files.isDirectory(output))
        output = output.resolve(input.getFileName());
    // the methods to remove
    Set<String> methodsToRemove = new HashSet<>();
    int i = 2;
    while (i < args.length) methodsToRemove.add(args[i++]);
    // read class file
    ClassFile cf;
    try (InputStream in = Files.newInputStream(input)) {
        cf = ClassFile.read(in);
    }
    final int magic = cf.magic;
    final int major_version = cf.major_version;
    final int minor_version = cf.minor_version;
    final ConstantPool cp = cf.constant_pool;
    final AccessFlags access_flags = cf.access_flags;
    final int this_class = cf.this_class;
    final int super_class = cf.super_class;
    final int[] interfaces = cf.interfaces;
    final Field[] fields = cf.fields;
    final Attributes class_attrs = cf.attributes;
    // remove the requested methods, no signature check at this time
    Method[] methods = cf.methods;
    i = 0;
    while (i < methods.length) {
        Method m = methods[i];
        String name = m.getName(cp);
        if (methodsToRemove.contains(name)) {
            int len = methods.length;
            Method[] newMethods = new Method[len - 1];
            if (i > 0)
                System.arraycopy(methods, 0, newMethods, 0, i);
            int after = methods.length - i - 1;
            if (after > 0)
                System.arraycopy(methods, i + 1, newMethods, i, after);
            methods = newMethods;
            String paramTypes = m.descriptor.getParameterTypes(cp);
            System.out.format("Removed method %s%s from %s%n", name, paramTypes, cf.getName());
            continue;
        }
        i++;
    }
    // TBD, prune constant pool of entries that are no longer referenced
    // re-write class file
    cf = new ClassFile(magic, minor_version, major_version, cp, access_flags, this_class, super_class, interfaces, fields, methods, class_attrs);
    try (OutputStream out = Files.newOutputStream(output)) {
        new ClassWriter().write(cf, out);
    }
}