How to subclass an abstract class with 1+ args constructor using ByteBuddy

I would like to proxy java.net.HttpURLConnection which has one constructor: HttpURLConnection(URL u). How can I subclass such a class with ByteBuddy without creating custom "Empty" class with the non-arg constructor?

HttpURLConnection(URL u)

new ByteBuddy().subclass(HttpURLConnection.class)
.method(ElementMatchers.any())
.intercept(InvocationHandlerAdapter.of(proxyHandler))
.make()
.load(HttpURLConnection.class.getClassLoader())
.getLoaded()
.newInstance();


Currently, it fails due to

Caused by: java.lang.NoSuchMethodException: net.bytebuddy.renamed.java.net.HttpURLConnection$ByteBuddy$Mr8B9wE2.<init>()
at java.lang.Class.getConstructor0(Class.java:3082)


I would like to delegate a custom URL to that super constructor it is possible.

URL

But if I create a custom class

public class ProxiedHttpURLConnection extends HttpURLConnection

protected ProxiedHttpURLConnection()
super(null); // <---





and use that one in new ByteBuddy().subclass(ProxiedHttpURLConnection.class) it works fine. There is simple issue with a contractor, not quite sure how to do it.

new ByteBuddy().subclass(ProxiedHttpURLConnection.class)

1 Answer
1

You can define a custom constructor and invoke a specific super constructor using the MethodCall instrumentation, e.g.

MethodCall

builder = builder.defineConstructor(Visibility.PUBLIC)
.intercept(MethodCall.invoke(HttpURLConnection.class.getDeclaredConstructor(URL.class))
.with((Object) null))


By default, Byte Buddy immitates the super class constructors, you can therefore lookup a declared constructor that takes a URL and provide the null argument manually.

You can avoid this creation by defining a ConstructorStrategy as a second argument to subclass.

ConstructorStrategy

subclass

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