Create a dynamic proxy for a class without no-argument constructor

Question

I want to create a proxy for a class instead of an interface. There are answers describing use of cglib or Javassist for this purpose (eg https://stackoverflow.com/a/4449998/ ), but I've run into a wrinkle, as the class I am interested in proxying doesn't have a no-argument constructor, so Enhancer.create() throws an exception. Looking at Javassist ProxyFactory javadoc, it needs constructor arguments as well.

The obvious workaround is finding constructor argument types by reflection and passing an array of nulls/0/etc. but this won't work if the constructor throws an exception.

Are there better alternatives (perhaps using some other library)?

Answer 1

You could use Objenesis which is implemented as a wrapper around several JVM specific classes. As a result, this library allows you to create an instance of a class without calling any of its constructors. However, using Objenesis is potentially unsafe since the JVM-specific classes are not portable or standardized. For this reason, libraries like Spring or Hibernate rather require a no-argument constructor.

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