Java 和类型擦除 - 如何从字符串“MyClass”生成 MyClass.class

Question

So I have a parameterized handler type where the type is a subclass of MessageBase .

public class ResponseHandler<T extends MessageBase> {

    private final T message;

    private ResponseHandler(final Class<T> clazz) {
        this.message = get(clazz);
    }

    public static <T extends MessageBase> ResponseHandler<T> of(Class<T> clazz) {
        return new ResponseHandler<>(clazz);
    }

    private T get(Class<T> clazz) {
        ...
    }
}

I also have a subset of DerivedMessage classes like DerivedMessage1 and DerivedMessage2 which both extend MessageBase . I want to be able to create the right ResponseHandler based on a string of the class name like this:

// defined some String s;
if (s == "com.package.DerivedMessage1") {
    ResponseHandler<DerivedMessage1> h1 = ResponseHandler.of(DerivedMessage1.class);
    // do something with h1
} else if (s == "com.package.DerivedMessage2") {
    ResponseHandler<DerivedMessage2> h2 = ResponseHandler.of(DerivedMessage2.class);
    // do something with h2
}

But I'm wondering if there's a way to do this generically for all DerivedMessage classes, which derive from MessageBase . I haven't found a way to do the DerivedMessage1.class from a string like "com.package.DerivedMessage1". I've tried Class.forName(string) , but it returns a weird capture? type that confuses me. Is there a way to accomplish this, or do I have to stick to the if statements?

Answer 1

you can use getCanonicalName() .

For example: DerivedMessage1.class.getCanonicalName() returns "com.package.DerivedMessage1"

so the conditions becomes

if (DerivedMessage1.class. getCanonicalName().equals(s))) {
    ResponseHandler<DerivedMessage1> h1 = ResponseHandler.of(DerivedMessage1.class);
    // do something with h1
}