Java调试器找到实例化对象的位置

Question

I'm debugging with Eclipse and got a parameter which is an anonymous-instantiated-interface. Is there a way to find out where it was created?

Answer 1

Unless you do a step by step debugging from the start of your application, there's no direct way to find out where it was instanciated using Eclipse.

The best way I've found to acheive that is to do a File Search (ctrl+h, File search tab) and search for new "yourInterface"() { , in all *.java files. This will find all places where you instanciate that interface in your code.

If you're able to reduce the scope with a working set, that will simplify finding which of the found places is the one you're looking for.

Answer 2

While debuging you can see the actual stack trace in the Debug perspective, just click back down the trace from where the execution is stopping at a break point till you get to the method where the instance of the anonymous class was created.

here is the call that returned the instance

hit F3 to locate the method.

Answer 3

You can temporarily modify your code to call this interface with any parameters (ie null ) at the place where you get it, and do a step into.

UPDATE

java.lang.reflect.Type is a basic interface instances of which are loaded inside JVM. Locating this place (most probably it is native code) where they are instantiated in most cases will give nothing.

This type is used to describe generics in fields, methods, classes, etc. Ie for a field declaration

List<? extends Foo> fooList = new ArrayList<Foo>();

it corresponds to <? extends Foo> <? extends Foo> . To find this declaration, you might want to:

• Call toString() in the debugger for this interface and search in your code for occurences
• Inspect this Type instance find out or to show us more info
• Use debugger to find out how it's being get with reflection (ie Field.getType or Method.getGenericParameterTypes() )

Answer 4

i didn't track this prolbem further, because i used an other solution. But what me helped was this piece of code where the variable "genericType" was the anonymous-instantiated-interface:

// Ensure that we're handling only List<MediaEntity> objects.
boolean isWritable;
if (List.class.isAssignableFrom(type) && genericType instanceof ParameterizedType) {
    ParameterizedType parameterizedType = (ParameterizedType) genericType;
    Type[] actualTypeArgs = (parameterizedType.getActualTypeArguments());
    isWritable = (actualTypeArgs.length == 1 && actualTypeArgs[0].equals(MediaEntity.class));
} else {
    isWritable = false;
}