How to reset ObjectInputStream objects graph cache to avoid memory bloat

Question

When loading huge files with ObjectInputStream, all read objects are buffered by stream for object graph resolving.
This cause huge memory overhead which isn't needed in my case (all objects read are interdependent).
Is there an equivalent to the reset() method of ObjectOutputStream which reset this buffer?

Code example:

try (FileInputStream fileInputStream = new FileInputStream(filename);
         BufferedInputStream bufferedInputStream = new BufferedInputStream(fileInputStream);
         ObjectInputStream objectInputStream = new ObjectInputStream(bufferedInputStream)) {
  while (object = objectInputStream.readObject()) {
    System.Out.println(object.toString());
  }
}

There is actually a reset method on the class but it does a complete different thing.
See Java APIs which cause memory bloat

user207421 · Accepted Answer · 2016-07-18T04:48:13.423

4

It's up to the sender to decide when to break the integrity of sent object graphs, by calling ObjectOutputStream.reset(). Not the receiver.

NB your code doesn't compile, and wouldn't be valid if it did:

while (object = objectInputStream.readObject()) {
}

This should be

try {
    while (true) {
        object = objectInputStream.readObject();
        // ...
    }
}
catch (EOFException exc) {
    // end of stream
}

There is a misconception abroad that readObject() returns null at end of stream. It doesn't. It throws EOFException. It can return null any time you wrote a null.

edited Jul 18 '16 at 04:48

answered Mar 28 '13 at 06:22

user207421

305,947
44
307
483

1

so this means you should never use ObjectInputStream.reset() ? – Mark Y. Apr 30 '13 at 05:10
@MarkY. `ObjectInputStream.reset()` is inherited from [`InputStream.reset()`](https://docs.oracle.com/javase/8/docs/api/java/io/InputStream.html#reset--), which does nothing except throw an `IOException`, so you certainly shouldn't use it. – user207421 Jul 18 '16 at 04:45

gerrytan · Answer 2 · 2013-03-28T06:20:02.263

0

Hmm it seems you need to use some sort of lazy loading techniques where you only load necessairy components of the object graph, not everything.

edited Mar 28 '13 at 06:20

answered Mar 28 '13 at 06:08

gerrytan

40,313
9
84
99

In other words you've never heard of `ObjectOutputStream.reset()`. – user207421 Apr 07 '20 at 08:53

How to reset ObjectInputStream objects graph cache to avoid memory bloat

2 Answers2

Linked