The WeakReference class, monitoring memory leak and garbage collection in a Java application

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 Below is a Stack implementation that uses an internal resizeable array structure.  public class MyStack< T > implements Stack< T > { private static final int CAPACITY = 100 ; private Object[] array ; private int pos = 0 ; public MyStack () { this . array = new Object[ CAPACITY ] ; } @Override public void push ( T item) { if ( pos >= array . length / 2 ) { Object[] newArray = new Object[ pos * 2 ] ; System. arraycopy ( array , 0 , newArray , 0 , array . length ) ; array = newArray ; } array [ pos ++] = item ; } @Override public T pop () { if (isEmpty()) { throw new RuntimeException( "empty stack" ) ; } @SuppressWarnings ( "unchecked" ) T item = ( T ) array [ pos - 1 ] ; pos -= 1 ; return item ; } @Override @SuppressWarnings ( "unchecked" ) public T peek...
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Axon Framework ve tanımı değişen Event sınıfları

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Axon Framework kullanarak geliştirdiğim CQRS uygulamasında karşılaştığım bir sorundan ve çözüm yollarından bahsedeceğim.
Uygulamada "event sourcing" yöntemini kullanıyorum ve Event nesneleri SQL veritabanına serialize edildikten sonra kaydediliyor. Serialize edilen veri içerisinde Event sınıfının tam ismi (paket ismi ile birlikte) geçtiği için, bu isimde yapılan bir değişiklik (örneğin paket yapısındaki bir refactoring) benim mevcut event verilerim ile uyumsuz hale geliyor.
Böyle durumlarda serialize edilmiş event verilerinin migrate edilmesi için 2 yöntemden bahsediliyor:

1) Genellikle bu durumda bir "Upcaster" yardımıyla eski tip eventler deserialize edilir. Yani uygulamamız deserialize sürecinde eski eventleri ele alabilmek için ayarlanmış olmalıdır. Axon framework'te EventUpcaster sınıfı incelenebilir.

2) Paket yapısında bir değişiklik olduğunda ve XStram kullanılıyorsa, eski paketten yeni pakete bir "alias" tanımlanabilir.

// makes sure old package is read in as new.package
serializer.addPackageAlias("old.package.name", "new.package.name");



Bahadır Konu
bah.konu(at)gmail(dot)com

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