有时(实际上很多,我们得到一个
Java的情况,其中两个对象指向同一个东西.现在,如果我们分开这些序列化,则序列化表单具有对象的单独副本是非常合适的,因为应该可以打开另一个对象.但是,如果我们现在反对他们,我们发现他们仍然分开.有没有办法把它们连在一起?
示例如下.
public class Example { private static class ContainerClass implements java.io.Serializable { private ReferencedClass obj; public ReferencedClass get() { return obj; } public void set(ReferencedClass obj) { this.obj = obj; } } private static class ReferencedClass implements java.io.Serializable { private int i = 0; public int get() { return i; } public void set(int i) { this.i = i; } } public static void main(String[] args) throws Exception { //Initialise the classes ContainerClass test1 = new ContainerClass(); ContainerClass test2 = new ContainerClass(); ReferencedClass ref = new ReferencedClass(); //Make both container class point to the same reference test1.set(ref); test2.set(ref); //This does what we expect: setting the integer in one (way of accessing the) referenced class sets it in the other one test1.get().set(1234); System.out.println(Integer.toString(test2.get().get())); //Now serialise the container classes java.io.ObjectOutputStream os = new java.io.ObjectOutputStream(new java.io.FileOutputStream("C:\\Users\\Public\\test1.ser")); os.writeObject(test1); os.close(); os = new java.io.ObjectOutputStream(new java.io.FileOutputStream("C:\\Users\\Public\\test2.ser")); os.writeObject(test2); os.close(); //And deserialise them java.io.ObjectInputStream is = new java.io.ObjectInputStream(new java.io.FileInputStream("C:\\Users\\Public\\test1.ser")); ContainerClass test3 = (ContainerClass)is.readObject(); is.close(); is = new java.io.ObjectInputStream(new java.io.FileInputStream("C:\\Users\\Public\\test2.ser")); ContainerClass test4 = (ContainerClass)is.readObject(); is.close(); //We expect the same thing as before,and would expect a result of 4321,but this doesn't happen as the referenced objects are now separate instances test3.get().set(4321); System.out.println(Integer.toString(test4.get().get())); } }
解决方法
readResolve()
method允许这个(当然,首先你必须定义你将如何决定哪些对象是“相同的”).但是更容易的是将两个对象序列化到同一个文件中 – ObjectOut / InputStream保存所有被序列化/反序列化的对象的记录,并且只会存储和返回对已经看到的对象的引用.