java静态变量序列化

如何在序列化期间保持静态变量的值(如果完全持久化).我在堆栈上读过类似的问题,它说静态变量本质上是瞬态的,即它们的状态或当前值不是序列化的.

我只是做了一个非常简单的例子,我将一个类序列化并将其保存到文件中,然后再次从文件重构该类.我惊奇地发现静态变量的值和序列化发生时的值都被保存了.

这是怎么发生的.这是因为在序列化期间会保存类模板及其实例信息.这是代码片段 –

public class ChildClass implements Serializable, Cloneable{

    /**
     * 
     */
    private static final long serialVersionUID = 5041762167843978459L;

    private static int staticState;
    int state = 0;

    public ChildClass(int state){
        this.state = state;
        staticState = 10001;
    }

    public String toString() {
        return "state" + state + " " + "static state " + staticState;
    }

    public static void setStaticState(int state) {
        staticState = state;
    }

这是我的主要课程

public class TestRunner {

    /**
     * @param args
     */
    public static void main(String[] args) {
        new TestRunner().run();
    }

    public TestRunner() {

    }

    public void run() {
        ChildClass c = new ChildClass(101);
        ChildClass.setStaticState(999999);
        FileOutputStream fo = null;
        ObjectOutputStream os = null;

        File file = new File("F:\\test");
        try {
            fo = new FileOutputStream(file);
            os = new ObjectOutputStream(fo);
            os.writeObject(c);
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } finally {

            try {
                if(null != os)os.close();
                if(null != fo) fo.close();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

        }


        FileInputStream fi = null;
        ObjectInputStream ois = null;
        ChildClass streamed;

        try {
            fi = new FileInputStream(file);
            ois = new ObjectInputStream(fi);
            Object o = ois.readObject();
            if(o instanceof ChildClass){
                streamed = (ChildClass)o;
                //ChildClass cloned = streamed.clone();
                System.out.println(streamed.toString());
            }
        } catch (IOException | ClassNotFoundException  e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } finally {
            try {
                if(null != ois)ois.close();
                if(null != fi) fi.close();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

        }
    }

注意：代码没有问题.我只是想知道如何保存类’ChildClass’中静态变量’staticState’的值.如果我通过网络传输此序列化数据,那么状态是否会被保存

解决方法:

静态字段值未序列化.输出正在打印静态字段的新值,因为您将其修改为999999,但在解除分类之前,您从未将其值重置为旧值.由于该字段是静态的,因此新值将反映在ChildClass的任何实例中.

要正确断言字段未序列化,请在反序列化对象之前将值重置为10001,您会注意到它的值不是999999.

...
ChildClass.setStaticState(10001);

FileInputStream fi = null;
ObjectInputStream ois = null;
ChildClass streamed;

...
// when de-serializing, the below will print "state101 static state 10001"
System.out.println(streamed.toString());

标签：static-variables,java,serialization
来源： https://codeday.me/bug/20191009/1875680.html