将对象附加到序列化文件

Question

假设你有一些AppendObjectOutputStream类(它是一个ObjectOutputStream!),它会覆盖writeStreamHeader(),如下所示:

@Override
public void writeStreamHeader() throws IOException
{
    reset();
}

现在,让我们假设您计划将多个对象保存到文件中; 每次程序运行时都有一个对象.即使在第一次运行中,您是否会使用AppendObjectOutputStream()？

Answer 1

您必须首次使用常规ObjectOutputStream编写流标头,否则在使用ObjectInputStream打开文件时将获得java.io.StreamCorruptedException.

public class Test1 implements Serializable {

    public static void main(String[] args) throws Exception {
        ObjectOutputStream os1 = new ObjectOutputStream(new FileOutputStream("test"));
        os1.writeObject(new Test1());
        os1.close();

        ObjectOutputStream os2 = new ObjectOutputStream(new FileOutputStream("test", true)) {
            protected void writeStreamHeader() throws IOException {
                reset();
            }
        };

        os2.writeObject(new Test1());
        os2.close();

        ObjectInputStream is = new ObjectInputStream(new FileInputStream("test"));
        System.out.println(is.readObject());
        System.out.println(is.readObject());