java - 序列化 java.util.Enumeration

Question

我如何序列化 Enumeration 对象到一个文件，然后反序列化它？我试图将其转换为 ArrayList 但此选项对我不起作用。我尝试了以下代码:

FileOutputStream fos            = null;
ObjectOutputStream outs         = null;
Enumeration<TreePath> stateEnum = com.jidesoft.tree.TreeUtils.saveExpansionStateByTreePath(tree);
ArrayList<TreePath> pathList    = new ArrayList<TreePath>();

while(stateEnum.hasMoreElements()){
    pathList.add(stateEnum.nextElement());
}
try {
    fos = new FileOutputStream(TREE_STATE_FILE);
    outs = new ObjectOutputStream(fos);
    outs.writeObject(pathList);
    outs.close();
} catch (IOException e) {
    _log.info("Failed to create " + TREE_STATE_FILE + " file: ", e);
}

但是当我尝试对其进行序列化时，我得到了空值。谢谢

Answer 1

IMO，Enumeration 的序列化并没有多大意义。 Enumeration 只是数据结构或其他业务逻辑之上的 float View 。为了序列化，你最好坚持序列化支持接口(interface)。为了可视化我正在写的内容，我设置了一个小代码片段:

import java.io.*;
import java.util.*;

import javax.swing.tree.TreePath;

public class EnumTest {

  public class MyEnumerator<T> {

    // set holding data
    List<T> data;

    public MyEnumerator(List<T> data) {
      this.data = data;
    }

    public List<T> getData() {
      return data;
    }

    public Enumeration<T> enumerate() {
      return new Enumeration<T>() {
        transient int i = 0;

        @Override
        public boolean hasMoreElements() {
          return i < data.size();
        }

        @Override
        public T nextElement() {
          return data.get(i++);
        }
      };
    }
  }

  public EnumTest() throws Exception {
    List<TreePath> TreePaths = Arrays.asList(new TreePath[] { new TreePath("3"), new TreePath("4"), new TreePath("5") });
    MyEnumerator<TreePath> myEnum1 = new MyEnumerator<TreePath>(TreePaths);
    print(myEnum1);

    FileOutputStream fos = new FileOutputStream("test.out");
    ObjectOutputStream oos = new ObjectOutputStream(fos);
    oos.writeObject(myEnum1.getData());
    oos.close();
    fos.close();

    System.out.println("* Serialization complete");

    FileInputStream fis = new FileInputStream("test.out");
    ObjectInputStream ois = new ObjectInputStream(fis);
    @SuppressWarnings("unchecked")
    List<TreePath> data = (List<TreePath>) ois.readObject();
    MyEnumerator<TreePath> myEnum2 = new MyEnumerator<TreePath>(data);
    print(myEnum2);

    System.out.println("* Deserialization complete");
  }

  private void print(MyEnumerator<TreePath> myEnum1) {
    Enumeration<TreePath> enm = myEnum1.enumerate();
    while (enm.hasMoreElements()) {
      System.out.println(enm.nextElement());
    }
  }

  public static void main(String[] args) throws Exception {
    new EnumTest();
  }
}

这围绕着序列化 Enumeration 本身的主题进行，方法是保留包含的数据并随后重建包装类 MyEnumerator。通过序列化/反序列化循环，您将获得一个不同的对象，但在语义上是相同的。