我有以下实现序列化的类。
<table id="detail_table" class="detail">
<thead>
<tr>
<th>ID</th>
<th colspan="2">Name</th>
</tr>
</thead>
<tbody>
<tr class="parent" id="row101" title="Click to expand/collapse"
style="cursor: pointer;">
<td>101</td>
<td colspan="2">File Management Tool</td>
</tr>
<tr class="child-row101" style="display: none;">
<td> </td>
<td>New File Tool</td>
</tr>
<tr class="child-row101" style="display: none;">
<td> </td>
<td>Transfer Report</td>
</tr>
我尝试使用以下代码将User类对象保存在文本文件中。基本上，我尝试先编写对象然后再读取它。
class User implements Serializable{
public User(String username, String password) {
this.username=username;
this.password=password;
}
private static final long serialVersionUID = 1L;
String username;
String password;
}
它给出输出public class SerializableExample {
public static void main(String[] args) {
User user = new User("userB","passwordB");
String filename = "E:\\Proj-docs\\userFile.txt";
FileOutputStream file;
try {
file = new FileOutputStream(filename);
ObjectOutputStream out = new ObjectOutputStream(file);
out.writeObject(user);
out.close();
file.close();
} catch (IOException e) {
e.printStackTrace();
}
User user2=null;
try {
FileInputStream file2 = new FileInputStream(filename);
ObjectInputStream in = new ObjectInputStream(file2);
user2= (User) in.readObject();
Optional checkNull = Optional.ofNullable(user2);
if(checkNull.isPresent()) {
System.out.println(user2.username + " "+user2.password);
}else {
System.out.println("Null Object");
}
}catch(IOException | ClassNotFoundException e) {
e.printStackTrace();
}
}
}
现在，假设我想更改用户对象并将其存储在同一文本文件中
userB passwordB现在，如果我阅读了User对象，它会给出public class SerializableExample {
public static void main(String[] args) {
User user = new User("userD","passwordD");
String filename = "E:\\Proj-docs\\userFile.txt";
FileOutputStream file;
try {
file = new FileOutputStream(filename);
ObjectOutputStream out = new ObjectOutputStream(file);
out.writeObject(user);
out.close();
file.close();
:
:
:
我的问题是，即使在更新用户之后，我是否仍可以使用serialVersionUID检索用户的旧版本（值为userD passwordD的用户）？我想看看在更新对象或向类中添加新属性而不更改串行uid时如何在Java序列化中使用版本控制。
谢谢您的输入。