StreamCorruptedException而反序列化對象

Question

我有一個類的UserData序列化對象，

import java.io.*; 

public final class UserData implements Serializable 
{ 
    private String name,username,password; 
    private boolean male; 
    private int age; 

    public void setName(String name) { this.name = new String(name); } 
    public void setUsername(String username) {this.username = new String(username); } 
    public void setPassword(String password) {this.password = new String(password); } 
    public void setAge(int age) { this.age = age; } 
    public void setGender(boolean gender) { this.male = gender; } 

    public String getName() { return new String(this.name); } 
    public String getUsername() { return new String(this.username); } 
    public String getPassword() { return new String(this.password); } 
    public int getAge() { return this.age; } 
    public boolean getGender() { return male; } 

    public static void writeUserDataToFile(UserData data,String fileName) 
    { 
     try 
     { 
      if(data == null) 
      { 
       return; 
      } 
      ObjectOutputStream objOutput = new ObjectOutputStream(new FileOutputStream(new File(fileName),true)); 
      objOutput.writeObject(data); 
      objOutput.flush(); 
      objOutput.close(); 
     } 
     catch(FileNotFoundException ex) 
     { 
      System.out.println("Error : Cannot Save Data , The given filename \""+fileName+"\" is not valid."); 
      return; 
     } 
     catch(NotSerializableException ex) 
     { 
      System.out.println("Error : It has been found that some data is not Serializable!"); 
      return; 
     } 
     catch(IOException ex) 
     { 
      System.out.println("Error : IOException has been encountered,"); 
      return; 
     } 
     catch(SecurityException S) 
     { 
      System.out.println("Error : Security Exception has been Encountered."); 
      return; 
     } 
     catch(Exception e) 
     { 
      System.out.println("Error : Unknown Exception thrown!"); 
      return; 
     } 
     System.out.println("Sucess : Data written to \""+fileName+"\"."); 
    } 
    public static UserData checkCredentials(String fileName,String userName,String passWord) 
    { 
     try 
     { 
      ObjectInputStream objInput = new ObjectInputStream(new FileInputStream(new File(fileName))); 
      UserData data; 
      while((data = (UserData)objInput.readObject())!=null) 
      { 
       if(userName.equals(data.getUsername()) && passWord.equals(data.getPassword())) 
        return data; 
      } 
      objInput.close(); 
     } 
     catch(Exception ex) 
     { 
      System.out.println("Error : Unknown Exception Caught while deserializing object."); 
      ex.printStackTrace(); 
     } 
     return null; 
    } 
} 

爲了測試這個類，我寫了另一個類，

public class TestUserData 
{ 
    public static void main(String args[]) 
    { 
     UserData data = new UserData(); 
     System.out.println("Serializing objects .... "); 
     for(int i=0;i<5;i++) 
     { 
      data.setName("John"); 
      data.setAge(10+i); 
      data.setGender((i%2==0)?true:false); 
      data.setUsername("John"+i); 
      data.setPassword(i+"John"); 
      UserData.writeUserDataToFile(data,"testSerial.dat"); 
     } 
     System.out.println("de-Serializing objects .... "); 
     for(int i=0;i<5;i++) 
     { 
      data = UserData.checkCredentials("testSerial.dat","John"+i,i+"John"); 
      if(data!=null) 
      { 
       System.out.println("Name : "+data.getName()); 
       System.out.println("Age : "+data.getAge()); 
       System.out.println("Gender : "+(data.getGender() ? "Male" : "Female")); 
      } 
      else 
      { 
       System.out.println("Data for Object "+i+" not de-serialized."); 
      } 
     } 
    } 
} 

輸出我得到

Serializing objects .... 
Sucess : Data written to "testSerial.dat". 
Sucess : Data written to "testSerial.dat". 
Sucess : Data written to "testSerial.dat". 
Sucess : Data written to "testSerial.dat". 
Sucess : Data written to "testSerial.dat". 
de-Serializing objects .... 
Name : John 
Age : 10 
Gender : Male 
Error : Unknown Exception Caught while deserializing object. 
java.io.StreamCorruptedException: invalid type code: AC 
    at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1374) 
    at java.io.ObjectInputStream.readObject(ObjectInputStream.java:369) 
    at UserData.checkCredentials(UserData.java:67) 
    at TestUserData.main(TestUserData.java:19) 
Data for Object 1 not de-serialized. 
Error : Unknown Exception Caught while deserializing object. 
java.io.StreamCorruptedException: invalid type code: AC 
    at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1374) 
    at java.io.ObjectInputStream.readObject(ObjectInputStream.java:369) 
    at UserData.checkCredentials(UserData.java:67) 
    at TestUserData.main(TestUserData.java:19) 
Data for Object 2 not de-serialized. 
Error : Unknown Exception Caught while deserializing object. 
java.io.StreamCorruptedException: invalid type code: AC 
    at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1374) 
    at java.io.ObjectInputStream.readObject(ObjectInputStream.java:369) 
    at UserData.checkCredentials(UserData.java:67) 
    at TestUserData.main(TestUserData.java:19) 
Data for Object 3 not de-serialized. 
Error : Unknown Exception Caught while deserializing object. 
java.io.StreamCorruptedException: invalid type code: AC 
    at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1374) 
    at java.io.ObjectInputStream.readObject(ObjectInputStream.java:369) 
    at UserData.checkCredentials(UserData.java:67) 
    at TestUserData.main(TestUserData.java:19) 
Data for Object 4 not de-serialized. 

在TestUserData類中，我是seri對5個UserData對象進行校準，序列化發生的很好，但在反序列化部分，它不能反序列化第一個對象。

我該如何改變才能使程序反序列化所有對象？

Answer 1

你不能像這樣追加到序列化文件。但是也有一些寫頭，所以在你的文件，你將有<header><data><header><data><header><data>...

的文件需要形式<header><data><data><data><data>

的所以當你的閱讀方法是正確的，你的儲蓄方法其實是錯誤的。您需要同時寫入所有進入同一文件的對象。