[英]Deserialized object fields are null
我已经成功序列化了自定义对象,但是当我反序列化它时,会发生这种情况:
-自定义对象不为空
-所有字段均为NULL
我知道我已经成功序列化了自定义对象,因为我已经阅读了序列化文件,并且看起来不错。
这是我的代码:
public class Preferences implements Serializable {
private static Preferences instance;
public static final long serialVersionUID = 3358037972944864859L;
public String accessToken;
protected Object readResolve() {
return getInstance();
}
private Preferences() {
}
private synchronized static void synchronize() {
if(instance == null) {
instance = new Preferences();
}
}
public static Preferences getInstance() {
if(instance == null) {
Preferences.synchronize();
}
return instance;
}
public void save(File file) {
try {
FileOutputStream fos = new FileOutputStream(file);
ObjectOutputStream out = new ObjectOutputStream(fos);
Preferences tempInstance = Preferences.getInstance();
out.writeObject(tempInstance);
out.close();
fos.close();
}catch(IOException e) {
e.printStackTrace();
}
}
public void load(File file) {
try {
FileInputStream fis = new FileInputStream(file);
ObjectInputStream in = new ObjectInputStream(fis);
if(file.length() > 0) {
Preferences tempInstance = (Preferences) in.readObject();
Log.e("", String.valueOf(tempInstance == null)); //prints FALSE
Log.e("", String.valueOf(tempInstance.accessToken == null)); //prints TRUE
}
in.close();
fis.close();
}catch(IOException | ClassNotFoundException e) {
e.printStackTrace();
}
}
}
这是我的测试代码:
public class CustomActivity extends AppCompatActivity {
private File dir = new File(Environment.getExternalStorageDirectory(), ".app");
private File backup = new File(dir, "backup.ser");
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
Log.e("APPLICATION", "START");
super.onCreate(savedInstanceState);
if(this instanceof ActivityLogin) {
if(!dir.exists()) {
dir.mkdirs();
}
Preferences.getInstance().load(backup);
}
}
@Override
protected void onUserLeaveHint() {
super.onUserLeaveHint();
try {
backup.createNewFile();
} catch (IOException e) {
e.printStackTrace();
}
Preferences.getInstance().save(backup);
Log.e("APPLICATION", "STOP");
}
}
有什么想法可能有问题吗?
您的课堂上有以下方法:
protected Object readResolve() {
return getInstance();
}
这告诉序列化机制:每当反序列化Preferences实例时,都将其替换为getInstance()
返回的实例。 因此,如果您调用load()并且您的Preferences实例的null令牌为空,则反序列化的Preferences也将为null的accessToken,因为它们是同一对象。
加
System.out.println(tempInstance == this);
到您的记录语句(或您在android中使用的任何记录),您将看到。
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