NotSerializableException wiht HashMap serialize

Question

I have a problem with serialize...I test this methods separate from class and worked correctly! But when I use this class get NotSerializableException

Code:
Property that must to be serialize:
public ArrayList<User> users;
This property is in UserManage class

This method for reading from database file:

public void readFromDataBaseFile(){
    File database=new File(this.saveUsersObject+"\\"+"Database.txt");
    if(!database.exists()){
        System.out.println("Exception:FileNotExist");
    }
    else{
        HashMap<String,Object> Data=(HashMap<String,Object>)FileHandler.readObjectInFile(database);
        this.users= (ArrayList) Data.get("users");
    }
}

And this method for writing to database file:

public void writeToDataBaseFile(){
    File database=new File(this.saveUsersObject+"\\"+"Database.txt");
    if(!database.exists()) {
        File parent=database.getParentFile();
        parent.mkdirs();
    }
    HashMap<String,Object> Data=allOfUsersToHashMap();
    if(Data.isEmpty()){
        System.out.println("DataBase HashMap Is Empty!");

    }
    else{
        FileHandler.writeObjectInFile(Data,database);
    }
}

Above method are in class UserManage.

below method is a helper method to writing an object in a file:

boolean writeObjectInFile(Object obj,File file):

public static boolean writeObjectInFile(Object obj,File file){
    String Path=file.getAbsolutePath();
    if(file.exists()){
        System.out.println("Object File Was Deleted!!");
        file.delete();
    }
    else{
        try
        {

            FileOutputStream fileOut = new FileOutputStream(Path);
            ObjectOutputStream out = new ObjectOutputStream(fileOut);
            out.writeObject(obj);
            out.close();
            fileOut.close();
            System.out.printf("Serialized data is saved To :"+file.getPath());
            return true;
        }catch(IOException i)
        {
            i.printStackTrace();
        }
    }

    return false;
}

And below method is a helper method to reading an object from a file:

Object readObjectInFile(File file):

 public static Object readObjectInFile(File file) {
    Object obj=null;
    if(file.isFile()){
        try
        {

            FileInputStream fileIn = new FileInputStream(file);
            ObjectInputStream in = new ObjectInputStream(fileIn);
            System.out.println(file.getAbsoluteFile());
            obj=in.readObject();
            fileIn.close();
            in.close();
            System.out.printf("DeSerialized data is Done From:"+file.getPath());
        }catch(IOException i)
        {
            i.printStackTrace();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }
    else {
        System.out.println("returned null :\\");
        System.out.println("Enter Address Of A File Not Folder Or Another! :\\");
    }
    return obj;
}

method allOfUsersToHashMap() in class UserManage:

public HashMap<String,Object> allOfUsersToHashMap(){
    HashMap<String,Object> Userdatabase=new HashMap<>();
    Userdatabase.put("users",this.users);
    return Userdatabase;
}

I must say when ArrayList<User> user is null this method worked correctly but when has user dont work!

What's the definition of the `User` class? It has to be `Serializable` to work with the standard serialization functionality. — wkl, Dec 16 '15 at 18:37
Can you check whether User class is Serializable I.e., implementing Serializable interface? — Madhusudana Reddy Sunnapu, Dec 16 '15 at 18:42
Do you think when I use `HashMap` need to serialize `User`?? @MadhusudanaReddySunnapu @birryree — MEAM, Dec 16 '15 at 18:44
I just add This `implements Serializable ` to class `User` but got that error again..Is it mistake by this work? @Louis Wasserman — MEAM, Dec 16 '15 at 18:49
@MEER Show us the complete error message. (It'll tell you what class it couldn't serialize.) — Louis Wasserman, Dec 16 '15 at 18:50
`java.io.WriteAbortedException: writing aborted; java.io.NotSerializableException: Client.User`@LouisWasserman — MEAM, Dec 16 '15 at 18:52
Just By adding `implements Serializable ` keyword to class name?@MadhusudanaReddySunnapu — MEAM, Dec 16 '15 at 18:55
I add `implements Serializable` to `User` class but it not work...search in google but not found any method that must be implement from this interface @MadhusudanaReddySunnapu @Louis Wasserman..I am new in java :) — MEAM, Dec 16 '15 at 19:11
http://stackoverflow.com/questions/34328413/implements-serializable-in-all-of-classes-but-get-notserializableexception @MadhusudanaReddySunnapu — MEAM, Dec 17 '15 at 06:56

score 5 · Accepted Answer · answered Dec 16 '15 at 18:36

5

If the User class doesn't implement the Serializable interface, the ArrayList won't be able to be serialized. See the JavaDoc for Serializable for implementation details: https://docs.oracle.com/javase/8/docs/api/java/io/Serializable.html

answered Dec 16 '15 at 18:36

upcrob

165
11

But I don't Use this class for serialize and first put this class to a hash map and then pass this `HashMap` to another static method in another class then serialize@upcrob – MEAM Dec 16 '15 at 18:38
`HashMap` is serializable! http://stackoverflow.com/questions/13207376/is-hashtable-hashmap-serializable-in-java – MEAM Dec 16 '15 at 18:42
1

@MEER: That doesn't matter. `HashMap` is serializable, sure, but if a single object in the `HashMap` isn't serializable, then it won't work. `User` still has to be serializable. – Louis Wasserman Dec 16 '15 at 18:42
HashMap is Serializable as well, but the objects it (or ArrayList) contains are not necessarily Serializable. If you want to serialize the ArrayList variable, User must be Serializable. – upcrob Dec 16 '15 at 18:43

score 1 · Answer 2 · edited May 23 '17 at 10:28

1

Does your User POJO meets all the requisites to be serialized?

Check this previous question: What is object serialization?

edited May 23 '17 at 10:28

Community

1
1

answered Dec 16 '15 at 18:43

juanitodread

156
2
7

NotSerializableException wiht HashMap serialize

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