Detailed Explanation of Serialization and Deserialization Mechanisms in Java

I. Basic Concepts of Serialization
Serialization is the process of converting a Java object into a byte sequence, while deserialization is the process of restoring a Java object from a byte sequence. This mechanism allows objects to exist independently of the program, facilitating network transmission or persistent storage.

II. Implementation Methods of Serialization

1. Implement the Serializable interface (a marker interface)

public class User implements Serializable {
    private String name;
    private int age;
    // A no-argument constructor must be provided
    public User() {}
    // getter/setter methods
}

2. Implement the Externalizable interface (requires overriding methods)

public class User implements Externalizable {
    private String name;
    private int age;
    
    @Override
    public void writeExternal(ObjectOutput out) throws IOException {
        out.writeUTF(name);  // Custom serialization logic
    }
    
    @Override
    public void readExternal(ObjectInput in) throws IOException {
        this.name = in.readUTF();  // Custom deserialization logic
    }
}

III. Specific Steps of Serialization

1. Create an object output stream:

User user = new User("Zhang San", 25);
try (ObjectOutputStream oos = new ObjectOutputStream(
        new FileOutputStream("user.dat"))) {
    oos.writeObject(user);  // Perform serialization
}

2. Detailed explanation of the serialization process:

• Check if the object implements the Serializable interface
• Use reflection to obtain all fields of the object
• Recursively serialize all referenced objects
• Convert object data into a byte stream and write it to the output source

IV. Specific Steps of Deserialization

1. Create an object input stream:

try (ObjectInputStream ois = new ObjectInputStream(
        new FileInputStream("user.dat"))) {
    User user = (User) ois.readObject();  // Perform deserialization
}

2. Detailed explanation of the deserialization process:

• Read the byte stream and parse metadata
• Use reflection to invoke the no-argument constructor to create an empty object
• Recursively deserialize all field values
• Restore the complete state of the object

V. Role of serialVersionUID

1. A version control identifier used to verify the compatibility of serialized objects
2. Correct way to declare it explicitly:

private static final long serialVersionUID = 1L;

3. If not explicitly declared, the JVM will automatically generate it based on the class structure. Changes to the class structure may cause deserialization to fail.

VI. Custom Serialization Strategies

1. Use the transient keyword to ignore fields:

private transient String password;  // Will not be serialized

2. Override the writeObject/readObject methods:

private void writeObject(ObjectOutputStream oos) 
        throws IOException {
    oos.defaultWriteObject();  // Default serialization
    oos.writeUTF(encrypt(password));  // Custom processing
}

private void readObject(ObjectInputStream ois) 
        throws IOException, ClassNotFoundException {
    ois.defaultReadObject();  // Default deserialization
    this.password = decrypt(ois.readUTF());  // Custom processing
}

VII. Notes on Serialization

1. Static variables are not serialized (they belong to the class level)
2. Parent class serialization rules:
   • If the parent class implements Serializable: the child class is automatically serializable
   • If the parent class does not implement it: a no-argument constructor is required, and parent class fields will not be serialized
3. Serialization issues with inner classes: it is recommended to use static inner classes

VIII. Practical Application Scenarios

1. Object network transmission (RPC calls)
2. Object persistent storage
3. Distributed cache storage
4. Deep copy implementation solutions

By understanding these details, you can avoid common serialization pitfalls and flexibly customize serialization strategies based on business requirements.