Input and Output - Java - page 412

such as a String , that data will get serialized properly. In other words, writeObject works
recursively . And carefully: if an object is referenced multiple times, it will only be serial-
izeed once. So, we can give it a List of MyData objects.

To be serializable, the data class must implement the empty Serializable interface. Also,
the keyword transient can be used for any data that should not be serialized. You might
need to do this for security or to prevent attempts to serialize a reference to an object of a
nonserializable class.

That said, making a class Serializable is not a decision that should be taken lightly. Con-
sideration should be given to enforcing class invariants during serialization, writing defens-
ive readObject or readResolve methods, initializing transient variables, etc.

Here transient is used to prevent unencrypted passwords from being saved where they
might be readable:

src/main/java/io/MyData.java

/** Simple data class used in Serialization demos. */
public public class class MyData MyData implements implements Serializable {

private private static static final final long long serialVersionUID = - 4965296908339881739L ;

String userName ;
String passwordCypher ;
transient

transient String passwordClear ;

/** This constructor is required by most APIs */
public public MyData () {

// Nothing to do

}

public public MyData ( String name , String clear ) {

setUserName ( name );
setPassword ( clear );

}

public public String getUserName () {

return return userName ;

}

public public void void setUserName ( String s ) {

this

this . userName = s ;

}