Serialization
It is important to note that only AWT listeners which conform to the
Serializable protocol will be saved when the object is stored. If an AWT object has listeners that aren't marked serializable, they will be dropped at
writeObject time. Developers will need, as always, to consider the implications of making an object serializable. One situation to watch out for is this:
import java.awt.*; import java.awt.event.*; import java.io.Serializable; class MyApp implements ActionListener, Serializable { BigObjectThatShouldNotBeSerializedWithAButton bigOne; Button aButton = new Button(); MyApp() { // Oops, now aButton has a listener with a reference // to bigOne! aButton.addActionListener(this); } public void actionPerformed(ActionEvent e) { System.out.println("Hello There"); } } In this example, serializing
aButton by itself will cause
MyApp and everything it refers to to be serialized as well. The problem is that the listener is serializable by coincidence, not by design. To separate the decisions about
MyApp and the
ActionListener being serializable one can use a nested class, as in the following example:
import java.awt.*; import java.awt.event.*; import java.io.Serializable; class MyApp java.io.Serializable { BigObjectThatShouldNotBeSerializedWithAButton bigOne; Button aButton = new Button(); class MyActionListener implements ActionListener { public void actionPerformed(ActionEvent e) { System.out.println("Hello There"); } } MyApp() { aButton.addActionListener(new MyActionListener()); } }
//please refer java doc of java.awt.Component class in java swing.
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