今天我遇到了一个非常讨厌的错误，它涉及在使用标准 Java 序列化 API 进行 GUI 反序列化期间触发摇摆侦听器。简明扼要地解释如何复制这种行为有点困难，所以我在下面发布了一个小测试用例。这个测试用例不会抛出任何异常，不会触发任何编译器警告，当然也没有明确定义的行为。 这是甲骨文包互操作文档中的错误、灰色区域，还是只是以前尝试过的东西？
只是为了阐明我最初的用例，我试图在从磁盘重新加载配置组件时自动更新资产编辑器中的几个选项卡。
package com.ihateswing.ssce;
import java.awt.BorderLayout;
public class SSCE implements Serializable {
private class Internal extends JPanel {
private final JComboBox<String> m_cb = new JComboBox<String>();
Internal(final JComboBox<String> cb) {
cb.addActionListener(new AbstractAction() {
@Override
public void actionPerformed(ActionEvent e) {
DefaultComboBoxModel<String> dcbm = new DefaultComboBoxModel<String>();
for (int i = 0; i < cb.getModel().getSize(); ++i) {
dcbm.addElement(cb.getModel().getElementAt(i));
}
m_cb.setModel(dcbm);
}
});
super.add(m_cb);
}
}
private JFrame frame;
private JComboBox<String> jce = new JComboBox<String>();
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
SSCE window = new SSCE();
window.frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
public SSCE() {
initialize();
}
private void readObject(java.io.ObjectInputStream stream) throws IOException, ClassNotFoundException {
stream.defaultReadObject();
jce.setSelectedIndex(0); // <-- Seems to have undefined behavior?
}
private void initialize() {
frame = new JFrame();
frame.setBounds(100, 100, 450, 300);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
jce.setModel(new DefaultComboBoxModel<String>());
frame.getContentPane().add(new Internal(jce), BorderLayout.NORTH);
frame.getContentPane().add(jce, BorderLayout.CENTER);
JButton btnAddRandomItem = new JButton("Break");
btnAddRandomItem.addActionListener(new AbstractAction() {
private static final long serialVersionUID = 1L;
private int i;
public void actionPerformed(ActionEvent e) {
try {
((DefaultComboBoxModel<String>) jce.getModel())
.addElement(String.valueOf(i++));
ByteArrayOutputStream baos = new ByteArrayOutputStream();
ObjectOutputStream out = new ObjectOutputStream(baos);
out.writeObject(SSCE.this);
ByteArrayInputStream in = new ByteArrayInputStream(baos
.toByteArray());
ObjectInputStream oin = new ObjectInputStream(in);
oin.readObject();
// The line below updates 'Internal' as expected, uncomment
// to see...
// however with the listener fired from the serialization
// method, it breaks?
// jce.setSelectedIndex(0);
} catch (Throwable t) {
t.printStackTrace();
}
}
});
frame.getContentPane().add(btnAddRandomItem, BorderLayout.SOUTH);
}
}
带输出的示例（单击“中断”5 次）
package com.ihateswing.ssce;
import java.awt.BorderLayout;
public class SSCE implements Serializable {
private class Internal extends JPanel {
private final JComboBox<String> m_cb = new JComboBox<String>();
Internal(final JComboBox<String> cb) {
cb.addActionListener(new AbstractAction() {
@Override
public void actionPerformed(ActionEvent e) {
DefaultComboBoxModel<String> dcbm = new DefaultComboBoxModel<String>();
for (int i = 0; i < cb.getModel().getSize(); ++i) {
dcbm.addElement(cb.getModel().getElementAt(i));
}
m_cb.setModel(dcbm);
System.out.println("Set Internal.m_cb's model with " + m_cb.getModel().getSize() + " elements");
}
});
super.add(m_cb);
}
}
private JFrame frame;
private JComboBox<String> jce = new JComboBox<String>();
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
SSCE window = new SSCE();
window.frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
public SSCE() {
initialize();
}
private void readObject(java.io.ObjectInputStream stream) throws IOException, ClassNotFoundException {
stream.defaultReadObject();
jce.setSelectedIndex(0); // <-- Seems to have undefined behavior?
}
private void initialize() {
frame = new JFrame();
frame.setBounds(100, 100, 450, 300);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
final Internal internal = new Internal(jce);
jce.setModel(new DefaultComboBoxModel<String>());
frame.getContentPane().add(internal, BorderLayout.NORTH);
frame.getContentPane().add(jce, BorderLayout.CENTER);
JButton btnAddRandomItem = new JButton("Break");
btnAddRandomItem.addActionListener(new AbstractAction() {
private static final long serialVersionUID = 1L;
private int i;
public void actionPerformed(ActionEvent e) {
try {
((DefaultComboBoxModel<String>) jce.getModel())
.addElement(String.valueOf(i++));
ByteArrayOutputStream baos = new ByteArrayOutputStream();
ObjectOutputStream out = new ObjectOutputStream(baos);
out.writeObject(SSCE.this);
ByteArrayInputStream in = new ByteArrayInputStream(baos
.toByteArray());
ObjectInputStream oin = new ObjectInputStream(in);
oin.readObject();
System.out.println("After returning, Internal.m_cb's model size is " + internal.m_cb.getModel().getSize() + " elements");
// The line below updates 'Internal' as expected, uncomment
// to see...
// however with the listener fired from the serialization
// method, it breaks?
// jce.setSelectedIndex(0);
} catch (Throwable t) {
t.printStackTrace();
}
}
});
frame.getContentPane().add(btnAddRandomItem, BorderLayout.SOUTH);
}
}
Set Internal.m_cb's model with 1 elements
Set Internal.m_cb's model with 1 elements
After returning, Internal.m_cb's model size is 1 elements
Set Internal.m_cb's model with 2 elements
After returning, Internal.m_cb's model size is 1 elements
Set Internal.m_cb's model with 3 elements
After returning, Internal.m_cb's model size is 1 elements
Set Internal.m_cb's model with 4 elements
After returning, Internal.m_cb's model size is 1 elements
Set Internal.m_cb's model with 5 elements
After returning, Internal.m_cb's model size is 1 elements