19.5 The JPasswordField Class

A JPasswordField is a text field in which an echo character (* by default) is displayed in place of the characters typed by the user. This feature is generally used when entering passwords to avoid showing the password on the screen. Except for the quirky display, JPasswordField behaves like an ordinary JTextField, though some steps have been taken to enhance the password field's security.

One reason that JPasswordField is a separate class from JTextField in Swing (which is not the case in the analogous AWT classes) is so the L&F can treat them differently by specifying different UI delegates. The UI delegate is responsible for hiding the input characters in a JPasswordField.

19.5.1 Properties

Table 19-5 shows the properties defined by JPasswordField. JPasswordField has its own unique UIClassID value. The value for accessibleContext property is AccessibleJPasswordField, an inner class that extends the JTextField.AccessibleJTextField class. The echoChar property specifies the character to be displayed in the field each time a key is pressed. This character is used to hide the actual input characters, though the L&F may choose to ignore it and hide the input characters some other way.

Table 19-5. JPasswordField properties

Property	Data type	get	is	set	Default value
accessibleContexto	AccessibleContext	·			AccessibleJPasswordField
echoChar	char	·		·	'*'
password	char[]	·
texto	string	·		·
UIClassIDo	String	·			"PasswordFieldUI"
ooverridden See also properties from the JTextCompoment class (Table 19-1).

In the interest of security, the getText( ) accessor methods have been deprecated in the JPasswordField field. To get the entered password, it is recommended that the getPassword( ) method be used instead. getPassword( ) returns a mutable char[] array, not an immutable String, so that you can clobber the password with '\0' characters when you are done with it.

19.5.2 Constructors

public JPasswordField( )

Create a new password text field with zero columns.

public JPasswordField(String text)

Create a new field containing the text (displayed using the echo character).

public JPasswordField(int columns)

Create a new password field with the requested number of columns.

public JPasswordField(String text, int columns)

Create a new password field with the specified number of columns, containing the supplied text (displayed using the echo character).

public JPasswordField(Document doc, String text, int columns)

This constructor (called by all the others) creates a new password field that uses the specified document model and number of columns. If text is null, the Document's current text is "displayed" with the echo character. Otherwise, text replaces the Document's content and is "displayed." This constructor sets the echo character as an asterisk (*).

19.5.3 Data Protection Methods

public void cut( )

public void copy( )

These methods are overridden to disable cut and copy behavior in password fields. They simply call the L&F's provideErrorFeedback( ) method, which typically emits a beep. If these methods were not overridden, it would be possible for hidden passwords to be copied from password fields and pasted into nonhidden fields.

public string getText(int offs, int len) throws BadLocationException

Defined in this class only for the purpose of being marked as deprecated. The getPassword( ) method should be used instead.

19.5.4 Miscellaneous Methods

public boolean echoCharIsSet( )

Indicate whether an echo character has been set. Note that a default echo character (*) is defined, so this method always returns true unless the echo character is explicitly set to '\0'.