public class SessionStorage extends Object
This class simplifies the common task of saving a little bit of an
application's GUI "session" state when the application shuts down,
and then restoring that state when the application is restarted.
Session state is stored on a per component basis, and only for
components with a name
and for
which a PropertySupport
object has been defined and registeres.
SessionState Properties that preserve the bounds
Rectangle
for Windows, the dividerLocation
for JSliderPanes
and the
selectedIndex
for JTabbedPanes
are defined by default. The
ApplicationContext
getSessionStorage
method
provides a shared SessionStorage
object.
A typical Application saves session state in its
shutdown()
method, and then restores
session state in startup()
:
public class MyApplication extends Application { @Override protected void shutdown() { getContext().getSessionStorage().save(mainFrame, "session.xml"); } @Override protected void startup() { ApplicationContext appContext = getContext(); appContext.setVendorId("Sun"); appContext.setApplicationId("SessionStorage1"); // ... create the GUI rooted by JFrame mainFrame appContext.getSessionStorage().restore(mainFrame, "session.xml"); } // ... }In this example, the bounds of
mainFrame
as well the
session state for any of its JSliderPane
or JTabbedPane
will be saved when the application shuts down, and
restored when the applications starts up again. Note: error
handling has been omitted from the example.
Session state is stored locally, relative to the user's
home directory, by the LocalStorage
save
and load
methods. The startup
method must set the
ApplicationContext
vendorId
and applicationId
properties to ensure that the correct
local directory
is selected on
all platforms. For example, on Windows XP, the full pathname
for filename "session.xml"
is typically:
${userHome}\Application Data\${vendorId}\${applicationId}\session.xmlWhere the value of
${userHome}
is the the value of
the Java System property "user.home"
. On Solaris or
Linux the file is:
${userHome}/.${applicationId}/session.xmland on OSX:
${userHome}/Library/Application Support/${applicationId}/session.xml
Modifier | Constructor and Description |
---|---|
protected |
SessionStorage(ApplicationContext context)
Constructs a SessionStorage object.
|
Modifier and Type | Method and Description |
---|---|
protected ApplicationContext |
getContext()
Returns
ApplicationContext which was used during creation of this
SessionStorage object. |
PropertySupport |
getProperty(Class cls)
Returns the
PropertySupport object that was
registered for the specified class
or a superclass. |
PropertySupport |
getProperty(Component component)
If a
sessionState PropertySupport object exists for the
specified Component return it, otherwise return null. |
void |
putProperty(Class cls,
PropertySupport propertySupport)
Register a
PropertySupport for the specified class. |
void |
restore(Component root,
String fileName)
Restores each named component in the specified hierarchy
from the session state loaded from
a file using
LocalStorage.load(fileName) . |
void |
save(Component root,
String fileName)
Saves the state of each named component in the specified hierarchy to
a file using
LocalStorage.save(fileName) . |
protected SessionStorage(ApplicationContext context)
PropertySupport
objects are registered by default:
Base Component Type | PropertySupport | PropertySupport Value |
---|---|---|
Window | WindowProperty | WindowState |
JTabbedPane | TabbedPaneProperty | TabbedPaneState |
JSplitPane | SplitPaneProperty | SplitPaneState |
JTable | TableProperty | TableState |
Applications typically would not create a SessionStorage
object directly, they'd use the shared ApplicationContext value:
ApplicationContext ctx = Application.getInstance(MyApplication.class).getContext(); SessionStorage ss = ctx.getSesssionStorage();
context
- ApplicationContext.getSessionStorage()
,
getProperty(Class)
,
getProperty(Component)
protected final ApplicationContext getContext()
ApplicationContext
which was used during creation of this
SessionStorage
object.public void save(Component root, String fileName) throws IOException
LocalStorage.save(fileName)
.
Each component is visited in breadth-first order: if a PropertySupport
exists
for that component,
and the component has a name
, then
its state
is saved.
Component names can be any string however they must be unique relative to the name's of the component's siblings. Most Swing components do not have a name by default, however there are some exceptions: JRootPane (inexplicably) assigns names to it's children (layeredPane, contentPane, glassPane); and all AWT components lazily compute a name, so JFrame, JDialog, and JWindow also have a name by default.
The type of sessionState values (i.e. the type of values
returned by PropertySupport.getSessionState
) must be one those
supported by XMLEncoder
and
XMLDecoder
, for example beans
(null constructor, read/write properties), primitives, and
Collections. Java bean classes and their properties must be
public. Typically beans defined for this purpose are little
more than a handful of simple properties. The JDK 6
@ConstructorProperties annotation can be used to eliminate
the need for writing set methods in such beans, e.g.
public class FooBar { private String foo, bar; // Defines the mapping from constructor params to properties @ConstructorProperties({"foo", "bar"}) public FooBar(String foo, String bar) { this.foo = foo; this.bar = bar; } public String getFoo() { return foo; } // don't need setFoo public String getBar() { return bar; } // don't need setBar }
root
- the root of the Component hierarchy to be saved.fileName
- the LocalStorage
filename.IOException
restore(java.awt.Component, java.lang.String)
,
ApplicationContext.getLocalStorage()
,
LocalStorage.save(java.lang.Object, java.lang.String)
,
getProperty(Component)
public void restore(Component root, String fileName) throws IOException
LocalStorage.load(fileName)
.
Each component is visited in breadth-first order: if a
PropertySupport
exists for that component,
and the component has a name
, then
its state is restored
.root
- the root of the Component hierarchy to be restored.fileName
- the LocalStorage
filename.IOException
save(java.awt.Component, java.lang.String)
,
ApplicationContext.getLocalStorage()
,
LocalStorage.save(java.lang.Object, java.lang.String)
,
getProperty(Component)
public PropertySupport getProperty(Class cls)
PropertySupport
object that was
registered
for the specified class
or a superclass. If no PropertySupport has been registered,
return null. To lookup the session state PropertySupport
for a Component
use getProperty(Component)
.
cls
- the class to which the returned PropertySupport
appliesPropertySupport
registered with putProperty
for
the specified class or the first one registered for a superclass
of cls
.IllegalArgumentException
- if cls
is nullgetProperty(Component)
,
putProperty(java.lang.Class, org.jdesktop.application.session.PropertySupport)
,
save(java.awt.Component, java.lang.String)
,
restore(java.awt.Component, java.lang.String)
public void putProperty(Class cls, PropertySupport propertySupport)
PropertySupport
for the specified class.
One can clear the PropertySupport
for a class by setting the entry to null:
sessionStorage.putProperty(myClass.class, null);Register a custom
PropertySupport
:
ApplicationContext ctx = Application.getInstance(MyApplication.class).getContext(); SessionStorage ss = ctx.getSesssionStorage(); ctx.putProperty(JTable.class, new ExtendedTableProperty());
cls
- the class to which propertySupport
applies.propertySupport
- the PropertySupport
object to register or null.IllegalArgumentException
- if cls
is null.getProperty(Component)
,
getProperty(Class)
,
save(java.awt.Component, java.lang.String)
,
restore(java.awt.Component, java.lang.String)
public final PropertySupport getProperty(Component component)
sessionState PropertySupport
object exists for the
specified Component return it, otherwise return null. This method
is used by the save
and restore
methods
to lookup the sessionState PropertySupport
object for each component
to whose session state is to be saved or restored.
The putProperty
method registers a PropertySupport object for
a class. One can specify a PropertySupport object for a single Swing
component by setting the component's client property, like this:
myJComponent.putClientProperty(PropertySupport.class, myPropertySupport);One can also create components that implement the
PropertySupport
interface directly.component
- the component to retrive the PropertySupport
fromcomponent
implements PropertySupport
, then
component
, if component
is a JComponent
with a
PropertySupport
valued
client property
under
(client property key) PropertySupport
, then
return that, otherwise return the value of
getProperty(component.getClass())
.
IllegalArgumentException
- if Component component
is null.JComponent.putClientProperty(java.lang.Object, java.lang.Object)
,
getProperty(Class)
,
putProperty(java.lang.Class, org.jdesktop.application.session.PropertySupport)
,
save(java.awt.Component, java.lang.String)
,
restore(java.awt.Component, java.lang.String)
Copyright © 2009–2014. All rights reserved.