java.beans

Class Beans

java.lang.Object

java.beans.Beans

public class Beans
extends Object

This class provides some general purpose beans control methods.

Constructor Summary

Constructors

Constructor and Description
Beans()

Method Summary

Methods

Modifier and Type	Method and Description
static Object	getInstanceOf(Object bean, Class<?> targetType) From a given bean, obtain an object representing a specified type view of that source object.
static Object	instantiate(ClassLoader cls, String beanName) Instantiate a JavaBean.
static Object	instantiate(ClassLoader cls, String beanName, BeanContext beanContext) Instantiate a JavaBean.
static Object	instantiate(ClassLoader cls, String beanName, BeanContext beanContext, AppletInitializer initializer) Instantiate a bean.
static boolean	isDesignTime() Test if we are in design-mode.
static boolean	isGuiAvailable() Determines whether beans can assume a GUI is available.
static boolean	isInstanceOf(Object bean, Class<?> targetType) Check if a bean can be viewed as a given target type.
static void	setDesignTime(boolean isDesignTime) Used to indicate whether of not we are running in an application builder environment.
static void	setGuiAvailable(boolean isGuiAvailable) Used to indicate whether of not we are running in an environment where GUI interaction is available.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Beans

public Beans()

Method Detail

instantiate

public static Object instantiate(ClassLoader cls,
                 String beanName)
                          throws IOException,
                                 ClassNotFoundException

Instantiate a JavaBean.

Parameters:

cls - the class-loader from which we should create the bean. If this is null, then the system class-loader is used.

beanName - the name of the bean within the class-loader. For example "sun.beanbox.foobah"

Throws:

ClassNotFoundException - if the class of a serialized object could not be found.

IOException - if an I/O error occurs.

instantiate

public static Object instantiate(ClassLoader cls,
                 String beanName,
                 BeanContext beanContext)
                          throws IOException,
                                 ClassNotFoundException

Instantiate a JavaBean.

Parameters:

cls - the class-loader from which we should create the bean. If this is null, then the system class-loader is used.

beanName - the name of the bean within the class-loader. For example "sun.beanbox.foobah"

beanContext - The BeanContext in which to nest the new bean

Throws:

ClassNotFoundException - if the class of a serialized object could not be found.

IOException - if an I/O error occurs.

instantiate

public static Object instantiate(ClassLoader cls,
                 String beanName,
                 BeanContext beanContext,
                 AppletInitializer initializer)
                          throws IOException,
                                 ClassNotFoundException

Instantiate a bean.

The bean is created based on a name relative to a class-loader. This name should be a dot-separated name such as "a.b.c".

In Beans 1.0 the given name can indicate either a serialized object or a class. Other mechanisms may be added in the future. In beans 1.0 we first try to treat the beanName as a serialized object name then as a class name.

When using the beanName as a serialized object name we convert the given beanName to a resource pathname and add a trailing ".ser" suffix. We then try to load a serialized object from that resource.

For example, given a beanName of "x.y", Beans.instantiate would first try to read a serialized object from the resource "x/y.ser" and if that failed it would try to load the class "x.y" and create an instance of that class.

If the bean is a subtype of java.applet.Applet, then it is given some special initialization. First, it is supplied with a default AppletStub and AppletContext. Second, if it was instantiated from a classname the applet's "init" method is called. (If the bean was deserialized this step is skipped.)

Note that for beans which are applets, it is the caller's responsiblity to call "start" on the applet. For correct behaviour, this should be done after the applet has been added into a visible AWT container.

Note that applets created via beans.instantiate run in a slightly different environment than applets running inside browsers. In particular, bean applets have no access to "parameters", so they may wish to provide property get/set methods to set parameter values. We advise bean-applet developers to test their bean-applets against both the JDK appletviewer (for a reference browser environment) and the BDK BeanBox (for a reference bean container).

Parameters:

cls - the class-loader from which we should create the bean. If this is null, then the system class-loader is used.

beanName - the name of the bean within the class-loader. For example "sun.beanbox.foobah"

beanContext - The BeanContext in which to nest the new bean

initializer - The AppletInitializer for the new bean

Throws:

ClassNotFoundException - if the class of a serialized object could not be found.

IOException - if an I/O error occurs.

getInstanceOf

public static Object getInstanceOf(Object bean,
                   Class<?> targetType)

From a given bean, obtain an object representing a specified type view of that source object.

The result may be the same object or a different object. If the requested target view isn't available then the given bean is returned.

This method is provided in Beans 1.0 as a hook to allow the addition of more flexible bean behaviour in the future.

Parameters:

bean - Object from which we want to obtain a view.

targetType - The type of view we'd like to get.

isInstanceOf

public static boolean isInstanceOf(Object bean,
                   Class<?> targetType)

Check if a bean can be viewed as a given target type. The result will be true if the Beans.getInstanceof method can be used on the given bean to obtain an object that represents the specified targetType type view.

Parameters:

bean - Bean from which we want to obtain a view.

targetType - The type of view we'd like to get.

Returns:

"true" if the given bean supports the given targetType.

isDesignTime

public static boolean isDesignTime()

Test if we are in design-mode.

Returns:

True if we are running in an application construction environment.

See Also:

DesignMode

isGuiAvailable

public static boolean isGuiAvailable()

Determines whether beans can assume a GUI is available.

Returns:

True if we are running in an environment where beans can assume that an interactive GUI is available, so they can pop up dialog boxes, etc. This will normally return true in a windowing environment, and will normally return false in a server environment or if an application is running as part of a batch job.

See Also:

Visibility

setDesignTime

public static void setDesignTime(boolean isDesignTime)
                          throws SecurityException

Used to indicate whether of not we are running in an application builder environment.

Note that this method is security checked and is not available to (for example) untrusted applets. More specifically, if there is a security manager, its checkPropertiesAccess method is called. This could result in a SecurityException.

Parameters:

isDesignTime - True if we're in an application builder tool.

Throws:

SecurityException - if a security manager exists and its checkPropertiesAccess method doesn't allow setting of system properties.

See Also:

SecurityManager.checkPropertiesAccess()

setGuiAvailable

public static void setGuiAvailable(boolean isGuiAvailable)
                            throws SecurityException

Used to indicate whether of not we are running in an environment where GUI interaction is available.

Note that this method is security checked and is not available to (for example) untrusted applets. More specifically, if there is a security manager, its checkPropertiesAccess method is called. This could result in a SecurityException.

Parameters:

isGuiAvailable - True if GUI interaction is available.

Throws:

SecurityException - if a security manager exists and its checkPropertiesAccess method doesn't allow setting of system properties.

See Also:

SecurityManager.checkPropertiesAccess()