java.beans
Class Introspector
Introspector is the class that does the bulk of the
design-time work in Java Beans. Every class must have
a BeanInfo in order for an RAD tool to use it; but, as
promised, you don't have to write the BeanInfo class
yourself if you don't want to. All you have to do is
call getBeanInfo() in the Introspector and it will use
standard JavaBeans-defined method signatures to
determine the information about your class.
Don't worry about it too much, though: you can provide
JavaBeans with as much customized information as you
want, or as little as you want, using the BeanInfo
interface (see BeanInfo for details).
Order of Operations
When you call getBeanInfo(class c), the Introspector
first searches for BeanInfo class to see if you
provided any explicit information. It searches for a
class named <bean class name>BeanInfo in different
packages, first searching the bean class's package
and then moving on to search the beanInfoSearchPath.
If it does not find a BeanInfo class, it acts as though
it had found a BeanInfo class returning null from all
methods (meaning it should discover everything through
Introspection). If it does, then it takes the
information it finds in the BeanInfo class to be
canonical (that is, the information speaks for its
class as well as all superclasses).
When it has introspected the class, calls
getBeanInfo(c.getSuperclass) and adds that information
to the information it has, not adding to any information
it already has that is canonical.
Introspection Design Patterns
When the Introspector goes in to read the class, it
follows a well-defined order in order to not leave any
methods unaccounted for. Its job is to step over all
of the public methods in a class and determine whether
they are part of a property, an event, or a method (in
that order).
Properties:
- If there is a
public boolean isXXX()
method, then XXX is a read-only boolean property.
boolean getXXX() may be supplied in
addition to this method, although isXXX() is the
one that will be used in this case and getXXX()
will be ignored. If there is a
public void setXXX(boolean) method,
it is part of this group and makes it a read-write
property. - If there is a
public <type> getXXX(int)
method, then XXX is a read-only indexed property of
type <type>. If there is a
public void setXXX(int,<type>)
method, then it is a read-write indexed property of
type <type>. There may also be a
public <type>[] getXXX() and a
public void setXXX(<type>)
method as well. - If there is a
public void setXXX(int,<type>)
method, then it is a write-only indexed property of
type <type>. There may also be a
public <type>[] getXXX() and a
public void setXXX(<type>)
method as well. - If there is a
public <type> getXXX() method,
then XXX is a read-only property of type
<type>. If there is a
public void setXXX(<type>)
method, then it will be used for the property and
the property will be considered read-write. - If there is a
public void setXXX(<type>)
method, then as long as XXX is not already used as
the name of a property, XXX is assumed to be a
write-only property of type <type>. - In all of the above cases, if the setXXX() method
throws
PropertyVetoException, then the
property in question is assumed to be constrained.
No properties are ever assumed to be bound
(Spec Note: this is not in the
spec, it just makes sense). See PropertyDescriptor
for a description of bound and constrained
properties.
Events:
If there is a pair of methods,
public void addXXX(<type>) and
public void removeXXX(<type>), where
<type> is a descendant of
java.util.EventListener, then the pair of
methods imply that this Bean will fire events to
listeners of type <type>.
If the addXXX() method throws
java.util.TooManyListenersException, then
the event set is assumed to be
unicast. See
EventSetDescriptor for a discussion of unicast event
sets.
Spec Note: the spec seems to say that
the listener type's classname must be equal to the XXX
part of addXXX() and removeXXX(), but that is not the
case in Sun's implementation, so I am assuming it is
not the case in general.
Methods:
Any public methods (including those which were used
for Properties or Events) are used as Methods.
static String | decapitalize(String name)- A helper method to convert a name to standard Java
naming conventions: anything with two capitals as the
first two letters remains the same, otherwise the
first letter is decapitalized.
|
static void | flushCaches()- Flush all of the Introspector's internal caches.
|
static void | flushFromCaches(Class clz)- Flush the Introspector's internal cached information for a given
class.
|
static BeanInfo | getBeanInfo(Class beanClass)- Get the BeanInfo for class
beanClass,
first by looking for explicit information, next by
using standard design patterns to determine
information about the class.
|
static BeanInfo | getBeanInfo(Class beanClass, Class stopClass)- Get the BeanInfo for class
beanClass,
first by looking for explicit information, next by
using standard design patterns to determine
information about the class.
|
static BeanInfo | getBeanInfo(Class beanClass, int flag)- Returns a instance for the given Bean class where a flag
controls the usage of explicit BeanInfo class to retrieve that
information.
|
static String[] | getBeanInfoSearchPath()- Get the search path for BeanInfo classes.
|
static void | setBeanInfoSearchPath(String[] beanInfoSearchPath)- Set the search path for BeanInfo classes.
|
clone, equals, extends Object> getClass, finalize, hashCode, notify, notifyAll, toString, wait, wait, wait |
decapitalize
public static String decapitalize(String name)
A helper method to convert a name to standard Java
naming conventions: anything with two capitals as the
first two letters remains the same, otherwise the
first letter is decapitalized. URL = URL, I = i,
MyMethod = myMethod.
name - the name to decapitalize.
flushCaches
public static void flushCaches()
Flush all of the Introspector's internal caches.
flushFromCaches
public static void flushFromCaches(Class clz)
Flush the Introspector's internal cached information for a given
class.
clz - the class to be flushed.
getBeanInfo
public static BeanInfo getBeanInfo(Class beanClass)
throws IntrospectionException Get the BeanInfo for class beanClass,
first by looking for explicit information, next by
using standard design patterns to determine
information about the class.
beanClass - the class to get BeanInfo about.
- the BeanInfo object representing the class.
getBeanInfo
public static BeanInfo getBeanInfo(Class beanClass,
Class stopClass)
throws IntrospectionException Get the BeanInfo for class beanClass,
first by looking for explicit information, next by
using standard design patterns to determine
information about the class. It crawls up the
inheritance tree until it hits topClass.
beanClass - the Bean class.stopClass - the class to stop at.
- the BeanInfo object representing the class.
getBeanInfo
public static BeanInfo getBeanInfo(Class beanClass,
int flag)
throws IntrospectionException Returns a instance for the given Bean class where a flag
controls the usage of explicit BeanInfo class to retrieve that
information.
You have three options:
With
USE_ALL_BEANINFO the result is the same as
getBeanInfo(Class).
Calling the method with
flag set to
IGNORE_IMMEDIATE_BEANINFO will let it use all
explicit BeanInfo classes for the beans superclasses
but not for the bean class itself. Furthermore eventset,
property and method information is retrieved by introspection
if the explicit
BeanInfos did not provide such data
(ie. return
null on
BeanInfo.getMethodDescriptors,
BeanInfo.getEventSetDescriptors and
BeanInfo.getPropertyDescriptors.)
When the method is called with
flagIGNORE_ALL_BEANINFO all the bean data is retrieved
by inspecting the class.
Note: Any unknown value for flag is interpreted
as IGNORE_ALL_BEANINFO.
beanClass - The class whose BeanInfo should be returned.flag - Controls the usage of explicit BeanInfo classes.
- A BeanInfo object describing the class.
getBeanInfoSearchPath
public static String[] getBeanInfoSearchPath()
Get the search path for BeanInfo classes.
- the BeanInfo search path.
setBeanInfoSearchPath
public static void setBeanInfoSearchPath(String[] beanInfoSearchPath)
Set the search path for BeanInfo classes.
beanInfoSearchPath - the new BeanInfo search
path.
java.beans.Introspector
Copyright (C) 1998, 2002, 2003 Free Software Foundation, Inc.
This file is part of GNU Classpath.
GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.
GNU Classpath is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License
along with GNU Classpath; see the file COPYING. If not, write to the
Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301 USA.
Linking this library statically or dynamically with other modules is
making a combined work based on this library. Thus, the terms and
conditions of the GNU General Public License cover the whole
combination.
As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
executable, regardless of the license terms of these independent
modules, and to copy and distribute the resulting executable under
terms of your choice, provided that you also meet, for each linked
independent module, the terms and conditions of the license of that
module. An independent module is a module which is not derived from
or based on this library. If you modify this library, you may extend
this exception to your version of the library, but you are not
obligated to do so. If you do not wish to do so, delete this
exception statement from your version.