Introspector

AI-generated Key Takeaways

• The Introspector class helps developers discover a JavaBean's properties, events, and methods.

• It analyzes the bean class and its superclasses, using explicit BeanInfo classes if available or reflection otherwise.

• Introspector caches BeanInfo objects for faster retrieval in subsequent calls.

• It provides methods to retrieve BeanInfo, flush caches, and configure search paths for BeanInfo classes.

• Developers can control the introspection process with flags like IGNORE_ALL_BEANINFO and IGNORE_IMMEDIATE_BEANINFO.

public class Introspector extends Object

The Introspector is a utility for developers to figure out which properties, events, and methods a JavaBean supports.

The Introspector class walks over the class/superclass chain of the target bean class. At each level it checks if there is a matching BeanInfo class which provides explicit information about the bean, and if so uses that explicit information. Otherwise it uses the low level reflection APIs to study the target class and uses design patterns to analyze its behaviour and then proceeds to continue the introspection with its baseclass.

To look for the explicit information of a bean:

1. The Introspector appends "BeanInfo" to the qualified name of the bean class, try to use the new class as the "BeanInfo" class. If the "BeanInfo" class exsits and returns non-null value when queried for explicit information, use the explicit information
2. If the first step fails, the Introspector will extract a simple class name of the bean class by removing the package name from the qualified name of the bean class, append "BeanInfo" to it. And look for the simple class name in the packages defined in the "BeanInfo" search path (The default "BeanInfo" search path is sun.beans.infos). If it finds a "BeanInfo" class and the "BeanInfo" class returns non-null value when queried for explicit information, use the explicit information

Constant Summary

int	IGNORE_ALL_BEANINFO	Constant values to indicate that the Introspector will ignore all BeanInfo class.
int	IGNORE_IMMEDIATE_BEANINFO	Constant values to indicate that the Introspector will ignore the BeanInfo class of the current bean class.
int	USE_ALL_BEANINFO	Constant values to indicate that the Introspector will use all BeanInfo class which have been found.

Public Method Summary

static String	decapitalize(String name) Decapitalizes a given string according to the rule: If the first or only character is Upper Case, it is made Lower Case UNLESS the second character is also Upper Case, when the String is returned unchanged
static void	flushCaches() Flushes all BeanInfo caches.
static void	flushFromCaches(Class<?> clazz) Flushes the BeanInfo caches of the specified bean class
static BeanInfo	getBeanInfo(Class<?> beanClass, Class<?> stopClass) Gets the BeanInfo object which contains the information of the properties, events and methods of the specified bean class.
static BeanInfo	getBeanInfo(Class<?> beanClass, int flags) Gets the BeanInfo object which contains the information of the properties, events and methods of the specified bean class.
static BeanInfo	getBeanInfo(Class<?> beanClass) Gets the BeanInfo object which contains the information of the properties, events and methods of the specified bean class.
static String[]	getBeanInfoSearchPath() Gets an array of search packages.
static void	setBeanInfoSearchPath(String[] path) Sets the search packages.

Inherited Method Summary

From class java.lang.Object

Object	clone() Creates and returns a copy of this Object.
boolean	equals(Object obj) Compares this instance with the specified object and indicates if they are equal.
void	finalize() Invoked when the garbage collector has detected that this instance is no longer reachable.
final Class<?>	getClass() Returns the unique instance of Class that represents this object's class.
int	hashCode() Returns an integer hash code for this object.
final void	notify() Causes a thread which is waiting on this object's monitor (by means of calling one of the wait() methods) to be woken up.
final void	notifyAll() Causes all threads which are waiting on this object's monitor (by means of calling one of the wait() methods) to be woken up.
String	toString() Returns a string containing a concise, human-readable description of this object.
final void	wait(long timeout, int nanos) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires.
final void	wait(long timeout) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires.
final void	wait() Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object.

Constants

public static final int IGNORE_ALL_BEANINFO

Constant values to indicate that the Introspector will ignore all BeanInfo class.

Constant Value: 3

public static final int IGNORE_IMMEDIATE_BEANINFO

Constant values to indicate that the Introspector will ignore the BeanInfo class of the current bean class.

Constant Value: 2

public static final int USE_ALL_BEANINFO

Constant values to indicate that the Introspector will use all BeanInfo class which have been found. This is the default one.

Constant Value: 1

Public Methods

public static String decapitalize (String name)

Decapitalizes a given string according to the rule:

• If the first or only character is Upper Case, it is made Lower Case
• UNLESS the second character is also Upper Case, when the String is returned unchanged

Parameters

name	- the String to decapitalize

Returns

• the decapitalized version of the String

public static void flushCaches ()

Flushes all BeanInfo caches.

public static void flushFromCaches (Class<?> clazz)

Flushes the BeanInfo caches of the specified bean class

Parameters

clazz	the specified bean class

public static BeanInfo getBeanInfo (Class<?> beanClass, Class<?> stopClass)

Gets the BeanInfo object which contains the information of the properties, events and methods of the specified bean class. It will not introspect the "stopclass" and its super class.

The Introspector will cache the BeanInfo object. Subsequent calls to this method will be answered with the cached data.

Parameters

beanClass	the specified beanClass.
stopClass	the sopt class which should be super class of the bean class. May be null.

Returns

• the BeanInfo of the bean class.

Throws

IntrospectionException

public static BeanInfo getBeanInfo (Class<?> beanClass, int flags)

Gets the BeanInfo object which contains the information of the properties, events and methods of the specified bean class.

1. If flag==IGNORE_ALL_BEANINFO, the Introspector will ignore all BeanInfo class.
2. If flag==IGNORE_IMMEDIATE_BEANINFO, the Introspector will ignore the BeanInfo class of the current bean class.
3. If flag==USE_ALL_BEANINFO, the Introspector will use all BeanInfo class which have been found.

The Introspector will cache the BeanInfo object. Subsequent calls to this method will be answered with the cached data.

Parameters

beanClass	the specified bean class.
flags	the flag to control the usage of the explicit BeanInfo class.

Returns

• the BeanInfo of the bean class.

Throws

IntrospectionException

public static BeanInfo getBeanInfo (Class<?> beanClass)

Gets the BeanInfo object which contains the information of the properties, events and methods of the specified bean class.

The Introspector will cache the BeanInfo object. Subsequent calls to this method will be answered with the cached data.

Parameters

beanClass	the specified bean class.

Returns

• the BeanInfo of the bean class.

Throws

IntrospectionException

public static String[] getBeanInfoSearchPath ()

Gets an array of search packages.

Returns

• an array of search packages.

public static void setBeanInfoSearchPath (String[] path)

Sets the search packages.

Parameters

path	the new search packages to be set.