* * 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:
* *
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.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.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.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.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>.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.
*
* 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.
*
* @author John Keiser
* @since JDK1.1
* @see java.beans.BeanInfo
*/
public class Introspector {
public static final int USE_ALL_BEANINFO = 1;
public static final int IGNORE_IMMEDIATE_BEANINFO = 2;
public static final int IGNORE_ALL_BEANINFO = 3;
static String[] beanInfoSearchPath = {"gnu.java.beans.info"};
static Hashtable You have three options: With {@link #USE_ALL_BEANINFO} the result is the same as
* {@link #getBeanInfo(Class)}. Calling the method with When the method is called with Note: Any unknown value for beanClass,
* first by looking for explicit information, next by
* using standard design patterns to determine
* information about the class.
*
* @param beanClass the class to get BeanInfo about.
* @return the BeanInfo object representing the class.
*/
public static BeanInfo getBeanInfo(Class beanClass)
throws IntrospectionException
{
BeanInfo cachedInfo;
synchronized(beanClass)
{
cachedInfo = beanInfoCache.get(beanClass);
if(cachedInfo != null)
{
return cachedInfo;
}
cachedInfo = getBeanInfo(beanClass,null);
beanInfoCache.put(beanClass,cachedInfo);
return cachedInfo;
}
}
/**
* Returns a {@BeanInfo} instance for the given Bean class where a flag
* controls the usage of explicit BeanInfo class to retrieve that
* information.
*
* flag set to
* {@link #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 {@link BeanInfo.getMethodDescriptors},
* {@link BeanInfo.getEventSetDescriptors} and
* {@link BeanInfo.getPropertyDescriptors}.)
* flag
*
* ,
* 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 flag is interpreted
* as {@link #IGNORE_ALL_BEANINFO}BeanInfo classes.
* @return A BeanInfo object describing the class.
* @throws IntrospectionException If something goes wrong while retrieving
* the bean data.
*/
public static BeanInfo getBeanInfo(Class beanClass, int flag)
throws IntrospectionException
{
IntrospectionIncubator ii;
BeanInfoEmbryo infoEmbryo;
switch(flag)
{
case USE_ALL_BEANINFO:
return getBeanInfo(beanClass);
case IGNORE_IMMEDIATE_BEANINFO:
Class superclass = beanClass.getSuperclass();
ExplicitInfo explicit = new ExplicitInfo(superclass, null);
ii = new IntrospectionIncubator();
if (explicit.explicitEventSetDescriptors != null)
ii.setEventStopClass(superclass);
if (explicit.explicitMethodDescriptors != null)
ii.setMethodStopClass(superclass);
if (explicit.explicitPropertyDescriptors != null)
ii.setPropertyStopClass(superclass);
ii.addMethods(beanClass.getMethods());
infoEmbryo = ii.getBeanInfoEmbryo();
merge(infoEmbryo, explicit);
infoEmbryo.setBeanDescriptor(new BeanDescriptor(beanClass, null));
return infoEmbryo.getBeanInfo();
case IGNORE_ALL_BEANINFO:
default:
ii = new IntrospectionIncubator();
ii.addMethods(beanClass.getMethods());
infoEmbryo = ii.getBeanInfoEmbryo();
infoEmbryo.setBeanDescriptor(new BeanDescriptor(beanClass, null));
return infoEmbryo.getBeanInfo();
}
}
/**
* Flush all of the Introspector's internal caches.
*
* @since 1.2
*/
public static void flushCaches()
{
beanInfoCache.clear();
// Clears all the intermediate ExplicitInfo instances which
// have been created.
// This makes sure we have to retrieve stuff like BeanDescriptors
// again. (Remember that FeatureDescriptor can be modified by the user.)
ExplicitInfo.flushCaches();
}
/**
* Flush the Introspector's internal cached information for a given
* class.
*
* @param clz the class to be flushed.
* @throws NullPointerException if clz is null.
* @since 1.2
*/
public static void flushFromCaches(Class clz)
{
synchronized (clz)
{
beanInfoCache.remove(clz);
}
}
/** Adds all explicity given bean info data to the introspected
* data.
*
* @param infoEmbryo Bean info data retrieved by introspection.
* @param explicit Bean info data retrieved by BeanInfo classes.
*/
private static void merge(BeanInfoEmbryo infoEmbryo, ExplicitInfo explicit)
{
PropertyDescriptor[] p = explicit.explicitPropertyDescriptors;
if(p!=null)
{
for(int i=0;itopClass.
*
* @param beanClass the Bean class.
* @param stopClass the class to stop at.
* @return the BeanInfo object representing the class.
*/
public static BeanInfo getBeanInfo(Class beanClass, Class stopClass)
throws IntrospectionException
{
ExplicitInfo explicit = new ExplicitInfo(beanClass, stopClass);
IntrospectionIncubator ii = new IntrospectionIncubator();
ii.setPropertyStopClass(explicit.propertyStopClass);
ii.setEventStopClass(explicit.eventStopClass);
ii.setMethodStopClass(explicit.methodStopClass);
ii.addMethods(beanClass.getMethods());
BeanInfoEmbryo currentInfo = ii.getBeanInfoEmbryo();
merge(currentInfo, explicit);
// Sets the info's BeanDescriptor to the one we extracted from the
// explicit BeanInfo instance(s) if they contained one. Otherwise we
// create the BeanDescriptor from scratch.
// Note: We do not create a copy the retrieved BeanDescriptor which will allow
// the user to modify the instance while it is cached. However this is how
// the RI does it.
currentInfo.setBeanDescriptor(
(explicit.explicitBeanDescriptor == null ?
new BeanDescriptor(beanClass, null) :
explicit.explicitBeanDescriptor));
return currentInfo.getBeanInfo();
}
/**
* Get the search path for BeanInfo classes.
*
* @return the BeanInfo search path.
*/
public static String[] getBeanInfoSearchPath()
{
return beanInfoSearchPath;
}
/**
* Set the search path for BeanInfo classes.
* @param beanInfoSearchPath the new BeanInfo search
* path.
*/
public static void setBeanInfoSearchPath(String[] beanInfoSearchPath)
{
Introspector.beanInfoSearchPath = beanInfoSearchPath;
}
/**
* 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.
*
* @param name the name to decapitalize.
* @return the decapitalized name.
*/
public static String decapitalize(String name)
{
try
{
if(!Character.isUpperCase(name.charAt(0)))
{
return name;
}
else
{
try
{
if(Character.isUpperCase(name.charAt(1)))
{
return name;
}
else
{
char[] c = name.toCharArray();
c[0] = Character.toLowerCase(c[0]);
return new String(c);
}
}
catch(StringIndexOutOfBoundsException E)
{
char[] c = new char[1];
c[0] = Character.toLowerCase(name.charAt(0));
return new String(c);
}
}
}
catch(StringIndexOutOfBoundsException E)
{
return name;
}
catch(NullPointerException E)
{
return null;
}
}
static BeanInfo copyBeanInfo(BeanInfo b)
{
java.awt.Image[] icons = new java.awt.Image[4];
for(int i=1;i<=4;i++)
{
icons[i-1] = b.getIcon(i);
}
return new ExplicitBeanInfo(b.getBeanDescriptor(),
b.getAdditionalBeanInfo(),
b.getPropertyDescriptors(),
b.getDefaultPropertyIndex(),
b.getEventSetDescriptors(),
b.getDefaultEventIndex(),
b.getMethodDescriptors(),
icons);
}
}
class ExplicitInfo
{
BeanDescriptor explicitBeanDescriptor;
BeanInfo[] explicitBeanInfo;
PropertyDescriptor[] explicitPropertyDescriptors;
EventSetDescriptor[] explicitEventSetDescriptors;
MethodDescriptor[] explicitMethodDescriptors;
int defaultProperty;
int defaultEvent;
java.awt.Image[] im = new java.awt.Image[4];
Class propertyStopClass;
Class eventStopClass;
Class methodStopClass;
static Hashtable explicitBeanInfos = new Hashtable();
static Vector emptyBeanInfos = new Vector();
ExplicitInfo(Class beanClass, Class stopClass)
{
while(beanClass != null && !beanClass.equals(stopClass))
{
BeanInfo explicit = findExplicitBeanInfo(beanClass);
if(explicit != null)
{
if(explicitBeanDescriptor == null)
{
explicitBeanDescriptor = explicit.getBeanDescriptor();
}
if(explicitBeanInfo == null)
{
explicitBeanInfo = explicit.getAdditionalBeanInfo();
}
if(explicitPropertyDescriptors == null)
{
if(explicit.getPropertyDescriptors() != null)
{
explicitPropertyDescriptors = explicit.getPropertyDescriptors();
defaultProperty = explicit.getDefaultPropertyIndex();
propertyStopClass = beanClass;
}
}
if(explicitEventSetDescriptors == null)
{
if(explicit.getEventSetDescriptors() != null)
{
explicitEventSetDescriptors = explicit.getEventSetDescriptors();
defaultEvent = explicit.getDefaultEventIndex();
eventStopClass = beanClass;
}
}
if(explicitMethodDescriptors == null)
{
if(explicit.getMethodDescriptors() != null)
{
explicitMethodDescriptors = explicit.getMethodDescriptors();
methodStopClass = beanClass;
}
}
if(im[0] == null && im[1] == null
&& im[2] == null && im[3] == null)
{
im[0] = explicit.getIcon(0);
im[1] = explicit.getIcon(1);
im[2] = explicit.getIcon(2);
im[3] = explicit.getIcon(3);
}
}
beanClass = beanClass.getSuperclass();
}
if(propertyStopClass == null)
{
propertyStopClass = stopClass;
}
if(eventStopClass == null)
{
eventStopClass = stopClass;
}
if(methodStopClass == null)
{
methodStopClass = stopClass;
}
}
/** Throws away all cached data and makes sure we re-instantiate things
* like BeanDescriptors again.
*/
static void flushCaches() {
explicitBeanInfos.clear();
emptyBeanInfos.clear();
}
static BeanInfo findExplicitBeanInfo(Class beanClass)
{
BeanInfo retval = (BeanInfo)explicitBeanInfos.get(beanClass);
if(retval != null)
{
return retval;
}
else if(emptyBeanInfos.indexOf(beanClass) != -1)
{
return null;
}
else
{
retval = reallyFindExplicitBeanInfo(beanClass);
if(retval != null)
{
explicitBeanInfos.put(beanClass,retval);
}
else
{
emptyBeanInfos.addElement(beanClass);
}
return retval;
}
}
static BeanInfo reallyFindExplicitBeanInfo(Class beanClass)
{
ClassLoader beanClassLoader = beanClass.getClassLoader();
BeanInfo beanInfo;
beanInfo = getBeanInfo(beanClassLoader, beanClass.getName() + "BeanInfo");
if (beanInfo == null)
{
String newName;
newName = ClassHelper.getTruncatedClassName(beanClass) + "BeanInfo";
for(int i = 0; i < Introspector.beanInfoSearchPath.length; i++)
{
if (Introspector.beanInfoSearchPath[i].equals(""))
beanInfo = getBeanInfo(beanClassLoader, newName);
else
beanInfo = getBeanInfo(beanClassLoader,
Introspector.beanInfoSearchPath[i] + "."
+ newName);
// Returns the beanInfo if it exists and the described class matches
// the one we searched.
if (beanInfo != null && beanInfo.getBeanDescriptor() != null &&
beanInfo.getBeanDescriptor().getBeanClass() == beanClass)
return beanInfo;
}
}
return beanInfo;
}
/**
* Returns an instance of the given class name when it can be loaded
* through the given class loader, or null otherwise.
*/
private static BeanInfo getBeanInfo(ClassLoader cl, String infoName)
{
try
{
return (BeanInfo) Class.forName(infoName, true, cl).newInstance();
}
catch (ClassNotFoundException cnfe)
{
return null;
}
catch (IllegalAccessException iae)
{
return null;
}
catch (InstantiationException ie)
{
return null;
}
}
}