javax.el.BeanELResolver Maven / Gradle / Ivy
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package javax.el;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.lang.ref.SoftReference;
import java.beans.FeatureDescriptor;
import java.beans.BeanInfo;
import java.beans.Introspector;
import java.beans.PropertyDescriptor;
import java.beans.IntrospectionException;
import java.util.Iterator;
import java.util.ArrayList;
import java.util.Map;
import java.util.HashMap;
import java.util.concurrent.ConcurrentHashMap;
/**
* Defines property resolution behavior on objects using the JavaBeans
* component architecture.
*
* This resolver handles base objects of any type, as long as the
* base is not null. It accepts any object as a property, and
* coerces it to a string. That string is then used to find a JavaBeans
* compliant property on the base object. The value is accessed using
* JavaBeans getters and setters.
*
* This resolver can be constructed in read-only mode, which means that
* {@link #isReadOnly} will always return true and
* {@link #setValue} will always throw
* PropertyNotWritableException.
*
* ELResolvers are combined together using
* {@link CompositeELResolver}s, to define rich semantics for evaluating
* an expression. See the javadocs for {@link ELResolver} for details.
*
* Because this resolver handles base objects of any type, it should
* be placed near the end of a composite resolver. Otherwise, it will
* claim to have resolved a property before any resolvers that come after
* it get a chance to test if they can do so as well.
*
* @see CompositeELResolver
* @see ELResolver
* @since JSP 2.1
*/
public class BeanELResolver extends ELResolver {
private boolean isReadOnly;
private static final int CACHE_SIZE = 1024;
private static final ConcurrentHashMap properties =
new ConcurrentHashMap(CACHE_SIZE);
/*
* Defines a property for a bean.
*/
protected final static class BeanProperty {
private Method readMethod;
private Method writeMethod;
private PropertyDescriptor descriptor;
public BeanProperty(Class baseClass,
PropertyDescriptor descriptor) {
this.descriptor = descriptor;
readMethod = getMethod(baseClass, descriptor.getReadMethod());
writeMethod = getMethod(baseClass, descriptor.getWriteMethod());
}
public Class getPropertyType() {
return descriptor.getPropertyType();
}
public boolean isReadOnly() {
return getWriteMethod() == null;
}
public Method getReadMethod() {
return readMethod;
}
public Method getWriteMethod() {
return writeMethod;
}
}
/*
* Defines the properties for a bean.
*/
protected final static class BeanProperties {
private final Map propertyMap =
new HashMap();
public BeanProperties(Class baseClass) {
PropertyDescriptor[] descriptors;
try {
BeanInfo info = Introspector.getBeanInfo(baseClass);
descriptors = info.getPropertyDescriptors();
} catch (IntrospectionException ie) {
throw new ELException(ie);
}
for (PropertyDescriptor pd: descriptors) {
propertyMap.put(pd.getName(),
new BeanProperty(baseClass, pd));
}
}
public BeanProperty getBeanProperty(String property) {
return propertyMap.get(property);
}
}
/**
* Creates a new read/write BeanELResolver.
*/
public BeanELResolver() {
this.isReadOnly = false;
}
/**
* Creates a new BeanELResolver whose read-only status is
* determined by the given parameter.
*
* @param isReadOnly true if this resolver cannot modify
* beans; false otherwise.
*/
public BeanELResolver(boolean isReadOnly) {
this.isReadOnly = isReadOnly;
}
/**
* If the base object is not null, returns the most
* general acceptable type that can be set on this bean property.
*
* If the base is not null, the
* propertyResolved property of the ELContext
* object must be set to true by this resolver, before
* returning. If this property is not true after this
* method is called, the caller should ignore the return value.
*
* The provided property will first be coerced to a String.
* If there is a BeanInfoProperty for this property and
* there were no errors retrieving it, the propertyType of
* the propertyDescriptor is returned. Otherwise, a
* PropertyNotFoundException is thrown.
*
* @param context The context of this evaluation.
* @param base The bean to analyze.
* @param property The name of the property to analyze. Will be coerced to
* a String.
* @return If the propertyResolved property of
* ELContext was set to true, then
* the most general acceptable type; otherwise undefined.
* @throws NullPointerException if context is null
* @throws PropertyNotFoundException if base is not
* null and the specified property does not exist
* or is not readable.
* @throws ELException if an exception was thrown while performing
* the property or variable resolution. The thrown exception
* must be included as the cause property of this exception, if
* available.
*/
public Class getType(ELContext context,
Object base,
Object property) {
if (context == null) {
throw new NullPointerException();
}
if (base == null || property == null){
return null;
}
BeanProperty bp = getBeanProperty(context, base, property);
context.setPropertyResolved(true);
return bp.getPropertyType();
}
/**
* If the base object is not null, returns the current
* value of the given property on this bean.
*
* If the base is not null, the
* propertyResolved property of the ELContext
* object must be set to true by this resolver, before
* returning. If this property is not true after this
* method is called, the caller should ignore the return value.
*
* The provided property name will first be coerced to a
* String. If the property is a readable property of the
* base object, as per the JavaBeans specification, then return the
* result of the getter call. If the getter throws an exception,
* it is propagated to the caller. If the property is not found or is
* not readable, a PropertyNotFoundException is thrown.
*
* @param context The context of this evaluation.
* @param base The bean on which to get the property.
* @param property The name of the property to get. Will be coerced to
* a String.
* @return If the propertyResolved property of
* ELContext was set to true, then
* the value of the given property. Otherwise, undefined.
* @throws NullPointerException if context is null.
* @throws PropertyNotFoundException if base is not
* null and the specified property does not exist
* or is not readable.
* @throws ELException if an exception was thrown while performing
* the property or variable resolution. The thrown exception
* must be included as the cause property of this exception, if
* available.
*/
public Object getValue(ELContext context,
Object base,
Object property) {
if (context == null) {
throw new NullPointerException();
}
if (base == null || property == null){
return null;
}
BeanProperty bp = getBeanProperty(context, base, property);
Method method = bp.getReadMethod();
if (method == null) {
throw new PropertyNotFoundException(
ELUtil.getExceptionMessageString(context,
"propertyNotReadable",
new Object[] { base.getClass().getName(),
property.toString()}));
}
Object value;
try {
value = method.invoke(base, new Object[0]);
context.setPropertyResolved(true);
} catch (ELException ex) {
throw ex;
} catch (InvocationTargetException ite) {
throw new ELException(ite.getCause());
} catch (Exception ex) {
throw new ELException(ex);
}
return value;
}
/**
* If the base object is not null, attempts to set the
* value of the given property on this bean.
*
* If the base is not null, the
* propertyResolved property of the ELContext
* object must be set to true by this resolver, before
* returning. If this property is not true after this
* method is called, the caller can safely assume no value was set.
*
* If this resolver was constructed in read-only mode, this method will
* always throw PropertyNotWritableException.
*
* The provided property name will first be coerced to a
* String. If property is a writable property of
* base (as per the JavaBeans Specification), the setter
* method is called (passing value). If the property exists
* but does not have a setter, then a
* PropertyNotFoundException is thrown. If the property
* does not exist, a PropertyNotFoundException is thrown.
*
* @param context The context of this evaluation.
* @param base The bean on which to set the property.
* @param property The name of the property to set. Will be coerced to
* a String.
* @param val The value to be associated with the specified key.
* @throws NullPointerException if context is null.
* @throws PropertyNotFoundException if base is not
* null and the specified property does not exist.
* @throws PropertyNotWritableException if this resolver was constructed
* in read-only mode, or if there is no setter for the property.
* @throws ELException if an exception was thrown while performing
* the property or variable resolution. The thrown exception
* must be included as the cause property of this exception, if
* available.
*/
public void setValue(ELContext context,
Object base,
Object property,
Object val) {
if (context == null) {
throw new NullPointerException();
}
if (base == null || property == null){
return;
}
if (isReadOnly) {
throw new PropertyNotWritableException(
ELUtil.getExceptionMessageString(context,
"resolverNotwritable",
new Object[] { base.getClass().getName() }));
}
BeanProperty bp = getBeanProperty(context, base, property);
Method method = bp.getWriteMethod();
if (method == null) {
throw new PropertyNotWritableException(
ELUtil.getExceptionMessageString(context,
"propertyNotWritable",
new Object[] { base.getClass().getName(),
property.toString()}));
}
try {
method.invoke(base, new Object[] {val});
context.setPropertyResolved(true);
} catch (ELException ex) {
throw ex;
} catch (InvocationTargetException ite) {
throw new ELException(ite.getCause());
} catch (Exception ex) {
if (null == val) {
val = "null";
}
String message = ELUtil.getExceptionMessageString(context,
"setPropertyFailed",
new Object[] { property.toString(),
base.getClass().getName(), val });
throw new ELException(message, ex);
}
}
/**
* If the base object is not null, returns whether a call
* to {@link #setValue} will always fail.
*
* If the base is not null, the
* propertyResolved property of the ELContext
* object must be set to true by this resolver, before
* returning. If this property is not true after this
* method is called, the caller can safely assume no value was set.
*
* If this resolver was constructed in read-only mode, this method will
* always return true.
*
* The provided property name will first be coerced to a
* String. If property is a writable property of
* base, false is returned. If the property is
* found but is not writable, true is returned. If the
* property is not found, a PropertyNotFoundException
* is thrown.
*
* @param context The context of this evaluation.
* @param base The bean to analyze.
* @param property The name of the property to analyzed. Will be coerced to
* a String.
* @return If the propertyResolved property of
* ELContext was set to true, then
* true if calling the setValue method
* will always fail or false if it is possible that
* such a call may succeed; otherwise undefined.
* @throws NullPointerException if context is null
* @throws PropertyNotFoundException if base is not
* null and the specified property does not exist.
* @throws ELException if an exception was thrown while performing
* the property or variable resolution. The thrown exception
* must be included as the cause property of this exception, if
* available.
*/
public boolean isReadOnly(ELContext context,
Object base,
Object property) {
if (context == null) {
throw new NullPointerException();
}
if (base == null || property == null){
return false;
}
context.setPropertyResolved(true);
if (isReadOnly) {
return true;
}
BeanProperty bp = getBeanProperty(context, base, property);
return bp.isReadOnly();
}
/**
* If the base object is not null, returns an
* Iterator containing the set of JavaBeans properties
* available on the given object. Otherwise, returns null.
*
* The Iterator returned must contain zero or more
* instances of {@link java.beans.FeatureDescriptor}. Each info object
* contains information about a property in the bean, as obtained by
* calling the BeanInfo.getPropertyDescriptors method.
* The FeatureDescriptor is initialized using the same
* fields as are present in the PropertyDescriptor,
* with the additional required named attributes "type" and
* "resolvableAtDesignTime" set as follows:
*
*
{@link ELResolver#TYPE} - The runtime type of the property, from
* PropertyDescriptor.getPropertyType().
* {@link ELResolver#RESOLVABLE_AT_DESIGN_TIME} - true.
*
*
*
* @param context The context of this evaluation.
* @param base The bean to analyze.
* @return An Iterator containing zero or more
* FeatureDescriptor objects, each representing a property
* on this bean, or null if the base
* object is null.
*/
public Iterator getFeatureDescriptors(
ELContext context,
Object base) {
if (base == null){
return null;
}
BeanInfo info = null;
try {
info = Introspector.getBeanInfo(base.getClass());
} catch (Exception ex) {
}
if (info == null) {
return null;
}
ArrayList list = new ArrayList(
info.getPropertyDescriptors().length);
for (PropertyDescriptor pd: info.getPropertyDescriptors()) {
pd.setValue("type", pd.getPropertyType());
pd.setValue("resolvableAtDesignTime", Boolean.TRUE);
list.add(pd);
}
return list.iterator();
}
/**
* If the base object is not null, returns the most
* general type that this resolver accepts for the
* property argument. Otherwise, returns null.
*
* Assuming the base is not null, this method will always
* return Object.class. This is because any object is
* accepted as a key and is coerced into a string.
*
* @param context The context of this evaluation.
* @param base The bean to analyze.
* @return null if base is null; otherwise
* Object.class.
*/
public Class getCommonPropertyType(ELContext context,
Object base) {
if (base == null){
return null;
}
return Object.class;
}
/*
* Get a public method form a public class or interface of a given method.
* Note that if a PropertyDescriptor is obtained for a non-public class that
* implements a public interface, the read/write methods will be for the
* class, and therefore inaccessible. To correct this, a version of the
* same method must be found in a superclass or interface.
**/
static private Method getMethod(Class cl, Method method) {
if (method == null) {
return null;
}
if (Modifier.isPublic (cl.getModifiers ())) {
return method;
}
Class [] interfaces = cl.getInterfaces ();
for (int i = 0; i < interfaces.length; i++) {
Class c = interfaces[i];
Method m = null;
try {
m = c.getMethod(method.getName(), method.getParameterTypes());
c = m.getDeclaringClass();
if ((m = getMethod(c, m)) != null)
return m;
} catch (NoSuchMethodException ex) {
}
}
Class c = cl.getSuperclass();
if (c != null) {
Method m = null;
try {
m = c.getMethod(method.getName(), method.getParameterTypes());
c = m.getDeclaringClass();
if ((m = getMethod(c, m)) != null)
return m;
} catch (NoSuchMethodException ex) {
}
}
return null;
}
private BeanProperty getBeanProperty(ELContext context,
Object base,
Object prop) {
String property = prop.toString();
Class baseClass = base.getClass();
BeanProperties bps = properties.get(baseClass);
if (bps == null) {
bps = new BeanProperties(baseClass);
properties.putIfAbsent(baseClass, bps);
}
BeanProperty bp = bps.getBeanProperty(property);
if (bp == null) {
throw new PropertyNotFoundException(
ELUtil.getExceptionMessageString(context,
"propertyNotFound",
new Object[] { baseClass.getName(),
property}));
}
return bp;
}
private void removeFromMap(Map map,
ClassLoader classloader) {
Iterator iter = map.keySet().iterator();
while (iter.hasNext()) {
Class mbeanClass = iter.next();
if (classloader.equals(mbeanClass.getClassLoader())) {
iter.remove();
}
}
}
/*
* This method is not part of the API, though it can be used (reflectively)
* by clients of this class to remove entries from the cache when the beans
* are being unloaded.
*
* A note about why WeakHashMap is not used. Measurements has shown
* that ConcurrentHashMap is much more scalable than synchronized
* WeakHashMap. A manual purge seems to be a good compromise.
*
* @param classloader The classLoader used to load the beans.
*/
private void purgeBeanClasses(ClassLoader classloader) {
removeFromMap(properties, classloader);
}
}