javax.el.ArrayELResolver Maven / Gradle / Ivy
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package javax.el;
import java.lang.reflect.Array;
import java.util.List;
import java.util.Iterator;
import java.beans.FeatureDescriptor;
/**
* Defines property resolution behavior on arrays.
*
* This resolver handles base objects that are Java language arrays.
* It accepts any object as a property and coerces that object into an
* integer index into the array. The resulting value is the value in the array
* at that index.
*
* 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.
*
* @see CompositeELResolver
* @see ELResolver
* @since JSP 2.1
*/
public class ArrayELResolver extends ELResolver {
/**
* Creates a new read/write ArrayELResolver.
*/
public ArrayELResolver() {
this.isReadOnly = false;
}
/**
* Creates a new ArrayELResolver whose read-only status is
* determined by the given parameter.
*
* @param isReadOnly true if this resolver cannot modify
* arrays; false otherwise.
*/
public ArrayELResolver(boolean isReadOnly) {
this.isReadOnly = isReadOnly;
}
/**
* If the base object is an array, returns the most general acceptable type
* for a value in this array.
*
* If the base is a array, 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.
*
* Assuming the base is an array, this method will always
* return base.getClass().getComponentType(), which is
* the most general type of component that can be stored at any given
* index in the array.
*
* @param context The context of this evaluation.
* @param base The array to analyze. Only bases that are Java language
* arrays are handled by this resolver.
* @param property The index of the element in the array to return the
* acceptable type for. Will be coerced into an integer, but
* otherwise ignored by this resolver.
* @return If the propertyResolved property of
* ELContext was set to true, then
* the most general acceptable type; otherwise undefined.
* @throws PropertyNotFoundException if the given index is out of
* bounds for this array.
* @throws NullPointerException if context is null
* @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 && base.getClass().isArray()) {
context.setPropertyResolved(true);
int index = toInteger (property);
if (index < 0 || index >= Array.getLength(base)) {
throw new PropertyNotFoundException();
}
return base.getClass().getComponentType();
}
return null;
}
/**
* If the base object is a Java language array, returns the value at the
* given index. The index is specified by the property
* argument, and coerced into an integer. If the coercion could not be
* performed, an IllegalArgumentException is thrown. If the
* index is out of bounds, null is returned.
*
* If the base is a Java language array, 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.
*
* @param context The context of this evaluation.
* @param base The array to analyze. Only bases that are Java language
* arrays are handled by this resolver.
* @param property The index of the value to be returned. Will be coerced
* into an integer.
* @return If the propertyResolved property of
* ELContext was set to true, then
* the value at the given index or null
* if the index was out of bounds. Otherwise, undefined.
* @throws IllegalArgumentException if the property could not be coerced
* into an integer.
* @throws NullPointerException if context is null.
* @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 && base.getClass().isArray()) {
context.setPropertyResolved(base, property);
int index = toInteger (property);
if (index >= 0 && index < Array.getLength(base)) {
return Array.get(base, index);
}
}
return null;
}
/**
* If the base object is a Java language array, attempts to set the
* value at the given index with the given value. The index is specified
* by the property argument, and coerced into an integer.
* If the coercion could not be performed, an
* IllegalArgumentException is thrown. If the index is
* out of bounds, a PropertyNotFoundException is thrown.
*
* If the base is a Java language array, 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.
*
* @param context The context of this evaluation.
* @param base The array to be modified. Only bases that are Java language
* arrays are handled by this resolver.
* @param property The index of the value to be set. Will be coerced
* into an integer.
* @param val The value to be set at the given index.
* @throws ClassCastException if the class of the specified element
* prevents it from being added to this array.
* @throws NullPointerException if context is null.
* @throws IllegalArgumentException if the property could not be coerced
* into an integer, or if some aspect of the specified element
* prevents it from being added to this array.
* @throws PropertyNotWritableException if this resolver was constructed
* in read-only mode.
* @throws PropertyNotFoundException if the given index is out of
* bounds for this array.
* @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 && base.getClass().isArray()) {
context.setPropertyResolved(base, property);
if (isReadOnly) {
throw new PropertyNotWritableException();
}
Class type = base.getClass().getComponentType();
if (val != null && ! type.isAssignableFrom(val.getClass())) {
throw new ClassCastException();
}
int index = toInteger (property);
if (index < 0 || index >= Array.getLength(base)) {
throw new PropertyNotFoundException();
}
Array.set(base, index, val);
}
}
/**
* If the base object is a Java language array, returns whether a call to
* {@link #setValue} will always fail.
*
* If the base is a Java language array, 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.
*
* If this resolver was constructed in read-only mode, this method will
* always return true. Otherwise, it returns
* false.
*
* @param context The context of this evaluation.
* @param base The array to analyze. Only bases that are a Java language
* array are handled by this resolver.
* @param property The index of the element in the array to return the
* acceptable type for. Will be coerced into an integer, but
* otherwise ignored by this resolver.
* @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 PropertyNotFoundException if the given index is out of
* bounds for this array.
* @throws NullPointerException if context is null
* @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 && base.getClass().isArray()) {
context.setPropertyResolved(true);
int index = toInteger (property);
if (index < 0 || index >= Array.getLength(base)) {
throw new PropertyNotFoundException();
}
}
return isReadOnly;
}
/**
* Always returns null, since there is no reason to
* iterate through set set of all integers.
*
* The {@link #getCommonPropertyType} method returns sufficient
* information about what properties this resolver accepts.
*
* @param context The context of this evaluation.
* @param base The array to analyze. Only bases that are a Java language
* array are handled by this resolver.
* @return null.
*/
public Iterator getFeatureDescriptors(
ELContext context,
Object base) {
return null;
}
/**
* If the base object is a Java language array, returns the most general
* type that this resolver accepts for the property argument.
* Otherwise, returns null.
*
* Assuming the base is an array, this method will always return
* Integer.class. This is because arrays accept integers
* for their index.
*
* @param context The context of this evaluation.
* @param base The array to analyze. Only bases that are a Java language
* array are handled by this resolver.
* @return null if base is not a Java language array;
* otherwise Integer.class.
*/
public Class getCommonPropertyType(ELContext context,
Object base) {
if (base != null && base.getClass().isArray()) {
return Integer.class;
}
return null;
}
private int toInteger(Object p) {
if (p instanceof Integer) {
return ((Integer) p).intValue();
}
if (p instanceof Character) {
return ((Character) p).charValue();
}
if (p instanceof Boolean) {
return ((Boolean) p).booleanValue()? 1: 0;
}
if (p instanceof Number) {
return ((Number) p).intValue();
}
if (p instanceof String) {
return Integer.parseInt((String) p);
}
throw new IllegalArgumentException();
}
private boolean isReadOnly;
}