org.apache.struts.faces.application.DynaActionFormELResolver Maven / Gradle / Ivy
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* to you under the Apache License, Version 2.0 (the
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package org.apache.struts.faces.application;
import java.beans.FeatureDescriptor;
import java.util.Collections;
import java.util.Iterator;
import java.util.Map;
import javax.el.CompositeELResolver;
import javax.el.ELContext;
import javax.el.ELException;
import javax.el.ELResolver;
import javax.el.PropertyNotWritableException;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.struts.action.DynaActionForm;
/**
* Defines property resolution behavior on instances of {@link DynaActionForm}.
*
* This resolver handles base objects of type {@code DynaActionForm}
* with requested property name {code map}.
*
* This resolver is in read-only mode, which means that {@link #isReadOnly}
* will always return {@code true} and {@link #setValue} will always throw
* {@code PropertyNotWritableException}.
*
* {@code ELResolver}s 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
* @see DynaActionForm#getMap()
* @since Struts 1.4.1
*/
public class DynaActionFormELResolver extends ELResolver {
/**
* The {@code Log} instance for this class.
*/
private static final Log LOG =
LogFactory.getLog(DynaActionFormELResolver.class);
/**
* Creates a new read {@code DynaActionFormELResolver}.
*/
public DynaActionFormELResolver() {
if (LOG.isDebugEnabled()) {
LOG.debug("Creating new Dyna-Action-From-ELResolver instance");
}
}
/**
* If the base object is a {@code DynaActionForm} and the requested
* property name is {code map} then the type {@code Map.class} will be
* returned.
*
* If the base is a {@code DynaActionForm} and the requested property
* name is {code map}, the {@code propertyResolved} property of the
* {@code ELContext} object must be set to {@code true} by this resolver,
* before returning. If this property is not {@code true} after this
* method is called, the caller should ignore the return value.
*
* Assuming the base is a {@code DynaActionForm} and the requested
* property name is {code map}, this method will always return
* {@code Map.class}. This is because a {@code DynaActionForm} with the
* property 'map' accepts only the object {@code Map} as the value for
* this given key.
*
* @param context The context of this evaluation.
* @param base The base to analyze. Only bases of type
* {@code DynaActionForm} are handled by this resolver.
* @param property The key to return the acceptable type for. Only keys
* with value {@code map} are handled by this resolver.
*
* @return If the {@code propertyResolved} property of {@code ELContext}
* was set to {@code true}, then the most general acceptable type;
* otherwise undefined.
*
* @throws NullPointerException if context is {@code 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.
*/
@Override
public Class getType(ELContext context, Object base, Object property) {
if (context == null) {
throw new NullPointerException();
}
if (test(base, property)) {
if (LOG.isTraceEnabled() ) {
LOG.trace("Returning property-type '" + property
+ "' for DynaActionForm '" + base + "'");
}
context.setPropertyResolved(true);
return Map.class;
}
return null;
}
/**
* If the base object is a {@code DynaActionForm} and the requested
* property name is {@code map}, returns the {@code map} of the
* {@code DynaActionForm}. Otherwise {@code null} is returned.
*
* If the base is a {@code DynaActionForm} and the requested property
* name is {@code map}, the {@code propertyResolved} property of the
* {@code ELContext} object must be set to {@code true} by this resolver,
* before returning. If this property is not {@code true} after this method
* is called, the caller should ignore the return value.
*
* Just as in {@link DynaActionForm#getMap()}, just because {@code null}
* is returned doesn't mean there is no mapping for the key; it's also
* possible that the method explicitly returns {@code null}.
*
* @param context The context of this evaluation.
* @param base The base to be analyzed. Only bases of type
* {@code DynaActionForm} are handled by this resolver.
* @param property The key whose associated value is to be returned. Only keys
* with value {@code map} are handled by this resolver.
*
* @return If the {@code propertyResolved} property of {@code ELContext}
* was set to {@code true}, then the value associated with the given key.
*
* @throws NullPointerException if context is {@code 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.
*/
@Override
public Object getValue(ELContext context, Object base, Object property) {
if (context == null) {
throw new NullPointerException();
}
if (test(base, property)) {
if (LOG.isTraceEnabled()) {
LOG.trace("Returning property-value '" + property
+ "' for DynaActionForm '" + base + "'");
}
context.setPropertyResolved(true);
return (((DynaActionForm) base).getMap());
}
return null;
}
/**
* If the base is a {@code DynaActionForm} and the requested property
* name is {@code map}, this method always throw
* {@code PropertyNotWritableException}, because the {@code map}
* property is a ready-only property of the {@code DynaActionForm}
* class.
*
* @param context The context of this evaluation.
* @param base The base to be modified. Only bases of type
* {@code DynaActionForm} are handled by this resolver.
* @param property The key with which the specified value is to be
* associated. Only keys with value {@code map} are handled by
* this resolver.
* @param value The value to be associated with the specified key.
* @throws NullPointerException if context is {@code null}.
* @throws PropertyNotWritableException is always throw, because
* the {@code map} property is a ready-only property of the
* {@code DynaActionForm} class.
* @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.
*/
@Override
public void setValue(ELContext context, Object base, Object property, Object value) {
if (context == null) {
throw new NullPointerException();
}
if (test(base, property)) {
if (LOG.isTraceEnabled()) {
LOG.trace("Set property-value '" + property
+ "' for DynaActionForm '" + base + "'");
}
throw new PropertyNotWritableException(property.toString());
}
}
/**
* If the base is a {@code DynaActionForm} and the requested property
* name is {@code map}, returns whether a call to {@link #setValue}
* will always fail. This method always returns {@code true}, because
* the {@code map} property is a ready-only property of the
* {@code DynaActionForm} class.
*
* If the base is a {@code DynaActionForm} and the requested property
* name is {@code map}, the {@code propertyResolved} property of the
* {@code ELContext} object must be set to {@code true} by this resolver,
* before returning. If this property is not {@code true} after this
* method is called, the caller should ignore the return value.
*
* @param context The context of this evaluation.
* @param base The base to analyze. Only bases of type
* {@code DynaActionForm} are handled by this resolver.
* @param property The key to return the read-only status for. Only keys
* with value {@code map} are handled by this resolver.
*
* @return If the {@code propertyResolved} property of {@code ELContext}
* was set to {@code true}, then {@code true} if calling the
* {@code setValue} method will always fail or {@code false} if it
* is possible that such a call may succeed; otherwise undefined.
*
* @throws NullPointerException if context is {@code 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.
*/
@Override
public boolean isReadOnly(ELContext context, Object base, Object property) {
if (context == null) {
throw new NullPointerException();
}
if (test(base, property)) {
if (LOG.isTraceEnabled()) {
LOG.trace("Return ready-only status for property '" + property
+ "' for DynaActionForm " + base + "'");
}
context.setPropertyResolved(true);
return true;
}
return false;
}
/**
* If the base object is a {@code DynaActionForm}, returns an
* {@code Iterator} containing the set of keys available in the
* {@code DynaActionForm}. Otherwise, returns {@code null}.
*
* The {@code Iterator} returned must contain zero or more
* instances of {@link FeatureDescriptor}. Each info object
* contains information about a key in the Map, and is initialized
* as follows:
*
* - displayName - The return value of calling the
* {@code toString} method on this key, or {@code null} if
* the key is {@code null}.
* - name - Same as displayName property.
* - shortDescription - JavaDoc-Code of
* {@link DynaActionForm#getMap()}
* - expert - {@code false}
* - hidden - {@code false}
* - preferred - {@code true}
*
* In addition, the following named attributes must be set in the
* returned {@code FeatureDescriptor}s:
*
* - {@link ELResolver#TYPE} - The return value of calling
* the {@code getClass()} method on this key, or
* {@code null} if the key is {@code null}.
* - {@link ELResolver#RESOLVABLE_AT_DESIGN_TIME} -
* {@code true}
*
*
* @param context The context of this evaluation.
* @param base The object whose keys are to be iterated over. Only
* bases of type {@code DynaActionForm} are handled by this
* resolver.
*
* @return An {@code Iterator} containing zero or more (possibly
* infinitely more) {@code FeatureDescriptor} objects, each
* representing a key in this {@code DynaActionForm}, or
* {@code null} if the base object is not a
* {@code DynaActionForm}.
*/
@Override
public Iterator getFeatureDescriptors(
ELContext context,
Object base) {
if (base instanceof DynaActionForm) {
if (LOG.isTraceEnabled()) {
LOG.trace("Get Feature-Descriptors for DynaActionForm '" + base + "'");
}
final FeatureDescriptor descriptor = new FeatureDescriptor();
descriptor.setName("map");
descriptor.setDisplayName("map");
descriptor.setExpert(false);
descriptor.setHidden(false);
descriptor.setPreferred(true);
descriptor.setShortDescription("Returns the Map containing the property "
+ "values. This is done mostly to facilitate accessing the "
+ "DynaActionForm through JavaBeans accessors, in order to use "
+ "the JavaServer Pages Standard Tag Library (JSTL).");
descriptor.setValue(TYPE, Map.class);
descriptor.setValue(RESOLVABLE_AT_DESIGN_TIME, Boolean.TRUE);
return Collections.singleton(descriptor).iterator();
}
return null;
}
/**
* If the base object is a {@code DynaActionForm}, returns the most
* general type that this resolver accepts for the {@code property}
* argument. Otherwise, returns {@code null}.
*
* Assuming the base is a {@code DynaActionForm}, this method will
* always return {@code 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 base to analyze. Only bases of type
* {@code DynaActionForm} are handled by this resolver.
*
* @return {@code null} if base is not a {@code DynaActionForm}; otherwise
* {@code Object.class}.
*/
@Override
public Class getCommonPropertyType(ELContext context, Object base) {
if (base instanceof DynaActionForm) {
if (LOG.isTraceEnabled()) {
LOG.trace("Get Common-Property-Type for DynaActionForm '" + base + "'");
}
return Object.class;
}
return null;
}
/**
* If the base object is a {@code DynaActionForm} and the requested
* property name is {@code map}.
*
* @param base The requested base object. Only bases of type
* {@code DynaActionForm} are handled by this resolver.
* @param property The requested key. Only keys
* with value {@code map} are handled by this resolver.
*
* @return {@code true} if request could handle with this resolver.
*/
private static boolean test(final Object base, final Object property) {
return base instanceof DynaActionForm && "map".equals(property);
}
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