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package javax.servlet.jsp.el;
import java.beans.FeatureDescriptor;
import java.util.Iterator;
import java.util.ArrayList;
import java.util.Enumeration;
import javax.servlet.jsp.PageContext;
import javax.servlet.jsp.JspContext;
import javax.el.ELContext;
import javax.el.ELResolver;
import javax.el.ELException;
/**
* Defines variable resolution behavior for scoped attributes.
*
* <p>This resolver handles all variable resolutions (where <code>base</code>
* is <code>null</code>. It searches <code>PageContext.findAttribute()</code>
* for a matching attribute. If not found, it will return <code>null</code>,
* or in the case of <code>setValue</code> it will create a new attribute
* in the page scope with the given name.</p>
*
* @see javax.el.ELResolver
* @since JSP 2.1
*/
public class ScopedAttributeELResolver extends ELResolver {
/**
* If the base object is <code>null</code>, searches the page,
* request, session and application scopes for an attribute with
* the given name and returns it, or <code>null</code> if no
* attribute exists with the current name.
*
* <p>The <code>propertyResolved</code> property of the
* <code>ELContext</code> object must be set to <code>true</code> by
* this resolver before returning if base is <code>null</code>. If
* this property is not <code>true</code> after this method is called,
* the caller should ignore the return value.</p>
*
* @param context The context of this evaluation.
* @param base Only <code>null</code> is handled by this resolver.
* Other values will result in an immediate return.
* @param property The name of the scoped attribute to resolve.
* @return If the <code>propertyResolved</code> property of
* <code>ELContext</code> was set to <code>true</code>, then
* the scoped attribute; otherwise undefined.
* @throws NullPointerException if context is <code>null</code>
* @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) {
context.setPropertyResolved(true);
if (property instanceof String) {
String attribute = (String) property;
PageContext ctxt = (PageContext)
context.getContext(JspContext.class);
return ctxt.findAttribute(attribute);
}
}
return null;
}
/**
* If the base object is <code>null</code>, returns
* <code>Object.class</code> to indicate that any type is valid to
* set for a scoped attribute.
*
* <p>The <code>propertyResolved</code> property of the
* <code>ELContext</code> object must be set to <code>true</code> by
* this resolver before returning if base is <code>null</code>. If
* this property is not <code>true</code> after this method is called,
* the caller should ignore the return value.</p>
*
* @param context The context of this evaluation.
* @param base Only <code>null</code> is handled by this resolver.
* Other values will result in an immediate return.
* @param property The name of the scoped attribute to resolve.
* @return If the <code>propertyResolved</code> property of
* <code>ELContext</code> was set to <code>true</code>, then
* <code>Object.class</code>; otherwise undefined.
* @throws NullPointerException if context is <code>null</code>
* @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<Object> getType(ELContext context,
Object base,
Object property) {
if (context == null) {
throw new NullPointerException();
}
if (base == null) {
context.setPropertyResolved(true);
return Object.class;
}
return null;
}
/**
* If the base object is <code>null</code>, sets an existing scoped
* attribute to the new value, or creates a new scoped attribute if one
* does not exist by this name.
*
* <p>If the provided attribute name matches the key of an attribute
* in page scope, request scope, session scope, or application scope, the
* corresponding attribute value will be replaced by the provided value.
* Otherwise, a new page scope attribute will be created with the
* given name and value.</p>
*
* <p>The <code>propertyResolved</code> property of the
* <code>ELContext</code> object must be set to <code>true</code> by
* this resolver before returning if base is <code>null</code>. If
* this property is not <code>true</code> after this method is called,
* the caller should ignore the return value.</p>
*
* @param context The context of this evaluation.
* @param base Only <code>null</code> is handled by this resolver.
* Other values will result in an immediate return.
* @param property The name of the scoped attribute to set.
* @param val The value for the scoped attribute.
* @throws NullPointerException if context is <code>null</code>.
* @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) {
context.setPropertyResolved(true);
if (property instanceof String) {
PageContext ctxt = (PageContext)
context.getContext(JspContext.class);
String attr = (String) property;
if (ctxt.getAttribute(attr, PageContext.REQUEST_SCOPE) != null)
ctxt.setAttribute(attr, val, PageContext.REQUEST_SCOPE);
else if (ctxt.getAttribute(attr, PageContext.SESSION_SCOPE) != null)
ctxt.setAttribute(attr, val, PageContext.SESSION_SCOPE);
else if (ctxt.getAttribute(attr, PageContext.APPLICATION_SCOPE) != null)
ctxt.setAttribute(attr, val, PageContext.APPLICATION_SCOPE);
else {
ctxt.setAttribute(attr, val, PageContext.PAGE_SCOPE);
}
}
}
}
/**
* If the base object is <code>null</code>, returns <code>false</code>
* to indicate that scoped attributes are never read-only.
*
* <p>The <code>propertyResolved</code> property of the
* <code>ELContext</code> object must be set to <code>true</code> by
* this resolver before returning if base is <code>null</code>. If
* this property is not <code>true</code> after this method is called,
* the caller should ignore the return value.</p>
*
* @param context The context of this evaluation.
* @param base Only <code>null</code> is handled by this resolver.
* Other values will result in an immediate return.
* @param property The name of the scoped attribute.
* @return If the <code>propertyResolved</code> property of
* <code>ELContext</code> was set to <code>true</code>, then
* <code>false</code>; otherwise undefined.
* @throws NullPointerException if context is <code>null</code>.
* @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) {
context.setPropertyResolved(true);
}
return false;
}
/**
* If the base object is <code>null</code>, returns an
* <code>Iterator</code> containing <code>FeatureDescriptor</code> objects
* with information about each scoped attribute resolved by this
* resolver. Otherwise, returns <code>null</code>.
*
* <p>The <code>Iterator</code> returned must contain one instance of
* {@link java.beans.FeatureDescriptor} for each scoped attribute found in
* any scope. Each info object contains information about
* a single scoped attribute, and is initialized as follows:
*
* <dl>
* <li>displayName - The name of the scoped attribute.</li>
* <li>name - Same as displayName property.</li>
* <li>shortDescription - A suitable description for the scoped
* attribute. Should include the attribute's current scope
* (page, request, session, application). Will vary by
* implementation.</li>
* <li>expert - <code>false</code></li>
* <li>hidden - <code>false</code></li>
* <li>preferred - <code>true</code></li>
* </dl>
* In addition, the following named attributes must be set in the
* returned <code>FeatureDescriptor</code>s:
* <dl>
* <li>{@link ELResolver#TYPE} - The current runtime type of the scoped attribute.</li>
* <li>{@link ELResolver#RESOLVABLE_AT_DESIGN_TIME} - <code>true</code>.</li>
* </dl></p>
*
* @param context The context of this evaluation.
* @param base Only <code>null</code> is handled by this resolver.
* Other values will result in a <code>null</code> return value.
* @return An <code>Iterator</code> containing one
* <code>FeatureDescriptor</code> object for each scoped attribute, or
* <code>null</code> if <code>base</code> is not <code>null</code>.
*/
public Iterator<FeatureDescriptor> getFeatureDescriptors(
ELContext context,
Object base) {
Enumeration attrs;
ArrayList<FeatureDescriptor> list = new ArrayList<FeatureDescriptor>();
PageContext ctxt = (PageContext) context.getContext(JspContext.class);
attrs = ctxt.getAttributeNamesInScope(PageContext.PAGE_SCOPE);
while (attrs.hasMoreElements()) {
String name = (String) attrs.nextElement();
Object value = ctxt.getAttribute(name, PageContext.PAGE_SCOPE);
FeatureDescriptor descriptor = new FeatureDescriptor();
descriptor.setName(name);
descriptor.setDisplayName(name);
descriptor.setShortDescription("page scope attribute");
descriptor.setExpert(false);
descriptor.setHidden(false);
descriptor.setPreferred(true);
descriptor.setValue("type", value.getClass());
descriptor.setValue("resolvableAtDesignTime", Boolean.TRUE);
list.add(descriptor);
}
attrs = ctxt.getAttributeNamesInScope(PageContext.REQUEST_SCOPE);
while (attrs.hasMoreElements()) {
String name = (String) attrs.nextElement();
Object value = ctxt.getAttribute(name, PageContext.REQUEST_SCOPE);
FeatureDescriptor descriptor = new FeatureDescriptor();
descriptor.setName(name);
descriptor.setDisplayName(name);
descriptor.setShortDescription("request scope attribute");
descriptor.setExpert(false);
descriptor.setHidden(false);
descriptor.setPreferred(true);
descriptor.setValue("type", value.getClass());
descriptor.setValue("resolvableAtDesignTime", Boolean.TRUE);
list.add(descriptor);
}
attrs = ctxt.getAttributeNamesInScope(PageContext.SESSION_SCOPE);
while (attrs.hasMoreElements()) {
String name = (String) attrs.nextElement();
Object value = ctxt.getAttribute(name, PageContext.SESSION_SCOPE);
FeatureDescriptor descriptor = new FeatureDescriptor();
descriptor.setName(name);
descriptor.setDisplayName(name);
descriptor.setShortDescription("session scope attribute");
descriptor.setExpert(false);
descriptor.setHidden(false);
descriptor.setPreferred(true);
descriptor.setValue("type", value.getClass());
descriptor.setValue("resolvableAtDesignTime", Boolean.TRUE);
list.add(descriptor);
}
attrs = ctxt.getAttributeNamesInScope(PageContext.APPLICATION_SCOPE);
while (attrs.hasMoreElements()) {
String name = (String) attrs.nextElement();
Object value = ctxt.getAttribute(name, PageContext.APPLICATION_SCOPE);
FeatureDescriptor descriptor = new FeatureDescriptor();
descriptor.setName(name);
descriptor.setDisplayName(name);
descriptor.setShortDescription("application scope attribute");
descriptor.setExpert(false);
descriptor.setHidden(false);
descriptor.setPreferred(true);
descriptor.setValue("type", value.getClass());
descriptor.setValue("resolvableAtDesignTime", Boolean.TRUE);
list.add(descriptor);
}
return list.iterator();
}
/**
* If the base object is <code>null</code>, returns
* <code>String.class</code>. Otherwise, returns <code>null</code>.
*
* @param context The context of this evaluation.
* @param base Only <code>null</code> is handled by this resolver.
* Other values will result in a <code>null</code> return value.
* @return <code>null</code> if base is not <code>null</code>; otherwise
* <code>String.class</code>.
*/
public Class<String> getCommonPropertyType(ELContext context,
Object base) {
if (base == null) {
return String.class;
}
return null;
}
}
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