jakarta.servlet.jsp.el.ImportELResolver Maven / Gradle / Ivy

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/*
 * Copyright (c) 2021 Contributors to the Eclipse Foundation.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v. 2.0, which is available at
 * http://www.eclipse.org/legal/epl-2.0.
 *
 * This Source Code may also be made available under the following Secondary
 * Licenses when the conditions for such availability set forth in the
 * Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
 * version 2 with the GNU Classpath Exception, which is available at
 * https://www.gnu.org/software/classpath/license.html.
 *
 * SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
 */
package jakarta.servlet.jsp.el;

import jakarta.el.ELContext;
import jakarta.el.ELClass;
import jakarta.el.ELResolver;
import jakarta.el.ELException;

/**
 * Defines variable resolution behavior for Class imports and static imports.
 *
 * @since JSP 3.1
 */
public class ImportELResolver extends ELResolver {

    /**
     * If the base object is null, searches the Class and static imports for an import with the given name
     * and returns it if an import exists with the given name.
     *
     * 
     * The propertyResolved property of the ELContext object must be set to true
     * by this resolver before returning if an import is matched. 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     Only null is handled by this resolver. Other values will result in an immediate
     *                 return.
     * @param property The name of the import to resolve.
     * @return If the propertyResolved property of ELContext was set to true,
     *         then the import; otherwise undefined.
     * @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.
     */
    @Override
    public Object getValue(ELContext context, Object base, Object property) {

        if (context == null) {
            throw new NullPointerException();
        }

        // check to see if the property is an imported class
        if (base == null && property instanceof String && context.getImportHandler() != null) {
            String attribute = (String) property;
            Object value = null;
            Class c = context.getImportHandler().resolveClass(attribute);
            if (c != null) {
                value = new ELClass(c);
                // A possible optimization is to set the ELClass
                // instance in an attribute map.
            }
            if (value != null) {
                context.setPropertyResolved(true);
            }
            return value;
        }
        return null;
    }

    /**
     * Always returns {@code null} since in normal usage {@link ScopedAttributeELResolver} will handle calls to
     * {@link ELResolver#getType(ELContext, Object, Object)}.
     *
     * @param context  The context of this evaluation.
     * @param base     Ignored
     * @param property Ignored
     * @return Always {@code null}
     * @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.
     */
    @Override
    public Class