AliasVariableMapperWrapper.java

/*
 * (C) Copyright 2012 Nuxeo SA (http://nuxeo.com/) and contributors.
 *
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the GNU Lesser General Public License
 * (LGPL) version 2.1 which accompanies this distribution, and is available at
 * http://www.gnu.org/licenses/lgpl.html
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details.
 *
 * Contributors:
 *     Anahide Tchertchian
 */
package org.nuxeo.ecm.platform.ui.web.binding.alias;

import java.util.HashMap;
import java.util.List;
import java.util.Map;

import javax.el.ELException;
import javax.el.ValueExpression;
import javax.el.VariableMapper;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.jboss.el.ValueExpressionLiteral;

/**
 * @since 5.6
 */
@SuppressWarnings({ "unchecked", "rawtypes" })
public class AliasVariableMapperWrapper extends VariableMapper {

    private static final Log log = LogFactory.getLog(AliasVariableMapperWrapper.class);

    protected final VariableMapper orig;

    protected final List<String> blockedPatterns;

    protected Map vars;

    public AliasVariableMapperWrapper(VariableMapper orig,
            List<String> blockedPatterns) {
        super();
        this.orig = orig;
        this.blockedPatterns = blockedPatterns;
    }

    /**
     * First tries to resolve against the inner Map, then the wrapped
     * ValueExpression, unless target is an {@link AliasVariableMapper} that
     * blocks this variable pattern.
     */
    public ValueExpression resolveVariable(String variable) {
        ValueExpression ve = null;
        try {
            if (this.vars != null) {
                ve = (ValueExpression) this.vars.get(variable);
            }
            if (ve == null) {
                // resolve to a value expression resolving to null if variable
                // is supposed to be blocked
                if (variable != null && blockedPatterns != null) {
                    for (String blockedPattern : blockedPatterns) {
                        if (blockedPattern == null) {
                            continue;
                        }
                        boolean doBlock = false;
                        if (blockedPattern.endsWith("*")) {
                            String pattern = blockedPattern.substring(0,
                                    blockedPattern.length() - 1);
                            if (variable.startsWith(pattern)) {
                                doBlock = true;
                            }
                        } else if (blockedPattern.equals(variable)) {
                            doBlock = true;
                        }
                        if (doBlock) {
                            if (log.isDebugEnabled()) {
                                log.debug(String.format(
                                        "Blocked expression var='%s'", variable));
                            }
                            return getNullValueExpression();
                        }
                    }
                }
                return this.orig.resolveVariable(variable);
            }
            return ve;
        } catch (StackOverflowError e) {
            throw new ELException("Could not Resolve Variable [Overflow]: "
                    + variable, e);
        }
    }

    protected ValueExpression getNullValueExpression() {
        return new ValueExpressionLiteral(null, Object.class);
    }

    public ValueExpression setVariable(String variable,
            ValueExpression expression) {
        if (this.vars == null) {
            this.vars = new HashMap();
        }
        return (ValueExpression) this.vars.put(variable, expression);
    }

}