ELContextBuilderImpl.java

/**
 * Copyright (c) 2013-2016, The SeedStack authors <http://seedstack.org>
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 */
package org.seedstack.seed.core.internal.el;

import com.google.common.base.Strings;
import org.seedstack.seed.SeedException;
import org.seedstack.seed.el.ELContextBuilder;

import javax.el.ELContext;
import javax.el.ExpressionFactory;
import javax.inject.Inject;
import java.lang.reflect.Method;

import static com.google.common.base.Preconditions.checkArgument;

/**
 * Implementation of ELContextBuilder.
 *
 * *
 */
class ELContextBuilderImpl implements ELContextBuilder {
    @Inject
    private ExpressionFactory expressionFactory;

    static ELContext createDefaultELContext(ExpressionFactory expressionFactory) {
        if (ELPlugin.EL3_OPTIONAL.isPresent()) {
            try {
                return ELPlugin.EL3_OPTIONAL.get().getConstructor(ExpressionFactory.class).newInstance(expressionFactory);
            } catch (Exception e) {
                throw new RuntimeException("Unable to instantiate StandardELContext");
            }
        } else if (ELPlugin.JUEL_OPTIONAL.isPresent()) {
            try {
                return ELPlugin.JUEL_OPTIONAL.get().newInstance();
            } catch (Exception e) {
                throw new RuntimeException("Unable to instantiate JUEL SimpleContext");
            }
        } else {
            throw new UnsupportedOperationException("StandardELContext is not supported in this environment (EL level 3+ required)");
        }
    }

    @Override
    public ELPropertyProvider defaultContext() {
        return new SubContextBuilderImpl(createDefaultELContext(expressionFactory));
    }

    @Override
    public ELPropertyProvider context(ELContext elContext) {
        return new SubContextBuilderImpl(elContext);
    }

    private static class SubContextBuilderImpl implements ELContextBuilder.ELPropertyProvider {
        private final ELContext elContext;

        SubContextBuilderImpl(ELContext elContext) {
            this.elContext = elContext;
        }

        @Override
        public ELPropertyProvider withProperty(String name, Object object) {
            checkArgument(!Strings.isNullOrEmpty(name), "A property name is required");
            elContext.getELResolver().setValue(elContext, null, name, object);
            return this;
        }

        @Override
        public ELPropertyProvider withFunction(String prefix, String localName, Method method) {
            checkArgument(!Strings.isNullOrEmpty(localName), "A function local name is required");
            if (ELPlugin.EL3_OPTIONAL.isPresent()) {
                elContext.getFunctionMapper().mapFunction(prefix, localName, method);
            } else if (ELPlugin.JUEL_OPTIONAL.isPresent()) {
                if (ELPlugin.JUEL_OPTIONAL.get().isAssignableFrom(elContext.getClass())) {
                    try {
                        ELPlugin.JUEL_OPTIONAL.get().getMethod("setFunction", String.class, String.class, Method.class).invoke(elContext, prefix, localName, method);
                    } catch (Exception e) {
                        throw SeedException.wrap(e, ExpressionLanguageErrorCode.UNEXPECTED_EXCEPTION);
                    }
                } else {
                    throw new UnsupportedOperationException("At EL level 2, function mapping is only supported by JUEL SimpleContext");
                }
            } else {
                throw new UnsupportedOperationException("Function mapping is not supported in this environment (EL level 3+ required)");
            }
            return this;
        }

        @Override
        public ELContext build() {
            return elContext;
        }
    }
}