net.ontopia.topicmaps.rest.resources.AbstractPagedResource.java Source code

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Here is the source code for net.ontopia.topicmaps.rest.resources.AbstractPagedResource.java

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/*
 * #!
 * Ontopia Rest
 * #-
 * Copyright (C) 2001 - 2016 The Ontopia Project
 * #-
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * !#
 */

package net.ontopia.topicmaps.rest.resources;

import java.io.IOException;
import java.util.Collection;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import net.ontopia.topicmaps.rest.Constants;
import net.ontopia.topicmaps.rest.utils.ContextUtils;
import net.ontopia.topicmaps.rest.utils.HeaderUtils;
import org.apache.commons.collections4.IteratorUtils;
import org.restlet.representation.Representation;
import org.restlet.representation.Variant;
import org.restlet.resource.ResourceException;

public class AbstractPagedResource extends AbstractOntopiaResource {

    protected boolean paging = Constants.PAGING_FALLBACK;
    protected int offset = Constants.PAGING_OFFSET_FALLBACK;
    protected int limit = Constants.PAGING_LIMIT_FALLBACK;

    @Override
    protected void doInit() throws ResourceException {
        super.doInit();

        paging = ContextUtils.getParameterAsBoolean(Constants.PAGING_PARAMETER, paging);
        offset = ContextUtils.getParameterAsInteger(Constants.DEFAULT_PAGING_OFFSET_PARAMETER, offset);
        limit = ContextUtils.getParameterAsInteger(Constants.DEFAULT_PAGING_LIMIT_PARAMETER, limit);
    }

    public long getOffset() {
        return offset;
    }

    public long getLimit() {
        return limit;
    }

    public boolean isPaging() {
        return paging;
    }

    public void setPaging(boolean paging) {
        this.paging = paging;
    }

    public void setOffset(int offset) {
        this.offset = offset;
    }

    public void setLimit(int limit) {
        this.limit = limit;
    }

    @Override
    @SuppressWarnings("unchecked")
    public Representation toRepresentation(Object source, Variant target) throws IOException {
        boolean pageable = isPageable(source, target);
        if (pageable) {
            source = page((Collection) source);
        }
        return super.toRepresentation(source, target);
    }

    protected boolean isPageable(Object source, Variant target) {
        return paging && (source instanceof Collection);
    }

    protected <C> Iterator<C> page(Collection<C> collection) {

        offset = getIntegerFromQuery(Parameters.OFFSET.getName(), offset);
        limit = getIntegerFromQuery(Parameters.LIMIT.getName(), limit);

        addPagingHeaders(collection.size(), offset, limit);

        int to = offset + limit;

        // shorcuts where possible
        // todo: not possible at the moment, but we might be able to create a new
        // QueryCollection with a query that has limit and offset in it.
        //      if (collection instanceof QueryCollection) {
        //         QueryCollection qc = (QueryCollection) collection;
        //         
        //      }

        // java optimized List.subList
        if (collection instanceof List) {
            try {
                return ((List<C>) collection).subList(offset, Math.min(collection.size(), to)).iterator();
            } catch (IndexOutOfBoundsException ioobe) {
                // offset > size
                return Collections.emptyIterator();
            }
        }

        // fallback to bounded iterator
        try {
            return IteratorUtils.boundedIterator(collection.iterator(), offset, limit);
        } catch (IllegalArgumentException iae) {
            // offset of limit negative
            return Collections.emptyIterator();
        }
    }

    protected void addPagingHeaders(int size, int offset, int limit) {
        HeaderUtils.addResponseHeader(getResponse(), "X-Paging-Count", Integer.toString(size));
        HeaderUtils.addResponseHeader(getResponse(), "X-Paging-Limit", Integer.toString(limit));
        HeaderUtils.addResponseHeader(getResponse(), "X-Paging-Offset", Integer.toString(offset));
        HeaderUtils.addResponseHeader(getResponse(), "X-Paging",
                offset + "-" + (Math.min(offset + limit, size) - 1) + "/" + size);
    }
}