PagedUniqueProcess.java

/* Copyright (c) 2014 OpenPlans - www.openplans.org. All rights reserved.
 * This code is licensed under the GPL 2.0 license, available at the root
 * application directory.
 */
package org.geoserver.wps.gs;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.logging.Logger;

import org.geoserver.catalog.AttributeTypeInfo;
import org.geotools.data.Query;
import org.geotools.data.simple.SimpleFeatureCollection;
import org.geotools.factory.CommonFactoryFinder;
import org.geotools.feature.visitor.UniqueVisitor;
import org.geotools.filter.text.cql2.CQLException;
import org.geotools.process.ProcessException;
import org.geotools.process.factory.DescribeParameter;
import org.geotools.process.factory.DescribeProcess;
import org.geotools.process.factory.DescribeResult;
import org.geotools.util.logging.Logging;
import org.json.simple.JSONObject;
import org.opengis.feature.simple.SimpleFeatureType;
import org.opengis.filter.Filter;
import org.opengis.filter.FilterFactory;
import org.opengis.filter.sort.SortBy;
import org.opengis.filter.sort.SortOrder;

/**
 * A WPS process to retrieve unique field values from a layer on Geoserver
 * catalog. Requires a valid layer name and a field name to extract the unique
 * values. It accepts sorting and paging parameters.
 * 
 * @author Cesar Martinez Izquierdo
 * @author Sandro Salari
 * @author Mauro Bartolomeoli
 */
@DescribeProcess(title = "PagedUnique", description = "Gets the list of unique values for the given featurecollection on a specified field, allows optional paging")
public class PagedUniqueProcess implements GeoServerProcess {

    /** The LOGGER. */
    private static final Logger LOGGER = Logging
            .getLogger(PagedUniqueProcess.class);
    
    private final FilterFactory FF = CommonFactoryFinder.getFilterFactory2();
    
    
    public static final class Results {
        private String featureTypeName;
        private String fieldName;
        private int size;
        private List<?> values;
        public Results(String featureTypeName, String fieldName, int size,
                List<?> values) {
            super();
            this.featureTypeName = featureTypeName;
            this.fieldName = fieldName;
            this.size = size;
            this.values = values;
        }
        public String getFeatureTypeName() {
            return featureTypeName;
        }
        public String getFieldName() {
            return fieldName;
        }
        public int getSize() {
            return size;
        }
        public List<?> getValues() {
            return values;
        }
        
    }
    
    @DescribeResult(name = "result", type = Results.class, description = "List of values")
    public Results execute(
            @DescribeParameter(name = "features", min = 1, max = 1, description = "Layer from which field values should be retrieved") SimpleFeatureCollection features,
            @DescribeParameter(name = "fieldName", min = 1, max = 1, description = "Field from which the values should be retrieved") String fieldName,
            @DescribeParameter(name = "startIndex", min = 0, max = 1, description = "The index of the first feature to retrieve") Integer startIndex,
            @DescribeParameter(name = "maxFeatures", min = 0, max = 1, description = "The maximum numbers of features to fetch") Integer maxFeatures
            )
            throws IOException, CQLException {
    
        // initial checks on params
        if (features == null) {
            throw new IllegalArgumentException("features param cannot be null");
        }
        if (fieldName == null || fieldName.isEmpty()) {
            throw new IllegalArgumentException("Empty or null fieldName provided!");
        }
        SimpleFeatureType featureType = features.getSchema();
        String featureTypeName = featureType.getTypeName();
        LOGGER.fine("PagedUnique process called on resource: " + featureTypeName
                + " - field: " + fieldName);
    
        
        UniqueVisitor visitor = new UniqueVisitor(FF.property(fieldName));
    
    
        Integer listSize = 0;
        List<String> list = new ArrayList<String>();
    
        try {
            // counts total elements
            features.accepts(visitor, null);
            if(visitor.getResult() == null || visitor.getResult().toList() == null) {
                listSize = 0;
                list = new ArrayList<String>(0);
            } else {
                listSize = visitor.getResult().toList().size();
                if(maxFeatures == null || maxFeatures > listSize) {
                    maxFeatures = listSize;
                }
                // Reset visitor and set pagination
                visitor.reset();
                if(startIndex != null) {
                    visitor.setStartIndex(startIndex);
                }
                if(maxFeatures != null) {
                    visitor.setMaxFeatures(maxFeatures);
                }
                visitor.setPreserveOrder(true);
            
                features.accepts(visitor, null);
                if(visitor.getResult() == null || visitor.getResult().toList() == null) {
                    list = new ArrayList<String>(0);
                } else {
                    list = visitor.getResult().toList();
                }
            
            }
            return new Results(featureTypeName, fieldName, listSize, list);
        } catch (Exception e) {
            throw new ProcessException("Error extracting unique values", e);
        }
            
    }

}