geojson.js

用来在地图上做操作GIS,在地图上做标记

/* Copyright (c) 2006-2007 MetaCarta, Inc., published under the BSD license.
 * See http://svn.openlayers.org/trunk/openlayers/release-license.txt 
 * for the full text of the license. */

/**
 * @requires OpenLayers/Format/JSON.js
 * @requires OpenLayers/Feature/Vector.js
 * @requires OpenLayers/Geometry/Point.js
 * @requires OpenLayers/Geometry/MultiPoint.js
 * @requires OpenLayers/Geometry/LineString.js
 * @requires OpenLayers/Geometry/MultiLineString.js
 * @requires OpenLayers/Geometry/Polygon.js
 * @requires OpenLayers/Geometry/MultiPolygon.js
 *
 * Class: OpenLayers.Format.GeoJSON
 * Read and write GeoJSON. Create a new parser with the
 *     <OpenLayers.Format.GeoJSON> constructor.
 *
 * Inherits from:
 *  - <OpenLayers.Format.JSON>
 */
OpenLayers.Format.GeoJSON = OpenLayers.Class(OpenLayers.Format.JSON, {

    /**
     * Constructor: OpenLayers.Format.GeoJSON
     * Create a new parser for GeoJSON.
     *
     * Parameters:
     * options - {Object} An optional object whose properties will be set on
     *     this instance.
     */
    initialize: function(options) {
        OpenLayers.Format.JSON.prototype.initialize.apply(this, [options]);
    },

    /**
     * APIMethod: read
     * Deserialize a GeoJSON string.
     *
     * Parameters:
     * json - {String} A GeoJSON string
     * type - {String} Optional string that determines the structure of
     *     the output.  Supported values are "Geometry", "Feature",
     *     "GeometryCollection", and "FeatureCollection".  If absent or null,
     *     a default of "FeatureCollection" is assumed.
     * filter - {Function} A function which will be called for every key and
     *     value at every level of the final result. Each value will be
     *     replaced by the result of the filter function. This can be used to
     *     reform generic objects into instances of classes, or to transform
     *     date strings into Date objects.
     *
     * Returns: 
     * {Object} The return depends on the value of the type argument. If type
     *     is "FeatureCollection" (the default), the return will be an array
     *     of <OpenLayers.Feature.Vector>. If type is "Geometry", the input json
     *     must represent a single geometry, and the return will be an
     *     <OpenLayers.Geometry>.  If type is "Feature", the input json must
     *     represent a single feature, and the return will be an
     *     <OpenLayers.Feature.Vector>.  If type is "GeometryCollection", the
     *     input json must represent a geometry collection, and the return will
     *     be an array of <OpenLayers.Geometry>.
     */
    read: function(json, type, filter) {
        type = (type) ? type : "FeatureCollection";
        var results = null;
        var obj = null;
        if (typeof json == "string") {
            obj = OpenLayers.Format.JSON.prototype.read.apply(this,
                                                              [json, filter]);
        } else { 
            obj = json;
        }    
        if(!obj) {
            OpenLayers.Console.error("Bad JSON: " + json);
        } else if(typeof(obj.type) != "string") {
            OpenLayers.Console.error("Bad GeoJSON - no type: " + json);
        } else if(this.isValidType(obj, type)) {
            switch(type) {
                case "Geometry":
                    try {
                        results = this.parseGeometry(obj);
                    } catch(err) {
                        OpenLayers.Console.error(err);
                    }
                    break;
                case "Feature":
                    try {
                        results = this.parseFeature(obj);
                        results.type = "Feature";
                    } catch(err) {
                        OpenLayers.Console.error(err);
                    }
                    break;
                case "GeometryCollection":
                    results = [];
                    for(var i=0; i<obj.geometries.length; ++i) {
                        try {
                            results.push(this.parseGeometry(obj.geometries[i]));
                        } catch(err) {
                            results = null;
                            OpenLayers.Console.error(err);
                        }
                    }
                    break;
                case "FeatureCollection":
                    // for type FeatureCollection, we allow input to be any type
                    results = [];
                    switch(obj.type) {
                        case "Feature":
                            try {
                                results.push(this.parseFeature(obj));
                            } catch(err) {
                                results = null;
                                OpenLayers.Console.error(err);
                            }
                            break;
                        case "FeatureCollection":
                            for(var i=0; i<obj.features.length; ++i) {
                                try {
                                    results.push(this.parseFeature(obj.features[i]));
                                } catch(err) {
                                    results = null;
                                    OpenLayers.Console.error(err);
                                }
                            }
                            break;
                        case "GeometryCollection":
                            for(var i=0; i<obj.geometries.length; ++i) {
                                try {
                                    var geom = this.parseGeometry(obj.geometries[i]);
                                    results.push(new OpenLayers.Feature.Vector(geom));
                                } catch(err) {
                                    results = null;
                                    OpenLayers.Console.error(err);
                                }
                            }
                            break;
                        default:
                            try {
                                var geom = this.parseGeometry(obj);
                                results.push(new OpenLayers.Feature.Vector(geom));
                            } catch(err) {
                                results = null;
                                OpenLayers.Console.error(err);
                            }
                    }
                break;
            }
        }
        return results;
    },
    
    /**
     * Method: isValidType
     * Check if a GeoJSON object is a valid representative of the given type.
     *
     * Returns:
     * {Boolean} The object is valid GeoJSON object of the given type.
     */
    isValidType: function(obj, type) {
        var valid = false;
        switch(type) {
            case "Geometry":
                if(OpenLayers.Util.indexOf(["Point", "MultiPoint", "LineString",
                                            "MultiLineString", "Polygon",
                                            "MultiPolygon", "Box"], obj.type) == -1) {
                    // unsupported geometry type
                    OpenLayers.Console.error("Unsupported geometry type: " +
                                              obj.type);
                } else {
                    valid = true;
                }
                break;
            case "FeatureCollection":
                // allow for any type to be converted to a feature collection
                valid = true;
                break
            default:
                // for GeometryCollection and Feature, types must match
                if(obj.type == type) {
                    valid = true;
                } else {
                    OpenLayers.Console.error("Cannot convert types from " +
                                              obj.type + " to " + type);
                }
        }
        return valid;
    },
    
    /**
     * Method: parseFeature
     * Convert a feature object from GeoJSON into an
     *     <OpenLayers.Feature.Vector>.
     *
     * Parameters:
     * obj - {Object} An object created from a GeoJSON object
     *
     * Returns:
     * {<OpenLayers.Feature.Vector>} A feature.
     */
    parseFeature: function(obj) {
        var feature, geometry, attributes;
        attributes = (obj.properties) ? obj.properties : {};
        try {
            geometry = this.parseGeometry(obj.geometry);            
        } catch(err) {
            // deal with bad geometries
            throw err;
        }
        feature = new OpenLayers.Feature.Vector(geometry, attributes);
        if(obj.id) {
            feature.fid = obj.id;
        }
        return feature;
    },
    
    /**
     * Method: parseGeometry
     * Convert a geometry object from GeoJSON into an <OpenLayers.Geometry>.
     *
     * Parameters:
     * obj - {Object} An object created from a GeoJSON object
     *
     * Returns: 
     * {<OpenLayers.Geometry>} A geometry.
     */
    parseGeometry: function(obj) {
        var geometry;
        if(!(obj.coordinates instanceof Array)) {
            throw "Geometry must have coordinates array: " + obj;
        }
        if(!this.parseCoords[obj.type.toLowerCase()]) {
            throw "Unsupported geometry type: " + obj.type;
        }
        try {
            geometry = this.parseCoords[obj.type.toLowerCase()].apply(this, [obj.coordinates]);
        } catch(err) {
            // deal with bad coordinates
            throw err;
        }
        return geometry;
    },
    
    /**
     * Property: parseCoords
     * Object with properties corresponding to the GeoJSON geometry types.
     *     Property values are functions that do the actual parsing.
     */
    parseCoords: {
        /**
         * Method: parseCoords.point
         * Convert a coordinate array from GeoJSON into an
         *     <OpenLayers.Geometry>.
         *
         * Parameters:
         * array - {Object} The coordinates array from the GeoJSON fragment.
         *
         * Returns:
         * {<OpenLayers.Geometry>} A geometry.
         */
        "point": function(array) {
            if(array.length != 2) {
                throw "Only 2D points are supported: " + array;
            }
            return new OpenLayers.Geometry.Point(array[0], array[1]);
        },
        
        /**
         * Method: parseCoords.multipoint
         * Convert a coordinate array from GeoJSON into an
         *     <OpenLayers.Geometry>.
         *
         * Parameters:
         * array {Object} The coordinates array from the GeoJSON fragment.
         *
         * Returns:
         * {<OpenLayers.Geometry>} A geometry.
         */
        "multipoint": function(array) {
            var points = [];
            var p = null;
            for(var i=0; i<array.length; ++i) {
                try {
                    p = this.parseCoords["point"].apply(this, [array[i]]);
                } catch(err) {
                    throw err;
                }
                points.push(p);
            }
            return new OpenLayers.Geometry.MultiPoint(points);
        },

        /**
         * Method: parseCoords.linestring
         * Convert a coordinate array from GeoJSON into an
         *     <OpenLayers.Geometry>.
         *
         * Parameters:
         * array - {Object} The coordinates array from the GeoJSON fragment.
         *
         * Returns:
         * {<OpenLayers.Geometry>} A geometry.
         */
        "linestring": function(array) {
            var points = [];
            var p = null;
            for(var i=0; i<array.length; ++i) {
                try {
                    p = this.parseCoords["point"].apply(this, [array[i]]);
                } catch(err) {
                    throw err;
                }
                points.push(p);
            }
            return new OpenLayers.Geometry.LineString(points);
        },
        
        /**
         * Method: parseCoords.multilinestring
         * Convert a coordinate array from GeoJSON into an
         *     <OpenLayers.Geometry>.
         *
         * Parameters:
         * array - {Object} The coordinates array from the GeoJSON fragment.
         *
         * Returns:
         * {<OpenLayers.Geometry>} A geometry.
         */
        "multilinestring": function(array) {
            var lines = [];
            var l = null;
            for(var i=0; i<array.length; ++i) {
                try {
                    l = this.parseCoords["linestring"].apply(this, [array[i]]);
                } catch(err) {
                    throw err;