Package edu.cnu.mdi.mapping.loader

Class GeoJsonCountryLoader

java.lang.Object

edu.cnu.mdi.mapping.loader.GeoJsonCountryLoader

All Implemented Interfaces:

ICountryLoader

public final class GeoJsonCountryLoader
extends Object
implements ICountryLoader

Utility for loading country boundary polygons from a GeoJSON FeatureCollection.

Designed primarily for Natural Earth 10m cultural vectors, but tolerates minor schema variations. Features with missing required properties or unsupported geometry types are silently skipped rather than causing a parse failure.

Expected GeoJSON schema

 {
   "type": "FeatureCollection",
   "features": [
     {
       "type": "Feature",
       "properties": {
         "ADMIN":  "United States of America",
         "ISO_A3": "USA"
       },
       "geometry": {
         "type": "Polygon" | "MultiPolygon",
         "coordinates": [...]   // degrees, longitude first
       }
     }, ...
   ]
 }
 

Coordinate handling

Input coordinates are in degrees (longitude, latitude order as required by GeoJSON RFC 7946). They are converted to radians and the longitude is wrapped to (-π, π] before being stored in the returned GeoJsonCountryLoader.CountryFeature.

Thread safety

This class has no mutable state. The internal ObjectMapper is thread-safe for reading and may be shared freely. The returned lists are unmodifiable.

This class is not instantiable.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static final class	GeoJsonCountryLoader.CountryFeature	Immutable representation of a single country feature consisting of an administrative name, an ISO-3166-1 alpha-3 code, and one or more polygon rings expressed as lists of geographic points in radians.

Constructor Summary

Constructors

Constructor	Description
GeoJsonCountryLoader()	No-arg constructor required for use as an ICountryLoader instance.

Method Summary

Modifier and Type	Method	Description
List<GeoJsonCountryLoader.CountryFeature>	load(Path path)	Loads country features from the given filesystem path.
List<GeoJsonCountryLoader.CountryFeature>	loadFromResource(String resourcePath)	Loads country features from a classpath resource.
static List<GeoJsonCountryLoader.CountryFeature>	loadFromResourceStatic(String resourcePath)	Static convenience overload: loads country features from a classpath resource.
static List<GeoJsonCountryLoader.CountryFeature>	loadStatic(Path geoJsonPath)	Static convenience overload: loads country features from a GeoJSON file.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

GeoJsonCountryLoader

public GeoJsonCountryLoader()

No-arg constructor required for use as an ICountryLoader instance.

Method Details

load

public List<GeoJsonCountryLoader.CountryFeature> load(Path path)
                                               throws IOException

Loads country features from the given filesystem path.

The path may point to the primary file of a multi-file format (e.g. the .shp file of a shapefile set) or to a self-contained file (e.g. a .geojson file). Implementations are responsible for locating any companion files (e.g. .dbf, .shx) relative to the supplied path.

— delegates to loadStatic(Path).

Specified by:

load in interface ICountryLoader

Parameters:

path - path to the data file; must not be null

Returns:

unmodifiable list of country features; never null

Throws:

IOException - if the file cannot be read or parsed

loadFromResource

public List<GeoJsonCountryLoader.CountryFeature> loadFromResource(String resourcePath)
                                                           throws IOException

Loads country features from a classpath resource.

The resource path must be absolute (begin with /) so that Class.getResourceAsStream(String) resolves it correctly. For multi-file formats this method may not be supportable (e.g. a shapefile set cannot be fully represented as a single classpath resource); in that case implementations should throw UnsupportedOperationException with a clear message.

— delegates to loadFromResourceStatic(String).

Specified by:

loadFromResource in interface ICountryLoader

Parameters:

resourcePath - absolute classpath resource path; must not be null

Returns:

unmodifiable list of country features; never null

Throws:

IOException - if the resource cannot be read or parsed

loadStatic

public static List<GeoJsonCountryLoader.CountryFeature> loadStatic(Path geoJsonPath)
                                                            throws IOException

Static convenience overload: loads country features from a GeoJSON file.

Parameters:

geoJsonPath - path to a GeoJSON FeatureCollection file

Returns:

unmodifiable list of GeoJsonCountryLoader.CountryFeature instances

Throws:

IOException - if an I/O or JSON parse error occurs

loadFromResourceStatic

public static List<GeoJsonCountryLoader.CountryFeature> loadFromResourceStatic(String resourcePath)
                                                                        throws IOException

Static convenience overload: loads country features from a classpath resource. The resource path must begin with /.

Parameters:

resourcePath - absolute classpath resource path

Returns:

unmodifiable list of GeoJsonCountryLoader.CountryFeature instances

Throws:

IOException - if the resource cannot be found, read, or parsed