How to get CRS (coordinate system) of a shapefile. Java

Question

I am reading a shapefile using org.geotols 9.4 and trying to get CRS code but org.opengis.referencing.crs.CoordinateReferenceSystem is null:

FileDataStore store = FileDataStoreFinder.getDataStore(shpFile);
CoordinateReferenceSystem crs = store.getFeatureSource().getSchema().getCoordinateReferenceSystem();
// crs is null

and parsing .prj throws an error:

  String wkt = new String(Files.readAllBytes(Paths.get(shpFile.getAbsolutePath().replace(".shp", ".prj"))));
  crs = CRS.parseWKT(wkt);
  // throws org.opengis.referencing.NoSuchIdentifierException: No transform for classification "Mercator_Auxiliary_Sphere"  

Projection file is:

PROJCS["WGS_1984_Web_Mercator_Auxiliary_Sphere",GEOGCS["GCS_WGS_1984",DATUM["D_WGS_1984",SPHEROID["WGS_1984",6378137.0,298.257223563]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],PROJECTION["Mercator_Auxiliary_Sphere"],PARAMETER["False_Easting",0.0],PARAMETER["False_Northing",0.0],PARAMETER["Central_Meridian",0.0],PARAMETER["Standard_Parallel_1",0.0],PARAMETER["Auxiliary_Sphere_Type",0.0],UNIT["Meter",1.0]]

I am looking for an answer to why geotools can not determine the CRS and for a solution to determine all CRS rather than a workaround with this particular projection/file.

Answer 1

The following code works for me:

    String wkt = "PROJCS[\"WGS_1984_Web_Mercator_Auxiliary_Sphere\",GEOGCS[\"GCS_WGS_1984\",DATUM[\"D_WGS_1984\",SPHEROID[\"WGS_1984\",6378137.0,298.257223563]],PRIMEM[\"Greenwich\",0.0],UNIT[\"Degree\",0.0174532925199433]],PROJECTION[\"Mercator_Auxiliary_Sphere\"],PARAMETER[\"False_Easting\",0.0],PARAMETER[\"False_Northing\",0.0],PARAMETER[\"Central_Meridian\",0.0],PARAMETER[\"Standard_Parallel_1\",0.0],PARAMETER[\"Auxiliary_Sphere_Type\",0.0],UNIT[\"Meter\",1.0]]";
    CoordinateReferenceSystem crs = CRS.parseWKT(wkt);
    assert crs != null;
    Integer actualCode = CRS.lookupEpsgCode(crs, false);
    System.out.println(actualCode);

and provides the result 3857 which sounds about right as ESRI:102100 is deprecated.

Just in case it was an authority issue I tested with both gt-epsg-hsql and gt-epsg-wkt and both were fine.