WFS layer from GeoServer with OL4 - String index out of range error

Question

I need to load a WFS layer from GeoServer 2.8 to a web app using OpenLayers 4.6.5 and JQuery 2.2.3 so that I can use Select to highlight a feature on click. I can preview the line layer as a WMS with no problems in GeoServer, but when I try loading in the app, in the network response gives this error:

  <ows:Exception exceptionCode="NoApplicableCode">
    <ows:ExceptionText>java.lang.RuntimeException: 
    java.lang.StringIndexOutOfBoundsException: String index out of range: -1
    java.lang.StringIndexOutOfBoundsException: String index out of range: -1
    String index out of range: -1
   </ows:ExceptionText>
  </ows:Exception>

There are no errors in the console.

What could be causing this? The ajax call is below:

var layerWFS = new ol.layer.Vector({
source: new ol.source.Vector({
    loader: function (extent) {
        $.ajax('http://servername:8080/geoserver/wfs', {
            type: 'GET',
            data: {
                service: 'WFS',
                version: '1.1.0',
                request: 'GetFeature',
                typename: 'lines',
                srsname: 'EPSG:2263',
            }
        }).done(function (response) {
            layerWFS
            .getSource()
            .addFeatures(new ol.format.WFS()
            .readFeatures(response));               
        });
    },

    strategy: ol.loadingstrategy.all,
    projection: 'EPSG:2263',
    crossOrigin: 'anonymous',
}),

here is a snippet of the GeoServer log file:

2020-03-30 12:10:50,790 INFO [geoserver.wfs] - Request: getServiceInfo 2020-03-30 12:10:50,806 INFO [geoserver.wfs] - Request: getFeature service = WFS version = 1.1.0 baseUrl = http://servername:8080/geoserver/ query[0]: srsName = EPSG:2263 typeName[0] = {http://boundlessgeo.com/}lines outputFormat = text/xml; subtype=gml/3.1.1 resultType = results 2020-03-30 12:10:50,853 ERROR [geoserver.ows] - java.lang.RuntimeException: java.lang.StringIndexOutOfBoundsException: String index out of range: -1 at org.geotools.xml.Encoder.encode(Encoder.java:738) at org.geotools.xml.Encoder.encode(Encoder.java:609) at org.geoserver.wfs.xml.GML3OutputFormat.encode(GML3OutputFormat.java:302) at org.geoserver.wfs.xml.GML3OutputFormat.write(GML3OutputFormat.java:279) at org.geoserver.wfs.WFSGetFeatureOutputFormat.write(WFSGetFeatureOutputFormat.java:196) at org.geoserver.ows.Dispatcher.response(Dispatcher.java:996) at org.geoserver.ows.Dispatcher.handleRequestInternal(Dispatcher.java:279) at org.springframework.web.servlet.mvc.AbstractController.handleRequest(AbstractController.java:153) at org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter.handle(SimpleControllerHandlerAdapter.java:48)

here is what I found later in log under 'caused by':

Caused by: java.lang.StringIndexOutOfBoundsException: String index out of range: -1 at java.lang.AbstractStringBuilder.setLength(Unknown Source) at java.lang.StringBuffer.setLength(Unknown Source) at org.geotools.gml2.simple.GMLWriter.coordinates(GMLWriter.java:302) at org.geotools.gml2.simple.GMLWriter.positions(GMLWriter.java:291) at org.geotools.gml2.simple.GMLWriter.posList(GMLWriter.java:348) at org.geotools.gml3.simple.LineStringEncoder.encode(LineStringEncoder.java:52) at org.geotools.gml3.simple.LineStringEncoder.encode(LineStringEncoder.java:34) at org.geotools.gml2.simple.FeatureCollectionEncoderDelegate.encodeValue(FeatureCollectionEncoderDelegate.java:196) at org.geotools.gml2.simple.FeatureCollectionEncoderDelegate.encodeFeature(FeatureCollectionEncoderDelegate.java:176) at org.geotools.gml2.simple.FeatureCollectionEncoderDelegate.encode(FeatureCollectionEncoderDelegate.java:130) at org.geotools.xml.Encoder.encode(Encoder.java:735)

Answer 1

I received this response from Josh at Planet Federal (formerly BoundlessGeo):

"That code is trying to build a string from all of the coordinates in the current feature by using a simple for-loop and iterating over all of the coordinates. When it's done, it's trying to reduce the size of the string builder to 1 less than the current value. However, it appears that the coordinate size is zero, so the string builder length is zero, and when it tries to set the value to 1 less than the current value (-1), it's producing that exception. Is there a chance some of your data does not have geometries?"

so we looked for empty geometries using st_isemtpy(geom) and found some, once those were removed the table loaded correctly as WFS (btw, we use using PostgresSQL tables).

side note - I had already looked for empty value is an IS NULL query, but that returned no rows...then I learned that there can be rows with an empty string.