routing.md

Routing via Java API

To use the following examples you need to specify the dependency in your Maven config correctly.

To do routing in your Java code you'll need just a few lines of code:

// create one GraphHopper instance
GraphHopper hopper = new GraphHopperOSM().forServer();
hopper.setDataReaderFile(osmFile);
// where to store graphhopper files?
hopper.setGraphHopperLocation(graphFolder);
hopper.setEncodingManager(new EncodingManager("car"));

// now this can take minutes if it imports or a few seconds for loading
// of course this is dependent on the area you import
hopper.importOrLoad();

// simple configuration of the request object, see the GraphHopperServlet classs for more possibilities.
GHRequest req = new GHRequest(latFrom, lonFrom, latTo, lonTo).
    setWeighting("fastest").
    setVehicle("car").
    setLocale(Locale.US);
GHResponse rsp = hopper.route(req);

// first check for errors
if(rsp.hasErrors()) {
   // handle them!
   // rsp.getErrors()
   return;
}

// use the best path, see the GHResponse class for more possibilities.
PathWrapper path = rsp.getBest();

// points, distance in meters and time in millis of the full path
PointList pointList = path.getPoints();
double distance = path.getDistance();
long timeInMs = path.getTime();

InstructionList il = path.getInstructions();
// iterate over every turn instruction
for(Instruction instruction : il) {
   instruction.getDistance();
   ...
}

// or get the json
List<Map<String, Object>> iList = il.createJson();

// or get the result as gpx entries:
List<GPXEntry> list = il.createGPXList();

Speed mode vs. Hybrid mode vs. Flexibile mode

The default option of GraphHopper is the speed mode. If you don't want to use the speed-up mode you can disable it before the import (see config.yml prepare.ch.weightings=no) or on a per request base by adding ch.disable=true to the request. If you want to use the hybrid mode you have to enable it before the import (see config.yml prepare.lm.weightings=fastest).

If you need multiple vehicle profiles you can specify a list of vehicle profiles (see config.yml e.g. graph.flag_encoders=car,bike or use new EncodingManager("car,bike")).

To calculate a route you have to pick one vehicle and optionally an algorithm like bidirectional_astar:

GraphHopper hopper = new GraphHopperOSM().forServer();
hopper.setCHEnabled(false);
hopper.setOSMFile(osmFile);
hopper.setGraphHopperLocation(graphFolder);
hopper.setEncodingManager(new EncodingManager("car,bike"));

hopper.importOrLoad();

GHRequest req = new GHRequest(latFrom, lonFrom, latTo, lonTo).
    setVehicle("bike").setAlgorithm(Parameters.Algorithms.ASTAR_BI);
GHResponse res = hopper.route(req);

Heading

The flexibile and hybrid mode allows to add a desired heading (north based azimuth between 0 and 360 degree) to any point. Adding a heading makes it more likely that a route starts towards the provided direction:

GHRequest req = new GHRequest().addPoint(new GHPoint (latFrom, lonFrom), favoredHeading).addPoint(new GHPoint (latTo, lonTo));

or to avoid u-turns at via points

req.getHints().put(Parameters.Routing.PASS_THROUGH, true);

A heading with the value 'NaN' won't be enforced and a heading not within [0, 360] will trigger an IllegalStateException. It is important to note that if you force the heading at via or end points the outgoing heading needs to be specified. I.e. if you want to force "coming from south" to a destination you need to specify the resulting "heading towards north" instead, which is 0.

Alternative Routes

The flexibile and hybrid mode allows you to calculate alternative routes via:

req.setAlgorithm(Parameters.Algorithms.ALT_ROUTE)

Note that this setting can affect speed of your routing requests.

You can tune the maximum numbers via:

req.getHints().put(Parameters.AltRoute.MAX_PATHS, "3");

See the Parameters class for further hints.

Java client (client-hc)

If you want to calculate routes using the GraphHopper Directions API or a self hosted instance of GraphHopper, you can use the Java and Android client-hc (there are also clients for Java Script and many other languages).

GraphHopperAPI gh = new GraphHopperWeb();
gh.load("http://your-graphhopper-service.com");

// or for the GraphHopper Directions API https://graphhopper.com/#directions-api
// gh.load("https://graphhopper.com/api/1/route");

GHResponse rsp = gh.route(new GHRequest(...));