Adding geospatial features to a java web app

A D D I N G G E O S P AT I A L F E AT U R E S
T O A J A V A W E B A P P
C O D E O N E 2 0 1 8

Matti Tahvonen
Web pages from 1994
Web apps from 1996 (JavaScript, Perl, PHP…)
Java web apps from 2006 (Vaadin R&D + helping our
customers)
Since 2014, mostly DevRel/marketing as daily job, but in
Vaadin that means that IDE is open all the time :-)
Orienteering, sailing, hiking, mountain biking, hunting…
OSS ADVOCATE
@mattitahvonen

W H Y A M I H E R E ?
- 1985 Started orienteering (endurance sport)
- 1994 I got interested about WWW
- 2006 Joined a Java company as our ﬁrst JS developer
- 2009 OpenLayers wrapper for Vaadin (Java)
- 2018 I can still do JS & browser magic, but prefer Java & JVM

T O D A Y
- You’ll realise how easy it is to add small (but professional)
GIS features to your existing business apps.
- Full stack Sailing Course Planner example (Open Source)
- Introduction to a set of handy GIS libraries and some
alternatives

SCP - SAILING COURSE PLANNER
OSS A PP TO PL AN AND SET UP SAILING COMPETITIONS

Adding geospatial features to a java web app

A R C H I T E C T U R E O V E R V I E W
PosgreSQL
PostGIS
JVM
Spring Boot, JTS,
Hibernate (spatial),
Geotools, Vaadin,
Leaﬂet
Mobile web app
for course set-up
Desktop/Tablet
optimised web app
for course design

PostgreSQL + PostGIS
Open Source
Excellent support for spatial indexes and
functions
Alternatives:
Oracle, MS SQL, MySQL/MariaSQL, GeoDB (H2 db
extension)…
Many NoSQL databases, like also support spatial
indexes and queries
Do you need spatial aware persistency solution at
all?
Persistency
Sailing Course Planner architecture

Database with spatial extensions?
With large datasets JVM can’t handle all in
memory. “Select entities in this viewport only”,
“Select entities overlapping given polygon” etc…
Datatypes, geospatial functions/operators and
indexes.
Support for somewhat standard SQL extensions
varies a lot among databases.
For some use cases, you don’t need one. Just
store features as blobs, or points in lat/lon
columns.
Persistency

CREATE EXTENSION postgis;
CREATE TABLE geometries (name varchar, geom geometry);
INSERT INTO geometries VALUES
('Point', 'POINT(0 0)'),
('Linestring', 'LINESTRING(0 0, 1 1, 2 1, 2 2)'),
('Polygon', 'POLYGON((0 0, 1 0, 1 1, 0 1, 0 0))'),
('PolygonWithHole', 'POLYGON((0 0, 10 0, 10 10, 0 10, 0 …
('Collection', 'GEOMETRYCOLLECTION(POINT(2 0),POLYGON(( …
SELECT name, ST_AsText(geom) FROM geometries;
SELECT name, ST_AsText(geom) FROM geometries WHERE
ST_Contains(
ST_GeomFromText('POLYGON((-1 -1,1 -1,1 1,-1 1,-1 -1))')
, geom
);
name | st_astext
-----------------+---------------------------------
Point | POINT(0 0)
Linestring | LINESTRING(0 0,1 1,2 1,2 2)
Polygon | POLYGON((0 0,1 0,1 1,0 1,0 0))
PolygonWithHole | POLYGON((0 0,10 0,10 10,0 10,0 …
Collection | GEOMETRYCOLLECTION(POINT(2 0), …
(5 rows)
name | st_astext
---------+--------------------------------
Point | POINT(0 0)
Polygon | POLYGON((0 0,1 0,1 1,0 1,0 0))
(2 rows)
Example derived from the PostGIS tutorial

JVM libraries in use
Spring Boot - application framework
JTS Java Topology Suite - datatypes for domain
model and basic planar math
Spring Data JPA/Hibernate (spatial)- object
relational mapping and database connectivity
Geotools - tools to handle geospatial data in Java
JSR 363, Units of Measurement - conversion of
distances to weird units
Vaadin - the plain Java UI library for web apps
Leaﬂet - a slippy map web component
JVM

Spring Boot
An application framework, makes easy to
develop and deploy web apps.
Alternatives
Plain servlet application, Java EE
Spring Boot

@SpringBootApplication
public class DemoApplication {
public static void main(String[] args) {
SpringApplication.run(DemoApplication.class, args);
}
@Route
public static class MainView extends VerticalLayout {
public MainView() {
add(new Span("Hello World!"));
}
}
}

JTS aka Java Topology Suite
The most commonly used library in Java apps
handling geographical information.
Object model (Point, LineString, Polygon…) for
planar linear geometry and a set of fundamental
geometric functions.
C++ port (GEOM) powers PostGIS, QGIS, Google
Earth etc..
Moving to Eclipse (LocationTech project)
Alternatives
Geolatte, Apache SIS, Spatial4j
JTS

GeometryFactory geometryFactory = new GeometryFactory();
Point point = geometryFactory.createPoint(
new Coordinate(1, 1)
);
LinearRing linearRing = geometryFactory.createLinearRing(
new Coordinate[]{
new Coordinate(0, 0),
new Coordinate(0, 0)
}
);
boolean contains = linearRing.contains(point); // true

Hibernate (spatial)
Hibernate 5 introduced an extension for
geographic types (JTS and Geolatte)
Previously a community extension
Provides also some spatial functions to HQL and
criteria API.
Alternatives
QueryDSL has a spatial extension
EclipseLink (JPA implementation) contains some
custom support for Oracle databases
Plain JDBC (data comes in/out as WKT)
JPA

@Entity
public class SpatialEvent extends AbstractEntity {
private String title;
@Temporal(TemporalType.DATE)
private Date date;
//@Column(columnDefinition = "POINT") // this type is known by MySQL
@Column(columnDefinition = "geometry")
private Point location;
// @Column(columnDefinition = "POLYGON") // this type is known by MySQL
@Column(columnDefinition = "geometry")
private LineString route;
//…
}
//Select only entities within current viewport
Polygon viewPort = geometryFactory.createPolygon( coordinates );
SpatialEvent event = entityManager.createQuery(
"select e " +
"from SpatialEvent e " +
"where within(e.location, :viewPort) = true", SpatialEvent.class)
.setParameter("window", viewPort)
.getSingleResult();
}

Spring Data JPA
Repository pattern for JPA
No special support for geometries, but one can
deﬁne SQL/JPQL/HQL explicitly.
Alternatives
DeltaSpike Data (CDI)
JPA

public interface SailingCourseRepository
extends JpaRepository<SailingCourse,Long> {
// findAll, count, save, delete, findBy(Example example) etc via super interface
@EntityGraph(attributePaths = {"mainBuoys", "helperBuoys", "coursePoints", "adminEmails"})
public SailingCourse findOneWithDetailsById(Long id);
@EntityGraph(attributePaths = {"mainBuoys", "helperBuoys", "coursePoints", "adminEmails"})
public SailingCourse findByUuid(String uuid);
@Query("SELECT DISTINCT s FROM SailingCourse s JOIN s.adminEmails e WHERE e = :email")
public List<SailingCourse> retrieveByEmail(@Param(“email") String email);
}

Geotools: tools for Java GIS apps
Geometry support provided by Java Topology
Suite (JTS)
Read/write many raster and vector formats
Tools for more complex analyses, like geodetic
calculations
Swing components
Alternatives
Spatial4j, Geolatte, Apache SIS
Geotools

double angle = 2 * Math.PI * degrees / 360;
Point centroid = getCentroid();
AffineTransformation at = new AffineTransformation()
.setToRotation(angle, centroid.getX(), centroid.getY());
for (MainBuoy mb : getMainBuoys()) {
Geometry transformed = at.transform(mb.getLocation());
mb.setLocation((Point) transformed);
}
for (HelperBuoy mb : getHelperBuoys()) {
Geometry transformed = at.transform(mb.getLocation());
mb.setLocation((Point) transformed);
}
Why Geotools?
Transformation of WSG84 coordinates using JTS
Don’t do this with geodesic coordinates!

gc = new GeodeticCalculator()
gc.setStartingGeographicPoint(
lastKnownPoint.getLon(),
lastKnownPoint.getLat()
);
gc.setDestinationPosition(
JTS.toDirectPosition(
targetBuoy.getLocation().getCoordinate(), crs)
);
int azimuth = (int) gc.getAzimuth();
if (azimuth < 0) {
// convert to "compass angle"
azimuth = azimuth + 360;
}
double orthodromicDistance = gc.getOrthodromicDistance();

C O U N T R I E S N O T U S I N G
M E T R I C S Y S T E M

Units of Measurement API
A new standard Java API for presenting and
handling units of measurement.
Libraries by default use SI units
Not that tightly related to geospatial features, but
you quite often need custom presentation for
that one nation (and sailors).
Alternatives
Dig constants from wikipedia and build your own
conversion methods
JSR 363 UOM

public static String formatDistance(double meters) {
LengthAmount l = new LengthAmount(meters, SI.METRE);
Quantity to = l.to(NonSI.NAUTICAL_MILE);
return String.format("%d m, %.2f nm", (int) meters, to.getValue());
}

Vaadin - Java UI framework to build
modern web apps
Creates XHR/WebSocket powered SPAa even
with plain Java code, without web expertise.
For both desktop and mobile devices.
Extensible and has 700+ community extensions.
Has good slippy map widgets based on Leaﬂet,
OpenLayers and Google Maps
Alternatives
JSF, Wicket, React (JS), Angular (JS), Vue (JS)
Vaadin

new VerticalLayout(
new Button("I'm a button"),
new DatePicker("Select a date"),
new ComboBox <>("Select an option"),
new Span("I'm a <span>")
);

Slim OSS alternative to Google Maps
Small well performing core
Good support for different base maps
Excellent for both desktop and mobile devices
Extensible, lot of community extensions
Alternatives
OpenLayers, Google Maps (license!!), Mapbox GL
JS (License)
Leaﬂet

Java/Vaadin API for LeafletJS
Wraps LeafletJS with Java API
Trivial to integrate to other JVM technologies, no
REST APIs or data conversions needed
Contains Vaadin fields to directly edit JTS data
types -> developer productivity
Extension for editing, heat map, marker cluster…
Alternatives
Vaadin OpenLayers integration, JSF integrations,
REST API + client side JS code (additional
complexity, but access to all low level details)
v-leaflet

LMap map = new LMap();
map.addLayer(new LOpenStreetMapLayer());
map.addLayer(new LMarker(-122.3, 37.7));
private TextField title = new TextField();
private DateField date = new DateField();
private PointField location = new PointField();
private LineStringField route = new LineStringField();
public void bindEntityToForm(SpatialEvent entity) {
layout.add(title, date, location, route);
// naming based binding to properties in SpatialEvent
BeanValidationBinder<SpatialEvent> binder =
new BeanValidationBinder<>(SpatialEvent.class);
binder.bindInstanceFields(this);
binder.setBean(entity);
}

KEY TAKEAWAYS
ADDING GEOS PATI AL FEATURES TO A JAVA WEB APP

D E V E L O P I N G B A S I C G E O S P AT I A L F E AT U R E S I S
E A S I E R T H A N YO U T H I N K

J A V A E C O S Y S T E M H A S A L O T O F H A N D Y
L I B R A R I E S F O R G I S

V A A D I N + L E A F L E T I S P R O B A B L Y T H E E A S I E S T
S O L U T I O N F O R J A V A D E V E L O P E R T O B U I L D U I

Vaadin booth in expo area
github.com/mstahv/scp
vaadin.com/forum
I’ll be there for more questions today & tomorrow.
Source code for the Sailing Course Planner example
A good place for Vaadin (+ geospatial) related questions
Vaadin BOF session today 20:30
BOF5640 in room 2010, today 08:30 PM

T H A N K S
@ M A T T I T A H V O N E N

Q U E S T I O N S ?
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Adding geospatial features to a java web app

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