[[spatial]]
== Spatial
:sourcedir: ../../../../../../test/java/org/hibernate/userguide/spatial
:extrasdir: extras

[[spatial-overview]]
=== Overview

Hibernate Spatial was originally developed as a generic extension to Hibernate for handling geographic data.
Since 5.0, Hibernate Spatial is now part of the Hibernate ORM project,
and it allows you to deal with geographic data in a standardized way.

Hibernate Spatial provides a standardized, cross-database interface to geographic data storage and query functions.
It supports most of the functions described by the OGC Simple Feature Specification. Supported databases are Oracle 10g/11g,
PostgreSQL/PostGIS, MySQL, Microsoft SQL Server and H2/GeoDB.

Spatial data types are not part of the Java standard library, and they are absent from the JDBC specification.
Over the years http://tsusiatsoftware.net/jts/main.html[JTS] has emerged the _de facto_ standard to fill this gap. JTS is
an implementation of the https://portal.opengeospatial.org/files/?artifact_id=829[Simple Feature Specification (SFS)]. Many databases
on the other hand implement the SQL/MM - Part 3: Spatial Data specification - a related, but broader specification. The biggest difference is that
SFS is limited to 2D geometries in the projected plane (although JTS supports 3D coordinates), whereas
SQL/MM supports 2-, 3- or 4-dimensional coordinate spaces.

Hibernate Spatial supports two different geometry models: http://tsusiatsoftware.net/jts/main.html[JTS] and
https://github.com/GeoLatte/geolatte-geom[geolatte-geom]. As already mentioned, JTS is the _de facto_
standard. Geolatte-geom (also written by the lead developer of Hibernate Spatial) is a more recent library that
supports many features specified in SQL/MM but not available in JTS (such as support for 4D geometries, and support for extended WKT/WKB formats).
Geolatte-geom also implements encoders/decoders for the database native types. Geolatte-geom has good interoperability with
JTS. Converting a Geolatte `geometry` to a JTS `geometry, for instance, doesn't require copying of the coordinates.
It also delegates spatial processing to JTS.

Whether you use JTS or Geolatte-geom, Hibernate spatial maps the database spatial types to your geometry model of choice. It will, however,
always use Geolatte-geom to decode the database native types.

Hibernate Spatial also makes a number of spatial functions available in HQL and in the Criteria Query API. These functions are
specified in both SQL/MM as SFS, and are commonly implemented in databases with spatial support (see <<spatial-configuration-dialect-features>>)

[[spatial-configuration]]
=== Configuration

Hibernate Spatial requires some configuration prior to start using it.

[[spatial-configuration-dependency]]
==== Dependency

You need to include the `hibernate-spatial` dependency in your build environment.
For Maven, you need to add the following dependency:

[[spatial-configuration-maven-example]]
.Maven dependency
====
[source,xml]
----
<dependency>
    <groupId>org.hibernate</groupId>
    <artifactId>hibernate-spatial</artifactId>
    <version>${hibernate.version}</version>
</dependency>
----
====

[[spatial-configuration-dialect]]
==== Dialects

Hibernate Spatial extends the Hibernate ORM dialects so that the spatial functions of the database are made available within HQL and JPQL.
So, for instance, instead of using the `PostgreSQL82Dialect`, we use the Hibernate Spatial extension of that dialect which is the `PostgisDialect`.

[[spatial-configuration-dialect-example]]
.Specifying a spatial dialect
====
[source,xml]
----
<property
    name="hibernate.dialect"
    value="org.hibernate.spatial.dialect.postgis.PostgisDialect"
/>
----
====

Not all databases support all the functions defined by Hibernate Spatial.
The table below provides an overview of the functions provided by each database. If the function is defined in the
https://portal.opengeospatial.org/files/?artifact_id=829[Simple Feature Specification], the description references the
relevant section.

:yes: icon:check[role="green"]
:no: icon:times[role="red"]
[[spatial-configuration-dialect-features]]
.Hibernate Spatial dialect function support
[cols=",,,,,,," |options="header",]
|================================
|Function | Description | PostgresSQL | Oracle 10g/11g | MySQL | SQLServer | GeoDB (H2) | DB2
|Basic functions on Geometry | | | | | | |
|`int dimension(Geometry)` | SFS §2.1.1.1 | {yes} | {yes} | {yes} | {yes} | {yes} | {yes}
|`String geometrytype(Geometry)` | SFS §2.1.1.1 | {yes} | {yes} | {yes} | {yes} | {yes} | {yes}
|`int srid(Geometry)` | SFS §2.1.1.1 | {yes} | {yes} | {yes} | {yes} | {yes} | {yes}
|`Geometry envelope(Geometry)` | SFS §2.1.1.1 | {yes} | {yes} | {yes} | {yes} | {yes} | {yes}
|`String astext(Geometry)` | SFS §2.1.1.1 | {yes} | {yes} | {yes} | {yes} | {yes} | {yes}
|`byte[] asbinary(Geometry)` | SFS §2.1.1.1 | {yes} | {yes} | {yes} | {yes} | {yes} | {yes}
|`boolean isempty(Geometry)` | SFS §2.1.1.1 | {yes} | {yes} | {yes} | {yes} | {yes} | {yes}
|`boolean issimple(Geometry)` | SFS §2.1.1.1 | {yes} | {yes} | {yes} | {yes} | {yes} | {yes}
|`Geometry boundary(Geometry)` | SFS §2.1.1.1 | {yes} | {yes} | {no} | {yes} | {yes} | {yes}
|Functions for testing Spatial Relations between geometric objects | | | | | | |
|`boolean equals(Geometry, Geometry)` | SFS §2.1.1.2 | {yes} | {yes} | {yes} | {yes} | {yes} | {yes}
|`boolean disjoint(Geometry, Geometry)` | SFS §2.1.1.2 | {yes} | {yes} | {yes} | {yes} | {yes} | {yes}
|`boolean intersects(Geometry, Geometry)` | SFS §2.1.1.2 | {yes} | {yes} | {yes} | {yes} | {yes} | {yes}
|`boolean touches(Geometry, Geometry)` | SFS §2.1.1.2 | {yes} | {yes} | {yes} | {yes} | {yes} | {yes}
|`boolean crosses(Geometry, Geometry)` | SFS §2.1.1.2 | {yes} | {yes} | {yes} | {yes} | {yes} | {yes}
|`boolean within(Geometry, Geometry)` | SFS §2.1.1.2 | {yes} | {yes} | {yes} | {yes} | {yes} | {yes}
|`boolean contains(Geometry, Geometry)` | SFS §2.1.1.2 | {yes} | {yes} | {yes} | {yes} | {yes} | {yes}
|`boolean overlaps(Geometry, Geometry)` | SFS §2.1.1.2 | {yes} | {yes} | {yes} | {yes} | {yes} | {yes}
|`boolean relate(Geometry, Geometry, String)` | SFS §2.1.1.2 | {yes} | {yes} | {no} | {yes} | {yes} | {yes}
|Functions that support Spatial Analysis | | | | | | |
|`double distance(Geometry, Geometry)` | SFS §2.1.1.3 | {yes} | {yes} | {no} | {yes} | {yes} | {yes}
|`Geometry buffer(Geometry, double)` | SFS §2.1.1.3 | {yes} | {yes} | {no} | {yes} | {yes} | {yes}
|`Geometry convexhull(Geometry)` | SFS §2.1.1.3 | {yes} | {yes} | {no} | {yes} | {yes} | {yes}^(1)^
|`Geometry intersection(Geometry, Geometry)` | SFS §2.1.1.3 | {yes} | {yes} | {no} | {yes} | {yes} | {yes}^(1)^
|`Geometry geomunion(Geometry, Geometry)` | SFS §2.1.1.3 (renamed from union) | {yes} | {yes} | {no} | {yes} | {yes} | {yes}^(1)^
|`Geometry difference(Geometry, Geometry)` | SFS §2.1.1.3 | {yes} | {yes} | {no} | {yes} | {yes} | {yes}^(1)^
|`Geometry symdifference(Geometry, Geometry)` | SFS §2.1.1.3 | {yes} | {yes} | {no} | {yes} | {yes} | {yes}^(1)^
|Common non-SFS functions | | | | | | |
|`boolean dwithin(Geometry, Geometry, double)` | Returns true if the geometries are within the specified distance of one another | {yes} | {yes} | {no} | {no} | {yes} | {yes}
|`Geometry transform(Geometry, int)` | Returns a new geometry with its coordinates transformed to the SRID referenced by the integer parameter | {yes} | {yes} | {no} | {no} | {no} | {no}
|Spatial aggregate Functions | | | | | | |
|`Geometry extent(Geometry)` | Returns a bounding box that bounds the set of returned geometries | {yes} | {yes} | {no} | {no} | {no} | {no}
|================================
^(1)^ Argument Geometries need to have the same dimensionality.

[[spatial-configuration-dialect-postgis]]
Postgis::
For Postgis from versions 1.3 and later, the best dialect to use is `org.hibernate.spatial.dialect.postgis.PostgisDialect`.
+
This translates the HQL spatial functions to the Postgis SQL/MM-compliant functions.
For older, pre v1.3 versions of Postgis, which are not SQL/MM compliant, the dialect `org.hibernate.spatial.dialect.postgis.PostgisNoSQLMM` is provided.

[[spatial-configuration-dialect-mysql]]
MySQL::
There are several dialects for MySQL:

`MySQLSpatialDialect`:::
	a spatially-extended version of Hibernate `MySQLDialect`
`MySQL5SpatialDialect`:::
	a spatially-extended version of Hibernate `MySQL5Dialect`
`MySQLSpatial56Dialect`:::
	a spatially-extended version of Hibernate `MySQL55Dialect`.

[NOTE]
====
MySQL versions before 5.6.1 had only limited support for spatial operators.
Most operators only took account of the minimum bounding rectangles (MBR) of the geometries, and not the geometries themselves.

This changed in version 5.6.1, when MySQL introduced `ST_*` spatial operators.
The dialect `MySQLSpatial56Dialect` uses these newer, more precise operators.

These dialects may, therefore, produce results that differ from that of the other spatial dialects.

For more information, see this page in the MySQL reference guide (esp. the section https://dev.mysql.com/doc/refman/5.7/en/spatial-relation-functions.html[Functions That Test Spatial Relations Between Geometry Objects])
====
[[spatial-configuration-dialect-oracle]]
Oracle10g/11g::

There is currently only one Oracle spatial dialect: `OracleSpatial10gDialect` which extends the Hibernate dialect `Oracle10gDialect`.
This dialect has been tested on both Oracle 10g and Oracle 11g with the `SDO_GEOMETRY` spatial database type.
+
This dialect can be configured using the Hibernate property:
+
`hibernate.spatial.connection_finder`:::
the fully-qualified class name for the implementation of the `ConnectionFinder` to use (see below).

.The `ConnectionFinder` interface
[NOTE]
====
The `SDOGeometryType` requires access to an `OracleConnection` object when converting a geometry to SDO_GEOMETRY.
In some environments, however, the `OracleConnection` is not available (e.g. because a Java EE container or connection pool proxy wraps the connection object in its own `Connection` implementation).
A `ConnectionFinder` knows how to retrieve the `OracleConnection` from the wrapper or proxy Connection object that is passed into prepared statements.

When the passed object is not already an `OracleConnection`, the default implementation will attempt to retrieve the `OracleConnection` by recursive reflection.
It will search for methods that return `Connection` objects, execute these methods and check the result.
If the result is of type `OracleConnection` the object is returned.
Otherwise, it recurses on it.

In may cases, this strategy will suffice.
If not, you can provide your own implementation of this interface on the classpath, and configure it in the `hibernate.spatial.connection_finder` property.
Note that implementations must be thread-safe and have a default no-args constructor.
====

SQL Server::
The dialect `SqlServer2008Dialect` supports the `GEOMETRY` type in SQL Server 2008 and later.

[NOTE]
====
The `GEOGRAPHY` type is not currently supported.
====

GeoDB (H2)::
The `GeoDBDialect` supports the GeoDB a spatial extension of the H2 in-memory database.
[NOTE]
====
The dialect has been tested with GeoDB version 0.7
====

DB2::
The `DB2SpatialDialect` supports the spatial extensions of the DB2 LUW database. 
The dialect has been tested with DB2 LUW 11.1.
The dialect does not support DB2 for z/OS or DB2 column-oriented databases.
[NOTE]
====

In order to use the DB2 Hibernate Spatial capabilities, it is necessary to first execute the following
SQL statements which will allow DB2 to accept Extended WellKnown Text (EWKT) data and return EWKT data.
One way to do this is to copy these statements into a file such as ewkt.sql and execute it in a DB2 command window
with a command like 'db2 -tvf ewkt.sql'.

[source, SQL, indent=0]
----
create or replace function db2gse.asewkt(geometry db2gse.st_geometry)
returns clob(2G)
specific db2gse.asewkt1
language sql
deterministic
no external action
reads sql data
return 'srid=' || varchar(db2gse.st_srsid(geometry)) || ';' || db2gse.st_astext(geometry);

create or replace function db2gse.geomfromewkt(instring varchar(32000))
returns db2gse.st_geometry
specific db2gse.fromewkt1
language sql
deterministic
no external action
reads sql data
return db2gse.st_geometry(
substr(instring,posstr(instring,';')+1, length(instring) - posstr(instring,';')),
integer(substr(instring,posstr(instring,'=')+1,posstr(instring,';')-(posstr(instring,'=')+1))));

create transform for db2gse.st_geometry ewkt (
 from sql with function db2gse.asewkt(db2gse.st_geometry), 
 to   sql with function db2gse.geomfromewkt(varchar(32000)) );

drop transform db2_program for db2gse.st_geometry;
create transform for db2gse.st_geometry db2_program (
 from sql with function db2gse.asewkt(db2gse.st_geometry), 
 to   sql with function db2gse.geomfromewkt(varchar(32000)) );
----

====



[[spatial-types]]
=== Types

Hibernate Spatial comes with the following types:

jts_geometry::
	Handled by `org.hibernate.spatial.JTSGeometryType` it maps a database geometry column type to a `org.locationtech.jts.geom.Geometry` entity property type.
geolatte_geometry::
	Handled by `org.hibernate.spatial.GeolatteGeometryType`, it maps a database geometry column type to an `org.geolatte.geom.Geometry` entity property type.

It suffices to declare a property as either a JTS or a Geolatte-geom `Geometry` and Hibernate Spatial will map it using the
relevant type.

Here is an example using JTS:
[[spatial-types-mapping-example]]
.Type mapping
====
[source, JAVA, indent=0]
----
include::{sourcedir}/SpatialTest.java[tags=spatial-types-mapping-example, indent=0]
----
====

We can now treat spatial geometries like any other type.

[[spatial-types-point-creation-example]]
.Creating a Point
====
[source, JAVA, indent=0]
----
include::{sourcedir}/SpatialTest.java[tags=spatial-types-point-creation-example]
----
====

Spatial Dialects defines many query functions that are available both in HQL and JPQL queries. Below we show how we
could use the `within` function to find all objects within a given spatial extent or window.

[[spatial-types-query-example]]
.Querying the geometry
====
[source, SQL, indent=0]
----
include::{sourcedir}/SpatialTest.java[tags=spatial-types-query-example]
----
====

