今天上午一位朋友問到了，關(guān)于hibernate中是否支持postgis函數(shù)的問題，我就這個問題，隨便聊幾句。
要想使用hibernate的空間數(shù)據(jù)操作，就要提到一個概念 java Topology Suite (字面上理解就是 空間拓撲的意思，簡稱
JTS,
注意：過需要聲明一點，本文中的JTS與進行java事務(wù)處理的JTS、JTA沒有聯(lián)系).
HIBERNATE中對空間數(shù)據(jù)作了支持（
Hibernate Spatial），
Hibernate Spatial是對處理空間數(shù)據(jù)的一個Hibernate擴展 ，
Hibernate Spatial 使用標準的方式處理地理信息數(shù)據(jù) ，并且提供了一個可以跨數(shù)據(jù)庫的處理的接口函數(shù)，
Hibernate Spatial 中包含了多種 OGC 簡單的處理函數(shù). 支持的數(shù)據(jù)庫為: Oracle 10g/11g, Postgresql/Postgis, and MySQL.
要想使用 Hibernate Spatial 就要引入JTS， JTS 從根本上而言其實并不是很復(fù)雜，它主要是完成了java對幾何對象、空間拓撲得核心操作算法。
下面通過簡單配置來說明一下如何使用（我們使用的數(shù)據(jù)庫是postgis）：
數(shù)據(jù)庫腳本：
sql:
CREATE TABLE events
(
id bigint NOT NULL,
event_date timestamp without time zone,
title character varying(255),
"location" geometry,
CONSTRAINT events_pkey PRIMARY KEY (id)
)
1，引入 jts-1.8.jar, hibernate3.jar 等包 ,同時還要應(yīng)用 hibernate-spatial-postgis-1.0-20070920.111959-1.jar 和
hibernate-spatial-1.0-20070920.111959-1.jar 包（如果不是postgre sql就要引用相應(yīng)的數(shù)據(jù)庫包）。
2，創(chuàng)建一個持久化類（po對象）
如下：
import java.util.Date;
import com.vividsolutions.jts.geom.Point;
public class Event 
{
private Long id;
private String title;
private Date date;
private Point location;
public Event() {}
public Long getId() {
return id;
}
private void setId(Long id) {
this.id = id;
}
public Date getDate() {
return date;
}
public void setDate(Date date) {
this.date = date;
}
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
public Point getLocation(){
return this.location;
}
public void setLocation(Point location){
this.location = location;
}
}
<hibernate-mapping>
<class name="Event" table="EVENTS">
<id name="id" column="EVENT_ID">
<generator class="native"/>
</id>
<property name="date" type="timestamp"
column="EVENT_DATE"/>
<property name="title"/>
<property name="location"
type="org.hibernatespatial.GeometryUserType"
column="location"/>
</class>
</hibernate-mapping>
<?xml version='1.0' encoding='utf-8'?>
<!DOCTYPE hibernate-configuration PUBLIC
"-//Hibernate/Hibernate Configuration DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
<session-factory>
<!-- Database connection settings -->
<property name="connection.driver_class">org.postgresql.Driver</property>
<property name="connection.url">jdbc:postgresql://localhost:5432/test</property>
<property name="connection.username">postgres</property>
<property name="connection.password">test</property>
<!-- JDBC connection pool (use the built-in) -->
<property name="connection.pool_size">1</property>
<!-- SPATIAL SQL dialect -->
<property name="dialect">org.hibernatespatial.postgis.PostgisDialect</property>
<!-- Enable Hibernate's automatic session context management -->
<property name="current_session_context_class">thread</property>
<!-- Disable the second-level cache -->
<property name="cache.provider_class">org.hibernate.cache.NoCacheProvider</property>
<!-- Echo all executed SQL to stdout -->
<property name="show_sql">true</property>
<!-- Drop and re-create the database schema on startup -->
<property name="hbm2ddl.auto">create</property>
<mapping resource="Event.hbm.xml"/>
</session-factory>
</hibernate-configuration>
注意：在上面的配置文件中， <property name="dialect">org.hibernatespatial.postgis.PostgisDialect</property>
這句配置起到了重要的作用，這里聲明了 hibernate 的方言。該方言聲明了對postgis的一些支持。
并且大家也應(yīng)該知道，在使用hibernate時候，如果需要自定義函數(shù)，要需要自定義方言。
5，第一個主類
import org.hibernate.Criteria;
import org.hibernate.Query;
import org.hibernate.Session;
import org.hibernatespatial.criterion.SpatialRestrictions;
import org.postgis.Geometry;
import org.postgis.LineString;
import org.postgis.MultiLineString;
import org.postgis.MultiPolygon;
import org.postgis.PGgeometry;
import org.postgis.Polygon;
import com.vividsolutions.jts.geom.Point;
import com.vividsolutions.jts.io.ParseException;
import com.vividsolutions.jts.io.WKTReader;
import com.vividsolutions.jts.geom.*;
import java.util.Date;
import java.util.List;
import util.HibernateUtil;
public class EventManager {
public int SRID = 4326;
public static void main(String[] args) {
EventManager mgr = new EventManager();
String testPiont = "2,3";
mgr.createAndStoreEvent("My Event", new Date(), testPiont);
HibernateUtil.getSessionFactory().close();
}
private void createAndStoreEvent(String title, Date theDate, String wktPoint) {
com.vividsolutions.jts.geom.Geometry geom = null;
try {
geom = pointFromText(wktPoint);
} catch (Exception e) {
throw new RuntimeException("Not a WKT string:" + wktPoint);
}
Session session = HibernateUtil.getSessionFactory().getCurrentSession();
session.beginTransaction();
Event theEvent = new Event();
theEvent.setTitle(title);
theEvent.setDate(theDate);
theEvent.setLocation((Point) geom);
session.save(theEvent);
session.flush();
session.getTransaction().commit();
List l= find("POLYGON((1 1,20 1,20 20, 1 20, 1 1))");
System.out.println(l.size());
List l1= find1("POLYGON((1 1,20 1,20 20, 1 20, 1 1))");
System.out.println(l1.size());
}
private List find(String wktFilter){
WKTReader fromText = new WKTReader();
com.vividsolutions.jts.geom.Geometry filter = null;
try{
filter = fromText.read(wktFilter);
filter.setSRID(SRID);
} catch(ParseException e){
throw new RuntimeException("Not a WKT String:" + wktFilter);
}
Session session = HibernateUtil.getSessionFactory().getCurrentSession();
session.beginTransaction();
System.out.println("Filter is : " + filter);
Criteria testCriteria = session.createCriteria(Event.class);
testCriteria.add(SpatialRestrictions.within("location", filter, filter));
List results = testCriteria.list();
session.getTransaction().commit();
return results;
}
private List find1(String wktFilter){
WKTReader fromText = new WKTReader();
com.vividsolutions.jts.geom.Geometry filter = null;
try{
filter = fromText.read(wktFilter);
filter.setSRID(SRID);
} catch(ParseException e){
throw new RuntimeException("Not a WKT String:" + wktFilter);
}
Session session = HibernateUtil.getSessionFactory().getCurrentSession();
session.beginTransaction();
Query query = session.createQuery("select within(location,'srid=4326;POLYGON ((1 1, 20 1, 20 20, 1 20, 1 1))') from Event ");
List list = query.list();
return list;
}
public Point pointFromText(String txt) throws Exception {
String tmp = txt;
if (!tmp.startsWith("POINT")) {
tmp = tmp.replace(",", " ");
tmp = "POINT(" + tmp + ")";
}
try {
WKTReader fromText = new WKTReader();
Geometry geom = fromText.read(tmp);
Point pt = (Point) fromText.read(tmp);
pt.setSRID(SRID);
return pt;
} catch (Exception e) {
return null;
}
}
}通過上面的方法，我們可以測試出來，hibernate已經(jīng)可以支持空間數(shù)據(jù)類型的數(shù)據(jù)操作了，可以實現(xiàn)空間數(shù)據(jù)入庫到空間數(shù)據(jù)對象影射到j(luò)ava對象中（插入和查詢方法），但是有一個問題，就是支持的空間數(shù)據(jù)操作方法太少了。例如 contains,disjoint,within等十幾個方法。這些方法都是簡單的空間數(shù)據(jù)操作方法，要想實現(xiàn)復(fù)雜的空間數(shù)據(jù)這還遠遠不夠的。相對于這方面來說ibatis 就很方便的使用了。
這方面的資料比較少，大家都交流 ，有什么好的經(jīng)驗大家分享一下。