GDAL(Geospatial Data AbstractionLibrary)是一个在X/MIT许可协议下的开源栅格空间数据转换库。它利用抽象数据模型来表达所支持的各种文件格式。它还有一系列命令行工具来进行数据转换和处理。

本文将使用GDAL/OGR库读写Postgresql数据库中的表，代码执行环境在ubuntu12.04，

直接上代码

#include "/usr/include/gdal/ogrsf_frmts.h"

#include "/usr/include/gdal/ogr_feature.h"

#include "/usr/include/gdal/ogr_geometry.h"

#include "/usr/include/gdal/gdal_priv.h"

///

//使用OGR读Postgresql

///

int getFeature( vector& RoadList //RoadRec是自定义数据结构

)

{

OGRRegisterAll();

const char* filepath =

"PG:dbname=test host=172.0.0.1 port=5432 user=postgres password=postgres";

const char* drivename = "Postgresql"; //标明是Postgresql数据库操作

const char* ptablename = "roadlist";//数据表名称 table name

OGRSFDriver* pdriver = NULL;

OGRLayer* player = NULL;

OGRDataSource* pDS = NULL;

//注册驱动，这样ogr就知道即将打开的是什么类型的文件

pdriver = OGRSFDriverRegistrar::GetRegistrar()->GetDriverByName(drivename);

if ( pdriver == NULL ) {

return FAILURE;

}

//驱动注册完毕打开数据库

pDS = pdriver->Open(filepath,0);

if ( NULL == pDS ) {

return FAILURE;

}

//打开数据库中的数据表

player = pDS->GetLayerByName(ptablename);

if ( NULL == player ) {

return FAILURE;

}

//OGRFeature*相当于指向数据表中一条记录的指针，根据它可以获取每一个字段

OGRFeature* pogrfeature = NULL;

player->ResetReading();

int gid = 0;

//循环遍历每一条记录，这里的遍历是按照表中数据的存储顺序遍历

//并不会按照主键唯一值顺序遍历，这和sql的select结果的顺序不一样

//想要一样应该创建索引，并将表数据按索引顺序存储

/*

CREATE INDEX roadlist_gid_idx

ON roadlist

USING btree

(gid);

cluster roadlist using roadlist_gid_idx;

*/

while( (pogrfeature = player->GetNextFeature()) != NULL )

{

gid++;

//获取一条记录中的几何属性字段的引用

OGRGeometry *pgeo = pogrfeature->GetGeometryRef();

if ( NULL != pgeo )

{

//判断一下是不是自己想要的类型，这里我的数据是道路，line数据

if ( wkbMultiLineString == pgeo->getGeometryType() || wkbLineString == pgeo->getGeometryType() )

{

OGRGeometry* pgeometry = pgeo;

//单独处理一下multilinestring的情况

if ( wkbMultiLineString == pgeo->getGeometryType() )

{

OGRMultiLineString* pmultilinestring = (OGRMultiLineString*)pgeo;

if( 1 != pmultilinestring->getNumGeometries() )

{

return FAILURE;

}

pgeometry = pmultilinestring->getGeometryRef(0);

}

//定义OGRLineString类型指针指向几何数据

//这样就可以使用OGRLineString提供的函数接口了

OGRLineString* pline = (OGRLineString *)pgeometry;

int pointnum = pline->getNumPoints();

RoadRec tmp;//自定义数据类型

//使用OGRFeature类提供的 GetFieldAsInteger

//方法获取每个字段的值，”link_id”,”road_name”都是字段名

tmp.link_id = pogrfeature->GetFieldAsInteger("link_id");

//tmp.src_id = pogrfeature->GetFieldAsInteger("src_id");

tmp.road_name = pogrfeature->GetFieldAsString("road_name");

tmp.one_way = pogrfeature->GetFieldAsInteger("one_way");

//获得几何属性的每一个点坐标信息

for ( int pointid = 0; pointid < pointnum;++pointid )

{

OGRPoint point;

pline->getPoint(pointid,&point);

GEO_POINT geo_point;

geo_point.x = point.getX();

geo_point.y = point.getY();

tmp.vstShplist.push_back(geo_point);

}

RoadList.push_back(tmp);

}

}

//释放Feature资源

OGRFeature::DestroyFeature(pogrfeature);

//cout<

}

//释放指向该数据库的指针

OGRDataSource::DestroyDataSource(pDS);

return SUCCESS;

}

///

//使用OGR写Postgresql

///

int setFeature( const vector& RoadList )

{

OGRRegisterAll();

const char* filepath =

"PG:dbname=test host=172.0.0.1 port=5432 user=postgres password=postgres";

const char* drivename = "Postgresql";

const char* ptablename = "roadlist";

OGRSFDriver* pdriver = NULL;

OGRLayer* player = NULL;

OGRDataSource* pDS = NULL;

pdriver = OGRSFDriverRegistrar::GetRegistrar()->GetDriverByName(drivename);

if ( pdriver == NULL ) {

return FAILURE;

}

pDS = pdriver->Open(filepath,0);

if ( NULL == pDS ) {

return FAILURE;

}

//相当于sql语句中的创建数据表，只是这里只先指定表名称和几何字段属性

player = pDS->CreateLayer( ptablename,NULL,wkbLineString,NULL );

if ( NULL == player )

{

return FAILURE;

}

//定义一个字段one_way

OGRFieldDefn* pfielddefn_oneway = new OGRFieldDefn("one_way",OFTInteger);

//在数据表中创建定义的字段

player->CreateField(pfielddefn_oneway);

OGRFieldDefn* pfielddefn_name = new OGRFieldDefn("road_name",OFTString);

player->CreateField(pfielddefn_name);

//删除字段定义指针

delete pfielddefn_oneway;

delete pfielddefn_name;

int roadnum = RoadList.size();

//循环写入每一条道路数据

for ( int roadcnt = 0; roadcnt < roadnum ;++roadcnt )

{

const RoadRec& roadrec = RoadList.at(roadcnt);

OGRLineString* pline = new OGRLineString;//要写入的几何字段

int pointnum = roadrec.vstShplist.size();

for ( int pointcnt = 0; pointcnt < pointnum ;++pointcnt )

{

const GEO_POINT& point = roadrec.vstShplist.at(pointcnt);

pline->addPoint(point.x,point.y);

}

OGRGeometry* pgeo = (OGRGeometry*)pline;

pgeo->setCoordinateDimension(2);//设置坐标系维度

//创建一个指向要写入的记录的指针

//指定要写入的数据库player->GetLayerDefn()

OGRFeature* pfeature = OGRFeature::CreateFeature( player->GetLayerDefn() );

//设置当前记录的字段值

pfeature->SetField("one_way",roadrec.one_way);

pfeature->SetField("road_name",roadrec.road_name.c_str());

if ( OGRERR_NONE != pfeature->SetGeometry( pgeo ) )

{

return FAILURE;

}

//将记录写入数据表

if ( OGRERR_NONE != player->CreateFeature( pfeature ) )

{

return FAILURE;

}

delete pline;

OGRFeature::DestroyFeature(pfeature);

}

OGRDataSource::DestroyDataSource(pDS);

return SUCCESS;

}

int main()

{

vector roadlist;

getFeature(roadlist);

cout<

setFeature(roadlist);

return 0;

}

编译链接：g++ -o feature feature_pro.cpp -lgdal

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