使用GDAL/OGR操作Postgresql数据库

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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<RoadRec>& 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 nameOGRSFDriver* 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<<link_id<<endl;}    //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<RoadRec>& 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<RoadRec> roadlist;getFeature(roadlist);cout<<roadlist.size()<<endl;    setFeature(roadlist);return 0;}
编译链接：g++ -o feature feature_pro.cpp -lgdal
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