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 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<<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