PostGIS 提供了非常多的函数可以直接实现空间操作及转换，下面用SQL语句查询空间表的数据并转成GeoJSON：
SELECT
row_to_json(fc)
FROM (
SELECT
'FeatureCollection' AS type
, array_to_json(array_agg(f)) AS features
FROM (
SELECT
'feature' AS type
, ST_AsGeoJSON(geom)::json as geometry --geom表中的空间字段
, (
SELECT
row_to_json(t)
FROM (
SELECT
id, user,content
) AS t
) AS properties
FROM test_table
) AS f
) AS fc
查询结果如下:
{
"type": "FeatureCollection",
"features": [
{
"type": "feature",
"geometry": {
"type": "Point",
"coordinates": [
87.6416250523,
43.6650995192
]
},
"properties": {
"id": "6500000182",
"user": "王晓波",
"content": "温性荒漠草原-小蓬"
}
},
{
"type": "feature",
"geometry": {
"type": "Point",
"coordinates": [
87.766879,
43.790263
]
},
"properties": {
"id": "6500000197",
"user": "王晓波",
"content": "温性草原-禾草，锦鸡儿"
}
}
]
}
