Spring 从 PostgreSQL 转换为 Geojson FeatureCollection

Question

我在将数据从 postgreSQL 转换为 geojson 并将数据公开到指定端点时遇到问题。

数据库中的数据（数据库名称：Shops）：

shop_id => BIGINT shop_name => VARCHAR Shop_position => geography => 使用 ST_AsGeoJson 后我们会收到经度和纬度 Shop_radius => 双倍

存储库：

import com.fasterxml.jackson.core.JsonProcessingException;
import lombok.RequiredArgsConstructor;
import lombok.extern.slf4j.Slf4j;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.stereotype.Repository;


import java.util.List;
import java.util.Map;


@Repository
@RequiredArgsConstructor
@Slf4j
public class GeoRepository {

    private final JdbcTemplate jdbcTemplate;
   
    String GET_SHOPS = "select 'FeatureCollection' As type, array_to_json(array_agg(f)) As features from (select 'Feature' As type,ST_AsGeoJSON(lg.\"Shop_position\") :: json as geometry,row_to_json((select t from (select \"Shop_id\",\"Shop_name\",\"Shop_radius\") As t )) As properties from public.\"Shops\" As lg) as f;";
   
    public List<Map<String,Object>> getDataFromDb(String query){

        List<Map<String,Object>> data = jdbcTemplate.queryForList(query);
        return data;
    }
    
    public List<Map<String,Object>> getShops() throws JsonProcessingException { return getDataFromDb(GET_SHOPS); }
}

服务：

import com.fasterxml.jackson.databind.ObjectMapper;
import com.liferay.portal.kernel.json.JSONObject;
import lombok.RequiredArgsConstructor;
import org.springframework.boot.admin_panel.exception.DataNotFoundException;
import org.springframework.boot.admin_panel.repository.GeoRepository;
import org.springframework.stereotype.Service;

@Service
@RequiredArgsConstructor
public class GeoService {

    private final GeoRepository geoRepository;
    private ObjectMapper mapper = new ObjectMapper();

    public String getGeoJsonShops(){
        try{
            if(geoRepository.getShops() == null){
                throw new DataNotFoundException("Shops data is not found");
            }else
            return mapper.writeValueAsString(geoRepository.getShops());
        }catch (Exception e){
            System.out.println("Error: " + e);
            throw new NullPointerException("NullPointException");
        }
    }
    
    }
}

控制器：

import com.liferay.portal.kernel.json.JSONObject;
import lombok.RequiredArgsConstructor;
import org.apache.tomcat.util.json.JSONParser;
import org.apache.tomcat.util.json.ParseException;
import org.springframework.boot.admin_panel.service.GeoService;
import org.springframework.http.HttpStatus;
import org.springframework.http.MediaType;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.*;

@RestController
@RequestMapping("/admin_panel")
@CrossOrigin
@RequiredArgsConstructor
public class DataController {

    private final DataService dataService;

    @RequestMapping(value = "/get_shops", method = RequestMethod.GET, produces = MediaType.APPLICATION_JSON_VALUE)
    public ResponseEntity getShops() {
        String outputData = geoService.getGeoJsonShops();
        if(outputData == null){
            return ResponseEntity.notFound().build();
        }else {
            return ResponseEntity.ok(outputData);
        }
    }
}

这个控制器返回：

[
    {
        "type": "FeatureCollection",
        "features": {
            "type": "json",
            "value": "[{\"type\":\"Feature\",\"geometry\":{\"type\":\"Point\",\"coordinates\":[34.642697,74.341718]},\"properties\":{\"Shop_id\":125,\"Shop_name\":\"Grocery_Lux_Shop\",Shop_radius\":0.34637}}]"
        }
    }
]

但是“value”属性内部存在一个问题，它不是 json 而是一个字符串。 我没有收到json的错误是什么？我猜这是一个糟糕的 SQL 语法。

有人可以帮我吗？ 我想接收类似这样的格式：

{"type" : "FeatureCollection", "features" : [{"type": "Feature", "geometry": {"type":"Point","coordinates":[1,1]}, "properties": {"id": 1, "name": "one"}}, {"type": "Feature", "geometry": {"type":"Point","coordinates":[2,2]}, "properties": {"id": 2, "name": "two"}}, {"type": "Feature", "geometry": {"type":"Point","coordinates":[3,3]}, "properties": {"id": 3, "name": "three"}}]}

Answer 1

我猜这是一个糟糕的 SQL 语法。

不，这不是一个糟糕的语法。返回的内容相当于javascripts JSON.stringify。

您需要使用 Jackson 对象映射器将“值”映射到 POJO。查看this 的答案以了解方法。