我遇到了以下问题：我试图从用户的手机中获取 x [英里/公里] 内的用户。我正在使用谷歌应用引擎的数据存储 api，我不知道是什么问题。问题是，当我使用迭代获取记录时——出现一个错误，告诉我我不能在组合过滤器中使用不同的属性。
package com.linkedlive.business;
import java.io.IOException;
import java.util.Iterator;
import javax.servlet.http.*;
import org.json.JSONArray;
import org.json.JSONObject;
import com.biomedica.server.geolocation.GeoLocation;
import com.biomedica.server.searchtools.SearchForGeolocEntitiy;
import com.google.appengine.api.datastore.DatastoreService;
import com.google.appengine.api.datastore.DatastoreServiceFactory;
import com.google.appengine.api.datastore.Entity;
import com.google.appengine.api.datastore.KeyFactory;
@SuppressWarnings("serial")
public class Venue extends HttpServlet {
public void doGet(HttpServletRequest req, HttpServletResponse resp)
throws IOException {
this.doPost(req, resp);
}
public void doPost(HttpServletRequest req, HttpServletResponse resp)
throws IOException {
DatastoreService datastore =
DatastoreServiceFactory.getDatastoreService();
String cmd=req.getParameter("cmd");
if(cmd.equals("venuenearby"))
{
GeoLocation geo=new GeoLocation();
SearchForGeolocEntitiy search=new
SearchForGeolocEntitiy("accounts");// this is a class that i created to set the
query filters see bellow
// get request parameters
float lat=Float.valueOf(req.getParameter("lat"));
float lng=Float.valueOf(req.getParameter("lng"));
float rad=Float.valueOf(req.getParameter("rad"));
// calculate the distance
Iterable<Entity>
ent=search.GetJSONForEntitiyNearByUsingBounds(lat,
lng,geo.getGeoLocationBounds(lat, lng, rad) );
Iterator<Entity> i=ent.iterator();
JSONObject json=new JSONObject();
JSONArray injson=new JSONArray();
json.put("result", "venuenearby");
while(i.hasNext())
{
try {
JSONObject j=new JSONObject();
Entity t=i.next();
j.put("key",
KeyFactory.keyToString(t.getKey()));
j.put("userid",
t.getProperty("userid"));
j.put("filepath",
t.getProperty("filepath"));
injson.put(j);
} catch (NullPointerException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
json.put("body",injson);
resp.getWriter().write(json.toString());
}
}
}
///////////////////////////////////////////////////////////////////////////////
////////////////////
////////////////////////// SearchForGeolocEntitiy
////////////////////////////////////
package com.biomedica.server.searchtools;
import java.lang.reflect.Array;
import java.util.Arrays;
import com.biomedica.server.geolocation.GeoLocation;
import com.google.appengine.api.datastore.DatastoreService;
import com.google.appengine.api.datastore.DatastoreServiceFactory;
import com.google.appengine.api.datastore.Entity;
import com.google.appengine.api.datastore.PreparedQuery;
import com.google.appengine.api.datastore.Query;
import com.google.appengine.api.datastore.Query.CompositeFilterOperator;
import com.google.appengine.api.datastore.Query.Filter;
import com.google.appengine.api.datastore.Query.FilterOperator;
import com.google.appengine.api.datastore.Query.FilterPredicate;
import com.google.appengine.api.datastore.Query.CompositeFilter;
public class SearchForGeolocEntitiy {
private String EntitiyName;
private Query q;
public SearchForGeolocEntitiy(String name)
{
EntitiyName=name;
q=new Query(name);
}
public Iterable<Entity> GetJSONForEntitiyNearBy(double lang,double
lat,double rad,int max_result)
{
DatastoreService datastore =
DatastoreServiceFactory.getDatastoreService();
// decleeraing filter object
Filter filter_min_lngt=new
FilterPredicate("lng", FilterOperator.GREATER_THAN, lang-rad);
Filter filter_max_lngt=new
FilterPredicate("lng", FilterOperator.LESS_THAN, lang+rad);
Filter filter_min_lat=new
FilterPredicate("lat", FilterOperator.GREATER_THAN, lat-rad);
Filter filter_max_lat=new
FilterPredicate("lat", FilterOperator.LESS_THAN, lat+rad);
Filter filter_lng=new
CompositeFilter(CompositeFilterOperator.AND,Arrays.asList(filter_min_lngt,filte
r_max_lngt));
Filter filter_lat=new
CompositeFilter(CompositeFilterOperator.AND,Arrays.asList(filter_min_lat,filter
_max_lat));
Filter filter=new
CompositeFilter(CompositeFilterOperator.AND,Arrays.asList(filter_lng,filter_lat
));
q.setFilter(filter);
PreparedQuery pq = datastore.prepare(q);
return pq.asIterable();
}
public Iterable<Entity> GetJSONForEntitiyNearByUsingSSID(String
EntityName,String entityID,String SSID)
{
DatastoreService datastore =
DatastoreServiceFactory.getDatastoreService();
// decleeraing filter object
Filter filter_entityID=new FilterPredicate(EntityName,
FilterOperator.EQUAL, entityID);
Filter filter_min_lngt=new
FilterPredicate("lng", FilterOperator.EQUAL, SSID);
Filter filter=new
CompositeFilter(CompositeFilterOperator.AND,Arrays.asList(filter_entityID,filte
r_min_lngt));
q.setFilter(filter);
PreparedQuery pq = datastore.prepare(q);
return pq.asIterable();
}
public Iterable<Entity> GetJSONForEntitiyNearByUsingBounds(float
lng,float lat,GeoLocation.GeoLocationBoundry bound)
{
DatastoreService datastore =
DatastoreServiceFactory.getDatastoreService();
Filter filter_min_lngt=new FilterPredicate("lng",
FilterOperator.LESS_THAN, bound.lng1);
Filter filter_max_lngt=new FilterPredicate("lng",
FilterOperator.LESS_THAN, bound.lng2);
Filter filter_min_lat=new FilterPredicate("lat",
FilterOperator.GREATER_THAN, bound.lat1);
Filter filter_max_lat=new FilterPredicate("lat",
FilterOperator.LESS_THAN, bound.lat2);
Filter filter_lng=new
CompositeFilter(CompositeFilterOperator.AND,Arrays.asList(filter_min_lngt,filte
r_max_lngt));
Filter filter_lat=new
CompositeFilter(CompositeFilterOperator.AND,Arrays.asList(filter_min_lat,filter
_max_lat));
Filter filter=new
CompositeFilter(CompositeFilterOperator.AND,Arrays.asList(filter_lng,filter_lat
));
q.setFilter(filter);
PreparedQuery pq = datastore.prepare(q);
return pq.asIterable();
}
}