循环调用 Google Maps API 对数十个地址进行地理编码并得到“java.lang.String cannot be cast to net.sf.json.JSONObject”答案

【问题标题】：Call Google Maps API in a loop to geocode dozens of addresses and get "java.lang.String cannot be cast to net.sf.json.JSONObject"循环调用 Google Maps API 对数十个地址进行地理编码并得到“java.lang.String cannot be cast to net.sf.json.JSONObject”
【发布时间】：2011-08-03 16:01:09
【问题描述】：

下面的代码是我用来调用 Google Maps API 以获取原始地址输入的地理编码地址的代码。

如果我一次处理几个地址，这会很好。

但是如果我在多个地址上循环运行它，我偶尔会意外地得到这个错误：

java.lang.String cannot be cast to net.sf.json.JSONObject

每次我运行循环时都会在不同的输入字符串上发生 - 所以它似乎与特定的输入数据无关。

我可能预计会在 Google Maps API 中遇到速率限制，但此错误似乎与此无关？

是吗？

package com.blogspot.unserializableone;

import java.io.ByteArrayOutputStream;
import java.net.URL;
import java.net.URLConnection;
import java.net.URLEncoder;

import net.sf.json.JSONException;
import net.sf.json.JSONObject;

import org.apache.commons.io.IOUtils;

public class GCoder {
    private static final String URL = "http://maps.google.com/maps/geo?output=json";
    private static final String DEFAULT_KEY = "ABQIAAAAxPbpriJFATP1kV4Jfg7FrhTHx8S3jtCwO1hw0XE3N9WOac4cqRQ8_vMKB22No44yFau5GRY7TcCHZA";

    public static GAddress geocode(String address, String key) throws Exception {
        URL url = new URL(URL + "&q=" + URLEncoder.encode(address, "UTF-8") + "&key=" + key);
        URLConnection conn = url.openConnection();
        ByteArrayOutputStream output = new ByteArrayOutputStream(1024);
        IOUtils.copy(conn.getInputStream(), output);
        output.close();
        GAddress gaddr = new GAddress();
        JSONObject json = JSONObject.fromObject(output.toString());
        JSONObject placemark = (JSONObject) query(json, "Placemark[0]");
        final String commonId = "AddressDetails.Country.AdministrativeArea";
        gaddr.setFullAddress(query(placemark, "address").toString());
        gaddr.setZipCode(query(placemark,
                commonId + ".SubAdministrativeArea.Locality.PostalCode.PostalCodeNumber").toString());
        gaddr.setAddress(query(placemark,
                commonId + ".SubAdministrativeArea.Locality.Thoroughfare.ThoroughfareName")
                .toString());
        gaddr.setCity(query(placemark, commonId + ".SubAdministrativeArea.SubAdministrativeAreaName")
                .toString());
        gaddr.setState(query(placemark, commonId + ".AdministrativeAreaName").toString());
        gaddr.setLat(Double.parseDouble(query(placemark, "Point.coordinates[1]").toString()));
        gaddr.setLng(Double.parseDouble(query(placemark, "Point.coordinates[0]").toString()));
        return gaddr;
    }

    public static GAddress geocode(String address) throws Exception {
        return geocode(address, DEFAULT_KEY);
    } /* allow query for json nested objects, ie. Placemark[0].address */

    private static Object query(JSONObject jo, String query) {
        try {
            String[] keys = query.split("\\.");
            Object r = queryHelper(jo, keys[0]);
            for (int i = 1; i < keys.length; i++) {
                r = queryHelper(JSONObject.fromObject(r), keys[i]);
            }
            return r;
        } catch (JSONException e) {
            return "";
        }
    } /* help in query array objects: Placemark[0] */

    private static Object queryHelper(JSONObject jo, String query) {
        int openIndex = query.indexOf('[');
        int endIndex = query.indexOf(']');
        if (openIndex > 0) {
            String key = query.substring(0, openIndex);
            int index = Integer.parseInt(query.substring(openIndex + 1, endIndex));
            return jo.getJSONArray(key).get(index);
        }
        return jo.get(query);
    }

    public static void main(String[] args) throws Exception {
        System.out.println(GCoder.geocode("28 275, Mercedes, Buenos Aires, Argentina"));
        System.out.println(GCoder.geocode("94103"));
        System.out
                .println(GCoder.geocode("peña 2700 capital federal cdad. autonoma de buenos aires"));
        System.out.println(GCoder
                .geocode("2700 peña, capital federal, ciudad autonoma de buenos aires, argentina"));
    }
}

【问题讨论】：

标签： java json google-maps geocoding

【解决方案1】：

看起来你的错误可能发生在这一行 --

    JSONObject placemark = (JSONObject) query(json, "Placemark[0]");

查看您的查询方法，您似乎也在吞下JSONException 并返回一个空字符串，然后该字符串无法转换为 JSON 对象。因此，它不是 Google Maps API 的例外，而是您的代码中的一些例外。我建议在 JSONException 上打印 stackTrace 以进一步调查。

【讨论】：