接着上一篇文章：查找附近网点geohash算法及实现 (Java版本) http://blog.csdn.net/sunrise_2013/article/details/42024813

参考文档：

http://www.slideshare.net/sandeepbhaskar2/geohash 介绍geohash原理及例子

http://geohash.gofreerange.com/ 演示实例

http://geohash.gofreerange.com/ 周边8格子实例

由于存在部分网点丢失的情况，为了解决边缘问题，需要计算这个块周围的八个格子，补充代码，实现周边8个编码的最近编码。

根据一个geohash值 获取周围8个geohash值的代码。

例如在方格4的左下部分的点和大方格1的右下部分的点离的很近，可是它们的geohash值一定是相差的相当远，因为头一次的分块就相差太大了，很多时候我们对geohash的值进行简单的排序比较，结果貌似真的能够找出相近的点，并且似乎还是按照距离的远近排列的，可是实际上会有一些点被漏掉了。

上述这个问题，可以通过搜索一个格子，周围八个格子的数据，统一获取后再进行过滤。这样就在编码层次解决了这个问题。

全部代码实例：

Geohase.java

package com.DistTest;

//Geohash.java

//Geohash library for Java

//ported from David Troy's Geohash library for Javascript

//- http://github.com/davetroy/geohash-js/tree/master

//(c) 2008 David Troy

//(c) 2008 Tom Carden

//Distributed under the MIT License

public class Geohash {

public static int BITS[] = { 16, 8, 4, 2, 1 };

public static String BASE32 = "0123456789bcdefghjkmnpqrstuvwxyz";

public static int RIGHT = 0;

public static int LEFT = 1;

public static int TOP = 2;

public static int BOTTOM = 3;

public static int EVEN = 0;

public static int ODD = 1;

public static String[][] NEIGHBORS;

public static String[][] BORDERS;

static {

NEIGHBORS = new String[4][2];

BORDERS = new String[4][2];

NEIGHBORS[BOTTOM][EVEN] = "bc01fg45238967deuvhjyznpkmstqrwx";

NEIGHBORS[TOP][EVEN] = "238967debc01fg45kmstqrwxuvhjyznp";

NEIGHBORS[LEFT][EVEN] = "p0r21436x8zb9dcf5h7kjnmqesgutwvy";

NEIGHBORS[RIGHT][EVEN] = "14365h7k9dcfesgujnmqp0r2twvyx8zb";

BORDERS[BOTTOM][EVEN] = "bcfguvyz";

BORDERS[TOP][EVEN] = "0145hjnp";

BORDERS[LEFT][EVEN] = "prxz";

BORDERS[RIGHT][EVEN] = "028b";

NEIGHBORS[BOTTOM][ODD] = NEIGHBORS[LEFT][EVEN];

NEIGHBORS[TOP][ODD] = NEIGHBORS[RIGHT][EVEN];

NEIGHBORS[LEFT][ODD] = NEIGHBORS[BOTTOM][EVEN];

NEIGHBORS[RIGHT][ODD] = NEIGHBORS[TOP][EVEN];

BORDERS[BOTTOM][ODD] = BORDERS[LEFT][EVEN];

BORDERS[TOP][ODD] = BORDERS[RIGHT][EVEN];

BORDERS[LEFT][ODD] = BORDERS[BOTTOM][EVEN];

BORDERS[RIGHT][ODD] = BORDERS[TOP][EVEN];

}

private static void refine_interval(double[] interval, int cd, int mask) {

if ((cd & mask) > 0) {

interval[0] = (interval[0] + interval[1]) / 2.0;

} else {

interval[1] = (interval[0] + interval[1]) / 2.0;

}

}

public static String calculateAdjacent(String srcHash, int dir) {

srcHash = srcHash.toLowerCase();

char lastChr = srcHash.charAt(srcHash.length() - 1);

int type = (srcHash.length() % 2) == 1 ? ODD : EVEN;

String base = srcHash.substring(0, srcHash.length() - 1);

if (BORDERS[dir][type].indexOf(lastChr) != -1) {

base = calculateAdjacent(base, dir);

}

return base + BASE32.charAt(NEIGHBORS[dir][type].indexOf(lastChr));

}

public static String[] getGeoHashExpand(String geohash) {

try {

String geohashTop = calculateAdjacent(geohash, TOP);

String geohashBottom = calculateAdjacent(geohash, BOTTOM);

String geohashRight = calculateAdjacent(geohash, RIGHT);

String geohashLeft = calculateAdjacent(geohash, LEFT);

String geohashTopLeft = calculateAdjacent(geohashLeft, TOP);

String geohashTopRight = calculateAdjacent(geohashRight, TOP);

String geohashBottomRight = calculateAdjacent(geohashRight, BOTTOM);

String geohashBottomLeft = calculateAdjacent(geohashLeft, BOTTOM);

String[] expand = { geohash, geohashTop, geohashBottom, geohashRight, geohashLeft, geohashTopLeft,

geohashTopRight, geohashBottomRight, geohashBottomLeft };

return expand;

} catch (Exception e) {

//logger.error("GeoHash Error",e);

return null;

}

}

public static double[][] decode(String geohash) {

boolean is_even = true;

double[] lat = new double[3];

double[] lon = new double[3];

lat[0] = -90.0;

lat[1] = 90.0;

lon[0] = -180.0;

lon[1] = 180.0;

double lat_err = 90.0;

double lon_err = 180.0;

for (int i = 0; i < geohash.length(); i++) {

char c = geohash.charAt(i);

int cd = BASE32.indexOf(c);

for (int j = 0; j < BITS.length; j++) {

int mask = BITS[j];

if (is_even) {

lon_err /= 2.0;

refine_interval(lon, cd, mask);

} else {

lat_err /= 2.0;

refine_interval(lat, cd, mask);

}

is_even = !is_even;

}

}

lat[2] = (lat[0] + lat[1]) / 2.0;

lon[2] = (lon[0] + lon[1]) / 2.0;

return new double[][] { lat, lon };

}

public static String encode(double latitude, double longitude) {

boolean is_even = true;

int i = 0;

double lat[] = new double[3];

double lon[] = new double[3];

int bit = 0;

int ch = 0;

int precision = 12;

String geohash = "";

lat[0] = -90.0;

lat[1] = 90.0;

lon[0] = -180.0;

lon[1] = 180.0;

while (geohash.length() < precision) {

if (is_even) {

double mid = (lon[0] + lon[1]) / 2.0;

if (longitude > mid) {

ch |= BITS[bit];

lon[0] = mid;

} else {

lon[1] = mid;

}

} else {

double mid = (lat[0] + lat[1]) / 2.0;

if (latitude > mid) {

ch |= BITS[bit];

lat[0] = mid;

} else {

lat[1] = mid;

}

}

is_even = !is_even;

if (bit < 4) {

bit++;

} else {

geohash += BASE32.charAt(ch);

bit = 0;

ch = 0;

}

}

return geohash;

}

}

测试实例：

package com.DistTest;

import java.sql.DriverManager;

import java.sql.ResultSet;

import java.sql.SQLException;

import java.sql.Connection;

import java.sql.Statement;

public class sqlTest {

public static void main(String[] args) throws Exception {

Connection conn = null;

String sql;

String sql1;

String url = "jdbc:mysql://132.97.194.62/test?"

+ "user=root&password=sheng&useUnicode=true&characterEncoding=UTF8";

try {

Class.forName("com.mysql.jdbc.Driver");// 动态加载mysql驱动

// System.out.println("成功加载MySQL驱动程序");

// 一个Connection代表一个数据库连接

conn = DriverManager.getConnection(url);

// Statement里面带有很多方法，比如executeUpdate可以实现插入，更新和删除等

Statement stmt = conn.createStatement();

double lon1=109.0145193757;

double lat1=34.236080797698;

//根据地理坐标，生成geohash编码

// Geohash ghash = new Geohash();

// String gcode=Geohash.encode(lat1, lon1).substring(0, 4);

String gcode="wqj6z";

String[] neargcode=Geohash.getGeoHashExpand(gcode);

for(int i=0;i

{

System.out.println(neargcode[i]);

}

sql = "select * from retailersinfotable where geohash like "

+ "'"+neargcode[0]+"%' or '"+neargcode[1]+"%' or '"+neargcode[2]+"%' "

+ "or '"+neargcode[3]+"%' or '"+neargcode[4]+"%' or '"+neargcode[5]+"%' "

+ "or '"+neargcode[6]+"%' or '"+neargcode[7]+"%' or '"+neargcode[8]+"%'";

System.out.println(sql);

ResultSet rs = stmt.executeQuery(sql);// executeQuery会返回结果的集合，否则返回空值

rs.last();

int rowCount = rs.getRow(); //获得ResultSet的总行数

System.out.println(rowCount);

rs.beforeFirst();

System.out.println("当前位置：经度"+lon1+" 维度："+lat1);

int i=0;

String[][] array = new String[rowCount][3];

while (rs.next()){

//从数据库取出地理坐标

double lon2=Double.parseDouble(rs.getString("Longitude"));

double lat2=Double.parseDouble(rs.getString("Latitude"));

//根据地理坐标，生成geohash编码

Geohash geohash = new Geohash();

String geocode=geohash.encode(lat2, lon2).substring(0, 9);

//计算两点间的距离

int dist=(int) Test.GetDistance(lon1, lat1, lon2, lat2);

array[i][0]=String.valueOf(i);

array[i][1]=geocode;

array[i][2]=Integer.toString(dist);

i++;

//System.out.println(lon2+"---"+lat2+"---"+geocode+"---"+dist);

}

array=sqlTest.getOrder(array); //二维数组排序

sqlTest.showArray(array); //打印数组

} catch (SQLException e) {

System.out.println("MySQL操作错误");

e.printStackTrace();

} finally {

conn.close();

}

}

/*

* 二维数组排序，比较array[][2]的值，返回二维数组

* */

public static String[][] getOrder(String[][] array){

for (int j = 0; j < array.length ; j++) {

for (int bb = 0; bb < array.length - 1; bb++) {

String[] ss;

int a1=Integer.valueOf(array[bb][2]); //转化成int型比较大小

int a2=Integer.valueOf(array[bb+1][2]);

if (a1>a2) {

ss = array[bb];

array[bb] = array[bb + 1];

array[bb + 1] = ss;

}

}

}

return array;

}

/*打印数组*/

public static void showArray(String[][] array){

for(int a=0;a

for(int j=0;j

System.out.print(array[a][j]+" ");

System.out.println();

}

}

/* public static void main(String[] args)

{

String aaa="wxsfdf";

Geohash geohash = new Geohash();

String[] str = geohash.getGeoHashExpand(aaa);

for(int i=0;i

{

System.out.println(str[i]);

}

}*/

}