因项目中需要用到地理位置信息的存储、查询、计算等，经过研究决定使用mysql（5.7版本）数据库的geometry类型字段来保存地理位置坐标，使用虚拟列（Virtual Generated Column）来保存geohash值，便于查询。
需要了解geometry如何使用及优势可参看：
mysql中geometry类型的简单使用
MySQL Geometry扩展在地理位置计算中的效率优势
本文主要讲解扩展mybatis和通用mapper，使其支持geometry类型字段的新增、修改、查询
首先创建一张表，作为本文的案例
CREATE TABLE `t_user` (
`id` varchar(45) NOT NULL,
`name` varchar(10) NOT NULL COMMENT '姓名',
`gis` geometry NOT NULL COMMENT '空间位置信息',
`geohash` varchar(20) GENERATED ALWAYS AS (st_geohash(`gis`,8)) VIRTUAL NOT NULL COMMENT 'geo哈希',
PRIMARY KEY (`id`),
UNIQUE KEY `id` (`id`),
SPATIAL KEY `idx_gis` (`gis`),
KEY `idx_geohash` (`geohash`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COMMENT='用户';创建对应的实体类
@Table(name = "t_user")
public class User {
private String id;
private String name;
@Column
private GeoPoint gis;
@VirtualGenerated
private String geohash;
}其中GeoPoint类型是我们自定义的类型，用来对应mysql的geometry类型
public class GeoPoint {
public GeoPoint(BigDecimal lng, BigDecimal lat) {
this.lng = lng;
this.lat = lat;
}
/* 经度 */
private BigDecimal lng;
/* 纬度 */
private BigDecimal lat;
}@VirtualGenerated注解是我们自定义的注解，用来标识虚拟列字段，使insert、update时能够忽略该字段
使tk通用mapper的insert支持geometry类型
tk通用mapper默认生成的insert语句xml是这样
<insert>
INSERT INTO t_user
<trim prefix="(" suffix=")" suffixOverrides=",">
<if test="id != null">id,</if>
<if test="name != null">name,</if>
<if test="gis != null">gis,</if>
</trim>
<trim prefix="VALUES(" suffix=")" suffixOverrides=",">
<if test="id != null">#{id},</if>
<if test="name != null">#{name},</if>
<if test="gis != null">#{gis},</if>
</trim>
</insert>而我们希望生成的insert语句xml是这样
<insert>
INSERT INTO t_user
<trim prefix="(" suffix=")" suffixOverrides=",">
<if test="id != null">id,</if>
<if test="name != null">name,</if>
<if test="gis != null">gis,</if>
</trim>
<trim prefix="VALUES(" suffix=")" suffixOverrides=",">
<if test="id != null">#{id},</if>
<if test="name != null">#{name},</if>
<if test="gis != null">geomfromtext('point(${gis.lng} ${gis.lat})'),</if>
</trim>
</insert>于是…开始我们的修改,查看通用mapper的源码得知，通用insert主要是通过BaseInsertMapper和BaseInsertProvider这两个类实现的，所以我们仿造着创建GeoBaseInsertMapper.java 和 GeoBaseInsertProvider.java，其中GeoBaseInsertProvider.java直接复制BaseInsertProvider来修改即可
GeoBaseInsertMapper.java如下：
@RegisterMapper
public interface GeoBaseInsertMapper<T> {
@InsertProvider(type = GeoBaseInsertProvider.class, method = "dynamicSQL")
int insert(T record);
@InsertProvider(type = GeoBaseInsertProvider.class, method = "dynamicSQL")
int insertSelective(T record);
}最主要的是GeoBaseInsertProvider.java
将
public class GeoBaseInsertProvider extends MapperTemplate {
public GeoBaseInsertProvider(Class<?> mapperClass, MapperHelper mapperHelper) {
super(mapperClass, mapperHelper);
}
public String insert(MappedStatement ms) {
Class<?> entityClass = getEntityClass(ms);
StringBuilder sql = new StringBuilder();
//获取全部列
Set<EntityColumn> columnList = EntityHelper.getColumns(entityClass);
EntityColumn logicDeleteColumn = SqlHelper.getLogicDeleteColumn(entityClass);
processKey(sql, entityClass, ms, columnList);
sql.append(SqlHelper.insertIntoTable(entityClass, tableName(entityClass)));
sql.append("<trim prefix=\"(\" suffix=\")\" suffixOverrides=\",\">");
//当某个列有主键策略时，不需要考虑他的属性是否为空，因为如果为空，一定会根据主键策略给他生成一个值
for (EntityColumn column : columnList) {
if (!column.isInsertable()) {
continue;
}
//忽略虚拟列
if (column.getEntityField().isAnnotationPresent(VirtualGenerated.class)) {
continue;
}
sql.append(column.getColumn() + ",");
}
sql.append("</trim>");
sql.append("<trim prefix=\"VALUES(\" suffix=\")\" suffixOverrides=\",\">");
for (EntityColumn column : columnList) {
if (!column.isInsertable()) {
continue;
}
//忽略虚拟列
if (column.getEntityField().isAnnotationPresent(VirtualGenerated.class)) {
continue;
}
if (logicDeleteColumn != null && logicDeleteColumn == column) {
sql.append(SqlHelper.getLogicDeletedValue(column, false)).append(",");
continue;
}
//优先使用传入的属性值,当原属性property!=null时，用原属性
//自增的情况下,如果默认有值,就会备份到property_cache中,所以这里需要先判断备份的值是否存在
if (column.isIdentity()) {
sql.append(SqlHelper.getIfCacheNotNull(column, column.getColumnHolder(null, "_cache", ",")));
} else {
//判断字段是GeoPoint类型时，调用getGeoColumnHolder方法来生成
if (column.getJavaType() == GeoPoint.class) {
//<if test="property != null">geomfromtext('point(108.9498710632 34.2588125935)'),</if>
sql.append(SqlHelper.getIfNotNull(column, getGeoColumnHolder(column), isNotEmpty()));
} else {
//其他情况值仍然存在原property中
sql.append(SqlHelper.getIfNotNull(column, column.getColumnHolder(null, null, ","), isNotEmpty()));
}
}
//当属性为null时，如果存在主键策略，会自动获取值，如果不存在，则使用null
if (column.isIdentity()) {
sql.append(SqlHelper.getIfCacheIsNull(column, column.getColumnHolder() + ","));
} else {
//判断字段是GeoPoint类型时，调用getGeoColumnHolder方法来生成
if (column.getJavaType() == GeoPoint.class) {
//<if test="property == null">geomfromtext('point(108.9498710632 34.2588125935)'),</if>
sql.append(SqlHelper.getIfIsNull(column, getGeoColumnHolder(column), isNotEmpty()));
} else {
//当null的时候，如果不指定jdbcType，oracle可能会报异常，指定VARCHAR不影响其他
sql.append(SqlHelper.getIfIsNull(column, column.getColumnHolder(null, null, ","), isNotEmpty()));
}
}
}
sql.append("</trim>");
return sql.toString();
}
/*
* insert GEO字段占位符
*/
private String getGeoColumnHolder(EntityColumn column){
return String.format("geomfromtext('point(${%s.lng} ${%s.lat})'),",column.getProperty(),column.getProperty());
}
//忽略以下部分代码
}让你的mapper接口继承GeoBaseInsertMapper 就能使insert方法支持geometry类型了，同时能够忽略虚拟列。
@Repository
public interface UserMapper extends GeoBaseInsertMapper<User>{
}如果你理解了通用insert的修改，update的修改也同样如此，相信难不倒你，这里就不再贴代码了。
使mybatis查询支持将geometry类型字段映射到GeoPoint类型
mybatis通过定义typeHandler将数据类型映射为java类型，mybatis内置了多种常见的typeHandler，但没有支持geometry，好在mybatis提供了足够的扩展性，我们可以自定义typeHandler，这里还需要在pom.xml引入jts库来解析
<dependency>
<groupId>com.vividsolutions</groupId>
<artifactId>jts</artifactId>
<version>${jts.version}</version>
</dependency>接下来是自定义的MysqlGeoPointTypeHandler
/*
* mybatis查询结果集中 mysql的geometry类型映射到GeoPoint对象
*/
@MappedTypes(value = {GeoPoint.class})
public class MysqlGeoPointTypeHandler extends BaseTypeHandler<GeoPoint> {
private WKBReader _wkbReader;
public MysqlGeoPointTypeHandler(int srid) {
GeometryFactory _geometryFactory = new GeometryFactory(new PrecisionModel(), srid);
_wkbReader = new WKBReader(_geometryFactory);
}
@Override
public void setNonNullParameter(PreparedStatement ps, int i, GeoPoint parameter, JdbcType jdbcType) {
//因为GeoPoint对象里包含经度和纬度两个值，无法直接适配到一个参数，所以也不会使用到这个方法
}
@Override
public GeoPoint getNullableResult(ResultSet rs, String columnName) throws SQLException {
return fromMysqlWkb(rs.getBytes(columnName));
}
@Override
public GeoPoint getNullableResult(ResultSet rs, int columnIndex) throws SQLException {
return fromMysqlWkb(rs.getBytes(columnIndex));
}
@Override
public GeoPoint getNullableResult(CallableStatement cs, int columnIndex) throws SQLException {
return fromMysqlWkb(cs.getBytes(columnIndex));
}
/*
* bytes转GeoPoint对象
*/
private GeoPoint fromMysqlWkb(byte[] bytes) {
if (bytes == null) {
return null;
}
try {
byte[] geomBytes = ByteBuffer.allocate(bytes.length - 4).order(ByteOrder.LITTLE_ENDIAN)
.put(bytes, 4, bytes.length - 4).array();
Geometry geometry = _wkbReader.read(geomBytes);
Point point = (Point) geometry;
return new GeoPoint(new BigDecimal(String.valueOf(point.getX())), new BigDecimal(String.valueOf(point.getY())));
} catch (Exception e) {
}
return null;
}
}然后我们需要将MysqlGeoPointTypeHandler添加到mybatis配置中，这样mybatis在遇到GeoPoint时就知道怎么映射了。
这里演示用java代码来配置mybatis，也可以在mybatis.xml文件中配置
@Configuration
@MapperScan(basePackages = {"com.carson.**.mapper"}, sqlSessionTemplateRef = "sqlSessionTemplate")
public class MybatisConfig {
@Bean
public SqlSessionFactory sqlSessionFactory(DataSource dataSource) {
SqlSessionFactoryBean bean = new SqlSessionFactoryBean();
bean.setDataSource(dataSource);
bean.setVfs(SpringBootVFS.class);
//添加XML目录
ResourcePatternResolver resolver = new PathMatchingResourcePatternResolver();
try {
bean.setMapperLocations(resolver.getResources("classpath:mybatis/**/*Mapper.xml"));
bean.setTypeAliasesPackage("com.carson.pojo");
//添加MysqlGeoPointTypeHandler
bean.setTypeHandlers(new TypeHandler[]{new MysqlGeoPointTypeHandler()});
bean.getObject().getConfiguration().setMapUnderscoreToCamelCase(true);
return bean.getObject();
} catch (Exception e) {
e.printStackTrace();
throw new RuntimeException(e);
}
}
}完成这些以后查询的结果集里包含geometry类型的字段，就能映射到GeoPoint了，从而可以获取经纬度
源码在哪里？ talk is cheap,show me the code！
如果你懒得看以上长篇大论，只想要开箱即用的代码，就在这里了，有帮助的话记得给个star哦！
