因項目中需要用到地理位置信息的存儲、查詢、計算等，經過研究決定使用mysql（5.7版本）數據庫的geometry類型字段來保存地理位置坐標，使用虛擬列（Virtual Generated Column）來保存geohash值，便於查詢。
需要了解geometry如何使用及優勢可參看：
mysql中geometry類型的簡單使用
MySQL Geometry擴展在地理位置計算中的效率優勢
本文主要講解擴展mybatis和通用mapper，使其支持geometry類型字段的新增、修改、查詢
首先創建一張表，作為本文的案例
CREATE TABLE `t_user` (
`id` varchar(45) NOT NULL,
`name` varchar(10) NOT NULL COMMENT '姓名',
`gis` geometry NOT NULL COMMENT '空間位置信息',
`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='用戶';
創建對應的實體類
@Table(name = "t_user")
public class User {
private String id;
private String name;
@Column
private GeoPoint gis;
@VirtualGenerated
private String geohash;
}
其中GeoPoint類型是我們自定義的類型，用來對應mysql的geometry類型
public class GeoPoint {
public GeoPoint(BigDecimal lng, BigDecimal lat) {
this.lng = lng;
this.lat = lat;
}
/* 經度 */
private BigDecimal lng;
/* 緯度 */
private BigDecimal lat;
}
@VirtualGenerated注解是我們自定義的注解，用來標識虛擬列字段，使insert、update時能夠忽略該字段
使tk通用mapper的insert支持geometry類型
tk通用mapper默認生成的insert語句xml是這樣
<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>
而我們希望生成的insert語句xml是這樣
<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>
於是...開始我們的修改,查看通用mapper的源碼得知，通用insert主要是通過BaseInsertMapper和BaseInsertProvider這兩個類實現的，所以我們仿造着創建GeoBaseInsertMapper.java 和 GeoBaseInsertProvider.java，其中GeoBaseInsertProvider.java直接復制BaseInsertProvider來修改即可
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
將
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();
//獲取全部列
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=\",\">");
//當某個列有主鍵策略時，不需要考慮他的屬性是否為空，因為如果為空，一定會根據主鍵策略給他生成一個值
for (EntityColumn column : columnList) {
if (!column.isInsertable()) {
continue;
}
//忽略虛擬列
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;
}
//忽略虛擬列
if (column.getEntityField().isAnnotationPresent(VirtualGenerated.class)) {
continue;
}
if (logicDeleteColumn != null && logicDeleteColumn == column) {
sql.append(SqlHelper.getLogicDeletedValue(column, false)).append(",");
continue;
}
//優先使用傳入的屬性值,當原屬性property!=null時，用原屬性
//自增的情況下,如果默認有值,就會備份到property_cache中,所以這里需要先判斷備份的值是否存在
if (column.isIdentity()) {
sql.append(SqlHelper.getIfCacheNotNull(column, column.getColumnHolder(null, "_cache", ",")));
} else {
//判斷字段是GeoPoint類型時，調用getGeoColumnHolder方法來生成
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 {
//其他情況值仍然存在原property中
sql.append(SqlHelper.getIfNotNull(column, column.getColumnHolder(null, null, ","), isNotEmpty()));
}
}
//當屬性為null時，如果存在主鍵策略，會自動獲取值，如果不存在，則使用null
if (column.isIdentity()) {
sql.append(SqlHelper.getIfCacheIsNull(column, column.getColumnHolder() + ","));
} else {
//判斷字段是GeoPoint類型時，調用getGeoColumnHolder方法來生成
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 {
//當null的時候，如果不指定jdbcType，oracle可能會報異常，指定VARCHAR不影響其他
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} ${%s.lat})'),",column.getProperty(),column.getProperty());
}
//忽略以下部分代碼
}
讓你的mapper接口繼承GeoBaseInsertMapper
@Repository
public interface UserMapper extends GeoBaseInsertMapper<User>{
}
如果你理解了通用insert的修改，update的修改也同樣如此，相信難不倒你，這里就不再貼代碼了。
使mybatis查詢支持將geometry類型字段映射到GeoPoint類型
mybatis通過定義typeHandler將數據類型映射為java類型，mybatis內置了多種常見的typeHandler，但沒有支持geometry，好在mybatis提供了足夠的擴展性，我們可以自定義typeHandler，這里還需要在pom.xml引入jts庫來解析
<dependency>
<groupId>com.vividsolutions</groupId>
<artifactId>jts</artifactId>
<version>${jts.version}</version>
</dependency>
接下來是自定義的MysqlGeoPointTypeHandler
/*
* mybatis查詢結果集中 mysql的geometry類型映射到GeoPoint對象
*/
@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) {
//因為GeoPoint對象里包含經度和緯度兩個值，無法直接適配到一個參數，所以也不會使用到這個方法
}
@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轉GeoPoint對象
*/
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;
}
}
然后我們需要將MysqlGeoPointTypeHandler添加到mybatis配置中，這樣mybatis在遇到GeoPoint時就知道怎么映射了。
這里演示用java代碼來配置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目錄
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);
}
}
}
完成這些以后查詢的結果集里包含geometry類型的字段，就能映射到GeoPoint了，從而可以獲取經緯度
源碼在哪里？ talk is cheap,show me the code！
如果你懶得看以上長篇大論，只想要開箱即用的代碼，就在這里了，有幫助的話記得給個star哦！