To Java delevopers, TDengine provides `taos-jdbcdriver` according to the JDBC(3.0) API. Users can find and download it through [Sonatype Repository][1].
由于 TDengine 是使用 c 语言开发的，使用 taos-jdbcdriver 驱动包时需要依赖系统对应的本地函数库。
Since the native language of TDengine is C, the necessary TDengine library should be checked before using the taos-jdbcdriver:
* libtaos.so
在 linux 系统中成功安装 TDengine 后，依赖的本地函数库 libtaos.so 文件会被自动拷贝至 /usr/lib/libtaos.so，该目录包含在 Linux 自动扫描路径上，无需单独指定。
* libtaos.so (Linux)
After TDengine is installed successfully, the library `libtaos.so` will be automatically copied to the `/usr/lib/`, which is the system's default search path.
* taos.dll
在 windows 系统中安装完客户端之后，驱动包依赖的 taos.dll 文件会自动拷贝到系统默认搜索路径 C:/Windows/System32 下，同样无需要单独指定。
* taos.dll (Windows)
After TDengine client is installed, the library `taos.dll` will be automatically copied to the `C:/Windows/System32`, which is the system's default search path.
> Note: Please make sure that [TDengine Windows client][14] has been installed if developing on Windows. Now although TDengine client would be defaultly installed together with TDengine server, it can also be installed [alone][15].
Since TDengine is time-series database, there are still some differences compared with traditional databases in using TDengine JDBC driver:
* TDengine doesn't allow to delete/modify a single record, and thus JDBC driver also has no such method.
* No support for transaction
* No support for union between tables
* No support for nested query，`There is at most one open ResultSet for each Connection. Thus, TSDB JDBC Driver will close current ResultSet if it is not closed and a new query begins`.
After downloading the [TDengine][3] source code, execute `mvn clean package` in the directory `src/connector/jdbc` and then the corresponding jar file is generated.
> _now+1s_ is 1 second later than current server time. The time unit includes: _a_(millisecond), _s_(second), _m_(minute), _h_(hour), _d_(day), _w_(week), _n_(month), _y_(year).
> query is consistent with relational database. The subscript start with 1 when retrieving return results. It is recommended to use the column name to retrieve results.
### 关闭资源
### Close all
```java
resultSet.close();
stmt.close();
conn.close();
```
> `注意务必要将 connection 进行关闭`，否则会出现连接泄露。
## 与连接池使用
> `please make sure the connection is closed to avoid the error like connection leakage`
## Using connection pool
**HikariCP**
* 引入相应 HikariCP maven 依赖：
* dependence in pom.xml：
```xml
<dependency>
<groupId>com.zaxxer</groupId>
...
...
@@ -482,7 +479,7 @@ conn.close();
</dependency>
```
* 使用示例如下：
* Examples：
```java
public static void main(String[] args) throws SQLException {
HikariConfig config = new HikariConfig();
...
...
@@ -508,8 +505,69 @@ conn.close();
connection.close(); // put back to conneciton pool
Connection connection = ds.getConnection(); // get connection
Statement statement = connection.createStatement(); // get statement
//query or insert
// ...
connection.close(); // put back to conneciton pool
}
```
> More instructions can refer to [User Guide][6]
**Notice**
* TDengine `v1.6.4.1` provides a function `select server_status()` to check heartbeat. It is highly recommended to use this function for `Validation Query`.
As follows，`1` will be returned if `select server_status()` is successfully executed。
```shell
taos> select server_status();
server_status()|
================
1 |
Query OK, 1 row(s) in set (0.000141s)
```
## Python Connector
...
...
@@ -821,3 +879,18 @@ An example of using the NodeJS connector to create a table with weather data and
An example of using the NodeJS connector to achieve the same things but without all the object wrappers that wrap around the data returned to achieve higher functionality can be found [here](https://github.com/taosdata/TDengine/tree/master/tests/examples/nodejs/node-example-raw.js)
