Connect with Java

Add Dependency

Maven

pom.xml

    <dependency>
      <groupId>com.taosdata.jdbc</groupId>
      <artifactId>taos-jdbcdriver</artifactId>
      <version>3.2.7</version>
    </dependency>

view source code

Spring

In the "pom.xml" file, please add the Spring Boot and TDengine Java connector dependencies:

  <parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>2.7.0</version>
    <relativePath/>
  </parent>
  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <java.version>8</java.version>
    <maven.compiler.source>1.8</maven.compiler.source>
    <maven.compiler.target>1.8</maven.compiler.target>
    <spring.boot.version>2.5.12</spring.boot.version>
    <taos.jdbc.version>3.2.7</taos.jdbc.version>
    <druid.version>1.2.8</druid.version>
    <mybatis.version>2.2.2</mybatis.version>
  </properties>
  <dependencies>
    <!--spring-->
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter</artifactId>
    </dependency>
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
    <!--mybatis-->
    <dependency>
      <groupId>org.mybatis.spring.boot</groupId>
      <artifactId>mybatis-spring-boot-starter</artifactId>
      <version>${mybatis.version}</version>
    </dependency>
    <!--connection pool-->
    <dependency>
      <groupId>com.alibaba</groupId>
      <artifactId>druid-spring-boot-starter</artifactId>
      <version>${druid.version}</version>
    </dependency>
    <dependency>
      <groupId>com.taosdata.jdbc</groupId>
      <artifactId>taos-jdbcdriver</artifactId>
      <version>${taos.jdbc.version}</version>
    </dependency>

view source code

Config

Run this command in your terminal to save the JDBC URL as variable, or if it is a Spring application, you can use the Spring configuration:

Bash

export TDENGINE_JDBC_URL="<jdbcURL>"

CMD

set TDENGINE_JDBC_URL=<jdbcURL>

Powershell

$env:TDENGINE_JDBC_URL='<jdbcURL>'

Spring

# spring server
server:
  port: 8088

spring:
  datasource:
    driver-class-name: com.taosdata.jdbc.rs.RestfulDriver
    url: jdbc:TAOS-RS://example.com?useSSL=true&token=xxxx
    # using connection pools
    type: com.alibaba.druid.pool.DruidDataSource
    druid:
      initial-size: 5
      min-idle: 5
      max-active: 20
      max-wait: 60000
      time-between-eviction-runs-millis: 60000
      min-evictable-idle-time-millis: 300000
      validation-query: SELECT 1
      pool-prepared-statements: true
      max-pool-prepared-statement-per-connection-size: 20
# mybatis
mybatis:
  mapper-locations: classpath:mapper/*.xml

view source code

IMPORTANT

Replace <jdbcURL> with real JDBC URL, it will seems like: jdbc:TAOS-RS://example.com?useSSL=true&token=xxxx.

To obtain the value of JDBC URL, please log in TDengine Cloud and click "Programming" on the left menu, then select "Java".

Connect

Java

Code bellow get JDBC URL from environment variables first and then create a Connection object, which is a standard JDBC Connection object.

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;


public class ConnectCloudExample {
    public static void main(String[] args) throws SQLException {
        String jdbcUrl = System.getenv("TDENGINE_JDBC_URL");
        System.out.println(jdbcUrl);
        try(Connection conn = DriverManager.getConnection(jdbcUrl)) {
            try(Statement stmt = conn.createStatement()) {
                stmt.executeQuery("select server_version()");
            }
        }
    }
}

view source code

Spring

1. Define an interface called "meterMapper", which uses the MyBatis framework to map from TDengine database super table to Java object:

@Mapper
public interface MeterMapper {

@Select("select * from meters limit 10")
List<Meter> find();

int create(@Param("meter")Meter meter, @Param("tableName")String tableName);

int save(@Param("meter")Meter meter, @Param("tableName")String tableName);

Meter lastRow(@Param("tableName")String tableName);
}

view source code

2. Create a 'meterMapper.xml' file under 'src/main/resources/mapper', and add the following SQL mapping:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
  "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.taos.example.dao.MeterMapper">
  <resultMap id="Meter" type="com.taos.example.dao.Meter">
    <result column="ts" property="ts"/>
    <result column="current" property="current"/>
    <result column="voltage" property="voltage"/>
    <result column="phase" property="phase"/>
    <result column="groupId" property="groupid"/>
    <result column="location" property="location"/>
  </resultMap>

  <insert id="create">
    CREATE TABLE IF NOT EXISTS #{tableName, jdbcType=VARCHAR} USING meters TAGS
    (#{meter.groupId, jdbcType=INTEGER}, #{meter.location, jdbcType=VARCHAR})
  </insert>

  <insert id="save">
    INSERT INTO #{tableName} VALUES (#{meter.ts}, #{meter.current}, #{meter.voltage}, #{meter.phase}) ;
  </insert>

  <select id="lastRow" resultMap="Meter">
    SELECT last_row(*) FROM meters;
  </select>
</mapper>

view source code

3. For more details about how to write or query data from TDngine Cloud instance through Spring, please refer to Spring Example

The client connection is then established. For how to write data and query data, please refer to Insert and Query.

For more details about how to write or query data via REST API, please check REST API.