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TDengine Java Client Library

taos-jdbcdriver is the official Java client library for TDengine. Java developers can use it to develop applications that access data in TDengine. taos-jdbcdriver implements standard JDBC driver interfaces.

info

TDengine's JDBC driver implementation is as consistent as possible with the relational database driver. Still, there are differences in the use scenarios and technical characteristics of TDengine and relational object databases. So 'taos-jdbcdriver' also has some differences from traditional JDBC drivers. It is important to keep the following points in mind:

  • TDengine does not currently support delete operations for individual data records.
  • Transactional operations are not currently supported.

Connection types

taos-jdbcdriver mainly provides 3 connection types, among which we recommend using websocket connection.

  • Native connection, which connects to TDengine instances natively through the TDengine client driver (taosc), supporting data writing, querying, subscriptions, schemaless writing, and bind interface.
  • REST connection, which is implemented through taosAdapter. Some features like schemaless and subscriptions are not supported.
  • Websocket connection which is implemented through taosAdapter. The set of features implemented by the WebSocket connection differs slightly from those implemented by the native connection.

For a detailed introduction of the connection types, please refer to: Establish Connection

Compatibility with JDBC and JRE Versions

  • JDBC: mainly supports JDBC 4.2 version, some features like schemaless and data subscription are provided individually.
  • JRE: supports JRE 8 or higher.

Supported platforms

Native connections are supported on the same platforms as the TDengine client driver. REST connection supports all platforms that can run Java.

Recent update logs

taos-jdbcdriver versionmajor changesTDengine version
3.2.8Improved autocommit, fixed commit offset on websocket connection bug, websocket prepareStatement uses one connection and meta data supports view.-
3.2.7Support VARBINARY and GEOMETRY types, and add time zone support for native connections. Support websocket auto reconnection3.2.0.0 or later
3.2.5Subscription add committed() and assignment() method3.1.0.3 or later
3.2.4Subscription add the enable.auto.commit parameter and the unsubscribe() method in the WebSocket connection-
3.2.3Fixed resultSet data parsing failure in some cases-
3.2.2Subscription add seek function3.0.5.0 or later
3.2.1JDBC REST connection supports schemaless/prepareStatement over WebSocket3.0.3.0 or later
3.2.0This version has been deprecated-
3.1.0JDBC REST connection supports subscription over WebSocket-
3.0.1 - 3.0.4fix the resultSet data is parsed incorrectly sometimes. 3.0.1 is compiled on JDK 11, you are advised to use other version in the JDK 8 environment-
3.0.0Support for TDengine 3.03.0.0.0 or later
2.0.42Fix wasNull interface return value in WebSocket connection-
2.0.41Fix decode method of username and password in REST connection-
2.0.39 - 2.0.40Add REST connection/request timeout parameters-
2.0.38JDBC REST connections add bulk pull function-
2.0.37Support json tags-
2.0.36Support schemaless writing-

Handling exceptions

After an error is reported, the error message and error code can be obtained through SQLException.

try (Statement statement = connection.createStatement()) {
// executeQuery
ResultSet tempResultSet = statement.executeQuery(sql);
// print result
printResult(tempResultSet);
} catch (SQLException e) {
System.out.println("ERROR Message: " + e.getMessage());
System.out.println("ERROR Code: " + e.getErrorCode());
e.printStackTrace();
}

view source code

There are four types of error codes that the JDBC client library can report:

  • Error code of the JDBC driver itself (error code between 0x2301 and 0x2350),
  • Error code of the native connection method (error code between 0x2351 and 0x2360)
  • Error code of the consumer method (error code between 0x2371 and 0x2380)
  • Error code of other TDengine function modules.

For specific error codes, please refer to.

Error CodeDescriptionSuggested Actions
0x2301connection already closedThe connection has been closed, check the connection status, or recreate the connection to execute the relevant instructions.
0x2302this operation is NOT supported currently!The current interface does not support the connection. You can use another connection mode.
0x2303invalid variablesThe parameter is invalid. Check the interface specification and adjust the parameter type and size.
0x2304statement is closedThe statement is closed. Check whether the statement is closed and used again, or whether the connection is normal.
0x2305resultSet is closedresult set The result set is released. Check whether the result set is released and used again.
0x2306Batch is empty!prepare statement Add parameters and then execute batch.
0x2307Can not issue data manipulation statements with executeQuery()The update operation should use execute update(), not execute query().
0x2308Can not issue SELECT via executeUpdate()The query operation should use execute query(), not execute update().
0x230dparameter index out of rangeThe parameter is out of bounds. Check the proper range of the parameter.
0x230econnection already closedThe connection has been closed. Please check whether the connection is closed and used again, or whether the connection is normal.
0x230funknown sql type in tdengineCheck the data type supported by TDengine.
0x2310can't register JDBC-JNI driverThe native driver cannot be registered. Please check whether the url is correct.
0x2312url is not setCheck whether the REST connection url is correct.
0x2314numeric value out of rangeCheck that the correct interface is used for the numeric types in the obtained result set.
0x2315unknown taos type in tdengineWhether the correct TDengine data type is specified when converting the TDengine data type to the JDBC data type.
0x2317wrong request type was used in the REST connection.
0x2318data transmission exception occurred during the REST connection. Please check the network status and try again.
0x2319user is requiredThe user name information is missing when creating the connection
0x231apassword is requiredPassword information is missing when creating a connection
0x231chttpEntity is null, sql:Execution exception occurred during the REST connection
0x231dcan't create connection with server withinIncrease the connection time by adding the httpConnectTimeout parameter, or check the connection to the taos adapter.
0x231efailed to complete the task within the specified timeIncrease the execution time by adding the messageWaitTimeout parameter, or check the connection to the taos adapter.
0x2350unknown errorUnknown exception, please return to the developer on github.
0x2352Unsupported encodingAn unsupported character encoding set is specified under the native Connection.
0x2353internal error of database, please see taoslog for more detailsAn error occurs when the prepare statement is executed on the native connection. Check the taos log to locate the fault.
0x2354JNI connection is NULLWhen the command is executed, the native Connection is closed. Check the connection to TDengine.
0x2355JNI result set is NULLThe result set is abnormal. Please check the connection status and try again.
0x2356invalid num of fieldsThe meta information of the result set obtained by the native connection does not match.
0x2357empty sql stringFill in the correct SQL for execution.
0x2359JNI alloc memory failed, please see taoslog for more detailsMemory allocation for the native connection failed. Check the taos log to locate the problem.
0x2371consumer properties must not be null!The parameter is empty when you create a subscription. Please fill in the correct parameter.
0x2372configs contain empty key, failed to set consumer propertyThe parameter key contains a null value. Please enter the correct parameter.
0x2373failed to set consumer property,The parameter value contains a null value. Please enter the correct parameter.
0x2375topic reference has been destroyedThe topic reference is released during the creation of the data subscription. Check the connection to TDengine.
0x2376failed to set consumer topic, topic name is emptyDuring data subscription creation, the subscription topic name is empty. Check that the specified topic name is correct.
0x2377consumer reference has been destroyedThe subscription data transfer channel has been closed. Please check the connection to TDengine.
0x2378consumer create errorFailed to create a data subscription. Check the taos log according to the error message to locate the fault.
0x2379seek offset must not be a negative numberThe seek interface parameter cannot be negative. Use the correct parameter
0x237avGroup not found in result setsubscription is not bound to the VGroup due to the rebalance mechanism

TDengine DataType vs. Java DataType

TDengine currently supports timestamp, number, character, Boolean type, and the corresponding type conversion with Java is as follows:

TDengine DataTypeJDBCType
TIMESTAMPjava.sql.Timestamp
INTjava.lang.Integer
BIGINTjava.lang.Long
FLOATjava.lang.Float
DOUBLEjava.lang.Double
SMALLINTjava.lang.Short
TINYINTjava.lang.Byte
BOOLjava.lang.Boolean
BINARYbyte array
NCHARjava.lang.String
JSONjava.lang.String
VARBINARYbyte[]
GEOMETRYbyte[]

Note: Only TAG supports JSON types Due to historical reasons, the BINARY type data in TDengine is not truly binary data and is no longer recommended for use. Please use VARBINARY type instead.
GEOMETRY type is binary data in little endian byte order, which complies with the WKB specification. For detailed information, please refer to Data Type For WKB specifications, please refer to Well Known Binary (WKB) For Java connector, the jts library can be used to easily create GEOMETRY type objects, serialize them, and write them to TDengine. Here is an example Geometry example

Installation Steps

Pre-installation preparation

Before using Java client library to connect to the database, the following conditions are required.

  • Java 1.8 or above runtime environment and Maven 3.6 or above installed
  • TDengine client driver installed (required for native connections, not required for REST connections), please refer to Installing Client Driver

Install the client library

taos-jdbcdriver has been published on the Sonatype Repository and synchronized to other major repositories.

Add following dependency in the pom.xml file of your Maven project:

<dependency>
<groupId>com.taosdata.jdbc</groupId>
<artifactId>taos-jdbcdriver</artifactId>
<version>3.2.8</version>
</dependency>

Establishing a connection

TDengine's JDBC URL specification format is: jdbc:[TAOS|TAOS-RS]://[host_name]:[port]/[database_name]?[user={user}|&password={password}|&charset={charset}|&cfgdir={config_dir}|&locale={locale}|&timezone={timezone}]

For establishing connections, native connections differ slightly from REST connections.

Note: adding batchfetch to the REST connection and setting it to true will enable the WebSocket connection.

Class.forName("com.taosdata.jdbc.rs.RestfulDriver");
String jdbcUrl = "jdbc:TAOS-RS://taosdemo.com:6041/power?user=root&password=taosdata";
Connection conn = DriverManager.getConnection(jdbcUrl);

In the above example, a RestfulDriver with a JDBC REST connection is used to establish a connection to a database named power with hostname taosdemo.com on port 6041. The URL specifies the user name as root and the password as taosdata.

There is no dependency on the client driver when Using a JDBC REST connection. Compared to a JDBC native connection, only the following are required:

  1. driverClass specified as "com.taosdata.jdbc.rs.RestfulDriver".
  2. jdbcUrl starting with "jdbc:TAOS-RS://".
  3. use 6041 as the connection port.

The configuration parameters in the URL are as follows:

  • user: Log in to the TDengine username. The default value is 'root'.
  • password: User login password, the default value is 'taosdata'.
  • batchfetch: true: pulls result sets in batches when executing queries; false: pulls result sets row by row. The default value is: false. batchfetch uses HTTP for data transfer. JDBC REST supports batch pulls. taos-jdbcdriver and TDengine transfer data via WebSocket connection. Compared with HTTP, WebSocket enables JDBC REST connection to support large data volume querying and improve query performance.
  • charset: specify the charset to parse the string, this parameter is valid only when set batchfetch to true.
  • batchErrorIgnore: true: when executing executeBatch of Statement, if one SQL execution fails in the middle, continue to execute the following SQL. false: no longer execute any statement after the failed SQL. The default value is: false.
  • httpConnectTimeout: REST connection timeout in milliseconds, the default value is 60000 ms.
  • httpSocketTimeout: socket timeout in milliseconds, the default value is 60000 ms. It only takes effect when batchfetch is false.
  • messageWaitTimeout: message transmission timeout in milliseconds, the default value is 60000 ms. It only takes effect when batchfetch is true.
  • useSSL: connecting Securely Using SSL. true: using SSL connection, false: not using SSL connection.
  • httpPoolSize: size of REST concurrent requests. The default value is 20.

Note: Some configuration items (e.g., locale, timezone) do not work in the REST connection.

note
  • Unlike the native connection method, the REST interface is stateless. When using the JDBC REST connection, you need to specify the database name of the table and super table in SQL. For example:
INSERT INTO power.d1001 USING power.meters TAGS(2,'California.SanFrancisco') VALUES (NOW, 10.30000, 219, 0.31000);
  • If the dbname is specified in the URL, the JDBC REST connection uses /rest/sql/dbname as the default URL for RESTful requests. In this case, it is not necessary to specify the dbname in SQL. For example, if the URL is jdbc:TAOS-RS://127.0.0.1:6041/power, then the SQL can be executed: INSERT INTO d1001 USING meters TAGS(2,'California.SanFrancisco') VALUES (NOW, 10.30000, 219, 0.31000);

Specify the URL and Properties to get the connection

In addition to getting the connection from the specified URL, you can use Properties to specify parameters when the connection is established.

Note:

  • The client parameter set in the application is process-level. If you want to update the parameters of the client, you need to restart the application. This is because the client parameter is a global parameter that takes effect only the first time the application is set.
  • The following sample code is based on taos-jdbcdriver-3.1.0 version or above.
public Connection getConn() throws Exception{
Class.forName("com.taosdata.jdbc.TSDBDriver");
String jdbcUrl = "jdbc:TAOS://taosdemo.com:6030/power?user=root&password=taosdata";
Properties connProps = new Properties();
connProps.setProperty(TSDBDriver.PROPERTY_KEY_CHARSET, "UTF-8");
connProps.setProperty(TSDBDriver.PROPERTY_KEY_LOCALE, "en_US.UTF-8");
connProps.setProperty(TSDBDriver.PROPERTY_KEY_TIME_ZONE, "UTC-8");
connProps.setProperty("debugFlag", "135");
connProps.setProperty("maxSQLLength", "1048576");
Connection conn = DriverManager.getConnection(jdbcUrl, connProps);
return conn;
}

public Connection getRestConn() throws Exception{
Class.forName("com.taosdata.jdbc.rs.RestfulDriver");
String jdbcUrl = "jdbc:TAOS-RS://taosdemo.com:6041/power?user=root&password=taosdata";
Properties connProps = new Properties();
connProps.setProperty(TSDBDriver.PROPERTY_KEY_BATCH_LOAD, "true");
Connection conn = DriverManager.getConnection(jdbcUrl, connProps);
return conn;
}

In the above example, a connection is established to taosdemo.com, port is 6030/6041, and database named power. The connection specifies the user name as root and the password as taosdata in the URL and specifies the character set, language environment, time zone, and whether to enable bulk fetching in the connProps.The url specifies the user name as root and the password as taosdata.

The configuration parameters in properties are as follows.

  • TSDBDriver.PROPERTY_KEY_USER: login TDengine user name, default value 'root'.
  • TSDBDriver.PROPERTY_KEY_PASSWORD: user login password, default value 'taosdata'.
  • TSDBDriver.PROPERTY_KEY_BATCH_LOAD: true: pull the result set in batch when executing query; false: pull the result set row by row. The default value is: false.
  • TSDBDriver.PROPERTY_KEY_BATCH_ERROR_IGNORE: true: when executing executeBatch of Statement, if there is a SQL execution failure in the middle, continue to execute the following sql. false: no longer execute any statement after the failed SQL. The default value is: false.
  • TSDBDriver.PROPERTY_KEY_CONFIG_DIR: only works when using JDBC native connection. Client configuration file directory path, default value /etc/taos on Linux OS, default value C:/TDengine/cfg on Windows OS, default value /etc/taos on macOS.
  • TSDBDriver.PROPERTY_KEY_CHARSET: In the character set used by the client, the default value is the system character set.
  • TSDBDriver.PROPERTY_KEY_LOCALE: this only takes effect when using JDBC native connection. Client language environment, the default value is system current locale.
  • TSDBDriver.PROPERTY_KEY_TIME_ZONE: only takes effect when using JDBC native connection. In the time zone used by the client, the default value is the system's current time zone. Due to historical reasons, we only support some specifications of the POSIX standard, such as UTC-8 (representing timezone Shanghai in China), GMT-7, Europe/Paris.
  • TSDBDriver.HTTP_CONNECT_TIMEOUT: REST connection timeout in milliseconds, the default value is 60000 ms. It only takes effect when using JDBC REST connection.
  • TSDBDriver.HTTP_SOCKET_TIMEOUT: socket timeout in milliseconds, the default value is 60000 ms. It only takes effect when using JDBC REST connection and batchfetch is false.
  • TSDBDriver.PROPERTY_KEY_MESSAGE_WAIT_TIMEOUT: message transmission timeout in milliseconds, the default value is 60000 ms. It only takes effect when using JDBC REST connection and batchfetch is true.
  • TSDBDriver.PROPERTY_KEY_USE_SSL: connecting Securely Using SSL. true: using SSL connection, false: not using SSL connection. It only takes effect when using JDBC REST connection.
  • TSDBDriver.HTTP_POOL_SIZE: size of REST concurrent requests. The default value is 20.

For JDBC native connections, you can specify other parameters, such as log level, SQL length, etc., by specifying URL and Properties. For more detailed configuration, please refer to Client Configuration.

Priority of configuration parameters

If the configuration parameters are duplicated in the URL, Properties, or client configuration file, the priority of the parameters, from highest to lowest, are as follows:

  1. JDBC URL parameters, as described above, can be specified in the parameters of the JDBC URL.
  2. Properties connProps
  3. the configuration file taos.cfg of the TDengine client driver when using a native connection

For example, if you specify the password as taosdata in the URL and specify the password as taosdemo in the Properties simultaneously, JDBC will use the password in the URL to establish the connection.

Usage examples

Create database and tables

// create database
stmt.executeUpdate("CREATE DATABASE IF NOT EXISTS power");

// use database
stmt.executeUpdate("USE power");

// create table
stmt.executeUpdate("CREATE STABLE IF NOT EXISTS meters (ts TIMESTAMP, current FLOAT, voltage INT, phase FLOAT) TAGS (groupId INT, location BINARY(24))");

view source code

Note: If you do not use USE power to specify the database, all subsequent operations on the table need to add the database name as a prefix, such as power.meters.

Insert data

// insert data
String insertQuery = "INSERT INTO " +
"power.d1001 USING power.meters TAGS(2,'California.SanFrancisco') " +
"VALUES " +
"(NOW + 1a, 10.30000, 219, 0.31000) " +
"(NOW + 2a, 12.60000, 218, 0.33000) " +
"(NOW + 3a, 12.30000, 221, 0.31000) " +
"power.d1002 USING power.meters TAGS(3, 'California.SanFrancisco') " +
"VALUES " +
"(NOW + 1a, 10.30000, 218, 0.25000) ";
int affectedRows = stmt.executeUpdate(insertQuery);
System.out.println("insert " + affectedRows + " rows.");

view source code

NOW is an internal function. The default is the current time of the client's computer. NOW + 1s represents the current time of the client plus 1 second, followed by the number representing the unit of time: a (milliseconds), s (seconds), m (minutes), h (hours), d (days), w (weeks), n (months), y (years).

Querying data

// query data
ResultSet resultSet = stmt.executeQuery("SELECT * FROM meters");

Timestamp ts;
float current;
String location;
while(resultSet.next()){
ts = resultSet.getTimestamp(1);
current = resultSet.getFloat(2);
location = resultSet.getString("location");

System.out.printf("%s, %f, %s\n", ts, current, location);
}

view source code

The query is consistent with operating a relational database. When using subscripts to get the contents of the returned fields, you have to start from 1. However, we recommend using the field names to get the values of the fields in the result set.

Execute SQL with reqId

The reqId is very similar to TraceID in distributed tracing systems. In a distributed system, a request may need to pass through multiple services or modules to be completed. The reqId is used to identify and associate all related operations of this request, allowing us to track and understand the complete execution path of the request. Here are some primary usage of reqId:

  • Request Tracing: By associating the same reqId with all related operations of a request, we can trace the complete path of the request within the system.
  • Performance Analysis: By analyzing a request's reqId, we can understand the processing time of the request across various services or modules, thereby identifying performance bottlenecks.
  • Fault Diagnosis: When a request fails, we can identify the location of the issue by examining the reqId associated with that request.

If the user does not set a reqId, the client library will generate one randomly internally, but it is still recommended for the user to set it, as it can better associate with the user's request.

AbstractStatement aStmt = (AbstractStatement) connection.createStatement();
aStmt.execute("CREATE DATABASE IF NOT EXISTS power", 1L);
aStmt.executeUpdate("USE power", 2L);
try (ResultSet rs = aStmt.executeQuery("SELECT * FROM meters limit 1", 3L)) {
while(rs.next()){
Timestamp timestamp = rs.getTimestamp(1);
System.out.println("timestamp = " + timestamp);
}
}
aStmt.close();

view source code

Writing data via parameter binding

TDengine has significantly improved the bind APIs to support data writing (INSERT) scenarios. Writing data in this way avoids the resource consumption of SQL syntax parsing, resulting in significant write performance improvements in many cases.

Note:

  • JDBC REST connections do not currently support bind interface
  • The following sample code is based on taos-jdbcdriver-3.2.1 version or above
  • The setString method should be called for binary type data, and the setNString method should be called for nchar type data
  • Do not use db.? in prepareStatement when specify the database with the table name, should directly use ?, then specify the database in setTableName, for example: prepareStatement.setTableName("db.t1").
public class ParameterBindingBasicDemo {

// modify host to your own
private static final String host = "127.0.0.1";
private static final Random random = new Random(System.currentTimeMillis());
private static final int numOfSubTable = 10, numOfRow = 10;

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

String jdbcUrl = "jdbc:TAOS://" + host + ":6030/";
Connection conn = DriverManager.getConnection(jdbcUrl, "root", "taosdata");

init(conn);

String sql = "INSERT INTO ? USING meters TAGS(?,?) VALUES (?,?,?,?)";

try (TSDBPreparedStatement pstmt = conn.prepareStatement(sql).unwrap(TSDBPreparedStatement.class)) {

for (int i = 1; i <= numOfSubTable; i++) {
// set table name
pstmt.setTableName("d_bind_" + i);

// set tags
pstmt.setTagInt(0, i);
pstmt.setTagString(1, "location_" + i);

// set column ts
ArrayList<Long> tsList = new ArrayList<>();
long current = System.currentTimeMillis();
for (int j = 0; j < numOfRow; j++)
tsList.add(current + j);
pstmt.setTimestamp(0, tsList);

// set column current
ArrayList<Float> f1List = new ArrayList<>();
for (int j = 0; j < numOfRow; j++)
f1List.add(random.nextFloat() * 30);
pstmt.setFloat(1, f1List);

// set column voltage
ArrayList<Integer> f2List = new ArrayList<>();
for (int j = 0; j < numOfRow; j++)
f2List.add(random.nextInt(300));
pstmt.setInt(2, f2List);

// set column phase
ArrayList<Float> f3List = new ArrayList<>();
for (int j = 0; j < numOfRow; j++)
f3List.add(random.nextFloat());
pstmt.setFloat(3, f3List);
// add column
pstmt.columnDataAddBatch();
}
// execute column
pstmt.columnDataExecuteBatch();
}

conn.close();
}

private static void init(Connection conn) throws SQLException {
try (Statement stmt = conn.createStatement()) {
stmt.execute("CREATE DATABASE IF NOT EXISTS power");
stmt.execute("USE power");
stmt.execute("CREATE STABLE IF NOT EXISTS meters (ts TIMESTAMP, current FLOAT, voltage INT, phase FLOAT) TAGS (groupId INT, location BINARY(24))");
}
}
}

view source code

This is the Detailed Example

The methods to set VALUES columns:

public void setInt(int columnIndex, ArrayList<Integer> list) throws SQLException
public void setFloat(int columnIndex, ArrayList<Float> list) throws SQLException
public void setTimestamp(int columnIndex, ArrayList<Long> list) throws SQLException
public void setLong(int columnIndex, ArrayList<Long> list) throws SQLException
public void setDouble(int columnIndex, ArrayList<Double> list) throws SQLException
public void setBoolean(int columnIndex, ArrayList<Boolean> list) throws SQLException
public void setByte(int columnIndex, ArrayList<Byte> list) throws SQLException
public void setShort(int columnIndex, ArrayList<Short> list) throws SQLException
public void setString(int columnIndex, ArrayList<String> list, int size) throws SQLException
public void setNString(int columnIndex, ArrayList<String> list, int size) throws SQLException
public void setVarbinary(int columnIndex, ArrayList<byte[]> list, int size) throws SQLException
public void setGeometry(int columnIndex, ArrayList<byte[]> list, int size) throws SQLException

Note: both String and byte[] require the user to declare the width of the corresponding column in the size parameter of the table definition

The methods to set TAGS values:

public void setTagNull(int index, int type)
public void setTagBoolean(int index, boolean value)
public void setTagInt(int index, int value)
public void setTagByte(int index, byte value)
public void setTagShort(int index, short value)
public void setTagLong(int index, long value)
public void setTagTimestamp(int index, long value)
public void setTagFloat(int index, float value)
public void setTagDouble(int index, double value)
public void setTagString(int index, String value)
public void setTagNString(int index, String value)
public void setTagJson(int index, String value)
public void setTagVarbinary(int index, byte[] value)
public void setTagGeometry(int index, byte[] value)

Schemaless Writing

TDengine supports schemaless writing. It is compatible with InfluxDB's Line Protocol, OpenTSDB's telnet line protocol, and OpenTSDB's JSON format protocol. For more information, see Schemaless Writing.

public class SchemalessJniTest {
private static final String host = "127.0.0.1";
private static final String lineDemo = "meters,groupid=2,location=California.SanFrancisco current=10.3000002f64,voltage=219i32,phase=0.31f64 1626006833639000000";
private static final String telnetDemo = "stb0_0 1707095283260 4 host=host0 interface=eth0";
private static final String jsonDemo = "{\"metric\": \"meter_current\",\"timestamp\": 1626846400,\"value\": 10.3, \"tags\": {\"groupid\": 2, \"location\": \"California.SanFrancisco\", \"id\": \"d1001\"}}";

public static void main(String[] args) throws SQLException {
final String url = "jdbc:TAOS://" + host + ":6030/?user=root&password=taosdata";
try (Connection connection = DriverManager.getConnection(url)) {
init(connection);

SchemalessWriter writer = new SchemalessWriter(connection);
writer.write(lineDemo, SchemalessProtocolType.LINE, SchemalessTimestampType.NANO_SECONDS);
writer.write(telnetDemo, SchemalessProtocolType.TELNET, SchemalessTimestampType.MILLI_SECONDS);
writer.write(jsonDemo, SchemalessProtocolType.JSON, SchemalessTimestampType.NOT_CONFIGURED);
}
}

private static void init(Connection connection) throws SQLException {
try (Statement stmt = connection.createStatement()) {
stmt.execute("CREATE DATABASE IF NOT EXISTS power");
stmt.execute("USE power");
}
}
}

view source code

Schemaless with reqId

This reqId can be used to request link tracing.

writer.write(lineDemo, SchemalessProtocolType.LINE, SchemalessTimestampType.NANO_SECONDS, 1L);

Data Subscription

The TDengine Java client library supports subscription functionality with the following application API.

Create a Topic

Connection connection = DriverManager.getConnection(url, properties);
Statement statement = connection.createStatement();
statement.executeUpdate("CREATE TOPIC IF NOT EXISTS topic_meters AS SELECT ts, current, voltage, phase, groupid, location FROM meters");

view source code

The three parameters of the subscribe() method have the following meanings.

  • topic_meters: the subscribed topic (name). This is the unique identifier of the subscription.
  • sql: the query statement of the subscription which can only be a SELECT statement. Only the original data should be queried, and data can only be queried in temporal order..

The preceding example uses the SQL statement SELECT ts, current, voltage, phase, groupid, location FROM meters and creates a subscription named topic_meters.

Create a Consumer

Properties config = new Properties();
config.setProperty("td.connect.type", "jni");
config.setProperty("bootstrap.servers", "localhost:6030");
config.setProperty("auto.offset.reset", "latest");
config.setProperty("msg.with.table.name", "true");
config.setProperty("enable.auto.commit", "true");
config.setProperty("auto.commit.interval.ms", "1000");
config.setProperty("group.id", "group1");
config.setProperty("client.id", "1");
config.setProperty("value.deserializer", "com.taosdata.example.AbsConsumerLoop$ResultDeserializer");
config.setProperty("value.deserializer.encoding", "UTF-8");

this.consumer = new TaosConsumer<>(config);

view source code

  • bootstrap.servers: ip:port where the TDengine server is located, or ip:port where the taosAdapter is located if WebSocket connection is used.
  • enable.auto.commit: Specifies whether to commit automatically.
  • group.id: consumer: Specifies the group that the consumer is in.
  • value.deserializer: To deserialize the results, you can inherit com.taosdata.jdbc.tmq.ReferenceDeserializer and specify the result set bean. You can also inherit com.taosdata.jdbc.tmq.Deserializer and perform custom deserialization based on the SQL result set.
  • td.connect.type: Specifies the type connect with TDengine, jni or WebSocket. default is jni
  • httpConnectTimeout: WebSocket connection timeout in milliseconds, the default value is 5000 ms. It only takes effect when using WebSocket type.
  • messageWaitTimeout: socket timeout in milliseconds, the default value is 10000 ms. It only takes effect when using WebSocket type.
  • httpPoolSize: Maximum number of concurrent requests on the a connection。It only takes effect when using WebSocket type.

For more information, see Consumer Parameters. Note that the default value of auto.offset.reset in data subscription on the TDengine server has changed since version 3.2.0.0.

Subscribe to consume data

while (!shutdown.get()) {
ConsumerRecords<ResultBean> records = consumer.poll(Duration.ofMillis(100));
for (ConsumerRecord<ResultBean> record : records) {
ResultBean bean = record.value();
process(bean);
}
}

view source code

poll obtains one message each time it is run.

Assignment subscription Offset

// get topicPartition
Set<TopicPartition> assignment() throws SQLException;
// get offset
long position(TopicPartition partition) throws SQLException;
Map<TopicPartition, Long> position(String topic) throws SQLException;
Map<TopicPartition, Long> beginningOffsets(String topic) throws SQLException;
Map<TopicPartition, Long> endOffsets(String topic) throws SQLException;
Map<TopicPartition, OffsetAndMetadata> committed(Set<TopicPartition> partitions) throws SQLException;

// Overrides the fetch offsets that the consumer will use on the next poll(timeout).
void seek(TopicPartition partition, long offset) throws SQLException;
void seekToBeginning(Collection<TopicPartition> partitions) throws SQLException;
void seekToEnd(Collection<TopicPartition> partitions) throws SQLException;

Example usage is as follows.

String topic = "topic_meters";
Map<TopicPartition, Long> offset = null;
try (TaosConsumer<AbsConsumerLoop.ResultBean> consumer = new TaosConsumer<>(config)) {
consumer.subscribe(Collections.singletonList(topic));
for (int i = 0; i < 10; i++) {
if (i == 3) {
// Saving consumption position
offset = consumer.position(topic);
}
if (i == 5) {
// reset consumption to the previously saved position
for (Map.Entry<TopicPartition, Long> entry : offset.entrySet()) {
consumer.seek(entry.getKey(), entry.getValue());
}
}
ConsumerRecords<AbsConsumerLoop.ResultBean> records = consumer.poll(Duration.ofMillis(500));
}
}

view source code

Commit offset

If enable.auto.commit is false, offset can be submitted manually.

void commitSync() throws SQLException;
void commitSync(Map<TopicPartition, OffsetAndMetadata> offsets) throws SQLException;
// async commit only support jni connection
void commitAsync(OffsetCommitCallback<V> callback) throws SQLException;
void commitAsync(Map<TopicPartition, OffsetAndMetadata> offsets, OffsetCommitCallback<V> callback) throws SQLException;

Close subscriptions

// Unsubscribe
consumer.unsubscribe();
// Close consumer
consumer.close()

For more information, see Data Subscription.

Full Sample Code

In addition to the native connection, the Java client library also supports subscribing via websocket.

public abstract class AbsConsumerLoopFull {
private final TaosConsumer<ResultBean> consumer;
private final List<String> topics;
private final AtomicBoolean shutdown;
private final CountDownLatch shutdownLatch;

public AbsConsumerLoopFull() throws SQLException {

Properties config = new Properties();
config.setProperty("td.connect.type", "jni");
config.setProperty("bootstrap.servers", "localhost:6030");
config.setProperty("auto.offset.reset", "latest");
config.setProperty("msg.with.table.name", "true");
config.setProperty("enable.auto.commit", "true");
config.setProperty("auto.commit.interval.ms", "1000");
config.setProperty("group.id", "group1");
config.setProperty("client.id", "1");
config.setProperty("value.deserializer", "com.taosdata.example.AbsConsumerLoop$ResultDeserializer");
config.setProperty("value.deserializer.encoding", "UTF-8");

this.consumer = new TaosConsumer<>(config);

this.topics = Collections.singletonList("topic_meters");
this.shutdown = new AtomicBoolean(false);
this.shutdownLatch = new CountDownLatch(1);
}

public abstract void process(ResultBean result);

public void pollData() throws SQLException {
try {
consumer.subscribe(topics);
while (!shutdown.get()) {
ConsumerRecords<ResultBean> records = consumer.poll(Duration.ofMillis(100));
for (ConsumerRecord<ResultBean> record : records) {
ResultBean bean = record.value();
process(bean);
}
}
consumer.unsubscribe();
} finally {
consumer.close();
shutdownLatch.countDown();
}
}

public void shutdown() throws InterruptedException {
shutdown.set(true);
shutdownLatch.await();
}

public static class ResultDeserializer extends ReferenceDeserializer<ResultBean> {

}

public static class ResultBean {
private Timestamp ts;
private double current;
private int voltage;
private double phase;
private int groupid;
private String location;

public Timestamp getTs() {
return ts;
}

public void setTs(Timestamp ts) {
this.ts = ts;
}

public double getCurrent() {
return current;
}

public void setCurrent(double current) {
this.current = current;
}

public int getVoltage() {
return voltage;
}

public void setVoltage(int voltage) {
this.voltage = voltage;
}

public double getPhase() {
return phase;
}

public void setPhase(double phase) {
this.phase = phase;
}

public int getGroupid() {
return groupid;
}

public void setGroupid(int groupid) {
this.groupid = groupid;
}

public String getLocation() {
return location;
}

public void setLocation(String location) {
this.location = location;
}
}
}

view source code

Note: The value of value.deserializer should be adjusted based on the package path of the test environment.

Use with connection pool

HikariCP

Example usage is as follows.

public static void main(String[] args) throws SQLException {
HikariConfig config = new HikariConfig();
// jdbc properties
config.setJdbcUrl("jdbc:TAOS://127.0.0.1:6030/log");
config.setUsername("root");
config.setPassword("taosdata");
// connection pool configurations
config.setMinimumIdle(10); //minimum number of idle connection
config.setMaximumPoolSize(10); //maximum number of connection in the pool
config.setConnectionTimeout(30000); //maximum wait milliseconds for get connection from pool
config.setMaxLifetime(0); // maximum life time for each connection
config.setIdleTimeout(0); // max idle time for recycle idle connection
config.setConnectionTestQuery("SELECT SERVER_STATUS()"); //validation query

HikariDataSource ds = new HikariDataSource(config); //create datasource

Connection connection = ds.getConnection(); // get connection
Statement statement = connection.createStatement(); // get statement

//query or insert
// ...
statement.close();
connection.close(); // put back to connection pool
}

view source code

getConnection(), you need to call the close() method after you finish using it. It doesn't close the connection. It just puts it back into the connection pool. For more questions about using HikariCP, please see the official instructions.

Druid

Example usage is as follows.

public static void main(String[] args) throws Exception {
String url = "jdbc:TAOS://127.0.0.1:6030/log";

DruidDataSource dataSource = new DruidDataSource();
// jdbc properties
dataSource.setDriverClassName("com.taosdata.jdbc.TSDBDriver");
dataSource.setUrl(url);
dataSource.setUsername("root");
dataSource.setPassword("taosdata");
// pool configurations
dataSource.setInitialSize(10);
dataSource.setMinIdle(10);
dataSource.setMaxActive(10);
dataSource.setMaxWait(30000);
dataSource.setValidationQuery("SELECT SERVER_STATUS()");

Connection connection = dataSource.getConnection(); // get connection
Statement statement = connection.createStatement(); // get statement
//query or insert
// ...

statement.close();
connection.close(); // put back to connection pool
}

view source code

For more questions about using druid, please see Official Instructions.

More sample programs

The source code of the sample application is under TDengine/examples/JDBC:

  • JDBCDemo: JDBC sample source code.
  • connectionPools: using taos-jdbcdriver in connection pools such as HikariCP, Druid, dbcp, c3p0, etc.
  • SpringJdbcTemplate: using taos-jdbcdriver in Spring JdbcTemplate.
  • mybatisplus-demo: using taos-jdbcdriver in Springboot + Mybatis.
  • springbootdemo: using taos-jdbcdriver in Springboot.
  • consumer-demo: consumer TDengine data example, the consumption rate can be controlled by parameters.

JDBC example

Frequently Asked Questions

  1. Why is there no performance improvement when using Statement's addBatch() and executeBatch() to perform batch data writing/update?

    Cause: In TDengine's JDBC implementation, SQL statements submitted by addBatch() method are executed sequentially in the order they are added, which does not reduce the number of interactions with the server and does not bring performance improvement.

    Solution: 1. splice multiple values in a single insert statement; 2. use multi-threaded concurrent insertion; 3. use parameter-bound writing

  2. java.lang.UnsatisfiedLinkError: no taos in java.library.path

    Cause: The program did not find the dependent native library taos.

    Solution: On Windows you can copy C:\TDengine\driver\taos.dll to the C:\Windows\System32 directory, on Linux the following soft link will be created ln -s /usr/local/taos/driver/libtaos.so.x.x.x.x /usr/lib/libtaos.so will work, on macOS the lib soft link will be /usr/local/lib/libtaos.dylib.

  3. java.lang.UnsatisfiedLinkError: taos.dll Can't load AMD 64 bit on a IA 32-bit platform

    Cause: Currently, TDengine only supports 64-bit JDK.

    Solution: Reinstall the 64-bit JDK.

  4. java.lang.NoSuchMethodError: setByteArray

    Cause: taos-jbdcdriver 3.* only supports TDengine 3.0 and later.

    Solution: Use taos-jdbcdriver 2.* with your TDengine 2.* deployment.

  5. java.lang.NoSuchMethodError: java.nio.ByteBuffer.position(I)Ljava/nio/ByteBuffer; ... taos-jdbcdriver-3.0.1.jar

Cause: taos-jdbcdriver 3.0.1 is compiled on JDK 11.

Solution: Use taos-jdbcdriver 3.0.2.

For additional troubleshooting, see FAQ.

API Reference

taos-jdbcdriver doc