8.14. JDBC Converter

The JDBC converter allows you to create SimpleFeatures directly from a SQL select statement against an existing database, using standard JDBC libraries. To use the JDBC converter, specify type = "jdbc" in your converter definition.

Warning

The JDBC converter does not sanitize queries. Be careful with inputs, as a malicious actor could potentially execute SQL injection attacks.

8.14.1. Configuration

The JDBC connection string used to connect to the database must be specified using the connection element, for example jdbc:mysql://localhost/test?user=foo&password=bar.

The JDBC converter relies on standard JDBC libraries, and requires the correct JDBC driver for the database being used. Ensure the correct driver is on the classpath; for GeoMesa binary distributions, it can be placed in the lib folder.

The JDBC converter takes SQL select statements as input. Because a select statement can return arbitrary columns, it is import to ensure that the fields returned match the converter definition.

8.14.2. Transform Functions

The transform element supports referencing the columns of the SQL result set through $ notation. Fields are identified by index as in a standard ResultSet (i.e. the first field is index 1, the second 2, etc). The 0 index is a concatenated string of all other fields - this matches the behavior of file-based converters, and can be useful for, e.g. generating a unique ID. Field values will have the native type binding of the database column. For example, VARCHAR will be converted to String, TIMESTAMP will become a java.sql.Date, etc.

The JDBC converter also supports the standard transform functions; see Transformation Function Overview for more details.

8.14.3. Command Line Ingestion

Standard command line ingest expects a data file to operate on. You may place select statements in a file (one per line), or you may use stdin to pipe the select statement to the ingest command:

$ echo "select * from example limit 5" | geomesa ingest ... -c example_jdbc -C example-jdbc -s example-jdbc
INFO  Creating schema example-jdbc
INFO  Running ingestion in local mode
INFO  Ingesting from stdin with 1 thread
[============================================================] 100% complete 5 ingested 0 failed in 00:00:01
INFO  Local ingestion complete in 00:00:01
INFO  Ingested 5 features with no failures.

8.14.4. Example Usage

Assume the following table in MySQL:

mysql> describe example;
+-------+-------------+------+-----+-------------------+-----------------------------+
| Field | Type        | Null | Key | Default           | Extra                       |
+-------+-------------+------+-----+-------------------+-----------------------------+
| id    | bigint(20)  | NO   | PRI | NULL              |                             |
| name  | varchar(20) | YES  |     | NULL              |                             |
| dtg   | timestamp   | NO   |     | CURRENT_TIMESTAMP | on update CURRENT_TIMESTAMP |
| lat   | double      | YES  |     | NULL              |                             |
| lon   | double      | YES  |     | NULL              |                             |
+-------+-------------+------+-----+-------------------+-----------------------------+
5 rows in set (0.00 sec)

The target simple feature type is defined as:

"example-jdbc" = {
  attributes = [
    { name = "name", type = "String" }
    { name = "dtg",  type = "Date" }
    { name = "geom", type = "Point", srid = 4326, default = true }
  ]
}

The converter is defined as:

"example-jdbc" = {
  type       = "jdbc"
  connection = "jdbc:mysql://localhost/test?user=foo&password=bar"
  id-field   = "toString($1)",
  fields = [
    { name = "name",     transform = "$2"                }
    { name = "dtg",      transform = "$3"                }
    { name = "lon",      transform = "$4"                }
    { name = "lat",      transform = "$5"                }
    { name = "geom",     transform = "point($lon, $lat)" }
  ]
}

And the input to the converter would be:

"select * from example"

The required driver JAR would be:

mysql-connector-java-5.1.44.jar