Build a PostgreSQL Interface for FTP Data using the CData JDBC Driver

There are a vast number of PostgreSQL clients available on the Internet. From standard Drivers to BI and Analytics tools, PostgreSQL is a popular interface for data access. Using our JDBC Drivers, you can now create PostgreSQL entry-points that you can connect to from any standard client.

To access FTP data as a PostgreSQL database, use the CData JDBC Driver for FTP and a JDBC foreign data wrapper (FDW). In this article, we compile the FDW, install it, and query FTP data from PostgreSQL Server.

Connect to FTP Data as a JDBC Data Source

To connect to FTP as a JDBC data source, you will need the following:

• Driver JAR path: The JAR is located in the lib subfolder of the installation directory.

• Driver class:

  cdata.jdbc.ftp.FTPDriver
  

• JDBC URL: The URL must start with "jdbc:ftp:" and can include any of the connection properties in name-value pairs separated with semicolons.

  To connect to FTP or SFTP servers, specify at least RemoteHost and FileProtocol. Specify the port with RemotePort.

  Set User and Password to perform Basic authentication. Set SSHAuthMode to use SSH authentication. See the Getting Started section of the data provider help documentation for more information on authenticating via SSH.

  Set SSLMode and SSLServerCert to secure connections with SSL.

  The data provider lists the tables based on the available folders in your FTP server. Set the following connection properties to control the relational view of the file system:

  • RemotePath: Set this to the current working directory.
  • TableDepth: Set this to control the depth of folders to list as views.
  • FileRetrievalDepth: Set this to retrieve and list files recursively from the root table.

  Stored Procedures are available to download files, upload files, and send protocol commands. See the Data Model chapter of the FTP data provider documentation for more information.

  Built-in Connection String Designer

  For assistance in constructing the JDBC URL, use the connection string designer built into the FTP JDBC Driver. Either double-click the JAR file or execute the jar file from the command-line.

  java -jar cdata.jdbc.ftp.jar
  

  Fill in the connection properties and copy the connection string to the clipboard.

  👁 Using the built-in connection string designer to generate a JDBC URL (Salesforce is shown.)
  

  A typical JDBC URL is below:

  jdbc:ftp:RemoteHost=MyFTPServer;
  

Build the JDBC Foreign Data Wrapper

The Foreign Data Wrapper can be installed as an extension to PostgreSQL, without recompiling PostgreSQL. The jdbc2_fdw extension is used as an example (downloadable here).

1. Add a symlink from the shared object for your version of the JRE to /usr/lib/libjvm.so. For example:

   ln -s /usr/lib/jvm/java-6-openjdk/jre/lib/amd64/server/libjvm.so /usr/lib/libjvm.so
   

2. Start the build:

   make install USE_PGXS=1
   

Query FTP Data as a PostgreSQL Database

After you have installed the extension, follow the steps below to start executing queries to FTP data:

1. Log into your database.
2. Load the extension for the database:

   CREATE EXTENSION jdbc2_fdw;
   

3. Create a server object for FTP:

   CREATE SERVER FTP 
   FOREIGN DATA WRAPPER jdbc2_fdw OPTIONS (
   drivername 'cdata.jdbc.ftp.FTPDriver',
   url 'jdbc:ftp:RemoteHost=MyFTPServer;',
   querytimeout '15',
   jarfile '/home/MyUser/CData/CData\ JDBC\ Driver\ for\ Salesforce MyDriverEdition/lib/cdata.jdbc.ftp.jar'); 
   

4. Create a user mapping for the username and password of a user known to the MySQL daemon.

   CREATE USER MAPPING for postgres SERVER FTP OPTIONS (
   username 'admin', 
   password 'test');
   

5. Create a foreign table in your local database:

   postgres=# CREATE FOREIGN TABLE mydirectory (
   mydirectory_id text,
   mydirectory_Filesize text,
   mydirectory_Filename numeric) 
   SERVER FTP OPTIONS (
   table_name 'mydirectory');
   

You can now execute read/write commands to FTP:

postgres=# SELECT * FROM mydirectory;