bug in jdbc

i got the buggy driver from http://jdbc.postgresql.org/download/pgjdbc2.jar
jdbc7.0-1.2 driver working OK

there is exception :

Something unusual has occured to cause the driver to fail. Please report this exception: Exception: java.sql.SQLException: ERROR: No such function 'pg_encoding_to_char' with the specified attributes

Stack Trace:

java.sql.SQLException: ERROR: No such function 'pg_encoding_to_char' with the specified attributes

at org.postgresql.core.QueryExecutor.execute(QueryExecutor.java:94)
at org.postgresql.Connection.ExecSQL(Connection.java:398)
at org.postgresql.Connection.ExecSQL(Connection.java:381)
at org.postgresql.Connection.openConnection(Connection.java:314)
at org.postgresql.Driver.connect(Driver.java:149)
at java.sql.DriverManager.getConnection(DriverManager.java:517)
at java.sql.DriverManager.getConnection(DriverManager.java:177)
at board.userbase(board.java)
at board.doPost(board.java)
at board.doGet(board.java)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:271)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:311)
at org.apache.jserv.JServConnection.processRequest(JServConnection.java:317)
at org.apache.jserv.JServConnection.run(JServConnection.java:188)
at java.lang.Thread.run(Thread.java:484)
End of Stack Trace