Question

I have a simple Clojure program that queries an Oracle database and prints out results in a comma delimited format. This program works just fine running it normally through Clojure.main. I want to compile this program and followed the instructions from here:

http://java.ociweb.com/mark/clojure/article.html#Compiling

I compiled and ran another simple program using this method described just fine. So I don’t think this has anything to do with this method of compiling. This program compiles just fine but when I attempt to run the compiled class it returns this error:

Exception in thread “main”
java.lang.RuntimeException:
java.lang.RuntimeException:
java.sql.SQLException: Exhausted
Resultset
at clojure.lang.LazySeq.sval(LazySeq.java:47)
at clojure.lang.LazySeq.seq(LazySeq.java:56)
at clojure.lang.RT.seq(RT.java:440)
at clojure.core$seq__4245.invoke(core.clj:105)
at bill.myquery$dump_db_csv__24.invoke(myquery.clj:27)
at bill.myquery$main_49.invoke(myquery.clj:41)
at clojure.lang.AFn.applyToHelper(AFn.java:171)
at clojure.lang.AFn.applyTo(AFn.java:164)
at bill.myquery.main(Unknown Source)
Caused by: java.lang.RuntimeException:
java.sql.SQLException: Exhausted
Resultset
at clojure.lang.LazySeq.sval(LazySeq.java:47)
at clojure.lang.LazySeq.seq(LazySeq.java:56)
at clojure.lang.Cons.next(Cons.java:37)
at clojure.lang.RT.boundedLength(RT.java:1128)
at clojure.lang.RestFn.applyTo(RestFn.java:135)
at clojure.core$apply__4370.invoke(core.clj:438)
at clojure.core$resultset_seq_6276$thisfn_6290$fn__6291.invoke(core.clj:3842)
at clojure.lang.LazySeq.sval(LazySeq.java:42)
… 8 more Caused by: java.sql.SQLException: Exhausted
Resultset
at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:112)
at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:146)
at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:208)
at oracle.jdbc.driver.OracleResultSetImpl.getObject(OracleResultSetImpl.java:900)
at clojure.core$resultset_seq__6276$row_values_6284$fn_6286.invoke(core.clj:3839)
at clojure.core$map_5053$fn_5055.invoke(core.clj:1760)
at clojure.lang.LazySeq.sval(LazySeq.java:42)

Here it is:

(ns bill.myquery (:gen-class))

;; Import java.sql classes
(import '(java.sql DriverManager Connection PreparedStatement ResultSet))

;; load jdbc/odbc driver
(. Class forName "oracle.jdbc.driver.OracleDriver")

(def dbname "myOracleServer:1522:myOracleDatabase")
(def service_account "account")
(def service_password "password")

(def conn (. DriverManager (getConnection (str "jdbc:oracle:thin:@" dbname) service_account service_password)))

(def sql "
        SELECT name, address, phone
        FROM addresss_book
        ORDER BY name")

;; Function to dump data with comma delimited fields
(defn dump-db-csv [db]
  (doseq [rec db] ;; for all rows
    (doseq [[key value] rec] ;; for all fields
        (if (= key :phone) ;; if last field
              (print (.trim (str value))) ;; don't print comma
              (print (format "%s%s" (.trim (str value)) ","))))
    (println)))

;; Execute query and get recordset
(def rs (.. conn (prepareStatement sql) (executeQuery)))

;; convert recordset to sequence
(def rset (resultset-seq rs))

;; Main call the function to print rows
(defn -main (dump-db-csv rset))

;; close the recordset
(. rs (close))

Answer 1

Don’t use def – everything from the top level is executed at class load time (or even at compile time), so you close result set (rs) before running -main. Always open and close connection in a single function – it will prevent a lot of errors.

Also consider using clojure.contrib.sql. Nice examples can be found at wikibooks.

For both methods don’t forget to use doall for any possible lazy sequences.