Clojure Program Doesn't Work After Compiling
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:15开发者_运维技巧22: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))
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.
I took Andrei's advice and used clojure.contrib.sql. It does make this even more simple and less error prone. I still didn't want to give up def for the db and sql global variables.
Thanks Andrei
(ns my.query (:use [clojure.contrib.sql]))
(def *db* {:classname "oracle.jdbc.driver.OracleDriver" ; must be in classpath
:subprotocol "oracle:thin"
:subname "myserver:1521:mydatabase"
; Any additional keys are passed to the driver
; as driver-specific properties.
:user "account"
:password "password" })
(def *sql* "select * from phonebook")
(defn dump-db-csv []
(with-connection *db*
(transaction
(with-query-results rs [*sql*]
(doseq [row rs] ;; for all rows
(doseq [[key value] row] ;; for all fields
(if (= key :phone) ;; if last field
(print (.trim (str value))) ;; do not print comma
(print (format "%s%s" (.trim (str value)) ","))))
(println))))))
;; Main - call the function to print rows
(dump-db-csv)
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