Clojure JDBC: 找不到Postgres驱动程序

Question

我正在开发一个需要与数据库通信的Web服务，因此我正在装备我的基本库以便在我的桌面上访问PostgreSQL。

Jun 5, 2013 1:27:46 PM com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask run
WARNING: com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@15c313da -- Acquisition     
Attempt Failed!!! Clearing pending acquires. 
While trying to acquire a needed new resource, we failed to succeed more than the maximum number of allowed acquisition attempts (30). 
Last acquisition attempt exception:
java.sql.SQLException: No suitable driver
at java.sql.DriverManager.getDriver(DriverManager.java:264)

在我的数据库库中，我有以下内容。

(ns myapp.db
     (:import [com.mchange.v2.c3p0 ComboPooledDataSource]))

(def specification {
    :classname "postgresql"
    :subprotocol "org.postgresql.Driver"
    :subname "//localhost:5432;database=test"
})

(defn pooled-data-source [specification]
    (let [datasource (ComboPooledDataSource.)]
        (.setDriverClass datasource (:classname specification))
        (.setJdbcUrl datasource (str "jdbc:" (:subprotocol specification) ":" (:subname specification)))
        (.setUser datasource (:user specification))
        (.setPassword datasource (:password specification))
        (.setMaxIdleTimeExcessConnections datasource (* 30 60))
        (.setMaxIdleTime datasource (* 3 60 60))
        {:datasource datasource}))

(def connection-pool
    (delay
        (pooled-data-source specification)))

(defn connection [] @connection-pool)

然后在我的单元测试中：

(ns myapp.db-test
    (:use clojure.test)
    (:require [myapp.db]
              [clojure.java.jdbc :as jdbc]))

(let [db (myapp.db/connection)]
    (jdbc/with-connection db)
        (jdbc/with-query-results rs ["select * from foo"]
            (doseq [row rs]
                (println row)))))

然而，在REPL中这确实有效，所以我知道数据库正在运行并接受连接。

user=> (require '[clojure.java.jdbc :as sql])
user=> (sql/with-connection "postgresql://localhost:5432/test"  
            (sql/with-query-results results ["select * from foo"] 
                (doseq [result results] (println result))))
{:y 2, :x 1}
nil
user=>

非常感谢您的帮助！

我的project.clj文件如下：

(defproject myapp "0.1.0"
    :description "myapp"
    :dependencies [
        [org.clojure/clojure "1.5.1"]
        [org.clojure/java.jdbc "0.3.0-alpha4"]
        [postgresql "9.1-901.jdbc4"]
        [c3p0/c3p0 "0.9.1.2"]])

- David Williams

Answer 1

我建议您修正您的规格。

(def specification {
    :subprotocol "postgresql"
    :classname "org.postgresql.Driver"
    :subname "//localhost:5432/test"})

- daniel

Answer 2

可能还有其他问题（我非常是Clojure的新手），但您的规范中“:classname”和“:subprotocol”肯定是颠倒了。 “:classname”应该是“org.postgresql.Driver”。“:subprotocol”应该是“postgresql”。

- Steve Waldman