如何在Clojure中访问SQLite数据库？

Question

(ns db-example
   (:use [clojure.contrib.sql :only (with-connection with-query-results)] )
   (:import (java.sql DriverManager)))

;; need this to load the sqlite3 driver (as a side effect of evaluating the expression)
(Class/forName "org.sqlite.JDBC")

(def +db-path+  "...")
(def +db-specs+ {:classname  "org.sqlite.JDBC",
                 :subprotocol   "sqlite",
                 :subname       +db-path+})

(def +transactions-query+ "select * from my_table")

(with-connection +db-specs+
  (with-query-results results [+transactions-query+]
    ;; results is an array of column_name -> value maps
    ))

- Bill

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这段代码有问题吗？ - Robert Harvey

Answer 1

你必须从 with-query-results 宏中实际返回一些内容。而且因为绑定到 results 的序列是惰性的，让我们消耗它：

(with-connection +db-specs+  
   (with-query-results results [+transactions-query+]  
     (doall results)))  

这是在使用clojure.contrib.sql时常见的模式，与SQLite JDBC适配器无关。

顺便说一下，我从来没有手动执行(Class/forName driver-class-str)，这显然是你的Java习惯。驱动程序在contrib.sql的内部某个地方被加载。

- Wojciech Kaczmarek