我正在尝试将clojure程序连接到postgresql db。我有所需的依赖项。这是我的repository.clj文件
(ns webdev.repository
(:require [clojure.java.jdbc :as db] ))
(defn create-tables [db]
(db/execute! db ["create table if not exists movies(id serial not null,
name varchar not null, primary key (id));"])
(db/execute! db ["create table if not exists users(id varchar not null,
f_name varchar not null, l_name varchar not null, primary key(id));"])
)
这是我的core.clj文件的一部分
(ns webdev.core
(:require [webdev.repository :as repo])
(:require [ring.adapter.jetty :as jetty]
[ring.middleware.reload :refer [wrap-reload]]
[compojure.core :refer [defroutes GET]]
[compojure.route :refer [not-found]]
[ring.handler.dump :refer [handle-dump]]
))
(def db "postgresql://localhost:5432/webdev")
(repo/create-tables db) ;;call to create the tables
...
...
运行此命令时，出现错误提示
Caused by: org.postgresql.util.PSQLException: This ResultSet is closed.
at org.postgresql.jdbc2.AbstractJdbc2ResultSet.checkClosed(AbstractJdbc2ResultSet.java:2654)
at org.postgresql.jdbc2.AbstractJdbc2ResultSet.setFetchSize(AbstractJdbc2ResultSet.java:1771)
at org.postgresql.jdbc4.Jdbc4Statement.createResultSet(Jdbc4Statement.java:39)
at org.postgresql.jdbc2.AbstractJdbc2Statement$StatementResultHandler.handleResultRows(AbstractJdbc2Statement.java:211)
at org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:1773)
at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:257)
at org.postgresql.jdbc2.AbstractJdbc2Statement.execute(AbstractJdbc2Statement.java:512)
无法找出我在做什么。
编辑
选择语句似乎有效。但是插入和创建表语句会给出错误“此结果集已关闭”
答案 0 :(得分：1)
以下是使用H2的示例：https://github.com/cloojure/demo-jdbc
您可以克隆存储库并通过lein test运行。正如cfrick所说，创建数据库的调用不应在编译阶段运行的顶层进行。相反，对create-table的调用应该在从-main调用的函数内部（或在示例中作为单元测试的一部分）。
(ns tst.demo.jdbc
(:use demo.core tupelo.core tupelo.test)
(:require
[clojure.java.jdbc :as jdbc]
[hikari-cp.core :as pool]
))
(def raw-db-spec
{:classname "org.h2.Driver"
:subprotocol "h2:mem" ; the prefix `jdbc:` is added automatically
:subname "demo;DB_CLOSE_DELAY=-1" ; `;DB_CLOSE_DELAY=-1` very important!!!
; http://www.h2database.com/html/features.html#in_memory_databases
; http://makble.com/using-h2-in-memory-database-in-clojure
:user "sa" ; "system admin"
:password "" ; empty string by default
})
(dotest
; creates & drops a connection (& transaction) for each command
(jdbc/db-do-commands raw-db-spec ["drop table if exists langs"
"drop table if exists releases"])
; Creates and uses a connection for all commands
(jdbc/with-db-connection
[conn raw-db-spec]
(jdbc/db-do-commands
conn
[(jdbc/create-table-ddl :langs
[[:id :serial]
[:lang "varchar not null"]])
(jdbc/create-table-ddl :releases
[[:id :serial]
[:desc "varchar not null"]
[:langId "numeric"]])]))
; create & use a connection for multiple commands
(jdbc/with-db-connection
[conn raw-db-spec]
(jdbc/insert-multi! raw-db-spec :langs ; => ({:id 1} {:id 2})
[{:lang "Clojure"}
{:lang "Java"}])
(let [result (jdbc/query raw-db-spec ["select * from langs"])]
(is= result [{:id 1, :lang "Clojure"}
{:id 2, :lang "Java"}])))
; Wraps all commands in a single transaction
(jdbc/with-db-transaction
[tx raw-db-spec]
(let [clj-id (grab :id (only (jdbc/query tx ["select id from langs where lang='Clojure'"])))]
(jdbc/insert-multi! tx :releases
[{:desc "ancients" :langId clj-id}
{:desc "1.8" :langId clj-id}
{:desc "1.9" :langId clj-id}]))
(let [java-id (grab :id (only (jdbc/query tx ["select id from langs where lang='Java'"])))]
(jdbc/insert-multi! tx :releases
[{:desc "dusty" :langId java-id}
{:desc "8" :langId java-id}
{:desc "9" :langId java-id}
{:desc "10" :langId java-id}])))
; Creates and uses a connection for each command
(let [
; note cannot wrap select list in parens or get "bulk" output
result-0 (jdbc/query raw-db-spec ["select langs.lang, releases.desc
from langs join releases
on (langs.id = releases.langId)
where (lang = 'Clojure') "])
result-1 (jdbc/query raw-db-spec ["select l.lang, r.desc
from langs as l
join releases as r
on (l.id = r.langId)
where (l.lang = 'Clojure') "])
result-2 (jdbc/query raw-db-spec ["select langs.lang, releases.desc
from langs, releases
where ( (langs.id = releases.langId)
and (lang = 'Clojure') ) "])
result-3 (jdbc/query raw-db-spec ["select l.lang, r.desc
from langs as l, releases as r
where ( (l.id = r.langId)
and (l.lang = 'Clojure') ) "])
]
(nl)
(spyx-pretty result-0)
;(sets= result-0 result-1 result-2 result-3 ; #todo use this
; [{:lang "Clojure", :desc "1.8"}
; {:lang "Clojure", :desc "1.9"}
; {:lang "Clojure", :desc "ancients"}])
(is (= (set [{:lang "Clojure", :desc "1.8"}
{:lang "Clojure", :desc "1.9"}
{:lang "Clojure", :desc "ancients"}])
(set result-0)
(set result-1)
(set result-2)
(set result-3))) ))
答案 1 :(得分：1)
(ns ^{:doc "Database access functions, mostly from Luminus template."}
your-project.db.core
(:require
[clojure.java.jdbc :as jdbc]
[conman.core :as conman]
[hugsql.core :as hugsql]
[mount.core :refer [defstate]]
[postgre-types.json :refer [add-json-type add-jsonb-type]]))
(defstate ^:dynamic *db*
:start (conman/connect! {:jdbc-url-env (env :database-url)
:jdbc-url "jdbc:postgresql://127.0.0.1/yourdb_dev?user=user&password=thisisnotsecure"
:driver-class-name "org.postgresql.Driver"})
:stop (conman/disconnect! *db*))
(conman/bind-connection *db* "sql/queries.auto.sql" "sql/queries.sql")
但更简单的是，这是您使用Luminus免费获得的。只需启动您的项目
lein new luminus my-project +postgres
它开箱即用。
摘要：除非您正在学习成为轮毂制造商，否则不要重塑车轮。站在巨人的肩膀上。