如何从 Clojure 连接到 MySQL 数据库?

2022-01-02 00:00:00 clojure mysql

假设:您的机器上已经运行了 Clojure 和 MySQL.
你如何让他们说话?

Assumption: you already have both Clojure and MySQL running on your machine.
How do you make them talk?

推荐答案

假设:您的机器上已经同时运行了 Clojure 和 MySQL.

Assumption: you already have both Clojure and MySQL running on your machine.

  1. 签出并构建clojure-contrib:

git clone git://github.com/richhickey/clojure-contrib.git
cd clojure-contrib
build

将生成的 clojure-contrib.jar 放在您的 CLASSPATH 中.

Put the resulting clojure-contrib.jar on your CLASSPATH.

下载MySQL 连接器/J 并将 mysql-connector-java-5.1.7-bin.jar 放在您的 CLASSPATH

Download MySQL Connector/J and put the mysql-connector-java-5.1.7-bin.jar on your CLASSPATH

您可能必须使用以下参数运行 JVM:

-Djdbc.drivers=com.mysql.jdbc.Driver

  • 确定您的 MySQL 数据库的连接 URL

  • Determine the connection URL of your MySQL database

    例如，如果您在 MAMP 下运行 MySQL，那么您将在 JDBC 中使用的 URL 将如下所示类似:

    For example, if you are running MySQL under MAMP then the URL that you would use in JDBC will look something like:

    conn = DriverManager.getConnection
        ("jdbc:mysql://localhost:8889/db_name?user=root&password=root")

    网址分为以下几个部分:

    The url is broken down into these components:

    • 协议:jdbc:
    • 子协议:mysql
    • db-host: localhost
    • 数据库端口:8889
    • 用户名
    • 密码

    制作这个clojure脚本，修改数据库连接参数以匹配你的URL，保存为test.clj，编译运行.

    Make this clojure script, modify the database connection parameters to match your URL, save as test.clj, compile and run.

        (use 'clojure.contrib.sql)               ;;' satisfy prettify

      (let [db-host "localhost"
            db-port 8889
            db-name "db_name"]
        (def db {:classname "com.mysql.jdbc.Driver"
               :subprotocol "mysql"
               :subname (str "//" db-host ":" db-port "/" db-name)
               :user "root"
               :password "root"})
        (with-connection db
          (with-query-results rs ["select * from languages"]
            (dorun (map #(println (:language :iso_code %)) rs)))))

            ; rs will be a sequence of maps,
            ; one for each record in the result set.

    NB 此代码改编自 Mark Volkmann 编写的类似代码 从 Clojure 访问 Postgres 数据库

    NB This code was adapted from similar code written by Mark Volkmann to access a Postgres database from Clojure

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