将 Clojure 数据结构转换为 Java 集合 [英] Converting Clojure data structures to Java collections

问题描述

什么是Clojure惯用的将数据结构转换为Java集合的方式，具体来说:

What is the Clojure-idiomatic way to convert a data structure to a Java collection, specifically:

• [] 到 java.util.ArrayList
• {} 到 java.util.HashMap
• #{} 到 java.util.HashSet
• () 到 java.util.LinkedList

• [] to a java.util.ArrayList
• {} to a java.util.HashMap
• #{} to a java.util.HashSet
• () to a java.util.LinkedList

是否有 clojure.contrib 库可以做到这一点?

Is there a clojure.contrib library to do this?

用例:为了让 Clojure 轻松融入我的组织，我正在考虑为 Clojure 中的全 Java REST 服务器编写单元测试套件.我已经用 Scala 编写了部分套件，但认为 Clojure 可能会更好，因为宏支持会减少大量样板代码(我需要测试几十个类似的 REST 服务调用).

USE CASE: In order to ease Clojure into my organization, I am considering writing a unit-test suite for an all-Java REST server in Clojure. I have written part of the suite in Scala, but think that Clojure may be better because the macro support will reduce a lot of the boilerplate code (I need to test dozens of similar REST service calls).

我正在使用 EasyMock 来模拟数据库连接(有没有更好的方法?)并且我的模拟方法需要返回 java.util.List<java.util.Map<String, Object>> 项目(代表数据库行集)给调用者.我会传入一个 [{ "first_name" "Joe" "last_name" "Smith" "date_of_birth" (date "1960-06-13") ... } ...] 结构到我的模拟并将其转换为所需的 Java 集合，以便它可以以预期的格式返回给调用者.

I am using EasyMock to mock the database connections (is there a better way?) and my mocked methods need to return java.util.List<java.util.Map<String, Object>> items (representing database row sets) to callers. I would pass in a [{ "first_name" "Joe" "last_name" "Smith" "date_of_birth" (date "1960-06-13") ... } ...] structure to my mock and convert it to the required Java collection so that it can be returned to the caller in the expected format.

推荐答案

Clojure 向量、集合和列表类实现了java.util.Collection 接口和ArrayList，HashSet 和 LinkedList 可以接受一个 java.util.Collection 构造函数参数.所以你可以简单地做:

Clojure vector, set and list classes implement the java.util.Collection interface and ArrayList, HashSet and LinkedList can take a java.util.Collection constructor argument. So you can simply do:

user=> (java.util.ArrayList. [1 2 3])
#<ArrayList [1, 2, 3]>
user=> (.get (java.util.ArrayList. [1 2 3]) 0)
1

类似地，Clojure 映射类实现了 java.util.Map 接口，HashMap 接受一个 java.util.Map 构造函数参数.所以:

Similarly, Clojure map class implements java.util.Map interface and HashMap takes a java.util.Map constructor argument. So:

user=> (java.util.HashMap. {"a" 1 "b" 2})
#<HashMap {b=2, a=1}>
user=> (.get (java.util.HashMap. {"a" 1 "b" 2}) "a")
1

你也可以做相反的事情，这样更容易:

You can also do the reverse and it is much easier:

ser=> (into [] (java.util.ArrayList. [1 2 3]))
[1 2 3]
user=> (into #{} (java.util.HashSet. #{1 2 3}))
#{1 2 3}
user=> (into '() (java.util.LinkedList. '(1 2 3)))
(3 2 1)
user=> (into {} (java.util.HashMap. {:a 1 :b 2}))
{:b 2, :a 1}

这篇关于将 Clojure 数据结构转换为 Java 集合的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！