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

问题描述

将数据结构转换为Java集合的Clojure-Idiomatic方法是什么？具体来说：

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

• [] 到 java.util.ArrayList


• {} code>到 java.util.HashMap


• ＃{} 到 java.util.HashSet


• （） 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库这个？

Is there a clojure.contrib library to do this?

USE CASE ：为了方便Clojure加入我的组织，我考虑编写一个单元测试套件Clojure中的REST服务器。我已经在Scala中编写了套件的一部分，但认为Clojure可能更好，因为宏支持会减少很多样板代码（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).

我使用EasyMock模拟数据库连接（有更好的方法吗？），我的mocked方法需要返回 java.util.List< java.util.Map& ，Object>> 项（表示数据库行集）。我会传入 [{first_nameJoelast_nameSmithdate_of_birth（date1960-06-13）...} ...] 结构到我的mock，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 java.util.Collection 接口和 ArrayList ， HashSet 和 LinkedList 可以使用 java.util.Collection 构造函数参数。所以你可以简单做：

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

同样，Clojure map类实现 java.util.Map interface和 HashMap 接受 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

您也可以执行相反的操作，它更容易：

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}

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