枚举Java中正则表达式的可能匹配项 [英] Enumerate Possible Matches of Regular Expression in Java

问题描述

出于测试目的，我想枚举Java中有限正则表达式的所有可能值。

对于某些情况，我有一个正则表达式用于匹配文字中允许的颜色值。下面是它的简化版本：

 （white | black）|（（light | dark））？（red | | green | blue | gray）
  

我想创建一个可以枚举所有这些值的单元测试，将它们中的每一个传递给我的实用程序类，这些实用程序类会从中生成 Color 对象，这样，如果我更改正则表达式，则在发生错误时我的单元测试将失败（即不支持新的颜色值。）

我当然知道枚举是可能的（），但是是否存在Java的现有库，该库将枚举正则表达式的所有可能匹配项？

编辑：：我已经实现了一个库。

解决方案

您是对的，没有在网上找到这样的工具
但是您可以尝试 Xeger 来自Google

<它可以从一个正则表达式中创建一个随机匹配的字符串，并且通过一些代码调整可能会达到您想要的效果。
生成一个随机匹配项：

 字符串regex = [ab] {4,6} c; 
 Xeger generator = new Xeger（regex）; 
字符串结果= generator.generate（）; 
 assert result.matches（regex）; 
  

Xeger代码非常简单，它由2个文件组成，它们之间包含5种方法。 />
使用dk.brics.automaton将正则表达式转换为自动机，然后遍历自动机转换，在每个节点中进行随机选择。

the主要功能是生成：

  private void generate（StringBuilder builder，State state）{
 List< Transition> transitions = state.getSortedTransitions（true）; 
 if（transitions.size（）== 0）{
 assert state.isAccept（）; 
的回报； 
} 
 int nroptions = state.isAccept（）吗？ transitions.size（）：transitions.size（）-1; 
 int选项= XegerUtils.getRandomInt（0，nroptions，随机）; 
 if（state.isAccept（）&& option == 0）{// 0被视为止损
 return; 
} 
 //继续进行下一个转换
转换transition = transitions.get（option-（state.isAccept（）？1：0））; 
 appendChoice（builder，transition）; 
 generate（builder，transition.getDest（））; 
} 
  

您可以看到要进行更改，以便获得所有可能的匹配项，您需要遍历每个可能节点中的所有可能组合（例如增加一个多位数字计数器）
，您将需要一个散列来防止循环，但是编码的时间不应超过5秒。

我也建议您先检查正则表达式是否确实是正则表达式，方法是检查它是否没有*，+和其他使该动作不可能的符号（只是为了使它成为完整的可重用工具）...

I want to enumerate all the possible values of a finite regular expression in Java for testing purposes.

For some context, I have a regular expression that I'm using to match allowable color values in words. Here's a shortened version of it as an example:

(white|black)|((light|dark) )?(red|green|blue|gray)

I wanted to create a unit test that would enumerate all these values and pass each of them to my utility class which produces a Color object from these, that way if I change the regular expression, my unit tests will fail if an error occurs (i.e. the new color value is unsupported).

I know enumeration is possible, of course (see this question), but is there an existing library for Java which will enumerate all the possible matches for a regex?

Edit: I've implemented a library that does this. See my answer below for links.

解决方案

You are right, didn't find such a tool online as well but you can try Xeger from google

it can create a random matching string from a regexp, and with some code tweaking might do what you want. generation a random match:

String regex = "[ab]{4,6}c";
Xeger generator = new Xeger(regex);
String result = generator.generate();
assert result.matches(regex);

Xeger code is very simple, it consists of 2 files which contain 5 methods between them..
it uses dk.brics.automaton to conver the regex to an automaton, then goes over the automaton transitions making random choices in every node.

the main function is generate:

   private void generate(StringBuilder builder, State state) {
    List<Transition> transitions = state.getSortedTransitions(true);
    if (transitions.size() == 0) {
        assert state.isAccept();
        return;
    }
    int nroptions = state.isAccept() ? transitions.size() : transitions.size() - 1;
    int option = XegerUtils.getRandomInt(0, nroptions, random);
    if (state.isAccept() && option == 0) {          // 0 is considered stop
        return;
    }
    // Moving on to next transition
    Transition transition = transitions.get(option - (state.isAccept() ? 1 : 0));
    appendChoice(builder, transition);
    generate(builder, transition.getDest());
}

you can see that in order to change it so you get all possible matches, you need to iterate over all possible combinations in every possible node (like incrementing a multi digit counter) you will need a hash to prevent loops, but that shouldn't take more than 5 senconds to code..

i would also suggest first checking that the regex is actually finate, by checking that it doesn't have *,+ and other symbols that make this action impossible (just to make this a complete tool for reuse)...

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