java - 解析 csv，不要在单引号或双引号内分割

Question

我尝试用 java 解析 csv 并遇到以下问题:第二列是用双引号括起来的字符串(也可能包含逗号)，除非字符串本身包含双引号，否则整个字符串用单引号括起来。例如

行可能像这样:

someStuff,"hello", someStuff
someStuff,"hello, SO", someStuff
someStuff,'say "hello, world"', someStuff
someStuff,'say "hello, world', someStuff

someStuff 是其他元素的占位符，也可以包含相同样式的引号

我正在寻找一种以逗号分隔行的通用方法，除非用单引号或双引号括起来，以便将第二列作为字符串。第二列是指字段:

• 你好
• 你好，SO
• 说“你好，世界”
• 说“你好，世界

我尝试了 OpenCSV 但失败了，因为只能指定一种类型的引号:

public class CSVDemo {

public static void main(String[] args) throws IOException {
    CSVDemo demo = new CSVDemo();
    demo.process("input.csv");
}

public void process(String fileName) throws IOException {
    String file = this.getClass().getClassLoader().getResource(fileName)
            .getFile();
    CSVReader reader = new CSVReader(new FileReader(file));
    String[] nextLine;
    while ((nextLine = reader.readNext()) != null) {
        System.out.println(nextLine[0] + " | " + nextLine[1] + " | "
                + nextLine[2]);
    }
}

opencsv 的解决方案在最后一行失败，其中只有一个双引号括在单引号中:

someStuff | hello |  someStuff
someStuff | hello, SO |  someStuff
someStuff | 'say "hello, world"' |  someStuff
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 1

Answer 1

如果您确实无法使用真正的 CSV 解析器，则可以使用正则表达式。这通常不是一个好主意，因为总是存在您无法处理的边缘情况，但如果格式严格按照您的描述进行，那么这可能会奏效。

public void test() {
    String[] tests = {"numeStuff,\"hello\", someStuff, someStuff",
        "numeStuff,\"hello, SO\", someStuff, someStuff",
        "numeStuff,'say \"hello, world\"', someStuff, someStuff"
    };
    /* Matches a field and a potentially empty separator.
     *
     *  ( - Field Group
     *     \"  - Start with a quote
     *     [^\"]*? - Non-greedy match on anything that is not a quote
     *     \" - End with a quote
     *   | - Or
     *     '  - Start with a strop
     *     [^']*? - Non-greedy match on anything that is not a strop
     *     ' - End with a strop
     *   | - Or
     *    [^\"'] - Not starting with a quote or strop
     *    [^,$]*? - Non-greedy match on anything that is not a comma or end-of-line
     *  ) - End field group
     *  ( - Separator group
     *   [,$] - Comma separator or end of line
     *  ) - End separator group
     */
    Pattern p = Pattern.compile("(\"[^\"]*?\"|'[^\']*?\'|[^\"'][^,\r\n]*?)([,\r\n]|$)");
    for (String t : tests) {
        System.out.println("Matching: " + t);
        Matcher m = p.matcher(t);
        while (m.find()) {
            System.out.println(m.group(1));
        }
    }
}