java使用正则提取数据

一、正则提取文本指定数据

需要对一个json结构做数据的提取,提取label和value的值，组成新的结构，西瓜:0、苹果:1、草莓:2
原始json字符串如下格式

[
  {
    "label": "西瓜",
    "value": 0
  },
  {
    "label": "苹果",
    "value": 1
  },
  {
    "label": "草莓",
    "value": 2
  },
  {
    "label": "柚子",
    "value": 3
  },
  {
    "label": "葡萄",
    "value": 4
  }
]

正则表达式

"label":\s"(.*)",\s+"value":\s(\d+)

结合正则的分组模式$1、$2可以提取，但是在实际java开发中，字符串格式发生了变化，字符串多了空格和换行等，因此需要再完善正则表达式。

该json字符串出现的变种如下:

变种1

[{"label":"西瓜","value":0},{"label":"苹果","value":1},{"label":"草莓","value":2},{"label":"柚子","value":3},{"label":"葡萄","value":4}]

变种2

[  {    "label": "西瓜",    "value": 0  },  {    "label": "苹果",    "value": 1  },  {    "label": "草莓",    "value": 2  },  {    "label": "柚子",    "value": 3  },  {    "label": "葡萄",    "value": 4  }]

新的正则写法

"label":"(.{1,2})","value":(\d{1,2})

只能匹配变种1，原始json字符串和变种2不适应，
最终调试改为如下正则写法，三种情况的json字符串都可以匹配。

"label":\s?"(.{1,2})",\s*"value":\s?(\d{1,2})

二、正则表达式详解

三、java正则表达式提取结果

import lombok.extern.slf4j.Slf4j;
import org.junit.Test;
 
import java.util.regex.Matcher;
import java.util.regex.Pattern;
 
 
@Slf4j
public class RegularExpressionTest {
 
    /**
     * 提取label和value的值
     * 
     * [
     * {
     * "label": "西瓜",
     * "value": 0
     * },
     * {
     * "label": "苹果",
     * "value": 1
     * },
     * {
     * "label": "草莓",
     * "value": 2
     * },
     * {
     * "label": "柚子",
     * "value": 3
     * },
     * {
     * "label": "葡萄",
     * "value": 4
     * }
     * ]
     * 
     * 因为json字符串在不同的工具复制来复制去，出现不同的格式，例如空格和换行，这里列举在实际处理中遇到的2终变种格式
     * 
     * [{"label":"西瓜","value":0},{"label":"苹果","value":1},{"label":"草莓","value":2},{"label":"柚子","value":3},{"label":"葡萄","value":4}]
     * 
     * [  {    "label": "西瓜",    "value": 0  },  {    "label": "苹果",    "value": 1  },  {    "label": "草莓",    "value": 2  },  {    "label": "柚子",    "value": 3  },  {    "label": "葡萄",    "value": 4  }]
     *
     * @param
     * @return void
     * @author fangyunhe
     * @time 2023/9/20 10:40
     **/
    @Test
    public void test() {
        String jsonStr = "[\n" +
                "  {\n" +
                "    \"label\": \"西瓜\",\n" +
                "    \"value\": 0\n" +
                "  },\n" +
                "  {\n" +
                "    \"label\": \"苹果\",\n" +
                "    \"value\": 1\n" +
                "  },\n" +
                "  {\n" +
                "    \"label\": \"草莓\",\n" +
                "    \"value\": 2\n" +
                "  },\n" +
                "  {\n" +
                "    \"label\": \"柚子\",\n" +
                "    \"value\": 3\n" +
                "  },\n" +
                "  {\n" +
                "    \"label\": \"葡萄\",\n" +
                "    \"value\": 4\n" +
                "  }\n" +
                "]";
        //String jsonStr = "[{\"label\":\"西瓜\",\"value\":0},{\"label\":\"苹果\",\"value\":1},{\"label\":\"草莓\",\"value\":2},{\"label\":\"柚子\",\"value\":3},{\"label\":\"葡萄\",\"value\":4}]";
        //String jsonStr = "[  {    \"label\": \"西瓜\",    \"value\": 0  },  {    \"label\": \"苹果\",    \"value\": 1  },  {    \"label\": \"草莓\",    \"value\": 2  },  {    \"label\": \"柚子\",    \"value\": 3  },  {    \"label\": \"葡萄\",    \"value\": 4  }]";
        String patternStr = "\"label\":\\s?\"(.{1,2})\",\\s*\"value\":\\s?(\\d{1,2})";
        Pattern pattern = Pattern.compile(patternStr);
        Matcher matcher = pattern.matcher(jsonStr);
        while (matcher.find()) {
            log.info(matcher.group(1) + ":" + matcher.group(2));
        }      
    }
}

执行结果

17:08:50.684 [main] INFO  demo.test.RegularExpressionTest - 西瓜:0
17:08:50.890 [main] INFO  demo.test.RegularExpressionTest - 苹果:1
17:08:51.453 [main] INFO  demo.test.RegularExpressionTest - 草莓:2
17:08:51.838 [main] INFO  demo.test.RegularExpressionTest - 柚子:3
17:08:52.406 [main] INFO  demo.test.RegularExpressionTest - 葡萄:4