使用场景

对于一些框架研发的时候，一些json配置文件我们可以使用占位符语法，然后可通过-Dkey=value传递到系统参数中，最后正则替换掉

代码

		<dependency><groupId>com.alibaba.fastjson2</groupId><artifactId>fastjson2</artifactId><version>2.0.23</version></dependency><dependency><!--一些方便的工具类--><groupId>org.apache.commons</groupId><artifactId>commons-lang3</artifactId><version>3.3.2</version></dependency>

package com.test;import org.apache.commons.io.IOUtils;
import org.apache.commons.lang3.StringUtils;import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;
import java.util.HashMap;
import java.util.Map;
import java.util.regex.Matcher;
import java.util.regex.Pattern;public class Test {private static final String username = "张三";private static final String passwrod = "game123(*&";private static final Pattern VARIABLE_PATTERN = Pattern.compile("(\\$)\\{?(\\w+)\\}?");public static void main(String[] args) throws IOException {System.setProperty("username", username);System.setProperty("password", passwrod);String jsonString = IOUtils.toString(new FileInputStream("C:\\Users\\penggan\\Desktop\\novel\\Flink15\\src\\main\\resources\\core.json"), StandardCharsets.UTF_8);String formatString = replaceVariable(jsonString);System.out.println(formatString);}public static String replaceVariable(final String param) {// 获取系统属性值-Dkey=value以填充${key}Map<String, String> mapping = new HashMap<String, String>();Matcher matcher = VARIABLE_PATTERN.matcher(param);while (matcher.find()) {String variable = matcher.group(2);String value = System.getProperty(variable);if (StringUtils.isBlank(value)) {value = matcher.group();}mapping.put(matcher.group(), value);}String retString = param;for (final String key : mapping.keySet()) {retString = retString.replace(key, mapping.get(key));}return retString;}
}