java 正则匹配json中占位符

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;
    }
}