替换字符串中 ${} 标识的变量

替换字符串中 ${} 标识的变量；记录一下以备不时之需

import org.junit.Test;

import java.util.HashMap;
import java.util.Map;
import java.util.regex.Matcher;
import java.util.regex.Pattern;


public class MyJavaTest {


    @Test
    public void compare() {
        Map properties = new HashMap<>();
        properties.put("name", "法外狂徒张三");
        String template = "${relevant.$.departments}:网络不是法外之地，${name}一定会被严惩";
        System.out.println(replaceVariable(template, properties)); // :网络不是法外之地，法外狂徒张三一定会被严惩
    }

    
    public static String replaceVariable(String template, Map properties) {
        StringBuffer sb = new StringBuffer();
        // 该表达式匹配${中的数字字母下划线，英文点和$
        Matcher matcher = Pattern.compile("\$\{[\.\$\w]+}").matcher(template);
        while (matcher.find()) {
            String param = matcher.group();
            String varible = param.substring(2, param.length() - 1);
            // 追加并替换变量
            Object value = properties.get(varible);
            matcher.appendReplacement(sb, value == null ? "" : String.valueOf(value));
        }
        // 复制输入序列的其余部分
        matcher.appendTail(sb);
        return sb.toString();
    }
}