有时候。非常多文本存入数据库或者文件里，某些变量或者模板中会存在占位符的情况，然而每次读取，一个个去字符串.replace去替换就非常麻烦，于是写个占位符替换工具类

详细代码：

import java.util.HashMap;
import java.util.Map;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * 配置文件或模板中的占位符替换工具类
 * Date: 15-5-8
 * Time: 下午4:12
 */
public class PlaceholderUtils {

	private static final Logger logger = LoggerFactory.getLogger(PlaceholderUtils.class);

	/**
	 * Prefix for system property placeholders: "${"
	 */
	public static final String PLACEHOLDER_PREFIX = "${";
	/**
	 * Suffix for system property placeholders: "}"
	 */
	public static final String PLACEHOLDER_SUFFIX = "}";

	public static String resolvePlaceholders(String text, Map<String, String> parameter) {
		if (parameter == null || parameter.isEmpty()) {
			return text;
		}
		StringBuffer buf = new StringBuffer(text);
		int startIndex = buf.indexOf(PLACEHOLDER_PREFIX);
		while (startIndex != -1) {
			int endIndex = buf.indexOf(PLACEHOLDER_SUFFIX, startIndex + PLACEHOLDER_PREFIX.length());
			if (endIndex != -1) {
				String placeholder = buf.substring(startIndex + PLACEHOLDER_PREFIX.length(), endIndex);
				int nextIndex = endIndex + PLACEHOLDER_SUFFIX.length();
				try {
					String propVal = parameter.get(placeholder);
					if (propVal != null) {
						buf.replace(startIndex, endIndex + PLACEHOLDER_SUFFIX.length(), propVal);
						nextIndex = startIndex + propVal.length();
					} else {
						logger.warn("Could not resolve placeholder ‘" + placeholder + "‘ in [" + text + "] ");
					}
				} catch (Exception ex) {
					logger.warn("Could not resolve placeholder ‘" + placeholder + "‘ in [" + text + "]: " + ex);
				}
				startIndex = buf.indexOf(PLACEHOLDER_PREFIX, nextIndex);
			} else {
				startIndex = -1;
			}
		}
		return buf.toString();
	}
	
	public static void main(String[] args) {
		String aa= "我们都是好孩子,${num}说是嘛？ 我认为${people}是傻蛋!";
		Map<String, String> map = new HashMap<String, String>();
		map.put("num","小二比");
		map.put("people","小明");
		System.out.println(PlaceholderUtils.resolvePlaceholders(aa, map));
	}

}

输出结果：

我们都是好孩子,小二比说是嘛？ 我认为小明是傻蛋