velocity string template merge

VelocityUtils.java

package com.jim.util;

import org.apache.velocity.VelocityContext;
import org.apache.velocity.app.VelocityEngine;

import java.io.StringWriter;
import java.util.Map;

/**
 * Created by qiaosj on 2017/1/10.
 */
public class TemplateUtils {
    private static VelocityEngine ve = null;

    public static String merge(String template, Map<String, Object> map) {
        if (template == null) return null;
        if (map == null || map.isEmpty()) return null;

        if (ve == null) {
            // 初始化并取得Velocity引擎
            ve = new VelocityEngine();
            ve.init();
        }

        // 取得velocity的上下文context
        VelocityContext vc = new VelocityContext();
        for (String key : map.keySet()) {
            Object val = map.get(key);
            vc.put(key, val);
        }

        // 输出流
        StringWriter writer = new StringWriter();

        ve.evaluate(vc, writer, "", template); // 关键方法

        return writer.toString();
    }
}