文件缓存类把文件放到缓存上

// 从缓存读取数据

String vehicleData = FileCache.Get("vdata_"+cityId, 5);//5分钟失效

// 保存到缓存

FileCache.Set("vdata_"+cityId, m);

package net.joystart.common.util;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileInputStream;
import java.io.FileWriter;
import java.io.UnsupportedEncodingException;
import java.text.DateFormat;
import java.util.Date;

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;

import net.joystart.common.util.date.DateSerializer;
import net.joystart.vehicle.service.impl.VehicleLock;

/***
 * 文件缓存类
 * 
 * @author lidongchun@bagechuxing.cn
 */
public class FileCache {

	private static String cachePath = ConfigUtil.pro.get("cachePath")
			.toString();

	// 获取缓存文件内容
	public static String Get(String key, int ttl) {
		try {
			String fileName = cachePath + "/" + key;
			String encoding = "UTF-8";
			File file = new File(fileName);

			long from = file.lastModified();
			long to = new Date().getTime();
			int minutes = (int) ((to - from) / 1000);
			if (minutes > ttl) {
				return null;
			}

			Long filelength = file.length();
			byte[] filecontent = new byte[filelength.intValue()];
			FileInputStream in = new FileInputStream(file);
			in.read(filecontent);
			in.close();
			return new String(filecontent, encoding);
		} catch (Exception e) {
			e.printStackTrace();
		}

		return null;
	}

	// 设置缓存文件内容
	public static boolean Set(String key, Object content) {
		VehicleLock lock = new VehicleLock(key);
		if (content instanceof String == false)  {
			GsonBuilder gb = new GsonBuilder();
		    gb.registerTypeAdapter(java.util.Date.class, new DateSerializer()).setDateFormat(DateFormat.LONG);
		    Gson gson = gb.create();
		    content = gson.toJson(content);
		}
		final String fileContent = String.valueOf(content);
		lock.wrap(new Runnable() {
			@Override
			public void run() {
				try {
					String pathname = cachePath + "/" + key;
					BufferedWriter out = new BufferedWriter(new FileWriter(
							pathname));
					out.write(fileContent);
					out.close();
				} catch (IOException e) {

				}
			}
		});
		return true;
	}
}