详解java解决分布式环境中高并发环境下数据插入重复问题

java 解决分布式环境中 高并发环境下数据插入重复问题

前言

原因：服务器同时接受到的重复请求
现象：数据重复插入 / 修改操作

解决方案 ： 分布式锁

对请求报文生成 摘要信息 + redis 实现分布式锁

工具类

分布式锁的应用

package com.nursling.web.filter.context;

import com.nursling.nosql.redis.RedisUtil;
import com.nursling.sign.SignType;
import com.nursling.sign.SignUtil;
import redis.clients.jedis.Jedis;

import javax.servlet.ServletRequest;
import javax.servlet.http.HttpServletRequest;
import java.util.HashMap;
import java.util.Map;


public class ContextLJ {

  private static final Integer JD = 0;

  
  public static boolean lock(String sign, String tiD) {
    synchronized (JD) { // 加锁
      Jedis jedis = RedisUtil.getJedis();
      String uTid = jedis.get(sign);
      if (uTid == null) {
 jedis.set(sign, tiD);
 jedis.expire(sign, 36);
 return true;
      }
      return false;
    }
  }

  
  public static boolean checklock(String sign, String tiD){
    Jedis jedis = RedisUtil.getJedis();
    String uTid = jedis.get(sign);
    return tiD.equals(uTid);
  }

  
  public static void clent (String sign, String tiD){
    if (checklock(sign, tiD)) {
      Jedis jedis = RedisUtil.getJedis();
      jedis.del(sign);
    }
  }

  
  public static String getSign(ServletRequest request){
    // 此工具是将 request中的请求内容 拼装成 key=value&key=value2 的形式 源码在线面
    Map map =SignUtil.getRequstMap((HttpServletRequest) request);
    String sign = null;
    try {
      // 这里使用md5方法生成摘要 SignUtil.getRequstMap 方法源码就不贴了
      sign = SignUtil.buildRequest(map, SignType.MD5);
    } catch (Exception e) {
      e.printStackTrace();
    }
    return sign;
  }
}

public static Map getRequstMap(HttpServletRequest req){
    Map params = new HashMap();
    Map requestParams = req.getParameterMap();
    for (Iterator iter = requestParams.keySet().iterator(); iter.hasNext();) {
      String name = (String) iter.next();
      String[] values = (String[]) requestParams.get(name);
      String valueStr = "";
      for (int i = 0; i < values.length; i++) {
 valueStr = (i == values.length - 1) ? valueStr + values[i]
     : valueStr + values[i] + ",";
      }
      params.put(name, valueStr);
    }
    return params;
  }

下面是过滤器代码

对分布式锁的利用

package com.nursling.web.filter.transaction;

import com.google.gson.Gson;
import com.nursling.common.RandomUtil;
import com.nursling.dao.util.TransactionUtils;
import com.nursling.model.ApiResult;
import com.nursling.model.ApiRtnCode;
import com.nursling.web.filter.context.ContextLJ;
import org.apache.log4j.Logger;

import javax.servlet.*;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;


public class TransactionFilter implements Filter {

  Logger log = Logger.getLogger(this.getClass());

  @Override
  public void init(FilterConfig filterConfig) throws ServletException {
  }

  @Override
  public void doFilter(ServletRequest request, ServletResponse myResp, FilterChain chain) throws IOException, ServletException {
    String sign = "sign_" + ContextLJ.getSign(request); // 生成摘要
    String tiD = RandomUtil.getRandomString(3) + "_" + Thread.currentThread().getId(); // 当前线程的身份
    try { 
      if (!ContextLJ.lock(sign, tiD)) {
 log.warn("放弃相同 并发请求" + sign);
 frequentlyError(myResp);
 return;
      }
      if (!ContextLJ.checklock(sign, tiD)) {
 log.warn("加锁验证失败 " + sign + " " + tiD);
 frequentlyError(myResp);
 return;
      }
      chain.doFilter(request, myResp); // 放行
    } catch (Exception e) { // 捕获到异常 进行异常过滤
      log.error("", e);
      retrunErrorInfo(myResp);
    } finally {
      ContextLJ.clent(sign, tiD);
    }
  }

  
  private void frequentlyError(ServletResponse myResp) throws IOException {
    ApiResult