快捷導(dǎo)航

J2ee 高并發(fā)情況下監(jiān)聽(tīng)器實(shí)例詳解

更新時(shí)間：2017年02月17日 09:33:06 作者：Smy_0114

這篇文章主要介紹了J2ee 高并發(fā)情況下監(jiān)聽(tīng)器實(shí)例詳解的相關(guān)資料,需要的朋友可以參考下

J2ee 高并發(fā)情況下監(jiān)聽(tīng)器實(shí)例詳解

引言：在高并發(fā)下限制最大并發(fā)次數(shù)，在web.xml中用過(guò)濾器設(shè)置參數(shù)（最大并發(fā)數(shù)），并設(shè)置其他相關(guān)參數(shù)。詳細(xì)見(jiàn)代碼。
第一步：配置web.xml配置，不懂的地方解釋一下：參數(shù)50通過(guò)參數(shù)名maxConcurrent用在filter的實(shí)現(xiàn)類中獲取，filter-class就是寫的實(shí)現(xiàn)類，

url-pattern就是限制并發(fā)時(shí)間的url，結(jié)束！

<filter> 
  <filter-name>ConcurrentCountFilter</filter-name> 
  <filter-class>com.procure.pass.ConcurrentCountFilter</filter-class> 
  <init-param> 
    <param-name>maxConcurrent</param-name> 
    <param-value>50</param-value> 
  </init-param> 
 </filter> 
 <filter-mapping> 
  <filter-name>ConcurrentCountFilter</filter-name> 
  <url-pattern>/a/pass/export</url-pattern> 
 </filter-mapping>

第二步：寫實(shí)現(xiàn)類實(shí)現(xiàn)filter，該接口有三個(gè)方法，詳見(jiàn)代碼。

import java.io.IOException; 
import java.util.concurrent.atomic.AtomicInteger; 
import javax.servlet.Filter; 
import javax.servlet.FilterChain; 
import javax.servlet.FilterConfig; 
import javax.servlet.ServletException; 
import javax.servlet.ServletRequest; 
import javax.servlet.ServletResponse; 
import javax.servlet.http.HttpServletResponse; 
import org.slf4j.Logger; 
import org.slf4j.LoggerFactory; 
 
/** 
 * Servlet Filter implementation class ConcurrentCountFilter 
 */ 
public class ConcurrentCountFilter implements Filter { 
  private static Logger log = LoggerFactory.getLogger(ConcurrentCountFilter.class); 
  private FilterConfig filterConfig; 
  private int maxConcurrent = -1; 
  //總計(jì)數(shù) 
  private static AtomicInteger count = new AtomicInteger(0); 
   
  /** 
   * 獲取當(dāng)前并發(fā)數(shù) 
   * @return 
   */ 
  public static int get(){  
      return count.get();  
    }  
  /** 
   * 增加并發(fā)數(shù)量 
   * @return 
   */ 
   public static int increase(){  
      return count.incrementAndGet();  
    } 
   /** 
   * 減少并發(fā)數(shù)量 
   * @return 
   */ 
   public static int decrement(){ 
     return count.decrementAndGet(); 
   } 
   
    
  /** 
   * 初始化 
   */ 
    public void init(FilterConfig filterConfig) throws ServletException { 
      //獲取配置的最大并發(fā)數(shù)量 
      String maxStr = filterConfig.getInitParameter("maxConcurrent"); 
      int num = -1; 
      if(maxStr != null && !"".equals(maxStr)){ 
        num = Integer.parseInt(maxStr); 
      } 
      if(num >= 1){ 
        this.maxConcurrent = num; 
      }else{ 
        this.maxConcurrent = -1; 
      } 
    } 
    /** 
     * 過(guò)濾主方法 
     */ 
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException { 
      try{ 
      //增加并發(fā)數(shù)量 
      int num = increase(); 
      if(maxConcurrent > 0){ 
        if(maxConcurrent >= num){ 
          chain.doFilter(request, response); 
          log.info("第一次并發(fā)數(shù)量："+count.get()); 
        }else{ 
          HttpServletResponse res = (HttpServletResponse) response; 
          res.sendError(HttpServletResponse.SC_SERVICE_UNAVAILABLE,"達(dá)到最大并發(fā)數(shù)限制"); 
          log.info("達(dá)到最大并發(fā)數(shù)"); 
          log.info("最大并發(fā)數(shù)量："+count.get()); 
        } 
      }else{ 
        chain.doFilter(request, response); 
        log.info("第二次并發(fā)數(shù)量："+count.get()); 
      } 
      }finally { 
        decrement(); 
        log.info("減小的并發(fā)量："+count.get()); 
      } 
     
    } 
  /** 
   * 退出銷毀 
   */ 
  public void destroy() { 
    this.filterConfig = null; 
    log.info("銷毀......"); 
  } 
}

代碼到此完。

吐槽一下自己在項(xiàng)目中遇到的坑：

1.response.sendError( int, string);在本文代碼中為res.sendError其中若直接如本文代碼那樣會(huì)返回一個(gè)503服務(wù)器帶出來(lái)的頁(yè)面，此頁(yè)面粗暴及其難看，

在此為了友好通知用戶，需做如下步驟，在web.xml中做如下配置代碼：

<error-page> 
  <error-code>503</error-code> 
  <location>/WEB-INF/views/error/503.jsp</location> 
 </error-page>

如果在web.xml中配置了上面信息，首先會(huì)過(guò)濾503(HttpServletResponse.SC_SERVICE_UNAVAILABLE)狀態(tài)碼下的此頁(yè)面而不會(huì)拋服務(wù)器的頁(yè)面。

其中503.jsp頁(yè)面需自己完成在此僅僅貼出來(lái)一個(gè)示例做參考，代碼如下：

<% 
response.setStatus(503); 
 
// 獲取異常類 
Throwable ex = Exceptions.getThrowable(request); 
if (ex != null){ 
  LoggerFactory.getLogger("500.jsp").error(ex.getMessage(), ex); 
} 
 
// 編譯錯(cuò)誤信息 
StringBuilder sb = new StringBuilder("錯(cuò)誤信息：\n"); 
if (ex != null) { 
  sb.append(Exceptions.getStackTraceAsString(ex)); 
} else { 
  sb.append("未知錯(cuò)誤.\n\n"); 
} 
 
// 如果是異步請(qǐng)求或是手機(jī)端，則直接返回信息 
if (Servlets.isAjaxRequest(request)) { 
  out.print(sb); 
} 
 
// 輸出異常信息頁(yè)面 
else { 
%> 
<%@page import="org.slf4j.Logger,org.slf4j.LoggerFactory"%> 
<%@page import="com.xahl_oa.internal.common.web.Servlets"%> 
<%@page import="com.xahl_oa.internal.common.utils.Exceptions"%> 
<%@page import="com.xahl_oa.internal.common.utils.StringUtils"%> 
<%@page contentType="text/html;charset=UTF-8" isErrorPage="true"%> 
<%@include file="/WEB-INF/views/include/taglib.jsp"%> 
<!DOCTYPE html> 
<html> 
<head> 
  <title>503 - 服務(wù)暫時(shí)不可用</title> 
  <%@include file="/WEB-INF/views/include/head.jsp" %> 
</head> 
<body> 
  <div class="container-fluid"> 
    <div class="page-header"><h1>服務(wù)暫時(shí)不可用請(qǐng)稍后再試.</h1></div> 
    <div class="errorMessage"> 
      錯(cuò)誤信息：<%=ex==null?"未知錯(cuò)誤.":StringUtils.toHtml(ex.getMessage())%> <br/> <br/> 
      服務(wù)器暫時(shí)不可用請(qǐng)稍后再試，謝謝！<br/> <br/> 
      <a href="javascript:" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" onclick="history.go(-1);" class="btn">返回上一頁(yè)</a>  
      <a href="javascript:" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" onclick="$('.errorMessage').toggle();" class="btn">查看詳細(xì)信息</a> 
    </div> 
    <div class="errorMessage hide"> 
      <%=StringUtils.toHtml(sb.toString())%> <br/> 
      <a href="javascript:" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" onclick="history.go(-1);" class="btn">返回上一頁(yè)</a>  
      <a href="javascript:" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" onclick="$('.errorMessage').toggle();" class="btn">隱藏詳細(xì)信息</a> 
      <br/> <br/> 
    </div> 
    <script>try{top.$.jBox.closeTip();}catch(e){}</script> 
  </div> 
</body> 
</html> 
<% 
} out = pageContext.pushBody(); 
%>

此頁(yè)面就比服務(wù)器拋出的頁(yè)面友好甚多。

感謝閱讀，希望能幫助到大家，謝謝大家對(duì)本站的支持！

您可能感興趣的文章: