【synchronized 用法实例讲解】
今天要带大家看的是synchronized 用法实例讲解,代码如下:
package com.asiainfolinkage.ems.web.controller.base;
import java.math.BigInteger;
import java.util.Date;
import java.util.HashMap;
import java.util.Map;
import java.util.Random;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;
/**
* 附带token的控制器
* @version 1.0 Copyright 2013年7月29日 下午3:38:30
*/
public abstract class TokenBaseController extends BaseController {
private static Map<STRING, String> springmvc_token = new HashMap<STRING, String>();
/** 生成一个唯一值的token */
public String generateGUID(HttpSession session) {
String token = "";
Date date = new Date();
synchronized (springmvc_token) {
try {
Object obj = session.getAttribute(Constants.SPRING_MVC_TOKENNAME);
if (obj != null)
springmvc_token = (Map<STRING, String>) session.getAttribute(Constants.SPRING_MVC_TOKENNAME);
token = new BigInteger(165, new Random()).toString(36).toUpperCase();
springmvc_token.put(Constants.DEFAULT_TOKEN_NAME + "." + token, token);
session.setAttribute(Constants.SPRING_MVC_TOKENNAME, springmvc_token);
Constants.TOKEN_VALUE = token;
} catch (IllegalStateException e) {
_log.error("generateGUID() mothod find bug,by token session...");
}
}
return token;
}
/** 验证表单token值和session中的token值是否一致 */
public boolean validToken(HttpServletRequest request) {
String inputToken = getInputToken(request);
if (inputToken == null) {
_log.warn("token is not valid!inputToken is NULL");
return false;
}
HttpSession session = request.getSession();
Map<STRING, String> tokenMap = (Map<STRING, String>) session.getAttribute(Constants.SPRING_MVC_TOKENNAME);
if (tokenMap == null || tokenMap.size() < 1) {
_log.warn("token is not valid!sessionToken is NULL");
return false;
}
String sessionToken = tokenMap.get(Constants.DEFAULT_TOKEN_NAME + "." + inputToken);
if (!inputToken.equals(sessionToken)) {
_log.warn("token is not valid!inputToken='" + inputToken + "',sessionToken = '" + sessionToken + "'");
return false;
}
tokenMap.remove(Constants.DEFAULT_TOKEN_NAME + "." + inputToken);
session.setAttribute(Constants.SPRING_MVC_TOKENNAME, tokenMap);
return true;
}
/** 获取表单中token值 */
private String getInputToken(HttpServletRequest request) {
Map params = request.getParameterMap();
if (!params.containsKey(Constants.DEFAULT_TOKEN_NAME)) {
_log.warn("Could not find token name in params.");
return null;
}
String[] tokens = (String[]) (String[]) params.get(Constants.DEFAULT_TOKEN_NAME);
if ((tokens == null) || (tokens.length < 1)) {
_log.warn("Got a null or empty token name.");
return null;
}
return tokens[0];
}
}
