//token
private final String token = "fengzheng";
 
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
 System.out.println("开始签名校验");
 String signature = request.getParameter("signature");
 String timestamp = request.getParameter("timestamp");
 String nonce = request.getParameter("nonce");
 String echostr = request.getParameter("echostr");
 
 ArrayList<String> array = new ArrayList<String>();
 array.add(signature);
 array.add(timestamp);
 array.add(nonce);
 
 //排序
 String sortString = sort(token, timestamp, nonce);
 //加密
 String mytoken = Decript.SHA1(sortString);
 //校验签名
 if (mytoken != null && mytoken != "" && mytoken.equals(signature)) {
 System.out.println("签名校验通过。");
 response.getWriter().println(echostr); //如果检验成功输出echostr，微信服务器接收到此输出，才会确认检验完成。
 } else {
 System.out.println("签名校验失败。");
 }
}
 
 
 
/**
 * 排序方法
 * @param token
 * @param timestamp
 * @param nonce
 * @return
 */
public static String sort(String token, String timestamp, String nonce) {
 String[] strArray = { token, timestamp, nonce };
 Arrays.sort(strArray);
 
 StringBuilder sbuilder = new StringBuilder();
 for (String str : strArray) {
 sbuilder.append(str);
 }
 
 return sbuilder.toString();
}

public class Decript {
 
 public static String SHA1(String decript) {
 try {
  MessageDigest digest = MessageDigest
   .getInstance("SHA-1");
  digest.update(decript.getBytes());
  byte messageDigest[] = digest.digest();
  // Create Hex String
  StringBuffer hexString = new StringBuffer();
  // 字节数组转换为 十六进制 数
  for (int i = 0; i < messageDigest.length; i++) {
  String shaHex = Integer.toHexString(messageDigest[i] & 0xFF);
  if (shaHex.length() < 2) {
   hexString.append(0);
  }
  hexString.append(shaHex);
  }
  return hexString.toString();
 
 } catch (NoSuchAlgorithmException e) {
  e.printStackTrace();
 }
 return "";
 }
}

<servlet>
 <servlet-name>Start</servlet-name>
 <servlet-class>org.fengzheng.wechat.Start</servlet-class>
</servlet>
<servlet-mapping>
 <servlet-name>Start</servlet-name>
 <url-pattern>/wechat</url-pattern>
</servlet-mapping>
　　

public class AccessToken {
 public String getAccessToken() {
 return accessToken;
 }
 
 public void setAccessToken(String accessToken) {
 this.accessToken = accessToken;
 }
 
 public int getExpiresin() {
 return expiresin;
 }
 
 public void setExpiresin(int expiresin) {
 this.expiresin = expiresin;
 }
 
 private String accessToken;
 
 private int expiresin;
}

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

@WebServlet(name = "AccessTokenServlet")
public class AccessTokenServlet extends HttpServlet {
 
 public void init() throws ServletException {
 TokenThread.appId = getInitParameter("appid"); //获取servlet初始参数appid和appsecret
 TokenThread.appSecret = getInitParameter("appsecret");
 System.out.println("appid:"+TokenThread.appId);
 System.out.println("appSecret:"+TokenThread.appSecret);
 new Thread(new TokenThread()).start(); //启动进程
 }
 
 protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
 
 }
 
 protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
 
 }
}

<servlet>
 <servlet-name>initAccessTokenServlet</servlet-name>
 <servlet-class>
  org.fengzheng.wechat.accesstoken.AccessTokenServlet
 </servlet-class>
 <init-param>
  <param-name>appid</param-name>
  <param-value>your appid</param-value>
 </init-param>
 <init-param>
  <param-name>appsecret</param-name>
  <param-value>your appsecret</param-value>
 </init-param>
 <load-on-startup>0</load-on-startup>
 </servlet>

import com.alibaba.fastjson.JSON;
import com.alibaba.fastjson.JSONObject;
import org.fengzheng.wechat.common.NetWorkHelper;


public class TokenThread implements Runnable {
 public static String appId = "";
 
 public static String appSecret= "";
<br>　　//注意是静态的
 public static AccessToken accessToken = null;
 
 public void run(){
 while (true){
  try{
  accessToken = this.getAccessToken();
  if(null!=accessToken){
   System.out.println(accessToken.getAccessToken());
   Thread.sleep(7000 * 1000); //获取到access_token 休眠7000秒
 
  }else{
   Thread.sleep(1000*3); //获取的access_token为空 休眠3秒
  }
  }catch(Exception e){
  System.out.println("发生异常："+e.getMessage());
  e.printStackTrace();
  try{
   Thread.sleep(1000*10); //发生异常休眠1秒
  }catch (Exception e1){
 
  }
  }
 }
 }
 
 
 /**
 * 获取access_token
 * @return
 */
 private AccessToken getAccessToken(){
 NetWorkHelper netHelper = new NetWorkHelper();
 String Url = String.format("https://api.weixin.qq.com/cgi-bin/token?grant_type=client_credential&appid=%s&secret=%s",this.appId,this.appSecret);
 String result = netHelper.getHttpsResponse(Url,"");
 System.out.println(result);
 //response.getWriter().println(result);
 JSONObject json = JSON.parseObject(result);
 AccessToken token = new AccessToken();
 token.setAccessToken(json.getString("access_token"));
 token.setExpiresin(json.getInteger("expires_in"));
 return token;
 }
}

public String getHttpsResponse(String hsUrl,String requestMethod) {
 URL url;
 InputStream is = null;
 String resultData = "";
 try {
  url = new URL(hsUrl);
  HttpsURLConnection con = (HttpsURLConnection) url.openConnection();
  TrustManager[] tm = {xtm};
 
  SSLContext ctx = SSLContext.getInstance("TLS");
  ctx.init(null, tm, null);
 
  con.setSSLSocketFactory(ctx.getSocketFactory());
  con.setHostnameVerifier(new HostnameVerifier() {
  @Override
  public boolean verify(String arg0, SSLSession arg1) {
   return true;
  }
  });
 
 
  con.setDoInput(true); //允许输入流，即允许下载
 
  //在android中必须将此项设置为false
  con.setDoOutput(false); //允许输出流，即允许上传
  con.setUseCaches(false); //不使用缓冲
  if(null!=requestMethod && !requestMethod.equals("")) {
  con.setRequestMethod(requestMethod); //使用指定的方式
  }
  else{
  con.setRequestMethod("GET"); //使用get请求
  }
  is = con.getInputStream(); //获取输入流，此时才真正建立链接
  InputStreamReader isr = new InputStreamReader(is);
  BufferedReader bufferReader = new BufferedReader(isr);
  String inputLine = "";
  while ((inputLine = bufferReader.readLine()) != null) {
  resultData += inputLine + "\n";
  }
  System.out.println(resultData);
 
  
  Certificate[] certs = con.getServerCertificates();
 
  int certNum = 1;
 
  for (Certificate cert : certs) {
  X509Certificate xcert = (X509Certificate) cert;
  }
 
 } catch (Exception e) {
  e.printStackTrace();
 }
 return resultData;
 }
 
X509TrustManager xtm = new X509TrustManager() {
 @Override
 public X509Certificate[] getAcceptedIssuers() {
  // TODO Auto-generated method stub
  return null;
 }
 
 @Override
 public void checkServerTrusted(X509Certificate[] arg0, String arg1)
  throws CertificateException {
  // TODO Auto-generated method stub
 
 }
 
 @Override
 public void checkClientTrusted(X509Certificate[] arg0, String arg1)
  throws CertificateException {
  // TODO Auto-generated method stub
 
 }
 };

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@ page import="org.fengzheng.wechat.accesstoken.TokenThread" %>
<html>
 <head>
 <title></title>
 </head>
 <body>
 access_token为：<%=TokenThread.accessToken.getAccessToken()%>
 </body>
</html>