步驟：
1、 使用第三方工具，生成內網對映
2、 微信公眾平臺使用測試賬號
3、 測試賬號中需要配置自己的域名，並關注該臨時測試使用的公眾號
4、 下載一個瀏覽器的二維碼外掛
4、 編碼測試

• 使用花生殼進行內網穿透
  
  注意，因為我使用的是8080埠，所以對映成內網埠設定為8080才有效

• 微信公眾號使用測試賬號以及配置

首先進入微信公眾號官網，登陸後的頁面下拉，左下角即有開發者工具

選擇測試賬號

進入後即可看到提供測試用的appID和appsecret，這在後續會用到

再關注這個公眾號

並且需要在網頁賬號這兒配置自己的域名

點選修改

最後下載個二維碼外掛，以便在微信手機端登入

• 編碼:java

1 第一步：使用者同意授權，獲取code
2 第二步：通過code換取網頁授權access_token
3 第三步：重新整理access_token（如果需要）
4 第四步：拉取使用者資訊(需scope為 snsapi_userinfo)
5 附：檢驗授權憑證（access_token）是否有效
具體資訊見官網

maven工程，pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation
 
="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>login</groupId>
    <artifactId>wechat</artifactId>
    <packaging>war</packaging>
    <version>1.0</version>
    <name>
 
wechat Maven Webapp</name>
    <url>http://maven.apache.org</url>
    <profiles>
        <profile>
            <id>jdk-1.8</id>
            <activation>
                <activeByDefault>true</activeByDefault>
                <jdk>1.8</jdk>
            </activation>
            <properties>
                <maven.compiler.source>1.8</maven.compiler.source>
                <maven.compiler.target>1.8</maven.compiler.target>
                <maven.compiler.compilerVersion>1.8</maven.compiler.compilerVersion>
            </properties>
        </profile>
    </profiles>
    <dependencies>
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>servlet-api</artifactId>
            <scope>provided</scope>
            <version>3.0-alpha-1</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>3.8.1</version>
            <scope>test</scope>
        </dependency>
        <!-- 沒用到 -->
        <dependency>
            <groupId>net.sf.json-lib</groupId>
            <artifactId>json-lib</artifactId>
            <version>2.4</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/org.apache.httpcomponents/httpclient -->
        <dependency>
            <groupId>org.apache.httpcomponents</groupId>
            <artifactId>httpclient</artifactId>
            <version>4.5.2</version>
        </dependency>
        <dependency>
            <groupId>org.apache.httpcomponents</groupId>
            <artifactId>httpcore</artifactId>
            <version>4.4.4</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/org.apache.httpcomponents/httpmime -->
        <dependency>
            <groupId>org.apache.httpcomponents</groupId>
            <artifactId>httpmime</artifactId>
            <version>4.5.2</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/commons-fileupload/commons-fileupload -->
        <dependency>
            <groupId>commons-fileupload</groupId>
            <artifactId>commons-fileupload</artifactId>
            <version>1.3.1</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/commons-io/commons-io -->
        <dependency>
            <groupId>commons-io</groupId>
            <artifactId>commons-io</artifactId>
            <version>2.4</version>
        </dependency>

        <!-- https://mvnrepository.com/artifact/org.json/json -->
        <dependency>
            <groupId>org.json</groupId>
            <artifactId>json</artifactId>
            <version>20160810</version>
        </dependency>
        <dependency>
            <groupId>org.apache.httpcomponents</groupId>
            <artifactId>httpcore</artifactId>
            <version>4.4.4</version>
        </dependency>
    </dependencies>
    <build>
        <finalName>wechat</finalName>
    </build>
</project>

web.xml

<!DOCTYPE web-app PUBLIC
 "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
 "http://java.sun.com/dtd/web-app_2_3.dtd" >

<web-app>
  <display-name>Archetype Created Web Application</display-name>
    <servlet>
        <servlet-name>LoginServlet</servlet-name>
        <servlet-class>servlet.LoginServlet</servlet-class>
    </servlet>
    <servlet>
        <servlet-name>CallBackServlet</servlet-name>
        <servlet-class>servlet.CallBackServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>LoginServlet</servlet-name>
        <url-pattern>/wxLogin</url-pattern>
    </servlet-mapping>
    <servlet-mapping>
        <servlet-name>CallBackServlet</servlet-name>
        <url-pattern>/wx/callBack</url-pattern>
    </servlet-mapping>
</web-app>

AuthUtil.java發起http請求的工具類
若不熟悉httpClient相關知識，可以參考這篇文章：
HttpClient伺服器模擬瀏覽器傳送請求

package Utils;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.util.EntityUtils;
import org.json.JSONObject;

import java.io.IOException;


public class AuthUtil {
    public static final String APPID="wx893db98985206df6";
    public static final String APPSECRET="a7681bcfbd70c0beb497715bfa1fb35a";
    public static JSONObject doGetJson(String url) throws IOException {
        JSONObject jsonObject=null;
        DefaultHttpClient defaultHttpClient=new DefaultHttpClient();
        HttpGet httpGet=new HttpGet(url);
        HttpResponse httpResponse = defaultHttpClient.execute(httpGet);
        HttpEntity httpEntity=httpResponse.getEntity();
        if(httpEntity!=null){
            String result= EntityUtils.toString(httpEntity,"UTF-8");
            jsonObject=new JSONObject(result);
            //System.out.println("jsonObject:  "+jsonObject);
        }
        httpGet.releaseConnection();
        return jsonObject;
    }
}

LoginServlet登入請求處理

package servlet;

import Utils.AuthUtil;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.net.URLEncoder;

/**
 * Created by asus on 2017/8/2.
 */

public class LoginServlet extends HttpServlet{
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String backUrl="http://3261045722cwy.vicp.io/wx/callBack";
        /**
        *這兒一定要注意！！首尾不能有多的空格（因為直接複製往往會多出空格），其次就是引數的順序不能變動
        **/
        String url="https://open.weixin.qq.com/connect/oauth2/authorize?appid=" + AuthUtil.APPID+
                "&redirect_uri=" + URLEncoder.encode(backUrl,"UTF-8")+
                "&response_type=code" +
                "&scope=snsapi_userinfo" +
                "&state=STATE#wechat_redirect";
        resp.sendRedirect(url);
    }
}

CallBackServlet處理回撥請求

package servlet;

import Utils.AuthUtil;
import org.json.JSONObject;

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

/**
 * Created by asus on 2017/8/2.
 */
public class CallBackServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("hahah");
        String code=req.getParameter("code");
        String url="https://api.weixin.qq.com/sns/oauth2/access_token?appid=" + AuthUtil.APPID+
                "&secret=" +AuthUtil.APPSECRET+
                "&code=" +code+
                "&grant_type=authorization_code";
        JSONObject jsonObject = AuthUtil.doGetJson(url);
        String openid=jsonObject.getString("openid");
        String token=jsonObject.getString("access_token");
        String infoUrl="https://api.weixin.qq.com/sns/userinfo?access_token=" +token+
                "&openid=" +openid+
                "&lang=zh_CN";
        JSONObject userInfo=AuthUtil.doGetJson(infoUrl);
        System.out.println(userInfo);
    }
}