js自动访问数据库

maven依赖

<dependencies> <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>4.11</version> <scope>test</scope> </dependency> <!-- https://mvnrepository.com/artifact/c3p0/c3p0 --> <dependency> <groupId>c3p0</groupId> <artifactId>c3p0</artifactId> <version>0.9.1.2</version> </dependency> <!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java --> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>5.1.39</version> </dependency> <!-- https://mvnrepository.com/artifact/commons-dbutils/commons-dbutils --> <dependency> <groupId>commons-dbutils</groupId> <artifactId>commons-dbutils</artifactId> <version>1.4</version> </dependency> <!-- https://mvnrepository.com/artifact/com.google.code.gson/gson --> <dependency> <groupId>com.google.code.gson</groupId> <artifactId>gson</artifactId> <version>2.8.5</version> </dependency> </dependencies>

Servlet

用的三层架构,service,dao层就不写了,用的是C3P0连接池,mysql为数据库

最后返回的是一个json字符串

//测试前端是否能访问 //System.out.println("getPlanePosition方法被调用了..."); PlaneService planeService = new PlaneServiceImpl(); PlanePosition planePosition = planeService.findPosition(); Gson gson = new Gson(); String jsonStr = gson.toJson(planePosition, PlanePosition.class); //设置响应头为json对象 response.setContentType("application/json;charset=utf-8"); //返回一个json对象 response.getWriter().print(jsonStr); //是否能输出正确的值 //System.out.println(jsonStr);

JSutils

之后需要用到的小工具

/** * 获取部署的项目地址 * @returns {string} */ function contextPath(){ // var curWwwPath = window.document.location.href; var pathName = window.document.location.pathname; // var pos = curWwwPath.indexOf(pathName); // var localhostPaht = curWwwPath.substring(0,pos); // var projectName = pathName.substring(0,pathName.substr(1).indexOf('/')+1); // return (localhostPaht + projectName); var number = pathName.indexOf("/", 1); return pathName.substring(0,number); } /** * 生成XMLHttpRequest * @returns {XMLHttpRequest} */ function ajaxFunction() { var xmlHttp; try { // Firefox, Opera 8.0+, Safari xmlHttp = new XMLHttpRequest(); } catch (e) { try {// Internet Explorer xmlHttp = new ActiveXObject("Msxml2.XMLHTTP"); } catch (e) { try { xmlHttp = new ActiveXObject("Microsoft.XMLHTTP"); } catch (e) { } } } return xmlHttp; }

html中js代码

模拟get方法

//全局变量 var yPosition; function get() { //1. 创建xmlhttprequest 对象 var request = ajaxFunction(); //2. 发送请求 用false是因为需要同步(true为异步) request.open("GET", "PlaneServlet?method=getPlanePosition", false); //3. 获取响应数据 注册监听的意思。 一会准备的状态发生了改变，那么就执行 = 号右边的方法 request.onreadystatechange = function () { //前半段表示 已经能够正常处理。 再判断状态码是否是200 if (request.readyState == 4 && request.status == 200) { //弹出响应的信息,测试用 // alert(request.responseText); //转为json对象 var obj = JSON.parse(request.responseText); //把服务器响应的json对象赋值给yPosition yPosition = obj.yPosition; // alert(yPosition); } }; request.send(); }

设置每2秒刷新一次

var myVar = setInterval(function () { ChangePosition(); }, 2000);

转载于:https://www.cnblogs.com/richardwlee/p/10452221.html