使用websocket的初衷是，要实时更新mysql中的报警信息到web页面显示
没怎么碰过web，代码写的是真烂，不过也算是功能实现了，放在这里也是鞭策自己，web也要多下些功夫
准备
引入依赖
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.38</version>
</dependency>
<dependency>
<groupId>javax</groupId>
<artifactId>javaee-api</artifactId>
<version>7.0</version>
<scope>provided</scope>
</dependency>先看看mysql中数据的格式
数据封装
public class AlarmMessage {
private String fanNo;
private String time;
private String description;
public AlarmMessage(String fanNo, String time, String description) {
this.fanNo = fanNo;
this.time = time;
this.description = description;
}
public String getFanNo() {
return fanNo;
}
public String getTime() {
return time;
}
public String getDescription() {
return description;
}
}jdbc从数据库中读取数据
public class DBUtil {
public List<AlarmMessage> getFromDB() throws SQLException, ClassNotFoundException, IllegalAccessException, InstantiationException {
List<AlarmMessage> list=new ArrayList<AlarmMessage>();
String dirver="com.mysql.jdbc.Driver";
String user="root";
String psd="root";
String database="streamingproblem";
String tablename="problem";
String url="jdbc:mysql://172.17.11.120:3306/"+database+"?user="+user+"&password="+psd;
Class.forName(dirver).newInstance();
Connection conn= DriverManager.getConnection(url);
Statement stat=conn.createStatement();
String sql="select * from "+tablename;
ResultSet rs=stat.executeQuery(sql);
while (rs.next()){
AlarmMessage alarmMessage=new AlarmMessage(rs.getString(2),rs.getString(3),rs.getString(4));
list.add(alarmMessage);
}
rs.close();
stat.close();
conn.close();
return list;
}
}开始写websocket
写一个线程用于发送新数据到页面，run中开启无限循环，用一个变量 currentIndex 记录当前数据量，当有新数据时，发送新数据
import javax.websocket.Session;
public class OneThread extends Thread {
private Session session;
private List<AlarmMessage> currentMessage;
private DBUtil dbUtil;
private int currentIndex;
public OneThread(Session session) {
this.session = session;
currentMessage = new ArrayList<AlarmMessage>();
dbUtil = new DBUtil();
currentIndex = 0;//此时是0条消息
}
@Override
public void run() {
while (true) {
List<AlarmMessage> list = null;
try {
try {
list = dbUtil.getFromDB();
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (InstantiationException e) {
e.printStackTrace();
}
} catch (SQLException e) {
e.printStackTrace();
}
if (list != null && currentIndex < list.size()) {
for (int i = currentIndex; i < list.size(); i++) {
try {
session.getBasicRemote().sendText(list.get(i).getFanNo()
+ "," + list.get(i).getTime()
+ "," + list.get(i).getDescription());
// session.getBasicRemote().sendObject(list.get(i)); //No encoder specified for object of class [class AlarmMessage]
} catch (IOException e) {
e.printStackTrace();
}
}
currentIndex = list.size();
}
try {
//一秒刷新一次
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}在onopen中启动发送数据线程
import javax.websocket.OnOpen;
import javax.websocket.Session;
import javax.websocket.server.ServerEndpoint;
@ServerEndpoint("/websocket")
public class websocket {
@OnOpen
public void onOpen(Session session){
OneThread thread =null;
thread=new OneThread(session);
thread.start();
}
}js实现websocket客户端
<%@ page import="java.sql.*" %>
<html>
<head>
<script type="text/javascript">
//先检验能不能运行起来，能不能连上，自动推送数据，先不做数据显示
//客户端就会与服务器进行连接
var webSocket = new WebSocket("ws://localhost:8081/websocket");
//这里只是调试用
//连接失败时回调
webSocket.onerror = function (event) {
makeDataOnWeb("error");
};
//这里只是调试用
//连接成功时回调，真的会执行括号中的代码！
webSocket.onopen = function (event) {
makeDataOnWeb("conn success");
};
webSocket.onmessage = function (event) {
makeDataOnWeb(event.data);
};
//这里只是调试用
webSocket.onclose = function (event) {
makeDataOnWeb("conn close");
};
function makeDataOnWeb(data) {
var a = data;
var divNode = document.getElementById("view");
var liNode = document.createElement("li");
liNode.innerHTML = a;
divNode.appendChild(liNode);
// divNode.insertBefore(liNode, divNode.children[0]);
//不能用insertAfter，好像不是这么用的
// var divNode = document.getElementById("view");
// var trNode = document.createElement("tr");
// var td1 = document.createElement("td");
// var td2 = document.createElement("td");
// var td3 = document.createElement("td");
// td1.innerHTML = a;
// td2.innerHTML = a;
// td3.innerHTML = a;
// trNode.appendChild(td1)
// trNode.appendChild(td2)
// trNode.appendChild(td3)
// var head = document.getElementById("head");
// document.write(a+"<br>");//直接写
// document.getElementsById("a").innerHTML="fadfadfa";//不输出任何内容
};
</script>
</head>
<body>
<%@page contentType="text/html; utf8" %>
<%@page language="java" %>
<%@page import="java.sql.*" %>
<%@page pageEncoding="UTF-8" %><!--解决中文乱码-->
<div id="view">
</div>
</body>
</html>