java前端长连接框架_Java如何实现长连接
實(shí)現(xiàn)原理：
長連接的維持，是要客戶端程序，定時(shí)向服務(wù)端程序，發(fā)送一個(gè)維持連接包的。
如果，長時(shí)間未發(fā)送維持連接包，服務(wù)端程序?qū)嚅_連接。
客戶端：
Client通過持有Socket的對象，可以隨時(shí)(使用sendObject方法)發(fā)送Massage Object(消息)給服務(wù)端。
如果keepAliveDelay毫秒(程序中是2秒)內(nèi)未發(fā)送任何數(shù)據(jù)，則自動(dòng)發(fā)送一個(gè)KeepAlive Object(心跳)給服務(wù)端，用于維持連接。
由于，我們向服務(wù)端，可以發(fā)送很多不同的消息對象，服務(wù)端也可以返回不同的對象。所以，對于返回對象的處理，要編寫具體的ObjectAction實(shí)現(xiàn)類進(jìn)行處理。通過Client.addActionMap方法進(jìn)行添加。這樣，程序會(huì)回調(diào)處理。
服務(wù)端：
由于客戶端會(huì)定時(shí)(keepAliveDelay毫秒)發(fā)送維持連接的信息過來，所以，服務(wù)端要有一個(gè)檢測機(jī)制。
即當(dāng)服務(wù)端receiveTimeDelay毫秒(程序中是3秒)內(nèi)未接收任何數(shù)據(jù)，則自動(dòng)斷開與客戶端的連接。
ActionMapping的原理與客戶端相似(相同)。
通過添加相應(yīng)的ObjectAction實(shí)現(xiàn)類，可以實(shí)現(xiàn)不同對象的響應(yīng)、應(yīng)答過程。
心跳反映的代碼：
package com.java.excel.keepalive;
import java.io.Serializable;
import java.text.SimpleDateFormat;
import java.util.Date;
/**
*
* 維持連接的消息對象(心跳對象)
*/
public class KeepAlive implements Serializable {
private static final long serialVersionUID = -2813120366138988480L;
/* 覆蓋該方法，僅用于測試使用。
* @see java.lang.Object#toString()
*/
@Override
public String toString() {
return new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(new Date())+"\t維持連接包";
}
}
服務(wù)端
package com.java.excel.keepalive;
import java.io.IOException;
import java.io.InputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.concurrent.ConcurrentHashMap;
public class Server {
/**
* 要處理客戶端發(fā)來的對象，并返回一個(gè)對象，可實(shí)現(xiàn)該接口。
*/
public interface ObjectAction{
Object doAction(Object rev, Server server);
}
public static final class DefaultObjectAction implements ObjectAction{
public Object doAction(Object rev,Server server) {
System.out.println("處理并返回："+rev);
return rev;
}
}
public static void main(String[] args) {
int port = 65432;
Server server = new Server(port);
server.start();
}
private int port;
private volatile boolean running=false;
private long receiveTimeDelay=3000;
private ConcurrentHashMap actionMapping = new ConcurrentHashMap();
private Thread connWatchDog;
public Server(int port) {
this.port = port;
}
public void start(){
if(running)return;
running=true;
connWatchDog = new Thread(new ConnWatchDog());
connWatchDog.start();
}
@SuppressWarnings("deprecation")
public void stop(){
if(running)running=false;
if(connWatchDog!=null)connWatchDog.stop();
}
public void addActionMap(Class cls,ObjectAction action){
actionMapping.put(cls, action);
}
class ConnWatchDog implements Runnable{
public void run(){
try {
ServerSocket ss = new ServerSocket(port,5);
while(running){
Socket s = ss.accept();
new Thread(new SocketAction(s)).start();
}
} catch (IOException e) {
e.printStackTrace();
Server.this.stop();
}
}
}
class SocketAction implements Runnable{
Socket s;
boolean run=true;
long lastReceiveTime = System.currentTimeMillis();
public SocketAction(Socket s) {
this.s = s;
}
public void run() {
while(running && run){
if(System.currentTimeMillis()-lastReceiveTime>receiveTimeDelay){
overThis();
}else{
try {
InputStream in = s.getInputStream();
if(in.available()>0){
ObjectInputStream ois = new ObjectInputStream(in);
Object obj = ois.readObject();
lastReceiveTime = System.currentTimeMillis();
System.out.println("接收：\t"+obj);
ObjectAction oa = actionMapping.get(obj.getClass());
oa = oa==null?new DefaultObjectAction():oa;
Object out = oa.doAction(obj,Server.this);
if(out!=null){
ObjectOutputStream oos = new ObjectOutputStream(s.getOutputStream());
oos.writeObject(out);
oos.flush();
}
}else{
Thread.sleep(10);
}
} catch (Exception e) {
e.printStackTrace();
overThis();
}
}
}
}
private void overThis() {
if(run)run=false;
if(s!=null){
try {
s.close();
} catch (IOException e) {
e.printStackTrace();
}
}
System.out.println("關(guān)閉："+s.getRemoteSocketAddress());
}
}
}
客戶端
package com.java.excel.keepalive;
import java.io.IOException;
import java.io.InputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.net.Socket;
import java.net.UnknownHostException;
import java.util.concurrent.ConcurrentHashMap;
public class Client {
/**
* 處理服務(wù)端發(fā)回的對象，可實(shí)現(xiàn)該接口。
*/
public static interface ObjectAction{
void doAction(Object obj,Client client);
}
public static final class DefaultObjectAction implements ObjectAction{
public void doAction(Object obj,Client client) {
System.out.println("處理：\t"+obj.toString());
}
}
public static void main(String[] args) throws UnknownHostException, IOException {
String serverIp = "127.0.0.1";
int port = 65432;
Client client = new Client(serverIp,port);
client.start();
}
private String serverIp;
private int port;
private Socket socket;
private boolean running=false; //連接狀態(tài)
private long lastSendTime; //最后一次發(fā)送數(shù)據(jù)的時(shí)間
//用于保存接收消息對象類型及該類型消息處理的對象
private ConcurrentHashMap actionMapping = new ConcurrentHashMap();
public Client(String serverIp, int port) {
this.serverIp=serverIp;
this.port=port;
}
public void start() throws UnknownHostException, IOException {
if(running)return;
socket = new Socket(serverIp,port);
System.out.println("本地端口："+socket.getLocalPort());
lastSendTime=System.currentTimeMillis();
running=true;
new Thread(new KeepAliveWatchDog()).start(); //保持長連接的線程，每隔2秒項(xiàng)服務(wù)器發(fā)一個(gè)一個(gè)保持連接的心跳消息
new Thread(new ReceiveWatchDog()).start(); //接受消息的線程，處理消息
}
public void stop(){
if(running)running=false;
}
/**
* 添加接收對象的處理對象。
* @param cls 待處理的對象，其所屬的類。
* @param action 處理過程對象。
*/
public void addActionMap(Class cls,ObjectAction action){
actionMapping.put(cls, action);
}
public void sendObject(Object obj) throws IOException {
ObjectOutputStream oos = new ObjectOutputStream(socket.getOutputStream());
oos.writeObject(obj);
System.out.println("發(fā)送：\t"+obj);
oos.flush();
}
class KeepAliveWatchDog implements Runnable{
long checkDelay = 10;
long keepAliveDelay = 1000;
public void run() {
while(running){
if(System.currentTimeMillis()-lastSendTime>keepAliveDelay){
try {
Client.this.sendObject(new KeepAlive());
} catch (IOException e) {
e.printStackTrace();
Client.this.stop();
}
lastSendTime = System.currentTimeMillis();
}else{
try {
Thread.sleep(checkDelay);
} catch (InterruptedException e) {
e.printStackTrace();
Client.this.stop();
}
}
}
}
}
class ReceiveWatchDog implements Runnable{
public void run() {
while(running){
try {
InputStream in = socket.getInputStream();
if(in.available()>0){
ObjectInputStream ois = new ObjectInputStream(in);
Object obj = ois.readObject();
System.out.println("接收：\t"+obj);
ObjectAction oa = actionMapping.get(obj.getClass());
oa = oa==null?new DefaultObjectAction():oa;
oa.doAction(obj, Client.this);
}else{
Thread.sleep(10);
}
} catch (Exception e) {
e.printStackTrace();
Client.this.stop();
}
}
}
}
}
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