Question

如何实现java http长连接推送数据

Answer 1

Feign在默认情况下使用的是JDK原生的URLConnection发送HTTP请求，没有连接池，但是对每个地址会保持一个长连接，即利用HTTP的persistence connection 。我们可以用Apache的HTTP Client替换Feign原始的http client, 从而获取连接池、超时时间等与性能息息相关的控制能力。Spring Cloud从Brixtion.SR5版本开始支持这种替换，首先在项目中声明Apache HTTP Client和feign-httpclient依赖

Answer 2

Feign在默认情况下使用的是JDK原生的URLConnection发送HTTP请求，没有连接池，但是对每个地址会保持一个长连接，即利用HTTP的persistence connection 。我们可以用Apache的HTTP Client替换Feign原始的http client, 从而获取连接池、超时时间等与性能息息相关的控制能力。Spring Cloud从Brixtion.SR5版本开始支持这种替换，首先在项目中声明Apache HTTP Client和feign-httpclient依赖

Answer 3

通过轮询来实现长连接
轮询：隔一段时间访问服务器，服务器不管有没有新消息都立刻返回。
http长连接实现代码：
客户端：
package houlei.csdn.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;

/**
* C/S架构的客户端对象，持有该对象，可以随时向服务端发送消息。
* <p>
* 创建时间：2010-7-18 上午12:17:25
* @author HouLei
* @since 1.0
*/
public class Client {

/**
* 处理服务端发回的对象，可实现该接口。
*/
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("处理：\t"+obj.toString());//诊断程序是否正常
}
}
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;
private long lastSendTime;
private ConcurrentHashMap<Class, ObjectAction> actionMapping = new ConcurrentHashMap<Class,ObjectAction>();

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();
new Thread(new ReceiveWatchDog()).start();
}

public void stop(){
if(running)running=false;
}

/**
* 添加接收对象的处理对象。
* @param cls 待处理的对象，其所属的类。
* @param action 处理过程对象。
*/
public void addActionMap(Class<Object> 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("发送：\t"+obj);
oos.flush();
}

class KeepAliveWatchDog implements Runnable{
long checkDelay = 10;
long keepAliveDelay = 2000;
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();