java实现http请求的同步和异步发送

http同步请求 ⼀般使⽤httpClient实现

private void sendRequest() throws Exception{ String path =\"/statistic/info\";

CloseableHttpClient httpClient = HttpClients.createDefault(); // 创建⼀个 GET 请求

HttpGet httpGet = new HttpGet(path); // 执⾏请求

CloseableHttpResponse response =httpClient.execute(httpGet); //取响应的结果

int statusCode =response.getStatusLine().getStatusCode(); System.out.println(statusCode);

String content = EntityUtils.toString(response.getEntity(), \"UTF-8\"); System.out.println(content); //关闭httpclient response.close(); httpClient.close();}

　　http异步请求

1.通过httpAsncClient实现

import org.apache.http.HttpResponse;

import org.apache.http.client.methods.HttpGet;import org.apache.http.concurrent.FutureCallback;

import org.apache.http.impl.nio.client.CloseableHttpAsyncClient;import org.apache.http.impl.nio.client.HttpAsyncClients;import org.apache.http.util.EntityUtils;import java.io.IOException;

import java.util.concurrent.CountDownLatch;

public class Main {

public static void main(String[] argv) {

CloseableHttpAsyncClient httpclient = HttpAsyncClients.createDefault(); httpclient.start();

final CountDownLatch latch = new CountDownLatch(1);

final HttpGet request = new HttpGet(\"https://www.alipay.com/\");

System.out.println(\" caller thread id is : \" + Thread.currentThread().getId());

httpclient.execute(request, new FutureCallback() {　　　　　　　@Override

public void completed(final HttpResponse response) { latch.countDown();

System.out.println(\" callback thread id is : \" + Thread.currentThread().getId()); System.out.println(request.getRequestLine() + \"->\" + response.getStatusLine()); try {

String content = EntityUtils.toString(response.getEntity(), \"UTF-8\"); System.out.println(\" response content is : \" + content); } catch (IOException e) { e.printStackTrace(); } }

　　　　　　　@Override

public void failed(final Exception ex) { latch.countDown();

System.out.println(request.getRequestLine() + \"->\" + ex);

System.out.println(\" callback thread id is : \" + Thread.currentThread().getId()); }

　　　　　　　@Override

public void cancelled() { latch.countDown();

System.out.println(request.getRequestLine() + \" cancelled\");

System.out.println(\" callback thread id is : \" + Thread.currentThread().getId()); }

}); try {

latch.await();

} catch (InterruptedException e) { e.printStackTrace(); } try {

httpclient.close();

} catch (IOException ignore) { } }}

2.还是通过同步请求，但是另起⼀个线程来计时，这种本质上有⼀个线程始终在堵塞，等待web端资源的返回。

HttpClient包中，三个设置超时的地⽅：

/* 从连接池中取连接的超时时间*/

ConnManagerParams.setTimeout(params, 1000); /*连接超时*/

HttpConnectionParams.setConnectionTimeout(params, 2000); /*请求超时*/

HttpConnectionParams.setSoTimeout(params, 4000);

ConnectionPoolTimeout：

定义了从ConnectionManager管理的连接池中取出连接的超时时间。出错会抛出ConnectionPoolTimeoutException

ConnectionTimeout：　　

定义了通过⽹络与server建⽴连接的超时时间，Httpclient包中通过⼀个异步线程去创建与server的socket连接，这就是该socket连接的超时时间。

当连接HTTPserver或者等待HttpConnectionManager管理的⼀个有效连接超时出错会抛出ConnectionTimeoutExceptionSocketTimeout：　　　　

这定义了Socket读数据的超时时间，即从server获取响应数据须要等待的时间。当读取或者接收Socket超时会抛出SocketTimeoutException

httpClient 请求头设置：

Accept、Connection、User-AgentAccept:表⽰浏览器可以接收到的类型*/*：表⽰所有类型

Connection:分为两种串⾏连接、持久连接（keep-alive）、管道化持久连接1.串⾏连接中，每次交互都要打开关闭连接

2.持久连接中，第⼀次交互会打开连接，交互结束后连接并不关闭，下次交互就省去了建⽴连接的过程。3.管道化持久连接，允许在持久连接的基础上，可选的使⽤传输管道，消除传输时延。User-Agent:⽤户