随着微服务的流行，服务之间的http调用越来越多，遇到的问题也比较多，写这边文章的目的也是将自己遇到的坑和解决方案跟大家分享
一、为什么要用Http连接池
1、降低延迟：如果不采用连接池，每次连接发起Http请求的时候都会重新建立TCP连接(经历3次握手)，用完就会关闭连接(4次挥手)，如果采用连接池则减少了这部分时间损耗，别小看这几次握手，本人经过测试发现，基本上3倍的时间延迟
2、支持更大的并发：如果不采用连接池，每次连接都会打开一个端口，在大并发的情况下系统的端口资源很快就会被用完，导致无法建立新的连接
二、代码
1、PoolingHttpClientFactory.java连接池管理类，支持http与https协议
import org.apache.http.client.config.RequestConfig;
import org.apache.http.client.config.RequestConfig.Builder;
import org.apache.http.config.Registry;
import org.apache.http.config.RegistryBuilder;
import org.apache.http.conn.socket.ConnectionSocketFactory;
import org.apache.http.conn.socket.PlainConnectionSocketFactory;
import org.apache.http.conn.ssl.SSLConnectionSocketFactory;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClientBuilder;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.impl.conn.PoolingHttpClientConnectionManager; public class PoolingHttpClientFactory {
private int timeOut = 30000;
private int maxConnectionTotal = 400;
private int maxConnectionPerRoute = 400;
private PoolingHttpClientConnectionManager poolConnManager;
private Builder builder;
private RequestConfig requestConfig;
private HttpClientBuilder hcb; private static PoolingHttpClientFactory pooling = new PoolingHttpClientFactory(); private PoolingHttpClientFactory() {
poolConnManager = createConnectionManager();
builder = RequestConfig.custom();
if(timeOut != 0){
builder.setConnectionRequestTimeout(timeOut).setConnectTimeout(timeOut).setSocketTimeout(timeOut);
}
requestConfig = builder.build();
hcb = HttpClients.custom().setConnectionManager(poolConnManager).setDefaultRequestConfig(requestConfig);
} public static PoolingHttpClientFactory getInstance() {
if (pooling == null) {
pooling = new PoolingHttpClientFactory();
}
return pooling;
} public CloseableHttpClient createHttpClient(){
CloseableHttpClient httpClient = hcb.build();
return httpClient;
} public PoolingHttpClientConnectionManager createConnectionManager(){
Registry<ConnectionSocketFactory> socketFactoryRegistry = RegistryBuilder.<ConnectionSocketFactory>create()
.register("http", PlainConnectionSocketFactory.getSocketFactory())
.register("https", SSLConnectionSocketFactory.getSocketFactory())
.build(); PoolingHttpClientConnectionManager poolConnManager = new PoolingHttpClientConnectionManager(socketFactoryRegistry);
if(maxConnectionTotal != 0){
poolConnManager.setMaxTotal(maxConnectionTotal);
}
if(maxConnectionPerRoute != 0){
poolConnManager.setDefaultMaxPerRoute(maxConnectionPerRoute);
}
return poolConnManager;
} public void setTimeOut(int timeOut) {
this.timeOut = timeOut;
}
public void setMaxConnectionTotal(int maxConnectionTotal) {
this.maxConnectionTotal = maxConnectionTotal;
}
public void setMaxConnectionPerRoute(int maxConnectionPerRoute) {
this.maxConnectionPerRoute = maxConnectionPerRoute;
}
}
2、连接池消费类：TestClient.java
import com.alibaba.fastjson.JSON;
import org.apache.commons.io.IOUtils;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.CloseableHttpClient;
import org.testng.annotations.Test;
import java.io.IOException;
import java.io.InputStream; public class TestClient {
PoolingHttpClientFactory connManager; public Object get(String path){
CloseableHttpClient httpClient = PoolingHttpClientFactory.getInstance().createHttpClient(); //创建实例对象
HttpGet httpget = new HttpGet(path);
String json=null;
CloseableHttpResponse response=null;
try {
response = httpClient.execute(httpget);
InputStream in=response.getEntity().getContent();
json= IOUtils.toString(in, "Utf8");
in.close();
} catch (UnsupportedOperationException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}finally {
if(response!=null){
try {
response.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
return JSON.parse(json);
}
public Object post(String path){
CloseableHttpClient httpClient = PoolingHttpClientFactory.getInstance().createHttpClient(); //创建实例对象
HttpPost httppost = new HttpPost(path);
String json=null;
CloseableHttpResponse response=null;
try {
response = httpClient.execute(httppost);
InputStream in=response.getEntity().getContent();
json= IOUtils.toString(in, "Utf8");
in.close();
} catch (UnsupportedOperationException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}finally {
if(response!=null){
try {
response.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
return JSON.parse(json);
}
三、原理及注意事项
连接池中连接都是在发起请求的时候建立，并且都是长连接
TestClient.java中的in.close();作用就是将用完的连接释放，下次请求可以复用，这里特别注意的是，如果不使用in.close();而仅仅使用response.close();结果就是连接会被关闭，并且不能被复用，这样就失去了采用连接池的意义。
连接池释放连接的时候，并不会直接对TCP连接的状态有任何改变，只是维护了两个Set，leased和avaliabled，leased代表被占用的连接集合，avaliabled代表可用的连接的集合，释放连接的时候仅仅是将连接从leased中remove掉了，并把连接放到avaliabled集合中