HttpClient的使用步骤：

1、使用Apache的HttpClient发送GET和POST请求的步骤如下:

1. 使用帮助类HttpClients创建CloseableHttpClient对象. 2. 基于要发送的HTTP请求类型创建HttpGet或者HttpPost实例.

3. 使用addHeader方法添加请求头部,诸如User-Agent, Accept-Encoding等参数.

4. 对于POST请求,创建NameValuePair列表,并添加所有的表单参数.然后把它填充进HttpPost实体.

5. 通过执行此HttpGet或者HttpPost请求获取CloseableHttpResponse实例

6. 从此CloseableHttpResponse实例中获取状态码,错误信息,以及响应页面等等.

7. 最后关闭HttpClient资源.

2、使用HttpClient发送请求、接收响应很简单，一般需要如下几步即可：

1. 创建HttpClient对象，HttpClients.createDefault()。

2. 创建请求方法的实例，并指定请求URL。如果需要发送GET请求，创建HttpGet对象；如果需要发送POST请求，创建HttpPost对象，HttpPost httpPost = new HttpPost(url)。

3. 如果需要发送请求参数，可调用HttpGet、HttpPost共同的setParams(HetpParams params)方法来添加请求参数；对于HttpPost对象而言，也可调用setEntity(HttpEntity entity)方法来设置请求参数。List valuePairs = new LinkedList();valuePairs.add(new BasicNameValuePair(entry.getKey(),entry.getValue()))；httpPost.setEntity(formEntity)。

4. 调用HttpClient对象的execute(HttpUriRequest request)发送请求，该方法返回一个HttpResponse。

5. 调用HttpResponse的getAllHeaders()、getHeaders(String name)等方法可获取服务器的响应头；调用HttpResponse的getEntity()方法可获取HttpEntity对象，该对象包装了服务器的响应内容。程序可通过该对象获取服务器的响应内容。

6. 释放连接。无论执行方法是否成功，都必须释放连接

httpClient实例：

实例一：

package http;

import java.io.IOException;

import java.io.UnsupportedEncodingException;

import java.util.HashMap;

import java.util.LinkedList;

import java.util.List;

import java.util.Map;

import java.util.Map.Entry;

import org.apache.commons.httpclient.HttpClient;

import org.apache.http.HttpEntity;

import org.apache.http.HttpResponse;

import org.apache.http.NameValuePair;

import org.apache.http.client.ClientProtocolException;

import org.apache.http.client.entity.UrlEncodedFormEntity;

import org.apache.http.client.methods.HttpPost;

import org.apache.http.message.BasicNameValuePair;

import org.apache.http.util.EntityUtils;

import org.apache.http.impl.client.HttpClients;

public class HttpTest {

public Boolean isRequestSuccessful(HttpResponse httpresponse){

return httpresponse.getStatusLine().getStatusCode()==200;

}

public String HttpPost(String param1,String param2,String url) throws Exception{

Map personMap = new HashMap();

personMap.put("param1",param1);

personMap.put("param1",param2);

List list = new LinkedList();

for(Entry entry:personMap.entrySet()){

list.add(new BasicNameValuePair(entry.getKey(),entry.getValue()));

}

HttpPost httpPost = new HttpPost(url);

UrlEncodedFormEntity formEntity = new UrlEncodedFormEntity(list,"utf-8");

httpPost.setEntity(formEntity);

HttpClient httpCient = HttpClients.CreatDefault();

HttpResponse httpresponse = null;

try{

httpresponse = httpClient.execute(httpPost);

HttpEntity httpEntity = httpresponse.getEntity();

String response = EntityUtils.toString(httpEntity, "utf-8");

return response;

}catch(ClientProtocolException e){

System.out.println("http请求失败，uri{},exception{}");

}catch(IOException e){

System.out.println("http请求失败，uri{},exception{}");

}

return null;

}

}

实例二：

package com.kingdee.opensys.common.util.http;

import java.io.IOException;

import java.util.concurrent.locks.Lock;

import java.util.concurrent.locks.ReentrantLock;

import org.apache.http.HttpEntity;

import org.apache.http.client.ClientProtocolException;

import org.apache.http.client.entity.GzipDecompressingEntity;

import org.apache.http.client.methods.CloseableHttpResponse;

import org.apache.http.client.methods.HttpRequestBase;

import org.apache.http.impl.client.CloseableHttpClient;

import org.apache.http.impl.client.HttpClientBuilder;

import org.apache.http.impl.conn.PoolingHttpClientConnectionManager;

import org.apache.http.util.EntityUtils;

import org.slf4j.Logger;

import org.slf4j.LoggerFactory;

public class HttpClientHelper {

private static Logger logger = LoggerFactory.getLogger(HttpClientHelper.class);

private static HttpClientHelper instance = null;

private static Lock lock = new ReentrantLock();

private static CloseableHttpClient httpClient;

public HttpClientHelper(){

instance = this;

}

public static HttpClientHelper getHttpClient(){

if(instance == null){

lock.lock();

try{

instance = new HttpClientHelper();

}catch(Exception e){

e.printStackTrace();

}finally{

lock.unlock();

}

}

return instance;

}

public void init(){

PoolingHttpClientConnectionManager pool = new PoolingHttpClientConnectionManager();

pool.setMaxTotal(500);

pool.setDefaultMaxPerRoute(50);

httpClient = HttpClientBuilder.create().setConnectionManager(pool).build();

}

public byte[] executeAndReturnByte(HttpRequestBase request) throws Exception{

HttpEntity entity = null;

CloseableHttpResponse response = null;

byte[] base = new byte[0];

if(request==null){

return base;

}

if(httpClient==null){

init();

}

if(httpClient==null){

logger.error("http获取异常");

return base;

}

response = httpClient.execute(request);

entity = response.getEntity();

if(response.getStatusLine().getStatusCode()==200){

String encode = (""+response.getFirstHeader("Content-Encoding")).toLowerCase();

if(encode.indexOf("gzip")>0){

entity = new GzipDecompressingEntity(entity);

}

base = EntityUtils.toByteArray(entity);

}else{

logger.error(""+response.getStatusLine().getStatusCode());

}

EntityUtils.consumeQuietly(entity);

response.close();

httpClient.close();

return base;

}

public String execute(HttpRequestBase request) throws Exception{

byte[] base = executeAndReturnByte(request);

if(base==null){

return null;

}

String result = new String(base,"UTF-8");

return result;

}

}

package com.kingdee.opensys.common.util.http;

import java.io.UnsupportedEncodingException;

import java.util.Iterator;

import java.util.LinkedList;

import java.util.List;

import java.util.Map;

import org.apache.http.HttpEntity;

import org.apache.http.client.config.RequestConfig;

import org.apache.http.client.entity.UrlEncodedFormEntity;

import org.apache.http.client.methods.HttpPost;

import org.apache.http.entity.StringEntity;

import org.apache.http.message.BasicNameValuePair;

import javax.servlet.http.HttpServletRequest;

public class HttpHelper {

private static String UTF8 = "UTF-8";

private static RequestConfig requestConfig;

public static String post(Map header,Map params,String url) throws Exception{

HttpPost post = null;

post = new HttpPost(url);

if(header!=null){

for(String key:header.keySet()){

post.addHeader(key, header.get(key));

}

}

if(params!=null){

List list = new LinkedList();

post.setConfig(getRequestConfig());

for(String key:params.keySet()){

list.add(new BasicNameValuePair(key,params.get(key)));

}

UrlEncodedFormEntity entity = new UrlEncodedFormEntity(list,UTF8);

post.setEntity(entity);

}

return HttpClientHelper.getHttpClient().execute(post);

}

public static String post(Map header,String jsonObject,String url) throws Exception{

HttpPost post = null;

post = new HttpPost(url);

if(header!=null){

for(String key:header.keySet()){

post.addHeader(key, header.get(key));

}

}

if(jsonObject.isEmpty()){

throw new Exception("jsonObject不能为空！");

}

HttpEntity entity = new StringEntity(jsonObject,"UTF-8");

return HttpClientHelper.getHttpClient().execute(post);

}

public static String post(Map params,String url) throws Exception{

HttpPost post = null;

post = new HttpPost(url);

List list = new LinkedList();

post.setConfig(getRequestConfig());

for(String key:params.keySet()){

list.add(new BasicNameValuePair(key,params.get(key)));

}

UrlEncodedFormEntity entity = new UrlEncodedFormEntity(list,UTF8);

post.setEntity(entity);

return HttpClientHelper.getHttpClient().execute(post);

}

public static RequestConfig getRequestConfig(){

if(requestConfig==null){

requestConfig = RequestConfig.custom().setConnectionRequestTimeout(20000)

.setConnectTimeout(20000).setSocketTimeout(20000).build();

}

return requestConfig;

}

public static String getClientIp(HttpServletRequest request){

String ip = request.getHeader("x-forwarded-for");

if(ip==null||ip.length()==0||"unknown".equalsIgnoreCase(ip)){

ip = request.getHeader("Proxy-Client-IP");

}

if(ip==null||ip.length()==0||"unknown".equalsIgnoreCase(ip)){

ip = request.getHeader("WL-Proxy-Client_IP");

}

if(ip==null||ip.length()==0||"unkonwn".equalsIgnoreCase(ip)){

ip = request.getRemoteAddr();

}

if(ip.length()<5){

ip="0.0.0.0";

}

return ip;

}

}