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;
}
}
