HttpClient的使用步驟：
1、使用Apache的HttpClient發送GET和POST請求的步驟如下:
1. 使用幫助類HttpClients創建CloseableHttpClient對象.?2. 基于要發送的HTTP請求類型創建HttpGet或者HttpPost實例.
3. 使用addHeader方法添加請求頭部,諸如User-Agent, Accept-Encoding等參數.
4. 對于POST請求,創建NameValuePair列表,并添加所有的表單參數.然后把它填充進HttpPost實體.
5. 通過執行此HttpGet或者HttpPost請求獲取CloseableHttpResponse實例
6. 從此CloseableHttpResponse實例中獲取狀態碼,錯誤信息,以及響應頁面等等.
7. 最后關閉HttpClient資源.
2、使用HttpClient發送請求、接收響應很簡單，一般需要如下幾步即可：
1.?創建HttpClient對象，HttpClients.createDefault()。
2.?創建請求方法的實例，并指定請求URL。如果需要發送GET請求，創建HttpGet對象；如果需要發送POST請求，創建HttpPost對象，HttpPost httpPost = new HttpPost(url)。
3.?如果需要發送請求參數，可調用HttpGet、HttpPost共同的setParams(HetpParams params)方法來添加請求參數；對于HttpPost對象而言，也可調用setEntity(HttpEntity entity)方法來設置請求參數。List valuePairs = new LinkedList();valuePairs.add(new BasicNameValuePair(entry.getKey(),entry.getValue()))；httpPost.setEntity(formEntity)。
4.?調用HttpClient對象的execute(HttpUriRequest request)發送請求，該方法返回一個HttpResponse。
5.?調用HttpResponse的getAllHeaders()、getHeaders(String name)等方法可獲取服務器的響應頭；調用HttpResponse的getEntity()方法可獲取HttpEntity對象，該對象包裝了服務器的響應內容。程序可通過該對象獲取服務器的響應內容。
6.?釋放連接。無論執行方法是否成功，都必須釋放連接
httpClient實例：
實例一：
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請求失敗，uri{},exception{}");
}catch(IOException e){
System.out.println("http請求失敗，uri{},exception{}");
}
return null;
}
}
實例二：
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獲取異常");
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不能為空！");
}
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;
}
}
