Http协议的重要性相信不用我多说了，HttpClient相比传统JDK自带的URLConnection，增加了易用性和灵活性（具体区别，日后我们再讨论），它不仅是客户端发送Http请求变得容易，而且也方便了开发人员测试接口（基于Http协议的），即提高了开发的效率，也方便提高代码的健壮性。因此熟练掌握HttpClient是很重要的必修内容，掌握HttpClient后，相信对于Http协议的了解会更加深入。

org.apache.commons.httpclient.HttpClient与org.apache.http.client.HttpClient的区别

Commons的HttpClient项目现在是生命的尽头，不再被开发,

已被Apache HttpComponents项目HttpClient和的HttpCore

模组取代，提供更好的性能和更大的灵活性。

一、简介

HttpClient是Apache Jakarta Common下的子项目，用来提供高效的、最新的、功能丰富的支持HTTP协议的客户端编程工具包，并且它支持HTTP协议最新的版本和建议。HttpClient已经应用在很多的项目中，比如Apache Jakarta上很著名的另外两个开源项目Cactus和HTMLUnit都使用了HttpClient。

下载地址: http://hc.apache.org/downloads.cgi

二、特性

1. 基于标准、纯净的java语言。实现了Http1.0和Http1.1

2. 以可扩展的面向对象的结构实现了Http全部的方法（GET, POST, PUT, DELETE, HEAD, OPTIONS, and TRACE）。

3. 支持HTTPS协议。

4. 通过Http代理建立透明的连接。

5. 利用CONNECT方法通过Http代理建立隧道的https连接。

6. Basic, Digest, NTLMv1, NTLMv2, NTLM2 Session, SNPNEGO/Kerberos认证方案。

7. 插件式的自定义认证方案。

8. 便携可靠的套接字工厂使它更容易的使用第三方解决方案。

9. 连接管理器支持多线程应用。支持设置最大连接数，同时支持设置每个主机的最大连接数，发现并关闭过期的连接。

10. 自动处理Set-Cookie中的Cookie。

11. 插件式的自定义Cookie策略。

12. Request的输出流可以避免流中内容直接缓冲到socket服务器。

13. Response的输入流可以有效的从socket服务器直接读取相应内容。

14. 在http1.0和http1.1中利用KeepAlive保持持久连接。

15. 直接获取服务器发送的response code和 headers。

16. 设置连接超时的能力。

17. 实验性的支持http1.1 response caching。

18. 源代码基于Apache License 可免费获取。

三、使用方法

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。

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。

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。

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

四、实例

主要用到的包：

package com.test;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.security.KeyManagementException;
import java.security.KeyStore;
import java.security.KeyStoreException;
import java.security.NoSuchAlgorithmException;
import java.security.cert.CertificateException;
import java.util.ArrayList;
import java.util.List;
import javax.net.ssl.SSLContext;
import org.apache.http.HttpEntity;
import org.apache.http.NameValuePair;
import org.apache.http.ParseException;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.entity.UrlEncodedFormEntity;
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.conn.ssl.SSLConnectionSocketFactory;
import org.apache.http.conn.ssl.SSLContexts;
import org.apache.http.conn.ssl.TrustSelfSignedStrategy;
import org.apache.http.entity.ContentType;
import org.apache.http.entity.mime.MultipartEntityBuilder;
import org.apache.http.entity.mime.content.FileBody;
import org.apache.http.entity.mime.content.StringBody;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.util.EntityUtils;
import org.apache.http.client.config.RequestConfig;
import org.junit.Test;
public class HttpClientTest {
　　//方法见下........
}

HttpClientUtils工具类

package com.bobo.code.web.controller.technology.httpcomponents;

import org.apache.http.HttpEntity;
import org.apache.http.HttpHost;
import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.HttpClient;
import org.apache.http.client.config.RequestConfig;
import org.apache.http.client.methods.HttpUriRequest;
import org.apache.http.client.methods.RequestBuilder;
import org.apache.http.conn.routing.HttpRoute;
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;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.util.EntityUtils;

import java.io.IOException;
import java.util.*;

public class HttpClientUtils {

private static PoolingHttpClientConnectionManager connectionManager = null;
private static HttpClientBuilder httpBuilder = null;
private static RequestConfig requestConfig = null;

private static int MAXCONNECTION = 10;

private static int DEFAULTMAXCONNECTION = 5;

private static String IP = "cnivi.com.cn";
private static int PORT = 80;

static {
//设置http的状态参数
requestConfig = RequestConfig.custom()
.setSocketTimeout(5000)
.setConnectTimeout(5000)
.setConnectionRequestTimeout(5000)
.build();

HttpHost target = new HttpHost(IP, PORT);
connectionManager = new PoolingHttpClientConnectionManager();
connectionManager.setMaxTotal(MAXCONNECTION);//客户端总并行链接最大数
connectionManager.setDefaultMaxPerRoute(DEFAULTMAXCONNECTION);//每个主机的最大并行链接数
connectionManager.setMaxPerRoute(new HttpRoute(target), 20);
httpBuilder = HttpClients.custom();
httpBuilder.setConnectionManager(connectionManager);
}

public static CloseableHttpClient getConnection() {
CloseableHttpClient httpClient = httpBuilder.build();
return httpClient;
}

public static HttpUriRequest getRequestMethod(Map<String, String> map, String url, String method) {
List<NameValuePair> params = new ArrayList<NameValuePair>();
Set<Map.Entry<String, String>> entrySet = map.entrySet();
for (Map.Entry<String, String> e : entrySet) {
String name = e.getKey();
String value = e.getValue();
NameValuePair pair = new BasicNameValuePair(name, value);
params.add(pair);
}
HttpUriRequest reqMethod = null;
if ("post".equals(method)) {
reqMethod = RequestBuilder.post().setUri(url)
.addParameters(params.toArray(new BasicNameValuePair[params.size()]))
.setConfig(requestConfig).build();
} else if ("get".equals(method)) {
reqMethod = RequestBuilder.get().setUri(url)
.addParameters(params.toArray(new BasicNameValuePair[params.size()]))
.setConfig(requestConfig).build();
}
return reqMethod;
}

public static void main(String args[]) throws IOException {
Map<String, String> map = new HashMap<String, String>();
map.put("account", "");
map.put("password", "");

HttpClient client = getConnection();
HttpUriRequest post = getRequestMethod(map, "http://cnivi.com.cn/login", "post");
HttpResponse response = client.execute(post);

if (response.getStatusLine().getStatusCode() == 200) {
HttpEntity entity = response.getEntity();
String message = EntityUtils.toString(entity, "utf-8");
System.out.println(message);
} else {
System.out.println("请求失败");
}
}
}

get方式

/**
* 发送 get请求
*/
public void get() {
CloseableHttpClient httpclient = HttpClients.createDefault();
try {
// 创建httpget.
HttpGet httpget = new HttpGet("http://www.baidu.com/");
System.out.println("executing request " + httpget.getURI());
// 执行get请求.
CloseableHttpResponse response = httpclient.execute(httpget);
try {
// 获取响应实体
HttpEntity entity = response.getEntity();
System.out.println("--------------------------------------");
// 打印响应状态
System.out.println(response.getStatusLine());
if (entity != null) {
// 打印响应内容长度
System.out.println("Response content length: " + entity.getContentLength());
// 打印响应内容
System.out.println("Response content: " + EntityUtils.toString(entity));
}
System.out.println("------------------------------------");
} finally {
response.close();
}
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (ParseException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
// 关闭连接,释放资源
try {
httpclient.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}

post方式

/**
* 发送 post请求访问本地应用并根据传递参数不同返回不同结果
*/
public void post() {
// 创建默认的httpClient实例.
CloseableHttpClient httpclient = HttpClients.createDefault();
// 创建httppost
HttpPost httppost = new HttpPost("http://localhost:8080/myDemo/Ajax/serivceJ.action");
// 创建参数队列
List<NameValuePair> formparams = new ArrayList<NameValuePair>();
formparams.add(new BasicNameValuePair("type", "house"));
UrlEncodedFormEntity uefEntity;
try {
uefEntity = new UrlEncodedFormEntity(formparams, "UTF-8");
httppost.setEntity(uefEntity);
System.out.println("executing request " + httppost.getURI());
CloseableHttpResponse response = httpclient.execute(httppost);
try {
HttpEntity entity = response.getEntity();
if (entity != null) {
System.out.println("--------------------------------------");
System.out.println("Response content: " + EntityUtils.toString(entity, "UTF-8"));
System.out.println("--------------------------------------");
}
} finally {
response.close();
}
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (UnsupportedEncodingException e1) {
e1.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
// 关闭连接,释放资源
try {
httpclient.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}

post方式乱码补充　

如果有乱码,可以偿试使用 StringEntity 来替换HttpEntity:

StringEntity content =new StringEntity(soapRequestData.toString(), Charset.forName("UTF-8"));// 第二个参数，设置后才会对，内容进行编码
content.setContentType("application/soap+xml; charset=UTF-8");
content.setContentEncoding("UTF-8");
httppost.setEntity(content);

具体SOAP协议代码如下:

package com.isoftstone.core.service.impl;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.nio.charset.Charset;
import java.util.Scanner;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.HttpClient;
import org.apache.http.client.entity.EntityBuilder;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.entity.ContentType;
import org.apache.http.entity.StringEntity;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;
import org.apache.log4j.Logger;
import org.jdom.Document;
import org.jdom.Element;

import com.isoftstone.core.common.constant.RequestConstants;
import com.isoftstone.core.common.tools.XmlTool;
import com.isoftstone.core.service.intf.ServiceOfStringPara;
/**
* 德勤定价系统,由核心主动调用
* @author King
*
*/
public class DeloittePricingSingleCarImpl implements ServiceOfStringPara {
private String serviceUrl = "http://10.30.0.35:7001/ZSInsUW/Auto/PricingService";

private static Logger log = Logger.getLogger(DeloittePricingSingleCarImpl.class.getName());

public String invoke(String sRequest) {

StringBuffer soapRequestData = new StringBuffer();
soapRequestData.append("<soapenv:Envelope");
soapRequestData.append(" xmlns:soapenv=\"http://schemas.xmlsoap.org/soap/envelope/\" ");
soapRequestData.append(" xmlns:prov=\"http://provider.webservice.zsins.dtt.com/\">");
soapRequestData.append(" <soapenv:Header/> ");
soapRequestData.append("<soapenv:Body>");
soapRequestData.append("<prov:executePrvPricing>");
soapRequestData.append("<arg0>");
soapRequestData.append("<![CDATA[" + sRequest + "]]>");
soapRequestData.append("</arg0>");
soapRequestData.append("</prov:executePrvPricing>");
soapRequestData.append(" </soapenv:Body>");
soapRequestData.append("</soapenv:Envelope>");

HttpClient httpclient = HttpClients.createDefault();
HttpPost httppost = new HttpPost(serviceUrl);

StringEntity content =new StringEntity(soapRequestData.toString(), Charset.forName("UTF-8"));// 第二个参数，设置后才会对，内容进行编码
content.setContentType("application/soap+xml; charset=UTF-8");
content.setContentEncoding("UTF-8");
httppost.setEntity(content);

//用下面的服务器端以UTF-8接收到的报文会乱码,原因未知
// HttpEntity reqEntity = EntityBuilder.create().setContentType(
// ContentType.TEXT_PLAIN) // .TEXT_PLAIN
// .setText(soapRequestData.toString()).build();
// httppost.setEntity(reqEntity);
// httppost.addHeader("Content-Type",
// "application/soap+xml; charset=utf-8");
HttpResponse response = null;
Document doc = null;
String returnXml = null;
String sentity = null;
try {
response = httpclient.execute(httppost);
HttpEntity resEntity = response.getEntity();
if (resEntity != null) {
sentity = EntityUtils.toString(resEntity, "UTF-8");
doc = XmlTool.getDocument(sentity, RequestConstants.ENCODE);
System.out.println(doc.toString());
Element eRoot = doc.getRootElement();
Element body = eRoot.getChild("Body", eRoot.getNamespace());
Element resp = (Element) body.getChildren().get(0);
Element returnele = resp.getChild("return");
returnXml = returnele.getText().toString();
}
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
} finally {
log.info("发送给德勤定价系统的请求报文：\n" + soapRequestData.toString());
log.info("德勤定价系统返回的响应报文：\n" + sentity);
log.info("返回给核心的的报文:\n" + returnXml);
}
return returnXml;
}

public String getServiceUrl() {
return serviceUrl;
}

public void setServiceUrl(String serviceUrl) {
this.serviceUrl = serviceUrl;
}

public static void main(String[] args) throws Exception{
File file = new File("D:/浙商项目资料/z浙江资料/t唐建华/德勤定价调试报文.txt");
System.out.println(file.exists());

String temp2 = null;
StringBuilder sb2 = new StringBuilder();
InputStreamReader isr = new InputStreamReader(new FileInputStream(file),"GBK");
BufferedReader br = new BufferedReader(isr);
temp2 = br.readLine();

while( temp2 != null ){
sb2.append(temp2);
temp2 = br.readLine();
}
String sss = sb2.toString();
// System.out.println(sss.toString());
new DeloittePricingSingleCarImpl().invoke(sss);
}
}

post提交表单

/**
* post方式提交表单（模拟用户登录请求）
*/
public void postForm() {
// 创建默认的httpClient实例.
CloseableHttpClient httpclient = HttpClients.createDefault();
// 创建httppost
HttpPost httppost = new HttpPost("http://localhost:8080/myDemo/Ajax/serivceJ.action");
// 创建参数队列
List<NameValuePair> formparams = new ArrayList<NameValuePair>();
formparams.add(new BasicNameValuePair("username", "admin"));
formparams.add(new BasicNameValuePair("password", "123456"));
UrlEncodedFormEntity uefEntity;
try {
uefEntity = new UrlEncodedFormEntity(formparams, "UTF-8");
httppost.setEntity(uefEntity);
System.out.println("executing request " + httppost.getURI());
CloseableHttpResponse response = httpclient.execute(httppost);
try {
HttpEntity entity = response.getEntity();
if (entity != null) {
System.out.println("--------------------------------------");
System.out.println("Response content: " + EntityUtils.toString(entity, "UTF-8"));
System.out.println("--------------------------------------");
}
} finally {
response.close();
}
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (UnsupportedEncodingException e1) {
e1.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
// 关闭连接,释放资源
try {
httpclient.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}

文件上传

/**
* 上传文件
*/
public void upload() {
CloseableHttpClient httpclient = HttpClients.createDefault();
try {
HttpPost httppost = new HttpPost("http://localhost:8080/myDemo/Ajax/serivceFile.action");

FileBody bin = new FileBody(new File("F:\\image\\sendpix0.jpg"));
StringBody comment = new StringBody("A binary file of some kind", ContentType.TEXT_PLAIN);

HttpEntity reqEntity = MultipartEntityBuilder.create().addPart("bin", bin).addPart("comment", comment).build();

httppost.setEntity(reqEntity);

System.out.println("executing request " + httppost.getRequestLine());
CloseableHttpResponse response = httpclient.execute(httppost);
try {
System.out.println("----------------------------------------");
System.out.println(response.getStatusLine());
HttpEntity resEntity = response.getEntity();
if (resEntity != null) {
System.out.println("Response content length: " + resEntity.getContentLength());
}
EntityUtils.consume(resEntity);
} finally {
response.close();
}
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
httpclient.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}

ssl连接

/**
* HttpClient连接SSL
*/
public void ssl() {
CloseableHttpClient httpclient = null;
try {
KeyStore trustStore = KeyStore.getInstance(KeyStore.getDefaultType());
FileInputStream instream = new FileInputStream(new File("d:\\tomcat.keystore"));
try {
// 加载keyStore d:\\tomcat.keystore
trustStore.load(instream, "123456".toCharArray());
} catch (CertificateException e) {
e.printStackTrace();
} finally {
try {
instream.close();
} catch (Exception ignore) {
}
}
// 相信自己的CA和所有自签名的证书
SSLContext sslcontext = SSLContexts.custom().loadTrustMaterial(trustStore, new TrustSelfSignedStrategy()).build();
// 只允许使用TLSv1协议
SSLConnectionSocketFactory sslsf = new SSLConnectionSocketFactory(sslcontext, new String[] { "TLSv1" }, null,
SSLConnectionSocketFactory.BROWSER_COMPATIBLE_HOSTNAME_VERIFIER);
httpclient = HttpClients.custom().setSSLSocketFactory(sslsf).build();
// 创建http请求(get方式)
HttpGet httpget = new HttpGet("https://localhost:8443/myDemo/Ajax/serivceJ.action");
System.out.println("executing request" + httpget.getRequestLine());
CloseableHttpResponse response = httpclient.execute(httpget);
try {
HttpEntity entity = response.getEntity();
System.out.println("----------------------------------------");
System.out.println(response.getStatusLine());
if (entity != null) {
System.out.println("Response content length: " + entity.getContentLength());
System.out.println(EntityUtils.toString(entity));
EntityUtils.consume(entity);
}
} finally {
response.close();
}
} catch (ParseException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (KeyManagementException e) {
e.printStackTrace();
} catch (NoSuchAlgorithmException e) {
e.printStackTrace();
} catch (KeyStoreException e) {
e.printStackTrace();
} finally {
if (httpclient != null) {
try {
httpclient.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}

关于RequestConfig的配置:

public void requestConfig(){
// 新建一个RequestConfig：
RequestConfig defaultRequestConfig = RequestConfig.custom()
//一、连接目标服务器超时时间：ConnectionTimeout-->指的是连接一个url的连接等待时间
.setConnectTimeout(5000)
//二、读取目标服务器数据超时时间：SocketTimeout-->指的是连接上一个url，获取response的返回等待时间
.setSocketTimeout(5000)
//三、从连接池获取连接的超时时间:ConnectionRequestTimeout
.setConnectionRequestTimeout(5000)
.build();

// 这个超时可以设置为客户端级别,作为所有请求的默认值：
CloseableHttpClient httpclient = HttpClients.custom()
.setDefaultRequestConfig(defaultRequestConfig)
.build();
// httpclient.execute(httppost);的时候可以让httppost直接享受到httpclient中的默认配置.

// Request不会继承客户端级别的请求配置，所以在自定义Request的时候，需要将客户端的默认配置拷贝过去：
HttpGet httpget = new HttpGet("http://www.apache.org/");
RequestConfig requestConfig = RequestConfig.copy(defaultRequestConfig)
.setProxy(new HttpHost("myotherproxy", 8080))
.build();
httpget.setConfig(requestConfig);
// httpget可以单独地使用新copy的requestConfig请求配置,不会对别的request请求产生影响
} httpGet或httpPost 的abort()和releaseConnection()差异

根所以上差异,可知模拟登录可以如下: 源自 http://bbs.csdn.net/topics/390195343

package com.bms.core;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

import org.apache.http.Consts;
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.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.util.EntityUtils;

import com.bms.util.CommonUtil;

public class Test2 {

/**
* @param args
* @throws IOException
* @throws ClientProtocolException
*/
public static void main(String[] args) throws ClientProtocolException, IOException {
DefaultHttpClient httpclient = new DefaultHttpClient();

HttpGet httpGet = new HttpGet("http://www.baidu.com");
String body = "";
HttpResponse response;
HttpEntity entity;
response = httpclient.execute(httpGet);
entity = response.getEntity();
body = EntityUtils.toString(entity);//这个就是页面源码了
httpGet.abort();//中断请求,接下来可以开始另一段请求
System.out.println(body);
//httpGet.releaseConnection();//释放请求.如果释放了相当于要清空session
//以下是post方法
HttpPost httpPost = new HttpPost("http://www.baidu.com");//一定要改成可以提交的地址,这里用百度代替
List <NameValuePair> nvps = new ArrayList <NameValuePair>();
nvps.add(new BasicNameValuePair("name", "1"));//名值对
nvps.add(new BasicNameValuePair("account", "xxxx"));
httpPost.setEntity(new UrlEncodedFormEntity(nvps, Consts.UTF_8));
response = httpclient.execute(httpPost);
entity = response.getEntity();
body = EntityUtils.toString(entity);
System.out.println("Login form get: " + response.getStatusLine());//这个可以打印状态
httpPost.abort();
System.out.println(body);
httpPost.releaseConnection();
}

} 转载：https://blog.csdn.net/zhuwukai/article/details/78644484