HttpClient使用详解
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，增长了易用性和灵活性（具体区别，往后咱们再讨论），它不只是客户端发送Http请求变得容易，并且也方便了开发人员测试接口（基于Http协议的），即提升了开发的效率，也方便提升代码的健壮性。所以熟练掌握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刻。java
1、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，而且它支持HTTP协议最新的版本和建议。HttpClient已经应用在不少的项目中，好比Apache Jakarta上很著名的另外两个开源项目Cactus和HTMLUnit都使用了HttpClient。apache
下载地址: http://hc.apache.org/downloads.cgi编程
2、特性
1. 基于标准、纯净的Java语言。实现了Http1.0和Http1.1tomcat
2. 以可扩展的面向对象的结构实现了Http所有的方法（GET, POST, PUT, DELETE, HEAD, OPTIONS, and TRACE）。服务器
3. 支持HTTPS协议。多线程
4. 经过Http代理创建透明的链接。socket
5. 利用CONNECT方法经过Http代理创建隧道的https链接。工具
6. Basic, Digest, NTLMv1, NTLMv2, NTLM2 Session, SNPNEGO/Kerberos认证方案。post
7. 插件式的自定义认证方案。测试
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. 链接管理器支持多线程应用。支持设置最大链接数，同时支持设置每一个主机的最大链接数，发现并关闭过时的链接。
10. 自动处理Set-Cookie中的Cookie。
11. 插件式的自定义Cookie策略。
12. Request的输出流能够避免流中内容直接缓冲到socket服务器。
13. Response的输入流能够有效的从socket服务器直接读取相应内容。
14. 在http1.0和http1.1中利用KeepAlive保持持久链接。
15. 直接获取服务器发送的response code和 headers。
16. 设置链接超时的能力。
17. 实验性的支持http1.1 response caching。
18. 源代码基于Apache License 可免费获取。
3、使用方法
使用HttpClient发送请求、接收响应很简单，通常须要以下几步便可。
1. 建立HttpClient对象。
2. 建立请求方法的实例，并指定请求URL。若是须要发送GET请求，建立HttpGet对象；若是须要发送POST请求，建立HttpPost对象。
3. 若是须要发送请求参数，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。程序可经过该对象获取服务器的响应内容。
6. 释放链接。不管执行方法是否成功，都必须释放链接
4、实例
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.junit.Test;
public class HttpClientTest {
@Test
public void jUnitTest() {
get();
}
/**
* HttpClient链接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) {
}
}
// 相信本身的CA和全部自签名的证书
SSLContext sslcontext = SSLContexts.custom().loadTrustMaterial(trustStore, new TrustSelfSignedStrategy()).build();
// 只容许使用TLSv1协议
SSLConnectionSocketFactory sslsf = new SSLConnectionSocketFactory(sslcontext, new String[] { "TLSv1" }, null,
SSLConnectionSocketFactory.BROWSER_COMPATIBLE_HOSTNAME_VERIFIER);
httpclient = HttpClients.custom().setSSLSocketFactory(sslsf).build();
// 建立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();
}
}
}
}
/**
* post方式提交表单（模拟用户登陆请求）
*/
public void postForm() {
// 建立默认的httpClient实例.
CloseableHttpClient httpclient = HttpClients.createDefault();
// 建立httppost
HttpPost httppost = new HttpPost("http://localhost:8080/myDemo/Ajax/serivceJ.action");
// 建立参数队列
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 {
// 关闭链接,释放资源
try {
httpclient.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
/**
* 发送 post请求访问本地应用并根据传递参数不一样返回不一样结果
*/
public void post() {
// 建立默认的httpClient实例.
CloseableHttpClient httpclient = HttpClients.createDefault();
// 建立httppost
HttpPost httppost = new HttpPost("http://localhost:8080/myDemo/Ajax/serivceJ.action");
// 建立参数队列
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 {
// 关闭链接,释放资源
try {
httpclient.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
/**
* 发送 get请求
*/
public void get() {
CloseableHttpClient httpclient = HttpClients.createDefault();
try {
// 建立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 {
// 关闭链接,释放资源
try {
httpclient.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
/**
* 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();
}
}
}
}
本实例是采用HttpClient4.3最新版本。该版本与以前的代码写法风格相差较大，你们多留意下。
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