HttpClient使用详解

2016/06/29 13:23
阅读数 546

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。

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

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();    
                }    
            }    
        }    
    }    
    
    /** 
     * 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();    
            }    
        }    
    }    
    
    /** 
     * 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();    
            }    
        }    
    }    
    
    /** 
     * 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();    
            }    
        }    
    }    
    
    /** 
     * 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。该版本与之前的代码写法风格相差较大,大家多留意下。

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