HttpClient使用详解

本文转载：http://blog.csdn.net/wangpeng047/article/details/19624529

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。
使用httpclient相关功能，在pom.xml中配置：
<!-- https://mvnrepository.com/artifact/org.apache.httpcomponents/httpclient -->

        <dependency>

            <groupId>org.apache.httpcomponents</groupId>

            <artifactId>httpclient</artifactId>

            <version>4.5.2</version>

        </dependency>

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(HttpParams 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

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.ap
ce5d
ache.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();  

            }  

        }  

    } 

该版本的httpclient与commons下的httpclient的代码写法风格相差较大，大家多留意下。