HttpClient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

所需JAR

<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>3.8.1</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.apache.httpcomponents</groupId>
<artifactId>httpcore</artifactId>
<version>4.4.6</version>
</dependency>
<dependency>
<groupId>org.apache.httpcomponents</groupId>
<artifactId>httpclient</artifactId>
<version>4.5.3</version>
</dependency>
<dependency>
<groupId>org.apache.httpcomponents</groupId>
<artifactId>httpmime</artifactId>
<version>4.5.2</version>
</dependency>

package cn.com.demo;

import java.io.File;
import java.net.URL;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;

import org.apache.http.HttpEntity;
import org.apache.http.NameValuePair;
import org.apache.http.client.config.RequestConfig;
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.DefaultHostnameVerifier;
import org.apache.http.conn.util.PublicSuffixMatcher;
import org.apache.http.conn.util.PublicSuffixMatcherLoader;
import org.apache.http.entity.ContentType;
import org.apache.http.entity.StringEntity;
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;

public class HttpClientUtil {
    private RequestConfig requestConfig = RequestConfig.custom().setSocketTimeout(15000).setConnectTimeout(15000)
            .setConnectionRequestTimeout(15000).build();
    // 单例模式
    private static HttpClientUtil instance = null;

    private HttpClientUtil() {
    }

    public static HttpClientUtil getInstance() {
        if (instance == null) {
            instance = new HttpClientUtil();
        }
        return instance;
    }

    /**
     * 发送 post请求
     * 
     * @param httpUrl
     *            地址
     */
    public String sendHttpPost(String httpUrl) {
        HttpPost httpPost = new HttpPost(httpUrl);// 创建httpPost
        return sendHttpPost(httpPost);
    }

    /**
     * 发送 post请求
     * 
     * @param httpUrl
     *            地址
     * @param params
     *            参数(格式:key1=value1&key2=value2)
     */
    public String sendHttpPost(String httpUrl, String params) {
        HttpPost httpPost = new HttpPost(httpUrl);
        try {
            StringEntity stringEntity = new StringEntity(params, "UTF-9=8");
            stringEntity.setContentType("application/x-www-form-urlencoded");
            httpPost.setEntity(stringEntity);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return sendHttpPost(httpPost);
    }

    /**
     * 发送 post请求
     * 
     * @param httpUrl
     *            地址
     * @param maps
     *            参数
     */
    public String sendHttpPost(String httpUrl, Map<String, String> maps) {
        HttpPost httpPost = new HttpPost(httpUrl);
        // 创建参数队列
        List<NameValuePair> nameValuePairs = new ArrayList<>();
        for (String key : maps.keySet()) {
            nameValuePairs.add(new BasicNameValuePair(key, maps.get(key)));
        }
        try {
            httpPost.setEntity(new UrlEncodedFormEntity(nameValuePairs, "UTF-8"));
        } catch (Exception e) {
            e.printStackTrace();
        }
        return sendHttpPost(httpPost);
    }

    /**
     * 发送 post请求（带文件）
     * 
     * @param httpUrl
     *            地址
     * @param maps
     *            参数
     * @param fileLists
     *            附件
     */
    public String sendHttpPost(String httpUrl, Map<String, String> maps, List<File> fileLists) {
        HttpPost httpPost = new HttpPost(httpUrl);
        MultipartEntityBuilder meBuilder = MultipartEntityBuilder.create();
        for (String key : maps.keySet()) {
            meBuilder.addPart(key, new StringBody(maps.get(key), ContentType.TEXT_PLAIN));
        }
        for (File file : fileLists) {
            FileBody fileBody = new FileBody(file);
            meBuilder.addPart("files", fileBody);
        }
        HttpEntity reqEntity = meBuilder.build();
        httpPost.setEntity(reqEntity);
        return sendHttpPost(httpPost);
    }

    /**
     * 发送Post请求
     * 
     * @param httpPost
     * @return
     */
    private String sendHttpPost(HttpPost httpPost) {
        CloseableHttpClient httpClient = null;
        CloseableHttpResponse response = null;
        HttpEntity entity = null;
        String responseContent = null;
        try {
            // 创建默认的httpClient实例
            httpClient = HttpClients.createDefault();
            httpPost.setConfig(requestConfig);
            // 执行请求
            response = httpClient.execute(httpPost);
            entity = response.getEntity();
            responseContent = EntityUtils.toString(entity, "UTF-8");
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                if (response != null) {
                    response.close();
                }
                if (httpClient != null) {
                    httpClient.close();
                }
            } catch (Exception e2) {
                e2.printStackTrace();
            }
        }
        return responseContent;
    }

    /**
     * 发送 get请求
     * 
     * @param httpUrl
     */
    public String sendHttpGet(String httpUrl) {
        HttpGet httpGet = new HttpGet(httpUrl);
        return sendHttpGet(httpGet);
    }

    /**
     * 发送 get请求Https
     * 
     * @param httpUrl
     */
    public String sendHttpsGet(String httpUrl) {
        HttpGet httpGet = new HttpGet(httpUrl);
        return sendHttpGet(httpGet);
    }

    /**
     * 发送Get请求
     * 
     * @param httpPost
     * @return
     */
    public String sendHttpGet(HttpGet httpGet) {
        CloseableHttpClient httpClient = null;
        CloseableHttpResponse response = null;
        HttpEntity entity = null;
        String responseContent = null;
        try {
            // 创建默认的httpClient实例
            httpClient = HttpClients.createDefault();
            httpGet.setConfig(requestConfig);
            // 执行请求
            response = httpClient.execute(httpGet);
            entity = response.getEntity();
            responseContent = EntityUtils.toString(entity, "UTF-8");
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                if (response != null) {
                    response.close();
                }
                if (httpClient != null) {
                    httpClient.close();
                }
            } catch (Exception e2) {
                e2.printStackTrace();
            }
        }
        return responseContent;
    }

    /**
     * 发送Get请求Https
     * 
     * @param httpPost
     * @return
     */
    private String sendHttpsGet(HttpGet httpGet) {
        CloseableHttpClient httpClient = null;
        CloseableHttpResponse response = null;
        HttpEntity entity = null;
        String responseContent = null;
        try {
            // 创建默认的httpClient实例
            PublicSuffixMatcher publicSuffixMatcher = PublicSuffixMatcherLoader
                    .load(new URL(httpGet.getURI().toString()));
            DefaultHostnameVerifier hostnameVerifier = new DefaultHostnameVerifier(publicSuffixMatcher);
            httpClient = HttpClients.custom().setSSLHostnameVerifier(hostnameVerifier).build();
            httpGet.setConfig(requestConfig);
            // 执行请求
            response = httpClient.execute(httpGet);
            entity = response.getEntity();
            responseContent = EntityUtils.toString(entity, "UTF-8");
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                if (response != null) {
                    response.close();
                }
                if (httpClient != null) {
                    httpClient.close();
                }
            } catch (Exception e2) {
                e2.printStackTrace();
            }
        }
        return responseContent;
    }
}

package cn.com.demo;

import java.io.File;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.junit.Test;

public class HttpClientUtilTest {
    @Test
    public void testSendHttpPost1() {
        String responseContent = HttpClientUtil.getInstance()
                .sendHttpPost("http://192.168.1.83:9090/manage!login?phone=1&password=1");
        System.out.println("response Content" + responseContent);
    }

    @Test
    public void testSendHttpPost2() {
        String responseContent = HttpClientUtil.getInstance().sendHttpPost("http://localhost:8089/test/send",
                "username=test01&password=123456");
        System.out.println("reponse content:" + responseContent);
    }

    @Test
    public void testSendHttpPost3() {
        Map<String, String> maps = new HashMap<String, String>();
        maps.put("username", "test01");
        maps.put("password", "123456");
        String responseContent = HttpClientUtil.getInstance().sendHttpPost("http://localhost:8089/test/send", maps);
        System.out.println("reponse content:" + responseContent);
    }

    @Test
    public void testSendHttpPost4() {
        Map<String, String> maps = new HashMap<String, String>();
        maps.put("username", "test01");
        maps.put("password", "123456");
        List<File> fileLists = new ArrayList<File>();
        fileLists.add(new File("D://test//httpclient//1.png"));
        fileLists.add(new File("D://test//httpclient//1.txt"));
        String responseContent = HttpClientUtil.getInstance().sendHttpPost("http://localhost:8089/test/sendpost/file",
                maps, fileLists);
        System.out.println("reponse content:" + responseContent);
    }

    @Test
    public void testSendHttpGet() {
        String responseContent = HttpClientUtil.getInstance()
                .sendHttpGet("http://localhost:8089/test/send?username=test01&password=123456");
        System.out.println("reponse content:" + responseContent);
    }

    @Test
    public void testSendHttpsGet() {
        String responseContent = HttpClientUtil.getInstance().sendHttpsGet("https://www.baidu.com");
        System.out.println("reponse content:" + responseContent);
    }
}