淘淘商城之httpclient

一、什么是httpclient

  HTTP 协议可能是现在 Internet 上使用得最多、最重要的协议了，越来越多的 Java 应用程序需要直接通过 HTTP 协议
  来访问网络资源；虽然在 JDK 的 java net包中已经提供了访问 HTTP 协议的基本功能，但是对于大部分应用程序来说，
  JDK 库本身提供的功能还不够丰富和灵活；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
      下载地址：http://hc.apache.org/

二、功能介绍

　以下列出的是 HttpClient 提供的主要的功能
　　（1）实现了所有 HTTP 的方法
　　（2）支持自动转向
　　（3）支持 HTTPS 协议
　　（4）支持代理服务器等
  要知道更多详细的功能可以参见 HttpClient 的主页

三、导入依赖

<dependency>
    <groupId>org.apache.httpcomponents</groupId>
    <artifactId>httpclient</artifactId>
    <version>${httpclient.version}</version>
</dependency>

四、用法示例

　  （1）执行get请求

public class DoGET {
    public static void main(String[] args) throws Exception {
        //创建Httpclient对象
        CloseableHttpClient httpclient = HttpClients.createDefault();
        //创建http GET请求
        HttpGet httpGet = new HttpGet("http://www.baidu.com/");
        CloseableHttpResponse response = null;
        try {
            //执行请求
            response = httpclient.execute(httpGet);
            //判断返回状态是否为200
            if (response.getStatusLine().getStatusCode() == 200) {
                String content = EntityUtils.toString(response.getEntity(), "UTF-8");
                System.out.println("内容长度：" + content.length());
                //FileUtils.writeStringToFile(new File("C:\\baidu.html"), content);
            }
        } finally {
            if (response != null) {
                response.close();
            }
            httpclient.close();
        }
    }
}

　  （2）执行带参数的get请求

public class DoGETParam {
    public static void main(String[] args) throws Exception {
        //创建Httpclient对象
        CloseableHttpClient httpclient = HttpClients.createDefault();
        //定义请求的参数
        URI uri = new URIBuilder("http://www.baidu.com/s").setParameter("wd", "java").build();
        System.out.println(uri);

        //创建http GET请求
        HttpGet httpGet = new HttpGet(uri);
        CloseableHttpResponse response = null;
        try {
            //执行请求
            response = httpclient.execute(httpGet);
            //判断返回状态是否为200
            if (response.getStatusLine().getStatusCode() == 200) {
                String content = EntityUtils.toString(response.getEntity(), "UTF-8");
                System.out.println(content);
            }
        } finally {
            if (response != null) {
                response.close();
            }
            httpclient.close();
        }
    }
}

　  （3）执行post请求

public class DoPOST {
    public static void main(String[] args) throws Exception {
        //创建Httpclient对象
        CloseableHttpClient httpclient = HttpClients.createDefault();

        //创建http POST请求
        HttpPost httpPost = new HttpPost("http://www.oschina.net/");

        CloseableHttpResponse response = null;
        try {
            //执行请求
            response = httpclient.execute(httpPost);
            //判断返回状态是否为200
            if (response.getStatusLine().getStatusCode() == 200) {
                String content = EntityUtils.toString(response.getEntity(), "UTF-8");
                System.out.println(content);
            }
        } finally {
            if (response != null) {
                response.close();
            }
            httpclient.close();
        }
    }
}

　  （4）执行带参数的post请求

public class DoPOSTParam {
    public static void main(String[] args) throws Exception {
        //创建Httpclient对象
        CloseableHttpClient httpclient = HttpClients.createDefault();

        //创建http POST请求
        HttpPost httpPost = new HttpPost("http://www.oschina.net/search");

        //设置2个post参数，一个是scope、一个是q
        List<NameValuePair> parameters = new ArrayList<NameValuePair>(0);
        parameters.add(new BasicNameValuePair("scope", "project"));
        parameters.add(new BasicNameValuePair("q", "java"));
        //构造一个form表单式的实体
        UrlEncodedFormEntity formEntity = new UrlEncodedFormEntity(parameters);
        //将请求实体设置到httpPost对象中
        httpPost.setEntity(formEntity);

        CloseableHttpResponse response = null;
        try {
            //执行请求
            response = httpclient.execute(httpPost);
            //判断返回状态是否为200
            if (response.getStatusLine().getStatusCode() == 200) {
                String content = EntityUtils.toString(response.getEntity(), "UTF-8");
                System.out.println(content);
            }
        } finally {
            if (response != null) {
                response.close();
            }
            httpclient.close();
        }
    }
}

　  （5）封装HttpClient通用工具类

public class HttpClientUtil {

    public static String doGet(String url, Map<String, String> param) {

        // 创建Httpclient对象
        CloseableHttpClient httpclient = HttpClients.createDefault();

        String resultString = "";
        CloseableHttpResponse response = null;
        try {
            // 创建uri
            URIBuilder builder = new URIBuilder(url);
            if (param != null) {
                for (String key : param.keySet()) {
                    builder.addParameter(key, param.get(key));
                }
            }
            URI uri = builder.build();

            // 创建http GET请求
            HttpGet httpGet = new HttpGet(uri);

            // 执行请求
            response = httpclient.execute(httpGet);
            // 判断返回状态是否为200
            if (response.getStatusLine().getStatusCode() == 200) {
                resultString = EntityUtils.toString(response.getEntity(), "UTF-8");
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                if (response != null) {
                    response.close();
                }
                httpclient.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return resultString;
    }

    public static String doGet(String url) {
        return doGet(url, null);
    }

    public static String doPost(String url, Map<String, String> param) {
        // 创建Httpclient对象
        CloseableHttpClient httpClient = HttpClients.createDefault();
        CloseableHttpResponse response = null;
        String resultString = "";
        try {
            // 创建Http Post请求
            HttpPost httpPost = new HttpPost(url);
            // 创建参数列表
            if (param != null) {
                List<NameValuePair> paramList = new ArrayList<>();
                for (String key : param.keySet()) {
                    paramList.add(new BasicNameValuePair(key, param.get(key)));
                }
                // 模拟表单
                UrlEncodedFormEntity entity = new UrlEncodedFormEntity(paramList);
                httpPost.setEntity(entity);
            }
            // 执行http请求
            response = httpClient.execute(httpPost);
            resultString = EntityUtils.toString(response.getEntity(), "utf-8");
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                response.close();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }

        return resultString;
    }

    public static String doPost(String url) {
        return doPost(url, null);
    }
}