HttpClient

1、介绍

　　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。

2、功能

（1）实现了所有 HTTP 的方法（GET,POST,PUT,HEAD 等）

（2）支持自动转向

（3）支持 HTTPS 协议

（4）支持代理服务器等

3、导入依赖

        <!-- httpclient -->
        <dependency>
            <groupId>org.apache.httpcomponents</groupId>
            <artifactId>httpclient</artifactId>
        </dependency>

4、使用方法

（1）执行get请求

@Test
    public void doGet() throws Exception {
        //创建一个httpclient对象
        CloseableHttpClient httpClient = HttpClients.createDefault();
        //创建一个GET对象
        HttpGet get = new HttpGet("http://www.baidu.com");
        //执行请求
        CloseableHttpResponse response = httpClient.execute(get);
        //取响应的结果
        int statusCode = response.getStatusLine().getStatusCode();
        System.out.println(statusCode);
        HttpEntity entity = response.getEntity();
        String string = EntityUtils.toString(entity, "utf-8");
        System.out.println(string);
        //关闭httpclient
        response.close();
        httpClient.close();
    }

（2）执行带参数的get请求

public void doGetWithParam() throws Exception{
        //创建一个httpclient对象
        CloseableHttpClient httpClient = HttpClients.createDefault();
        //创建一个uri对象
        URIBuilder uriBuilder = new URIBuilder("http://www.sogou.com/web");
        uriBuilder.addParameter("query", "李白");
        HttpGet get = new HttpGet(uriBuilder.build());
        //执行请求
        CloseableHttpResponse response = httpClient.execute(get);
        //取响应的结果
        int statusCode = response.getStatusLine().getStatusCode();
        System.out.println(statusCode);
        HttpEntity entity = response.getEntity();
        String string = EntityUtils.toString(entity, "utf-8");
        System.out.println(string);
        //关闭httpclient
        response.close();
        httpClient.close();
    }

（3）执行post请求

public void doPost() throws Exception {
        CloseableHttpClient httpClient = HttpClients.createDefault();
        //创建一个post对象
        HttpPost post = new HttpPost("http://localhost:8088/httpclient/post.html");
        //执行post请求
        CloseableHttpResponse response = httpClient.execute(post);
        String string = EntityUtils.toString(response.getEntity());
        System.out.println(string);
        response.close();
        httpClient.close();
    }

（4）执行带参数的post请求

@Test
    public void doPostWithParam() throws Exception{
        CloseableHttpClient httpClient = HttpClients.createDefault();       
        //创建一个post对象
        HttpPost post = new HttpPost("http://localhost:8088/httpclient/post.html");
        //创建一个Entity
        List<NameValuePair> kcList = new ArrayList<>();
        kcList.add(new BasicNameValuePair("username", "lisi"));
        kcList.add(new BasicNameValuePair("password", "123456"));      
        //包装成一个Entity对象
        StringEntity entity = new UrlEncodedFormEntity(kcList, "utf-8");
        //设置请求的内容
        post.setEntity(entity);     
        //执行post请求
        CloseableHttpResponse response = httpClient.execute(post);
        String string = EntityUtils.toString(response.getEntity());
        System.out.println(string);
        response.close();
        httpClient.close();
    }