一、概念

      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。
      HttpClient通俗的讲就是模拟了浏览器的行为，如果我们需要在后端向某一地址提交数据获取结果，就可以使用HttpClient。
      关于HttpClient（原生）具体的使用不属于我们本章的学习内容，我们这里这里为了简化HttpClient的使用，提供了工具类HttpClient（对原生HttpClient进行了封装）。

二、HttpClient工具类代码

public class HttpClient {
    private String url;
    private Map<String, String> param;
    private int statusCode;
    private String content;
    private String xmlParam;
    private boolean isHttps;

    public boolean isHttps() {
        return isHttps;
    }

    public void setHttps(boolean isHttps) {
        this.isHttps = isHttps;
    }

    public String getXmlParam() {
        return xmlParam;
    }

    public void setXmlParam(String xmlParam) {
        this.xmlParam = xmlParam;
    }

    public HttpClient(String url, Map<String, String> param) {
        this.url = url;
        this.param = param;
    }

    public HttpClient(String url) {
        this.url = url;
    }

    public void setParameter(Map<String, String> map) {
        param = map;
    }

    public void addParameter(String key, String value) {
        if (param == null)
            param = new HashMap<String, String>();
        param.put(key, value);
    }

    public void post() throws ClientProtocolException, IOException {
        HttpPost http = new HttpPost(url);
        setEntity(http);
        execute(http);
    }

    public void put() throws ClientProtocolException, IOException {
        HttpPut http = new HttpPut(url);
        setEntity(http);
        execute(http);
    }

    public void get() throws ClientProtocolException, IOException {
        if (param != null) {
            StringBuilder url = new StringBuilder(this.url);
            boolean isFirst = true;
            for (String key : param.keySet()) {
                if (isFirst) {
                    url.append("?");
                }else {
                    url.append("&");
                }
                url.append(key).append("=").append(param.get(key));
            }
            this.url = url.toString();
        }
        HttpGet http = new HttpGet(url);
        execute(http);
    }

    /**
     * set http post,put param
     */
    private void setEntity(HttpEntityEnclosingRequestBase http) {
        if (param != null) {
            List<NameValuePair> nvps = new LinkedList<NameValuePair>();
            for (String key : param.keySet()) {
                nvps.add(new BasicNameValuePair(key, param.get(key))); // 参数
            }
            http.setEntity(new UrlEncodedFormEntity(nvps, Consts.UTF_8)); // 设置参数
        }
        if (xmlParam != null) {
            http.setEntity(new StringEntity(xmlParam, Consts.UTF_8));
        }
    }

    private void execute(HttpUriRequest http) throws ClientProtocolException,
            IOException {
        CloseableHttpClient httpClient = null;
        try {
            if (isHttps) {
                SSLContext sslContext = new SSLContextBuilder()
                        .loadTrustMaterial(null, new TrustStrategy() {
                            // 信任所有
                            @Override
                            public boolean isTrusted(X509Certificate[] chain,
                                                     String authType)
                                    throws CertificateException {
                                return true;
                            }
                        }).build();
                SSLConnectionSocketFactory sslsf = new SSLConnectionSocketFactory(
                        sslContext);
                httpClient = HttpClients.custom().setSSLSocketFactory(sslsf)
                        .build();
            } else {
                httpClient = HttpClients.createDefault();
            }
            CloseableHttpResponse response = httpClient.execute(http);
            try {
                if (response != null) {
                    if (response.getStatusLine() != null) {
                        statusCode = response.getStatusLine().getStatusCode();
                    }
                    HttpEntity entity = response.getEntity();
                    // 响应内容
                    content = EntityUtils.toString(entity, Consts.UTF_8);
                }
            } finally {
                response.close();
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            httpClient.close();
        }
    }

    public int getStatusCode() {
        return statusCode;
    }

    public String getContent() throws ParseException, IOException {
        return content;
    }
}

三、HttpClient工具类使用的步骤

1. 导入依赖

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

2. 测试案例

/**
 * @Author TeaBowl
 * @Date 2021/2/1 4:50
 * @Version 1.0
 * HttpClient工具类的使用
 * 作用：发送Http、Https请求
 */
public class HttpClientTest {
    /**
     * 发送Http、Https请求
     *      发送指定参数
     *      可以获取相应的结果
     */
    @Test
    public void testHttpClient() throws IOException {
        //请求地址
        String url = "https://www.cnblogs.com/chawaner/";

        //创建HttpClient对象,对请求地址进行操作
        HttpClient httpClient = new HttpClient(url);

        //创建要发送的xml数据->post
        String xml = "<xml><name>茶碗儿</name></xml>";

        //使用HttpClient对象，设置请求的XML参数
        httpClient.setXmlParam(xml);

        //发送请求
        //设置当前请求为Https
        httpClient.setHttps(true);
        //发送XML数据，使用post请求
        httpClient.post();

        //获取响应数据
        String content = httpClient.getContent();
        System.out.println(content);
    }
}