HttpClient技术

1.什么是HttpClient?

2.HttpClient特点?

特点：

2.1. 基于标准、纯净的Java语言。实现了Http1.0和Http1.1

2.2. 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）。

2.3. 支持HTTPS协议。

2.4. 通过Http代理建立透明的连接。

2.5. 自动处理Set-Cookie中的Cookie。

3.HttpClient作用?

其主要作用就是通过Http协议，向某个URL地址发起请求，并且获取响应结果。

4.关于httpclient的工具类：

@Service
public class ApiService {

    // 创建Httpclient对象
    @Autowired(required=false)
    private CloseableHttpClient httpclient;

    /**
     * 无参的GET请求
     * @param url
     * @return
     * @throws Exception
     * @throws IOException
     */
    public String doGet(String url) throws Exception, IOException{

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

        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 data = EntityUtils.toString(response.getEntity(), "UTF-8");
                return data;
            }
        } finally {
            if (response != null) {
                response.close();
            }
        }
        return null;
    }    

    // 创建Httpclient对象  模拟浏览器发起访问  打开浏览器

    public HttpclientResult doPost(String url) throws ClientProtocolException, IOException{

        // 创建http POST请求  输入地址
        HttpPost httpPost = new HttpPost(url);

        httpPost.setHeader("User-Agent", "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/60.0.3112.113 Safari/537.36");
        CloseableHttpResponse response = null;
        try {
            // 执行请求   敲回车
            response = httpclient.execute(httpPost);
            // 判断返回状态是否为201
            Integer code = response.getStatusLine().getStatusCode();
            if (code == 201) {
                String data = EntityUtils.toString(response.getEntity(), "UTF-8");

                HttpclientResult result = new HttpclientResult(code, data);

                return result;
            }
        } finally {
            if (response != null) {
                response.close();
            }
        }
        return null;
    }

    /**
     * 有参GET
     * @param url
     * @return
     * @throws Exception
     * @throws IOException
     */
    public String doGetParam(String url,Map<String,String> params) throws Exception, IOException{

        // 定义请求的参数
        URIBuilder uriBuilder = new URIBuilder(url);

        if(params!=null && !params.isEmpty()){
            for(String key:params.keySet()){
                uriBuilder.setParameter(key, params.get(key));
           }
        }

        URI uri = uriBuilder.build();

        // 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 data = EntityUtils.toString(response.getEntity(), "UTF-8");
                return data;
            }
        } finally {
            if (response != null) {
                response.close();
            }
        }
        return null;
    }    

    /**
     * 有参post
     * @param url
     * @return
     * @throws ClientProtocolException
     * @throws IOException
     */
    public HttpclientResult doPostParam(String url,Map<String,String> params) throws ClientProtocolException, IOException{

        // 创建http POST请求  输入地址
        HttpPost httpPost = new HttpPost(url);

        if(params!=null&&!params.isEmpty()){
            List<NameValuePair> parameters = new ArrayList<NameValuePair>(0);
             for (String key : params.keySet()) {
                 parameters.add(new BasicNameValuePair(key, params.get(key)));
             }
             // 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);
        }

//        模拟浏览器访问
        httpPost.setHeader("User-Agent", "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/60.0.3112.113 Safari/537.36");

//   调用接口访问对象

        CloseableHttpResponse response = null;
        try {
            // 执行请求   敲回车
            response = httpclient.execute(httpPost);
            // 判断返回状态是否为201
            Integer code = response.getStatusLine().getStatusCode();
            String data = EntityUtils.toString(response.getEntity(), "UTF-8");

           HttpclientResult result = new HttpclientResult(code, data);

           return result;

        } finally {
            if (response != null) {
                response.close();
            }
        }

    }
}