httpclient介绍与使用

什么是httpclient
　　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/
使用范例

public class HttpClientTest {
    @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.sogou.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);//返回200
        HttpEntity entity = response.getEntity();
        String string = EntityUtils.toString(entity, "utf-8");
        System.out.println(string);//返回sogou主页的页面代码
        //关闭httpclient
        response.close();
        httpClient.close();
    }
    @Test
    public void doGetWithParam() throws Exception{
        CloseableHttpClient httpClient = HttpClients.createDefault();
        //创建一个uri对象
        URIBuilder uriBuilder = new URIBuilder("http://www.sogou.com/web");
        uriBuilder.addParameter("query", "花千骨");
        HttpGet get = new HttpGet(uriBuilder.build());
        CloseableHttpResponse response = httpClient.execute(get);
        int statusCode = response.getStatusLine().getStatusCode();
        System.out.println(statusCode);
        HttpEntity entity = response.getEntity();
        String string = EntityUtils.toString(entity, "utf-8");
        System.out.println(string);
        response.close();
        httpClient.close();
    }
    @Test
    public void doPost() throws Exception {
        CloseableHttpClient httpClient = HttpClients.createDefault();
        //创建一个post对象
        HttpPost post = new HttpPost("http://localhost:8082/httpclient/post.action");
        //执行post请求
        CloseableHttpResponse response = httpClient.execute(post);
        String string = EntityUtils.toString(response.getEntity());
        System.out.println(string);
        response.close();
        httpClient.close();
    }
    @Test
    public void doPostWithParam() throws Exception{
        CloseableHttpClient httpClient = HttpClients.createDefault();
        //创建一个post对象  
        HttpPost post = new HttpPost("http://localhost:8082/httpclient/post.action");
        //创建一个Entity。模拟一个表单
        List<NameValuePair> kvList = new ArrayList<>();
        kvList.add(new BasicNameValuePair("username", "张三"));
        kvList.add(new BasicNameValuePair("password", "123"));
        //包装成一个Entity对象 
        StringEntity entity = new UrlEncodedFormEntity(kvList, "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();
    }
}

 封装工具类

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) {
                e.printStackTrace();
            }
        }
        return resultString;
    }
    public static String doPost(String url) {
        return doPost(url, null);
    }
    public static String doPostJson(String url, String json) {
        // 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);
            // 创建请求内容
            StringEntity entity = new StringEntity(json, ContentType.APPLICATION_JSON);
            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) {
                e.printStackTrace();
            }
        }
        return resultString;
    }
}