做接口测试时，Http接口是最常见的一种接口类型，我们经常需要基于HttpClient包去发送get/post请求对Http接口进行测试。

1.HttpClient的maven配置：

            <dependency>
                <groupId>org.apache.httpcomponents</groupId>
                <artifactId>httpclient</artifactId>
                <version>4.5.3</version>
            </dependency>

2.通过HttpClient发送get请求：

public static String doGet(String uri, HashMap<String, String> headerMap) throws Exception {

        HttpClient client = HttpClients.createDefault();

        HttpGet request = new HttpGet(new URI(uri));

        // set header
        if (null != headerMap && headerMap.size() > 0) {
            for (String key : headerMap.keySet()) {
                request.setHeader(key, headerMap.get(key));
            }
        }

        HttpResponse response = client.execute(request);
        // 这里可以通过statusCode进行一些判断
        // response.getStatusLine().getStatusCode();
        HttpEntity entity = response.getEntity();
        String res = "";

        if (entity != null) {
            res = EntityUtils.toString(entity, "utf-8");
            EntityUtils.consume(entity);
        }

        return res;
}

public String getWeatherCities() {
        String res = "";
        try {
            res = HttpService.doGet("http://www.webxml.com.cn/WebServices/WeatherWebService.asmx/getSupportCity?byProvinceName=江苏");
        } catch (Exception e) {
            e.printStackTrace();
        }

        System.out.println(res);
        return res;
}

执行getWeatherCities()，打印返回值：

3.通过HttpClient发送Post请求，带参数

   /**
     * @return
     */
    public static String doPost(String uri, HashMap<String, String> params, HashMap<String, String> headerMap) throws Exception {
        HttpClient client = HttpClients.createDefault();

        HttpPost request = new HttpPost(new URI(uri));
        // set header
        if (null != headerMap && headerMap.size() > 0) {
            for (String key : headerMap.keySet()) {
                request.setHeader(key, headerMap.get(key));
            }
        }

        // set entity
        if (null != params && params.size() > 0) {

            List<NameValuePair> pairs = new ArrayList<NameValuePair>();
            for (String key : params.keySet()) {
                NameValuePair pair = new BasicNameValuePair(key, params.get(key));
                pairs.add(pair);
            }

            HttpEntity entity = new UrlEncodedFormEntity(pairs, "utf-8");

            request.setEntity(entity);
        }

        HttpResponse response = client.execute(request);
        // 这里可以通过statusCode进行一些判断
        // response.getStatusLine().getStatusCode();
        HttpEntity entity = response.getEntity();
        String res = "";

        if (entity != null) {
            res = EntityUtils.toString(entity, "utf-8");
            EntityUtils.consume(entity);
        }

        return res;
    }

    public String postWeatherCities() {
        String res = "";

        HashMap<String, String> paramMap = new HashMap<String, String>();
        paramMap.put("byProvinceName", "江苏");

        try {
            res = HttpService.doPost("http://www.webxml.com.cn/WebServices/WeatherWebService.asmx/getSupportCity", paramMap, null);
        } catch (Exception e) {
            e.printStackTrace();
        }

        System.out.println(res);
        return res;
    }

执行postWeatherCities，正确打印返回值：

总结下：
1、首先创建HttpClient对象
2、创建HttpGet/HttpPost对象，并设置header和entity，其中Post方法通过entity传入参数
3、HttpClient对象调用execute方法，传入HttpGet/HttpPost对象
4、返回HttpResponse对象，对entity的值进行处理获取返回值内容