客户端编程工具包 HttpClient

一、介绍

HttpClient 是 Apache Jakarta Common 下的子项目，可以用来提供高效的、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

1、作用

发送 HTTP 请求
接收响应数据

2、应用场景

当我们在使用扫描支付、查看地图、获取验证码、查看天气等功能时
其实，应用程序本身并未实现这些功能，都是在应用程序里访问提供这些功能的服务，访问这些服务需要发送 HTTP 请求，并且接收响应数据，可通过 HttpClient 来实现

3、核心 API

HttpClient：Http 客户端对象类型，使用该类型对象可发起 Http 请求
HttpClients：可认为是构建器，可创建 HttpClient 对象
CloseableHttpClient：实现类，实现了 HttpClient 接口
HttpGet：Get 方式请求类型
HttpPost：Post 方式请求类型

4、请求步骤

创建 HttpClient 对象
创建 Http 请求对象
调用 HttpClient 的 execute 方法发送请求

二、编码使用

1、导入 Maven 坐标

xml 复制代码

<dependency>
    <groupId>com.aliyun.oss</groupId>
    <artifactId>aliyun-sdk-oss</artifactId>
</dependency>

2、发送 Get 请求

步骤：

创建HttpClient对象
创建请求对象
发送请求，接受响应结果
解析结果
关闭资源

编码：

java 复制代码

@SpringBootTest
public class HttpClientTest {

    /**
     * 测试httpclient发送GET方式的请求
     */
    @Test
    public void testGET() throws Exception{
        //1.创建httpclient对象
        CloseableHttpClient httpClient = HttpClients.createDefault();

        //2.创建请求对象
        HttpGet httpGet = new HttpGet("http://localhost:8080/test");

        //3.发送请求，接受响应结果
        CloseableHttpResponse response = httpClient.execute(httpGet);

        //4.解析结果
        int statusCode = response.getStatusLine().getStatusCode();
        System.out.println("服务端返回的状态码为：" + statusCode);

        HttpEntity entity = response.getEntity();
        String body = EntityUtils.toString(entity);
        System.out.println("服务端返回的数据为：" + body);

        //5.关闭资源
        response.close();
        httpClient.close();
    }
}

3、发送 Post 请求

步骤：

创建HttpClient对象
创建请求对象
发送请求，接受响应结果
解析结果
关闭资源

编码：

java 复制代码

@SpringBootTest
public class HttpClientTest {

    /**
     * 测试httpclient发送POST方式的请求
     */
    @Test
    public void testPOST() throws Exception{
        //1.创建httpclient对象
        CloseableHttpClient httpClient = HttpClients.createDefault();

        //2.创建请求对象
        HttpPost httpPost = new HttpPost("http://localhost:8080/test");

        JSONObject jsonObject = new JSONObject();
        jsonObject.put("username","admin");
        jsonObject.put("password","123456");

        StringEntity entity = new StringEntity(jsonObject.toString());
        //指定请求编码方式
        entity.setContentEncoding("utf-8");
        //数据格式
        entity.setContentType("application/json");
        httpPost.setEntity(entity);

        //3.发送请求
        CloseableHttpResponse response = httpClient.execute(httpPost);

        //4.解析返回结果
        int statusCode = response.getStatusLine().getStatusCode();
        System.out.println("响应码为：" + statusCode);

        HttpEntity entity1 = response.getEntity();
        String body = EntityUtils.toString(entity1);
        System.out.println("响应数据为：" + body);

        //5.关闭资源
        response.close();
        httpClient.close();
    }
}

三、封装 HttpClientUtil 工具类

java 复制代码

/**
 * Http工具类
 */
public class HttpClientUtil {

    static final int TIMEOUT_MSEC = 5 * 1000;

    /**
     * 发送GET方式请求
     * @param url
     * @param paramMap
     * @return
     */
    public static String doGet(String url,Map<String,String> paramMap){
        // 创建Httpclient对象
        CloseableHttpClient httpClient = HttpClients.createDefault();

        String result = "";
        CloseableHttpResponse response = null;

        try{
            URIBuilder builder = new URIBuilder(url);
            if(paramMap != null){
                for (String key : paramMap.keySet()) {
                    builder.addParameter(key,paramMap.get(key));
                }
            }
            URI uri = builder.build();

            //创建GET请求
            HttpGet httpGet = new HttpGet(uri);

            //发送请求
            response = httpClient.execute(httpGet);

            //判断响应状态
            if(response.getStatusLine().getStatusCode() == 200){
                result = EntityUtils.toString(response.getEntity(),"UTF-8");
            }
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            try {
                response.close();
                httpClient.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

        return result;
    }

    /**
     * 发送POST方式请求
     * @param url
     * @param paramMap
     * @return
     * @throws IOException
     */
    public static String doPost(String url, Map<String, String> paramMap) throws IOException {
        // 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 (paramMap != null) {
                List<NameValuePair> paramList = new ArrayList();
                for (Map.Entry<String, String> param : paramMap.entrySet()) {
                    paramList.add(new BasicNameValuePair(param.getKey(), param.getValue()));
                }
                // 模拟表单
                UrlEncodedFormEntity entity = new UrlEncodedFormEntity(paramList);
                httpPost.setEntity(entity);
            }

            httpPost.setConfig(builderRequestConfig());

            // 执行http请求
            response = httpClient.execute(httpPost);

            resultString = EntityUtils.toString(response.getEntity(), "UTF-8");
        } catch (Exception e) {
            throw e;
        } finally {
            try {
                response.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

        return resultString;
    }

    /**
     * 发送POST方式请求
     * @param url
     * @param paramMap
     * @return
     * @throws IOException
     */
    public static String doPost4Json(String url, Map<String, String> paramMap) throws IOException {
        // 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);

            if (paramMap != null) {
                //构造json格式数据
                JSONObject jsonObject = new JSONObject();
                for (Map.Entry<String, String> param : paramMap.entrySet()) {
                    jsonObject.put(param.getKey(),param.getValue());
                }
                StringEntity entity = new StringEntity(jsonObject.toString(),"utf-8");
                //设置请求编码
                entity.setContentEncoding("utf-8");
                //设置数据类型
                entity.setContentType("application/json");
                httpPost.setEntity(entity);
            }

            httpPost.setConfig(builderRequestConfig());

            // 执行http请求
            response = httpClient.execute(httpPost);

            resultString = EntityUtils.toString(response.getEntity(), "UTF-8");
        } catch (Exception e) {
            throw e;
        } finally {
            try {
                response.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

        return resultString;
    }
    private static RequestConfig builderRequestConfig() {
        return RequestConfig.custom()
                .setConnectTimeout(TIMEOUT_MSEC)
                .setConnectionRequestTimeout(TIMEOUT_MSEC)
                .setSocketTimeout(TIMEOUT_MSEC).build();
    }

}