java發起http請求

使用HttpClient發送請求的一般步驟如下：
(1) 創建HttpClient對象。
(2) 創建請求方法的實例，並指定請求URL。如果需要發送GET請求，創建HttpGet對象；如果需要發送POST請求，創建HttpPost對象。
(3) 如果需要發送請求參數，可調用HttpGet對象的setParams(HetpParams params)方法來添加請求參數；對於HttpPost對象而言，可調用setEntity(HttpEntity entity)方法來設置請求參數。
(4) 調用HttpClient對象的execute(HttpUriRequest request)發送請求，該方法返回一個HttpResponse。
(5) 調用HttpResponse的getAllHeaders()、getHeaders(String name)等方法可獲取服務器的響應頭；調用HttpResponse的getEntity()方法可獲取HttpEntity對象，該對象包裝了服務器的響應內容。程序可通過該對象獲取服務器的響應內容。
(6) 釋放連接。無論執行方法是否成功，都必須釋放連接。

有兩種依賴包，commons和apache依賴包，選擇其中一種即可。以下是混用的，僅做參考即可。
引入工具依賴包如下：

<!-- commons-httpclient http請求工具依賴包 -->
<dependency>
    <groupId>commons-httpclient</groupId>
    <artifactId>commons-httpclient</artifactId>
    <version>3.1</version>
</dependency>
<!-- apache http請求工具依賴包 -->
<dependency>
    <groupId>org.apache.httpcomponents</groupId>
    <artifactId>httpclient</artifactId>
    <version>4.3.6</version>
</dependency>

方法如下所示：

import lombok.extern.slf4j.Slf4j;
import org.apache.commons.httpclient.HttpClient;
import org.apache.commons.httpclient.methods.PostMethod;
import org.apache.commons.httpclient.params.HttpMethodParams;
import org.apache.commons.lang.ArrayUtils;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.HttpStatus;
import org.apache.commons.httpclient.NameValuePair;
import org.apache.http.client.config.RequestConfig;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.entity.StringEntity;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;

import java.io.IOException;
import java.util.*;

@Slf4j
public class HttpClientTest {
    /**
     * 發起post請求 沒有任何body參數的情況
     *
     * @param url  請求的目標url地址
     * @param data 請求數據
     * @return 將響應結果轉換成string返回
     * @throws IOException 可能出現的異常
     */
    private static String postMsg(String url, String data) throws IOException {
        // 根據url地址發起post請求
        HttpPost httppost = new HttpPost(url);

        StringEntity stEntity;

        // 獲取到httpclient客戶端
        CloseableHttpClient httpclient = HttpClients.createDefault();
        try {
            // 設置請求的一些頭部信息
            httppost.addHeader("Content-Type", "application/json");
            httppost.addHeader("procode", "test");
            stEntity = new StringEntity(data, "UTF-8");
            httppost.setEntity(stEntity);
            // 設置請求的一些配置設置，主要設置請求超時，連接超時等參數
            RequestConfig requestConfig = RequestConfig.custom()
                .setConnectTimeout(5000).setConnectionRequestTimeout(1000).setSocketTimeout(5000)
                .build();
            httppost.setConfig(requestConfig);
            // 執行請求
            CloseableHttpResponse response = httpclient.execute(httppost);
            // 請求結果
            String resultString = "";
            if (response.getStatusLine().getStatusCode() == HttpStatus.SC_OK) {
                log.info("請求狀態：{}", response.getStatusLine().getStatusCode());
                // 獲取請求響應結果
                HttpEntity entity = response.getEntity();
                if (entity != null) {
                    // 將響應內容轉換為指定編碼的字符串
                    resultString = EntityUtils.toString(entity, "UTF-8");
                    log.info("Response content:{}", resultString);
                    return resultString;
                }
            } else {
                log.info("請求失敗！");
                return resultString;
            }
        } catch (Exception e) {
            throw e;
        } finally {
            httpclient.close();
        }
        return null;
    }

    /**
     * body有內容的post請求方法 controller可以用bean直接接收參數
     *
     * @param url      目標地址
     * @param params   封裝的參數
     * @param codePage 字符編碼
     * @return 將響應結果轉換成string返回
     * @throws Exception 可能出現的異常
     */
    private synchronized static String postData(String url, Map<String, String> params, String codePage) throws Exception {
        HttpClient httpClient = new HttpClient();
        // 請求相關超時時間設置
        httpClient.getHttpConnectionManager().getParams().setConnectionTimeout(10 * 1000);
        httpClient.getHttpConnectionManager().getParams().setSoTimeout(10 * 1000);

        PostMethod method = new PostMethod(url);
        if (params != null) {
            // 內容編碼設置
            method.getParams().setParameter(HttpMethodParams.HTTP_CONTENT_CHARSET, codePage);
            // 請求體信息設置
            method.setRequestBody(assembleRequestParams(params));
            // 請求頭設置
            method.setRequestHeader("procode", "test");
        }

        // 響應結果信息處理
        String result = "";
        try {
            httpClient.executeMethod(method);
            result = new String(method.getResponseBody(), codePage);
        } catch (Exception e) {
            throw e;
        } finally {
            // 釋放連接
            method.releaseConnection();
        }
        return result;
    }

    /**
     * 組裝http請求參數
     *
     * @param data 鍵值對
     * @return 返回一個名稱-值的鍵值對
     */
    private synchronized static NameValuePair[] assembleRequestParams(Map<String, String> data) {
        List<NameValuePair> nameValueList = new ArrayList<>();

        Iterator<Map.Entry<String, String>> it = data.entrySet().iterator();
        while (it.hasNext()) {
            Map.Entry<String, String> entry = it.next();
            nameValueList.add(new NameValuePair(entry.getKey(), entry.getValue()));
        }

        log.info("鍵值對參數：{}", ArrayUtils.toString(nameValueList.toArray(new NameValuePair[nameValueList.size()])));

        return nameValueList.toArray(new NameValuePair[nameValueList.size()]);
    }

    /**
     * get請求
     *
     * @param url 目標請求地址
     * @return 將響應結果轉換成string返回
     */
    private static String get(String url) {
        String result = "";
        try {
            // 根據地址獲取請求
            HttpGet request = new HttpGet(url);
            request.setHeader("procode", "test");

            // 獲取當前客戶端對
            CloseableHttpClient httpclient = HttpClients.createDefault();
            // 通過請求對象獲取響應對象
            HttpResponse response = httpclient.execute(request);
            // 判斷請求結果狀態碼
            if (response.getStatusLine().getStatusCode() == HttpStatus.SC_OK) {
                result = EntityUtils.toString(response.getEntity());
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        return result;
    }


    public static void main(String[] args) throws Exception {
        String url = "http://localhost:8080/sales-webapp/admin/report/smslist";
        // 發起post請求
        String resultPost = postMsg(url, "1");
        log.info("post返回結果：{}", resultPost);

        // 發起get請求
        String resultGet = get(url);
        log.info("get返回結果：{}", resultGet);

        // 測試body有參數的post方法
        Map<String, String> map = new HashMap<>(16);
        map.put("age", "13");
        map.put("name", "jason");
        String resultPostHaveBody = postData(url, map, "UTF-8");
        log.info("post帶有body請求返回結果：{}", resultPostHaveBody);
    }
}

參考博文：
（1） https://blog.csdn.net/q394895302/article/details/90256482 （講的清晰明了，分開講述兩種依賴包發get和post請求）
（2） https://blog.csdn.net/u014429653/article/details/106985970 （代碼清晰）