使用CloseableHttpClient 模擬發送HttpGet和HttpPost請求

項目中經常會用到模擬Http請求，而jdk 下的 rt.jar核心庫中也有 java.net提供了這方面的功能，但是總體而言，功能還是缺少靈活性和全面性，HttpClient的出現就是彌補了其缺失的功能。HttpClient不是瀏覽器客戶端，而是一個客戶端和服務端實現通信的Http組件庫。本篇文章主要講解CloseableHttpClient 的使用。

1. 項目中添加依賴的jar包

        <dependency>
            <groupId>org.apache.httpcomponents</groupId>
            <artifactId>httpclient</artifactId>
            <version>4.5.5</version>
            <exclusions>
                <exclusion>
                    <artifactId>commons-codec</artifactId>
                    <groupId>commons-codec</groupId>
                </exclusion>
            </exclusions>
        </dependency>

2. 上代碼，代碼中詳細介紹每個部分的作用

2.1 模擬HttpGet請求 

/**
 * 模擬HttpGet 請求
 * @param url
 * @return
 */
public static String HttpGet(String url){
    //單位毫秒
    RequestConfig requestConfig = RequestConfig.custom()
        .setConnectionRequestTimeout(3000).setConnectTimeout(3000)
        .setSocketTimeout(3000).build();//設置請求的狀態參數

    CloseableHttpClient httpclient = HttpClients.createDefault();//創建 CloseableHttpClient 
    HttpGet httpGet = new HttpGet(url);
    httpGet.setConfig(requestConfig);

    CloseableHttpResponse response = null;
    try {
        response = httpclient.execute(httpGet);//返回請求執行結果
        int statusCode = response.getStatusLine().getStatusCode();//獲取返回的狀態值
        if (statusCode != HttpStatus.SC_OK) {
            return null;
        } else {
            String result = EntityUtils.toString(response.getEntity(), "UTF-8");
            return result;
        }
    } catch (Exception e) {
        logger.error("httpget Exception handle-- > " + e);
    } finally {
        if (response != null){
            try {
                response.close();//關閉response
            } catch (IOException e) {
                logger.error("httpget IOException handle-- > " + e);
            }
        }
        if(httpclient != null){
            try {
                httpclient.close();//關閉httpclient
            } catch (IOException e) {
                logger.error("httpget IOException handle-- > " + e);
            }
        }
    }
    return null;
}

2.2 模擬HttpPost請求

/**
 * 模擬HttpPost請求
 * @param url
 * @param jsonString
 * @return
 */
public static String HttpPost(String url, String jsonString){
    CloseableHttpResponse response = null;
    CloseableHttpClient httpClient = HttpClientBuilder.create().build();//創建CloseableHttpClient
    HttpPost httpPost = new HttpPost(url);//實現HttpPost
    RequestConfig requestConfig = RequestConfig.custom().setSocketTimeout(3000).setConnectTimeout(3000).build();
    httpPost.setConfig(requestConfig); //設置httpPost的狀態參數
    httpPost.addHeader("Content-Type", "application/json");//設置httpPost的請求頭中的MIME類型爲json
    StringEntity requestEntity = new StringEntity(jsonString, "utf-8");
    httpPost.setEntity(requestEntity);//設置請求體
    try {
        response = httpClient.execute(httpPost, new BasicHttpContext());//執行請求返回結果
        if (response.getStatusLine().getStatusCode() != HttpStatus.SC_OK) {
            return null;
        }
        HttpEntity entity = response.getEntity();
        if (entity != null) {
            String resultStr = EntityUtils.toString(entity, "utf-8");
            return resultStr;
        } else {
            return null;
        }
    } catch (Exception e) {
        logger.error("httpPost method exception handle-- > " + e);
        return null;
    } finally {
        if (response != null){
            try {
                response.close();//最後關閉response
            } catch (IOException e) {
                logger.error("httpPost method IOException handle -- > " + e);
            }
        }if(httpClient != null){try {httpClient.close();} catch (IOException e) {logger.error("httpPost method exception handle-- > " + e);}
        }
    }
}