HTTPClient模擬Get和Post請求

一.模擬Get請求(無參)

首先導入HttpClient依賴

<dependency>
    <groupId>org.apache.httpcomponents</groupId>
    <artifactId>httpclient</artifactId>
    <version>4.5.2</version>
</dependency>

 

測試代碼

//Get請求
    public static void getRequest() throws IOException {
        //創建一個默認的鏈接
        CloseableHttpClient client = HttpClients.createDefault();
        //創建一個請求
        HttpGet httpGet=new HttpGet("https://www.cnblogs.com/chx9832");
        //執行請求獲取響應的結果
        CloseableHttpResponse response = client.execute(httpGet);
        //獲取響應的狀態碼
        int statusCode = response.getStatusLine().getStatusCode();
        System.out.println("服務器返回狀態碼："+statusCode);
        //服務器正常響應
        if(statusCode ==200){
            //獲取響應結果
            System.out.println(EntityUtils.toString(response.getEntity(),"UTF-8"));
        }
        //關閉結果對象
        response.close();
        //關閉鏈接
        client.close();
    }

通過main方法調用就可拿到目標地址的代碼段

 

 一.模擬Post請求(帶參)

與get請求類似,不同的是帶參需要創建參數隊列,並把參數封裝到請求體再set進請求中.

 

//模擬Post請求
    public static void postRequest() throws IOException {
        //創建鏈接
        CloseableHttpClient client = HttpClients.createDefault();
        //創建請求
        HttpPost httpPost=new HttpPost("http://localhost:8080/HttpClientServlet");

        //創建參數隊列
        List<NameValuePair> pairList=new ArrayList<>();
        pairList.add(new BasicNameValuePair("username","懷鑫"));
        //創建請求體，封裝參數
        UrlEncodedFormEntity entity=new UrlEncodedFormEntity(pairList,"UTF-8");
        //將請求體交給當前請求
        httpPost.setEntity(entity);

        //發送請求,接收結果
        CloseableHttpResponse response = client.execute(httpPost);
        System.out.println("接收到的結果為："+EntityUtils.toString(response.getEntity(),"UTF-8"));


        //關閉資源
        response.close();
        client.close();
    }

 

 

新建一個web項目,創建一個servlet模擬服務器,啟動tomcat等待請求

package com.chx;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

@WebServlet("/HttpClientServlet")
public class HttpClientServlet extends HttpServlet {
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //獲取數據
        String username = req.getParameter("username");
        System.out.println("接收的數據："+username);
        resp.setContentType("text/html;charset=utf-8");
        resp.getWriter().write("服務器正確接收到數據~");
    }

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doPost(req,resp);
    }
}

 

回到post請求方法啟動后執行效果

 

服務器端

 

 

 這樣,就完成了簡單的httpclient的get和post請求...

 

 

 

總結:

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、HttpPost共同的setParams(HttpParams params)方法來添加請求參數；對於HttpPost對象而言，也可調用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