HTTPClient和CloseableHttpClient

╰半夏微凉° 2023-10-02 19:32 16阅读 0赞

使用HttpClient发送请求的一般步骤  
(1) 创建HttpClient对象。  
(2)创建请求方法的实例，并指定请求URL。如果需要发送GET请求，创建HttpGet对象；如果需要发送POST请求，创建HttpPost对象。  
(3) 如果需要发送请求参数，可调用HttpGet同的setParams(HetpParams params)方法来添加请求参数；对于HttpPost对象而言，可调用setEntity(HttpEntity entity)方法来设置请求参数。  
(4) 调用HttpClient对象的execute(HttpUriRequest request)发送请求，该方法返回一个HttpResponse。  
(5) 调用HttpResponse的getAllHeaders()、getHeaders(String name)等方法可获取服务器的响应头；调用HttpResponse的getEntity()方法可获取HttpEntity对象，该对象包装了服务器的响应内容。程序可通过该对象获取服务器的响应内容。  
(6) 释放连接。无论执行方法是否成功，都必须释放连接

下面分别介绍使用HTTPClient和CloseableHTTPClient进行Get和Post请求的方式。

### HttpClient ###

使用commons-httpclient.jar，maven依赖如下：

<dependency>
          <groupId>commons-httpclient</groupId>
          <artifactId>commons-httpclient</artifactId>
          <version>3.1</version>
        </dependency>

java示例代码如下：

package com.example.study.demo.http;
     
    import org.apache.commons.httpclient.HttpClient;
    import org.apache.commons.httpclient.methods.GetMethod;
    import org.apache.commons.httpclient.methods.PostMethod;
     
    import java.io.IOException;
     
    /**
     * HttpClient使用示例
     * jar包：commons-httpclient.jar
     */
    public class HttpClientTest {
        
      private static void doGet() {
        
        HttpClient client = new HttpClient();
        GetMethod getMethod = new GetMethod("https://www.thepaper.cn/");
        int code = 0;
        try {
        
          code = client.executeMethod(getMethod);
          if (code == 200) {
        
            String res = getMethod.getResponseBodyAsString();
            System.out.println(res);
          }
        } catch (IOException e) {
        
          e.printStackTrace();
        }
      }
     
      private static void doPost() {
        
        String praiseUrl = "https://www.thepaper.cn/www/commentPraise.msp"; // 澎湃新闻评论点赞url
        HttpClient client = new HttpClient();
        PostMethod postMethod = new PostMethod(praiseUrl);
        // 必须设置下面这个Header
        postMethod.addRequestHeader("User-Agent", "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/58.0.3029.81 Safari/537.36");
        postMethod.addParameter("commentId", "18718372"); // 评论的id，抓包获得
        try {
        
          int code = client.executeMethod(postMethod);
          if (code == 200) {
        
            String res = postMethod.getResponseBodyAsString();
            System.out.println(res);
          }
        } catch (IOException e) {
        
          e.printStackTrace();
        }
      }
     
      public static void main(String[] args) {
        
        doGet();
        System.out.println("-----------分割线------------");
        System.out.println("-----------分割线------------");
        System.out.println("-----------分割线------------");
        doPost();
      }
    }

### CloseableHttpClient ###

使用httpclient.jar，maven依赖如下：

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

java示例代码如下：

package com.example.study.demo.http;
     
    import org.apache.http.HttpResponse;
    import org.apache.http.NameValuePair;
    import org.apache.http.client.ClientProtocolException;
    import org.apache.http.client.entity.UrlEncodedFormEntity;
    import org.apache.http.client.methods.HttpGet;
    import org.apache.http.client.methods.HttpPost;
    import org.apache.http.impl.client.CloseableHttpClient;
    import org.apache.http.impl.client.HttpClientBuilder;
    import org.apache.http.message.BasicNameValuePair;
    import org.apache.http.protocol.HTTP;
    import org.apache.http.util.EntityUtils;
     
    import java.io.IOException;
    import java.io.UnsupportedEncodingException;
    import java.util.ArrayList;
    import java.util.List;
     
    /**
     * CloseableHttpClient使用示例
     * jar包：httpclient.jar
     */
    public class CloseableHttpClientTest {
        
     
      public static void doGet() {
        
        CloseableHttpClient client = HttpClientBuilder.create().build();
        HttpGet get = new HttpGet("http://www.thepaper.cn");
        try {
        
          // 很奇怪，使用CloseableHttpClient来请求澎湃新闻的首页，GTE请求也必须加上下面这个Header，但是使用HTTPClient则不需要
          get.addHeader("User-Agent", "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/58.0.3029.81 Safari/537.36");
          HttpResponse response = client.execute(get);
          String res = EntityUtils.toString(response.getEntity());
          System.out.println(res);
        } catch (IOException e) {
        
          e.printStackTrace();
        }
      }
     
      public static void doPost() {
        
        CloseableHttpClient client = HttpClientBuilder.create().build();
        HttpPost post = new HttpPost("https://www.thepaper.cn/www/commentPraise.msp");
        try {
        
          post.addHeader("User-Agent", "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/58.0.3029.81 Safari/537.36");
          List<NameValuePair> params = new ArrayList<>();
          params.add(new BasicNameValuePair("commentId", "18718372"));
          post.setEntity(new UrlEncodedFormEntity(params, HTTP.UTF_8));
          HttpResponse response = client.execute(post);
          String res = EntityUtils.toString(response.getEntity());
          System.out.println(res);
        } catch (UnsupportedEncodingException e) {
        
          e.printStackTrace();
        } catch (ClientProtocolException e) {
        
          e.printStackTrace();
        } catch (IOException e) {
        
          e.printStackTrace();
        }
      }
     
     
      public static void main(String[] args) {
        
        doGet();
        System.out.println("-----------分割线------------");
        System.out.println("-----------分割线------------");
        System.out.println("-----------分割线------------");
        doPost();
     
      }
    }