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【Java爬虫】HttpClient样例

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HttpClient简介

HttpClient是Apache Jakarta Common下的子项目,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。HttpClient已经应用在很多的项目中。
下载地址:https://hc.apache.org/httpclient-legacy/
不过一般在项目中是直接调用pom依赖

<dependency>
  <groupId>org.apache.httpcomponents</groupId>
  <artifactId>httpclient</artifactId>
  <version>4.5.13</version>
</dependency>

一般使用步骤

使用HttpClient发送请求和接收响应一般有以下步骤:

  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、HttpPost共同的setParams(HttpParams params)方法来添加请求参数;对于HttpPost对象而言,也可调用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

发送Get请求

public void httpClientTest() throws Exception{
        CloseableHttpClient httpClient= HttpClients.createDefault();
        //不带参数
        //HttpGet get=new HttpGet("http://www.it.cn");
        //带参数
        HttpGet get=new HttpGet("http://yun.com/course/936.html?capid=1$czpc$jingjiaczpz-PC-1");
        CloseableHttpResponse response=httpClient.execute(get);
        StatusLine statusLine=response.getStatusLine();
        System.out.println(statusLine);
        int statusCode=statusLine.getStatusCode();
        System.out.println(statusCode);
        HttpEntity entity= response.getEntity();
        String html= EntityUtils.toString(entity,"utf-8");
        System.out.println(html);
        response.close();
        httpClient.close();
    }

发送Post请求

public void testPost() throws Exception{
        CloseableHttpClient httpClient=HttpClients.createDefault();
        HttpPost post=new HttpPost("http://yun.com/course/936.html");
        //创建list存放请求表单
        List<NameValuePair>form=new ArrayList<>();
        //较多的提交数据可以增元素
        form.add(new BasicNameValuePair("capid","1$czpc$jingjiaczpz-PC-1"));
       // form.add(new BasicNameValuePair("capid","1$czpc$jingjiaczpz-PC-1"));
        //form.add(new BasicNameValuePair("capid","1$czpc$jingjiaczpz-PC-1"));
        HttpEntity entity=new UrlEncodedFormEntity(form);
        post.setEntity(entity);
        CloseableHttpResponse response= httpClient.execute(post);
        String s = EntityUtils.toString(response.getEntity(), "utf-8");
        System.out.println(s);
        response.close();
        httpClient.close();
    }

请求连接池

public void testPoolingConnectManager() throws Exception{
        PoolingHttpClientConnectionManager cm=new PoolingHttpClientConnectionManager();
        CloseableHttpClient httpClient = HttpClients.custom().setConnectionManager(cm).build();
        HttpGet get=new HttpGet("http://www.it.cn");
        CloseableHttpResponse execute = httpClient.execute(get);
        String s = EntityUtils.toString(execute.getEntity(), "utf-8");
        System.out.println(s);
        execute.close();
        //此处不需要关闭连接池 会直接被连接池回收
    }

标签:execute,HttpGet,Java,请求,样例,new,HttpClient,httpClient
来源: https://blog.csdn.net/qq_29750461/article/details/123630816