java爬虫：HttpClient的简单使用

一：常用的类库有

• HttpClient
• Jsoup（通常用来解析返回的html页面）

二：常用的框架有

• WebMajic

三：HttpClient的使用

1：依赖

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

2：不带参数的get请求

    public static void get() throws IOException {
    	//创建HttpClient对象
        CloseableHttpClient httpClient = HttpClients.createDefault();
        //设置url
        HttpGet httpget = new HttpGet("http://www.ming3.top/");
        //发送请求
        CloseableHttpResponse response = httpClient.execute(httpget);
        System.out.println(response.toString());
        //获取返回值中的Entity数组对象（存放着html页面）
        String content = EntityUtils.toString(response.getEntity(), "UTF-8");
        System.out.println(content);
    }

3：带参数的post请求

    public static void post() throws IOException {
        // 创建Httpclient对象
        CloseableHttpClient httpclient = HttpClients.createDefault();
        // 创建http POST请求
        HttpPost httpPost = new HttpPost("http://www.ming3.top/wp-login.php");
        // 设置2个post参数，一个是log、一个是pwd
        List<NameValuePair> parameters = new ArrayList<NameValuePair>(0);
        parameters.add(new BasicNameValuePair("log", "eighteen"));
        parameters.add(new BasicNameValuePair("pwd", "[email protected]"));
        // 构造一个form表单式的实体
        UrlEncodedFormEntity formEntity = new UrlEncodedFormEntity(parameters);
        // 将请求实体设置到httpPost对象中
        httpPost.setEntity(formEntity);
        //伪装浏览器请求
        httpPost.setHeader("User-Agent", "Mozilla/5.0 (Windows NT 6.1; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/56.0.2924.87 Safari/537.36");
        // 执行请求
        CloseableHttpResponse response = httpclient.execute(httpPost);
        System.out.println(response);
        String content = EntityUtils.toString(response.getEntity(), "UTF-8");
        System.out.println(content);
    }

4：当然还有带参数的get和不带参数的post，这里不再举例

5：使用post进行登录操作之后，常会返回需要重定向操作
如图所示：返回值是302，需要重定向，需要设置cookie

Ps：

HttpClient简易使用，写的很好