Apache HttpClient - 基于表单的登录
使用 HttpClient 库，您可以发送请求，或者通过传递参数登录表单。
请按照以下步骤登录表单。
第 1 步 - 创建 HttpClient 对象
HttpClients类的createDefault ()方法返回CloseableHttpClient类的对象，该类是 HttpClient 接口的基本实现。使用此方法创建一个 HttpClient 对象 -
CloseableHttpClient httpClient = HttpClients.createDefault();
第 2 步 - 创建 RequestBuilder 对象
RequestBuilder类用于通过向请求添加参数来构建请求。如果请求类型是 PUT 或 POST，它将参数作为 URL 编码实体添加到请求中
使用 post() 方法创建一个 RequestBuilder 对象（POST 类型）。
//Building the post request object RequestBuilder reqbuilder = RequestBuilder.post();
步骤 3 - 将 Uri 和参数设置为 RequestBuilder。
使用 RequestBuilder 类的setUri()和addParameter()方法将 URI 和参数设置为 RequestBuilder 对象。
//Set URI and parameters
RequestBuilder reqbuilder = reqbuilder.setUri("http://httpbin.org/post");
reqbuilder = reqbuilder1.addParameter("Name", "username").addParameter("password", "password");
第 4 步 - 构建 HttpUriRequest 对象
设置所需参数后，使用build()方法构建HttpUriRequest对象。
//Building the HttpUriRequest object HttpUriRequest httppost = reqbuilder2.build();
第 5 步 - 执行请求
CloseableHttpClient 对象的execute 方法接受HttpUriRequest（接口）对象（即HttpGet、HttpPost、HttpPut、HttpHead 等）并返回响应对象。
通过将前面步骤中创建的 HttpUriRequest 传递给execute() 方法来执行它。
//Execute the request HttpResponse httpresponse = httpclient.execute(httppost);
例子
以下示例演示如何通过发送登录凭据来登录表单。在这里，我们向表单发送了两个参数 -用户名和密码，并尝试打印消息实体和请求状态。
import org.apache.http.HttpResponse;
import org.apache.http.client.methods.HttpUriRequest;
import org.apache.http.client.methods.RequestBuilder;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;
import java.io.IOException;
import java.net.URISyntaxException;
public class FormLoginExample {
public static void main(String args[]) throws Exception {
//Creating CloseableHttpClient object
CloseableHttpClient httpclient = HttpClients.createDefault();
//Creating the RequestBuilder object
RequestBuilder reqbuilder = RequestBuilder.post();
//Setting URI and parameters
RequestBuilder reqbuilder1 = reqbuilder.setUri("http://httpbin.org/post");
RequestBuilder reqbuilder2 = reqbuilder1.addParameter("Name",
"username").addParameter("password", "password");
//Building the HttpUriRequest object
HttpUriRequest httppost = reqbuilder2.build();
//Executing the request
HttpResponse httpresponse = httpclient.execute(httppost);
//Printing the status and the contents of the response
System.out.println(EntityUtils.toString(httpresponse.getEntity()));
System.out.println(httpresponse.getStatusLine());
}
}
输出
执行时，上述程序生成以下输出 -
{
"args": {},
"data": "",
"files": {},
"form": {
"Name": "username",
"password": "password"
},
"headers": {
"Accept-Encoding": "gzip,deflate",
"Connection": "close",
"Content-Length": "31",
"Content-Type": "application/x-www-form-urlencoded; charset = UTF-8",
"Host": "httpbin.org",
"User-Agent": "Apache-HttpClient/4.5.6 (Java/1.8.0_91)"
},
"json": null,
"origin": "117.216.245.180",
"url": "http://httpbin.org/post"
}
HTTP/1.1 200 OK
使用 Cookie 表单登录
如果您的表单存储 cookie，则不要创建默认的CloseableHttpClient对象。
通过实例化 BasicCookieStore 类来创建 CookieStore 对象。
//Creating a BasicCookieStore object BasicCookieStore cookieStore = new BasicCookieStore();
使用HttpClients类的custom()方法创建 HttpClientBuilder。
//Creating an HttpClientBuilder object HttpClientBuilder clientbuilder = HttpClients.custom();
使用 setDefaultCookieStore() 方法将 cookie 存储设置到客户端构建器。
//Setting default cookie store to the client builder object Clientbuilder = clientbuilder.setDefaultCookieStore(cookieStore);
使用build()方法构建CloseableHttpClient对象。
//Building the CloseableHttpClient object CloseableHttpClient httpclient = clientbuilder1.build();
通过传递执行请求来构建上面指定的HttpUriRequest对象。
如果页面存储了cookie，您传递的参数将被添加到cookie存储中。
您可以打印CookieStore对象的内容，您可以在其中看到您的参数（以及页面存储的先前参数）。
要打印 cookie，请使用getCookies()方法从CookieStore对象获取所有 cookie 。该方法返回一个List对象。使用迭代器打印列表对象内容，如下所示 -
//Printing the cookies
List list = cookieStore.getCookies();
System.out.println("list of cookies");
Iterator it = list.iterator();
if(it.hasNext()) {
System.out.println(it.next());
}