java爬虫.HttpClient.Post请求

HttpClient.Post请求

HttpPost请求响应的一般步骤：

1). 创建HttpClient对象,可以使用HttpClients.createDefault()；

2).

如果是无参数的GET请求：

则直接使用构造方法HttpPost(String url)创建HttpPost对象即可；

如果是带参数POST请求：

先构建HttpEntity对象并设置请求参数，

然后调用setEntity(HttpEntity entity)创建HttpPost对象。

3). 创建HttpResponse：

调用HttpClient对象的execute(HttpUriRequest request)发送请求，该方法返回一个HttpResponse。

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。

通过调用getStatusLine().getStatusCode()可以获取响应状态码。

4). 释放连接。

无参

package cn.csdn.crawlar.test;

import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.client.utils.URIBuilder;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;

import java.io.IOException;

public class HttpPostTest {

    public static void main(String[] args) throws Exception {
        //创建HttpClient对象
        CloseableHttpClient httpClient = HttpClients.createDefault();

        //设置请求地址是：https://www.icourse163.org/search.htm?search=java#/
        //创建URI地址
        String string="https://www.icourse163.org/search.htm";
        URIBuilder uriBuilder = new URIBuilder( string );

        //设置参数
        String param="search",value="java";
        uriBuilder.setParameter(param,value );

        //创建HttpPost对象，设置url访问地址
        HttpPost httpPost = new HttpPost(uriBuilder.build());

        //发起请求
        System.out.println("发起请求的信息"+httpPost);

        //try/catch/finally : Ctrl+Alt+T
        CloseableHttpResponse response = null;
        try {
            //使用HttpClient发起请求，获取response
            response = httpClient.execute(httpPost);

            //解析响应
            if (response.getStatusLine().getStatusCode() == 200) {
                String content = EntityUtils.toString(response.getEntity(), "utf8");
                System.out.println(content.length());
            }

        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            //关闭response
            try {
                response.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
            try {
                httpClient.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}      

我们可以清晰地看出请求方法由Get变成了Post。

含参

package cn.csdn.crawlar.test;

import org.apache.http.NameValuePair;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.util.EntityUtils;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

public class HttpPostTest含参 {

    public static void main(String[] args) throws Exception {
        //创建HttpClient对象
        CloseableHttpClient httpClient = HttpClients.createDefault();

        //设置请求地址是：https://www.icourse163.org/search.htm?search=java#/
        //创建URI地址
        String string="https://www.icourse163.org/search.htm";
        //创建HttpPost对象，设置url访问地址
        HttpPost httpPost = new HttpPost(string);

        //声明list集合，封装请求集合，封装表单中的参数
        List<NameValuePair> params = new ArrayList<NameValuePair>();
        String name="search",value="java";
        params.add(new BasicNameValuePair(name, value ) );

        //创建表单的Entity对象
        String charst="utf8";
        UrlEncodedFormEntity formEntity = new UrlEncodedFormEntity(params,charst);

        //设置表单Entity对象到POST请求中
        httpPost.setEntity(formEntity);

        //发起请求
        System.out.println("发起请求的信息"+httpPost);

        //try/catch/finally : Ctrl+Alt+T
        CloseableHttpResponse response = null;
        try {
            //使用HttpClient发起请求，获取response
            response = httpClient.execute(httpPost);

            //解析响应
            if (response.getStatusLine().getStatusCode() == 200) {
                String content = EntityUtils.toString(response.getEntity(), "utf8");
                System.out.println(content.length());
            }

        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            //关闭response
            try {
                response.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
            try {
                httpClient.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}      

点开网址链接就可以进入学习视频啦！

声明list集合，封装请求集合，封装表单中的参数
创建表单的Entity对象
设置表单Entity对象到POST请求中