爬虫笔记1

目录：

一.get请求，没有参数

二.get请求，有参数

三.post请求，没有参数

四.post请求，有参数

五.连接池创建连接

六.jsou解析

七.使用dom方式遍历文档

1.get请求，没有参数

package Demo1.CrawlerDemo1;

import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;

import java.io.IOException;
import java.net.URI;

import org.apache.http.HttpEntity;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.protocol.ResponseAuthCache;
import org.apache.http.impl.client.CloseableHttpClient;

public class Crawler {
    public static void main(String[] args) {
        //1.browser:create httpclient
        CloseableHttpClient httpClient=HttpClients.createDefault();
        //2.url
        HttpGet httpGet=new HttpGet("http://www.itcast.cn");
                //3.request
        CloseableHttpResponse response=null;
        try {
            response=httpClient.execute(httpGet);
            if(response.getStatusLine().getStatusCode()==200) {
                HttpEntity httpEntity=response.getEntity();
                String content=EntityUtils.toString(httpEntity,"utf-8");
                System.out.println(content);
            }
        } catch (ClientProtocolException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }finally {
            try {
                response.close();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            try {
                httpClient.close();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
                //4.get response
        
    }
    
    
}

2.get请求，有参数

package Demo1.CrawlerDemo1;

import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;

import java.io.IOException;
import java.net.URI;
import java.net.URISyntaxException;

import org.apache.http.HttpEntity;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.protocol.ResponseAuthCache;
import org.apache.http.client.utils.URIBuilder;
import org.apache.http.impl.client.CloseableHttpClient;
/**get请求带参数
 * 
 * @author 18430
 *
 */
public class CrawlerParameter {
    
    public static void main(String[] args) throws Exception {
    
        CloseableHttpClient httpClient=HttpClients.createDefault();
        
        
        URIBuilder uriBuilder=new URIBuilder("http://yun.itheima.com/search");
    
        uriBuilder.setParameter("keys", "java");
        //多个参数的设置
        //uriBuilder.setParameter("keys", "java").setParameter("keys", "java");
        
        HttpGet httpGet=new HttpGet(uriBuilder.build());
            
        CloseableHttpResponse response=null;
        try {
            response=httpClient.execute(httpGet);
            if(response.getStatusLine().getStatusCode()==200) {
                HttpEntity httpEntity=response.getEntity();
                String content=EntityUtils.toString(httpEntity,"utf-8");
                System.out.println(content);
            }
        } catch (ClientProtocolException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }finally {
            try {
                response.close();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            try {
                httpClient.close();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
                //4.get response
        
    }
    
    
}

3.post请求不带参数

package Demo1.CrawlerDemo1;

import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;

import java.io.IOException;
import java.net.URI;
import java.net.URISyntaxException;

import org.apache.http.HttpEntity;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.client.protocol.ResponseAuthCache;
import org.apache.http.client.utils.URIBuilder;
import org.apache.http.impl.client.CloseableHttpClient;
/**
 * post请求
 * @author 18430
 *
 */
public class CrawlerPost {
    
    public static void main(String[] args) throws Exception {
    
        CloseableHttpClient httpClient=HttpClients.createDefault();
        
        
        URIBuilder uriBuilder=new URIBuilder("http://www.itcast.cn");
    
        
        
        HttpPost httpPost=new HttpPost(uriBuilder.build());
            
        CloseableHttpResponse response=null;
        try {
            response=httpClient.execute(httpPost);
            if(response.getStatusLine().getStatusCode()==200) {
                HttpEntity httpEntity=response.getEntity();
                String content=EntityUtils.toString(httpEntity,"utf-8");
                System.out.println(content);
            }
        } catch (ClientProtocolException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }finally {
            try {
                response.close();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            try {
                httpClient.close();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
                //4.get response
        
    }
    
    
}

4.post请求，带参数

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

import org.apache.http.NameValuePair;
import org.apache.http.client.ClientProtocolException;
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;

public class PostWithParam {
public static void main(String[] args) throws Exception {
    CloseableHttpClient httpClient = HttpClients.createDefault();
    HttpPost httpPost = new HttpPost("http://yun.itheima.com/search");
    //申明list封装表单中的参数
    List<NameValuePair> params = new ArrayList<NameValuePair>();
    params.add(new BasicNameValuePair("keys","java"));
    
    //创建表单entity对象
    UrlEncodedFormEntity formEntity = new UrlEncodedFormEntity(params,"utf-8");
    
    //设置表单entity对象到post请求中
    httpPost.setEntity(formEntity);
    
    CloseableHttpResponse response = null;
    try {
        response = httpClient.execute(httpPost);
        if(response.getStatusLine().getStatusCode() == 200) {
            String content = EntityUtils.toString(response.getEntity(),"utf-8");
        System.out.println(content);
        }
    } catch (ClientProtocolException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}
}

 5.使用连接池

import java.io.IOException;

import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.impl.conn.PoolingHttpClientConnectionManager;
import org.apache.http.util.EntityUtils;

public class ConnectPool {
public static void main(String[] args) {
    //创建连接池管理器
    PoolingHttpClientConnectionManager cm = new PoolingHttpClientConnectionManager();
    //设置连接数
    cm.setMaxTotal(100);
    //设置每个主机的最大连接数
    cm.setDefaultMaxPerRoute(10);
    //使用连接池管理器发起请求
    doGet(cm);

}
private static void doGet(PoolingHttpClientConnectionManager cm) {
CloseableHttpClient httpClient = HttpClients.custom().setConnectionManager(cm).build();
HttpGet httpGet = new HttpGet("http://www.itcast.cn");
CloseableHttpResponse response = null; 
try {
    response =httpClient.execute(httpGet);
    if(response.getStatusLine().getStatusCode() == 200) {
    String content     = EntityUtils.toString(response.getEntity(),"utf-8");
    System.out.println(content.length());
    }
} catch (ClientProtocolException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
} catch (IOException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
}finally {
    //httpclient有连接池管理，不能关闭
    if(response != null) {
        try {
            response.close();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}
}
}

 6.Jsoup解析

package Demo1.CrawlerDemo1;

import java.io.File;
import java.net.URL;

import org.apache.commons.io.FileUtils;
import org.jsoup.Jsoup;
import org.jsoup.nodes.Document;
import org.junit.Test;

public class Jsoup1Test2 {
    @Test
    public void testUrl() throws Exception {
        // 解析url
        Document doc = Jsoup.parse(new URL("http://www.itcast.cn"), 1000);
        // 使用标签选择器获取title标签内容
        String title = doc.getElementsByTag("title").first().text();
        System.out.println(title);

    }

    @Test
    public void testString() throws Exception {
        // 解析字符串
        String content = FileUtils.readFileToString(
                new File(System.getProperty("user.dir") + "\src\main\java\resources\test.html"), "utf-8");
        Document doc = Jsoup.parse(content);
        String title = doc.getElementsByTag("title").first().text();
        System.out.println(title);
    }

    @Test
    public void testFile() throws Exception {
        // 解析文件
        Document doc = Jsoup.parse(new File(System.getProperty("user.dir") + "\src\main\java\resources\test.html"),
                "utf-8");
        String title = doc.getElementsByTag("title").first().text();
        System.out.println(title);
    }

}