Java爬虫 --第一个爬虫

新建maven项目

在pom.xml中添加坐标

首先在maven存储库搜索用来抓数据的HttpClient的坐标

<dependency>
     <groupId>org.apache.httpcomponentsgroupId>
     <artifactId>httpclientartifactId>
     <version>4.5.2version>
 dependency>

还有Apache Log4j(日志)

<dependency>
    <groupId>org.slf4jgroupId>
    <artifactId>slf4j-log4j12artifactId>
    <version>1.7.25version>
    
	
dependency>

将这两个坐标添加到中
然后在main > resources中新建log4j.properties

并在这个文件中写入

log4j.rootLogger=DEBUG,A1
log4j.logger.cn.itcast = DEBUG

log4j.appender.A1=org.apache.log4j.ConsoleAppender
log4j.appender.A1.layout=org.apache.log4j.PatternLayout
log4j.appender.A1.layout.ConversionPattern=%-d{yyyy-MM-dd HH:mm:ss,SSS} [%t] [%c]-[%p] %m%n

爬取一个网站源码

在main > java下新建一个包com.stuSpider
新建一个CrawlerFirst类

打开浏览器 – 创建HttpClient对象

CloseableHttpClient httpClient = HttpClients.createDefault();

输入网址 – 使用HttpGet对象请求

请求方法为GET, POST以后再说

HttpGet httpGet = new HttpGet("https://csdn.net");

按回车，发起请求，返回响应 – 使用HttpClient发起请求

用response接收响应

CloseableHttpResponse response = httpClient.execute(httpGet);

解析响应，获取数据

首先要判断状态码是否和浏览器上的一致 正常是200

response.getStatusLine().getStatusCode()可以获取状态码
用httpEntity接收响应体 response.getEntity()
EntityUtils.toString(httpEntity, "utf8");得到网页Response里的网页源码

if (response.getStatusLine().getStatusCode() == 200) {
	HttpEntity httpEntity = response.getEntity();
    String content = EntityUtils.toString(httpEntity, "utf8");
    System.out.println(content);
}

最后贴上我的代码

pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0modelVersion>

    <groupId>cn.stuspidergroupId>
    <artifactId>stuspider-firstartifactId>
    <version>1.0-SNAPSHOTversion>

    <dependencies>
        
        <dependency>
            <groupId>org.apache.httpcomponentsgroupId>
            <artifactId>httpclientartifactId>
            <version>4.5.2version>
        dependency>

        
        <dependency>
            <groupId>org.slf4jgroupId>
            <artifactId>slf4j-log4j12artifactId>
            <version>1.7.25version>

        dependency>
    dependencies>
project>

CrawlerFirst.java

package cn.stuspider;

import org.apache.http.HttpEntity;
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.util.EntityUtils;

import java.io.IOException;

public class CrawlerFirst {
    public static void main(String[] args) throws IOException {
        //1.打开浏览器---创建HttpClient对象
        CloseableHttpClient httpClient = HttpClients.createDefault();
        //2.输入网址---请求方法为GET，使用HttpGet对象
        HttpGet httpGet = new HttpGet("https://csdn.net");
        //3.按回车，发起请求，返回响应---使用HttpClient发起请求,response接收响应
        CloseableHttpResponse response = httpClient.execute(httpGet);
        //4.解析响应，获取数据
            //首先判断状态码是否和浏览器上的一致 正常是200   response.getStatusLine().getStatusCode()获取状态码
            //用httpEntity接收响应体(response.getEntity())
            //EntityUtils.toString(httpEntity, "utf8");得到网页Response里的网页源码
        if (response.getStatusLine().getStatusCode() == 200) {
            HttpEntity httpEntity = response.getEntity();
            String content = EntityUtils.toString(httpEntity, "utf8");
            System.out.println(content);
        }
    }
}

运行结果