java代码实现爬虫功能

实现思路

1、首先要找到你想要抓取信息的网站地址，通过浏览器F12观察接口，如果只是抓取文本信息，只需要找到对应返回json数据的接口。

2、通过java代码发送http请求获取对应的数据进行保存即可，如果是抓取网页上的信息，就需要观察html页面元素，根据dom节点进行解析再进行保存。

其实python实现思路也是一样，只不过python代码实现起来更简洁，在这里就不做演示了，感兴趣的朋友可以自己使用python实现一个爬虫程序。

应用场景

????????当需要在网页上获取大量的数据时，如果通过人工进行点击保存下载操作太费劲了，，比如获取图片素材、小说等，都可以利用代码实现。

java爬虫示例

今天就教大家利用java代码实现一段爬虫程序，获取网站上的图片。

目标网站：高清图片，堆糖，美图壁纸兴趣社区

主程序类

package com.memory.flink;

import org.apache.flink.table.expressions.E;

import java.io.*;
import java.net.URL;
import java.net.URLConnection;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;
import java.util.Set;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import java.util.stream.Collectors;

public class MainDownLoad {

    // 地址
    private static final String URL = "http://www.tooopen.com/view/1439719.html";
    // 获取img标签正则
    private static final String IMGURL_REG = "<img.*src=(.*?)[^>]*?>";
    // 获取src路径的正则
    private static final String IMGSRC_REG = "[a-zA-z]+://[^\\s]*";

    // TODO 数据集ID
    final static long dataSetId = 85597077;

    public static void download(Long dataSetId,String resourceName,String filePath) {
        filePath = filePath +resourceName+"//"+ dataSetId + "/";
        try {
            MainDownLoad cm=new MainDownLoad();
            Set<String> imageUrls = DownloadImageFormDuiTang.getImageUrls(dataSetId);
            List<String> imageList = new ArrayList(imageUrls);
            //下载图片
            cm.Download(imageList,filePath);

        }catch (Exception e){
            e.printStackTrace();
        }
    }
    public static void main(String[] args) {
        try {
            MainDownLoad cm=new MainDownLoad();
            Set<String> imageUrls = DownloadImage.getImageUrls(dataSetId);
            List<String> imageList = new ArrayList();
            for (String imageUrl : imageUrls) {
                //获得html文本内容
                String HTML = cm.getHtml(imageUrl);
                //获取图片标签
                List<String> imgUrl = cm.getImageUrl(HTML);
                // 筛选blog图片
                List<String> mainImageUrl = imgUrl.stream().filter(url -> url.indexOf("blog")!=-1).collect(Collectors.toList());
                //获取图片src地址
                List<String> imgSrc = cm.getImageSrc(mainImageUrl);
                for (String s : imgSrc) {
                    System.out.println(s);
                    imageList.add(s);
                }
//                break;
            }
            //下载图片
//            cm.Download(imageList,filePath);

        }catch (Exception e){
            e.printStackTrace();
        }

    }

    //获取HTML内容
    private String getHtml(String url)throws Exception{
        URL url1=new URL(url);
        URLConnection connection=url1.openConnection();
        InputStream in = null;
        InputStreamReader isr = null;
        BufferedReader br = null;
        try {
             in=connection.getInputStream();
             isr=new InputStreamReader(in);
             br=new BufferedReader(isr);
        }catch (Exception e){
            System.err.println("获取资源出错。" + e.getMessage());
        }
        String line;
        StringBuffer sb=new StringBuffer();
        while((line=br.readLine())!=null){
            sb.append(line,0,line.length());
            sb.append('\n');
        }
        br.close();
        isr.close();
        in.close();
        return sb.toString();
    }

    //获取ImageUrl地址
    private List<String> getImageUrl(String html){
        Matcher matcher=Pattern.compile(IMGURL_REG).matcher(html);
        List<String>listimgurl=new ArrayList<String>();
        while (matcher.find()){
            listimgurl.add(matcher.group());
        }
        return listimgurl;
    }

    //获取ImageSrc地址
    private List<String> getImageSrc(List<String> listimageurl){
        List<String> listImageSrc=new ArrayList<String>();
        for (String image:listimageurl){
            Matcher matcher=Pattern.compile(IMGSRC_REG).matcher(image);
            while (matcher.find()){
                listImageSrc.add(matcher.group().substring(0, matcher.group().length()-1));
            }
        }
        return listImageSrc;
    }

    //下载图片
    private void Download(List<String> listImgSrc, String filePath) {
        try {
            File file = new File(filePath);
            if (!file.exists()) {
                file.mkdirs();
            }
            //开始时间
            Date begindate = new Date();
            for (String url : listImgSrc) {
                if (url.indexOf(".gif_jpeg") != -1){
                    url = url.replace(".gif_jpeg",".gif");
                }
                //开始时间
                Date begindate2 = new Date();
                String imageName = url.substring(url.lastIndexOf("/") + 1, url.length());

                URL uri = new URL(url);
                InputStream in = uri.openStream();
                FileOutputStream fo = new FileOutputStream(new File(filePath+imageName));
                byte[] buf = new byte[1024];
                int length = 0;
                System.out.println("开始下载:" + url);
                while ((length = in.read(buf, 0, buf.length)) != -1) {
                    fo.write(buf, 0, length);
                }
                in.close();
                fo.close();
                System.out.println(imageName + "下载完成");
                //结束时间
                Date overdate2 = new Date();
                double time = overdate2.getTime() - begindate2.getTime();
                System.out.println("耗时：" + time / 1000 + "s");
            }
            Date overdate = new Date();
            double time = overdate.getTime() - begindate.getTime();
            System.out.println("总耗时：" + time / 1000 + "s");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

?获取每个章节的图片接口信息

package com.memory.flink;

import cn.hutool.http.HttpUtil;
import cn.hutool.json.JSONArray;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;

import java.util.*;

public class DownloadImage {
    static Set<Integer> imageIds = new HashSet<>();
//    static List<Integer> imageIds = new ArrayList<>();
    public static void main(String[] args) {
//        String url = "https://www.duitang.com/napi/blog/list/by_album/?album_id=108374401&limit=24&include_fields=top_comments%2Cis_root%2Csource_link%2Cbuyable%2Croot_id%2Cstatus%2Clike_count%2Clike_id%2Csender%2Creply_count&start=1&_=1648521141702";
        long dataSetId = 85597077;
        Set<Integer> imageIds = getImageIds(dataSetId);
         String baseUrl = "https://www.duitang.com/blog/?id=";
        for (Integer id : imageIds) {
            String imageUrl = baseUrl + id;
            System.out.println(imageUrl);
//            String result2 = HttpUtil.get(url, paramMap);
        }

    }

    /**
     * 根据数据集ID 获取集合
     * @param dataSetId
     * @return
     */
    public static Set<String> getImageUrls (long dataSetId) {

        Set<Integer> imageIds = getImageIds(dataSetId);
        Set<String> result = new HashSet();
        String baseUrl = "https://www.duitang.com/blog/?id=";
        for (Integer id : imageIds) {
            String imageUrl = baseUrl + id;
              // TODO  关闭打印
//            System.out.println(imageUrl);
//            String result2 = HttpUtil.get(url, paramMap);
            result.add(imageUrl);
        }
        return result;
    }
    public static Set<Integer> getImageIds (long album_id) {
        String url = "https://www.duitang.com/napi/blog/list/by_album/";
        Map<String, Object> paramMap = new HashMap<>();
        paramMap.put("album_id", album_id);
        paramMap.put("include_fields", "top_comments,is_root,source_link,buyable,root_id,status,like_count,like_id,sender,reply_count");
        paramMap.put("limit", 100);
        paramMap.put("start", 0);
        paramMap.put("_", System.currentTimeMillis());
        // 无参GET请求
        //String result = HttpUtil.get(url);
        // 带参GET请求
        String result2 = HttpUtil.get(url, paramMap);
        Map map = JSONUtil.toBean(result2, Map.class);
        JSONObject data = (JSONObject)map.get("data");
        JSONArray jsonArray = (JSONArray)data.get("object_list");

        for (Object o : jsonArray) {
            JSONObject image = (JSONObject)o;
            Integer id = (Integer)image.get("id");
            imageIds.add(id);
        }
        // 第二页
        paramMap.put("start", 100);
        result2 = HttpUtil.get(url, paramMap);
        map = JSONUtil.toBean(result2, Map.class);
        data = (JSONObject)map.get("data");
        jsonArray = (JSONArray)data.get("object_list");
        for (Object o : jsonArray) {
            JSONObject image = (JSONObject)o;
            Integer id = (Integer)image.get("id");
            imageIds.add(id);
        }
        paramMap.put("start", 200);
        result2 = HttpUtil.get(url, paramMap);
        map = JSONUtil.toBean(result2, Map.class);
        data = (JSONObject)map.get("data");
        jsonArray = (JSONArray)data.get("object_list");
        for (Object o : jsonArray) {
            JSONObject image = (JSONObject)o;
            Integer id = (Integer)image.get("id");
            imageIds.add(id);
        }
        paramMap.put("start", 300);
        result2 = HttpUtil.get(url, paramMap);
        map = JSONUtil.toBean(result2, Map.class);
        data = (JSONObject)map.get("data");
        jsonArray = (JSONArray)data.get("object_list");
        for (Object o : jsonArray) {
            JSONObject image = (JSONObject)o;
            Integer id = (Integer)image.get("id");
            imageIds.add(id);
        }
        System.out.println(jsonArray.size());
        System.out.println(imageIds);
        return imageIds;
    }
}

获取图片url?

package com.memory.flink;

import cn.hutool.http.HttpUtil;
import cn.hutool.json.JSONArray;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;

import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;

public class DownloadImageFormDuiTang {


    final static String baseUrl = "https://www.duitang.com/napi/album/list/by_search/";
    static Set<Long> dataSetIds = new HashSet<>();
    static Set<String> imageUrls = new HashSet<>();
    final static String resourceName = "动漫场景";
    final static String filePath = "C://material//";
    public static void main(String[] args) {
        long start = System.currentTimeMillis();
        Map<String, Object> paramMap = new HashMap<>();
        paramMap.put("kw", resourceName);
        paramMap.put("include_fields", "top_comments,is_root,source_link,item,buyable,root_id,status,like_count,like_id,sender,album,reply_count,favorite_blog_id");
        paramMap.put("after_id",0);
        paramMap.put("limit",10);
        paramMap.put("type", "feed");
        paramMap.put("_type", "");
        paramMap.put("_", System.currentTimeMillis());
        // 无参GET请求
        //String result = HttpUtil.get(url);
        // 带参GET请求
        String result2 = HttpUtil.get(baseUrl, paramMap);
        Map map = JSONUtil.toBean(result2, Map.class);
        JSONObject data = (JSONObject)map.get("data");
        JSONArray jsonArray = (JSONArray)data.get("object_list");
        for (Object o : jsonArray) {
            JSONObject image = (JSONObject)o;
            Long id = Long.valueOf(image.get("id").toString());
            dataSetIds.add(id);
        }
        // 1.获取数据集ID
        // 2.根据数据集ID获取图片
        for (Long datasetId : dataSetIds) {
            MainDownLoad.download(datasetId,resourceName,filePath);
        }
        long end = System.currentTimeMillis();
        System.out.println("下载资源完成，总耗时：" + (end-start) / 1000 + "s");
    }

    /**
     * 根据数据集ID 获取集合
     * @param dataSetId
     * @return
     */
    public static Set<String> getImageUrls (long dataSetId) {

        Set<String> imageUrls = getImageIds(dataSetId);
        return imageUrls;
    }
    public static Set<String> getImageIds (long album_id) {
        Set<String> result = new HashSet<>();
        String url = "https://www.duitang.com/napi/blog/list/by_album/";
        Map<String, Object> paramMap = new HashMap<>();
        paramMap.put("album_id", album_id);
        paramMap.put("include_fields", "top_comments,is_root,source_link,buyable,root_id,status,like_count,like_id,sender,reply_count");
        paramMap.put("limit", 100);
        paramMap.put("start", 0);
        paramMap.put("_", System.currentTimeMillis());
        // 无参GET请求
        //String result = HttpUtil.get(url);
        // 带参GET请求
        String result2 = HttpUtil.get(url, paramMap);
        Map map = JSONUtil.toBean(result2, Map.class);
        JSONObject data = (JSONObject)map.get("data");
        JSONArray jsonArray = (JSONArray)data.get("object_list");

        for (Object o : jsonArray) {
            JSONObject image = (JSONObject)o;
            JSONObject photo = (JSONObject)image.get("photo");
            String imgUrl = (String)photo.get("path");
            result.add(imgUrl);
        }
        // 第二页
        paramMap.put("start", 100);
        result2 = HttpUtil.get(url, paramMap);
        map = JSONUtil.toBean(result2, Map.class);
        data = (JSONObject)map.get("data");
        jsonArray = (JSONArray)data.get("object_list");
        for (Object o : jsonArray) {
            JSONObject image = (JSONObject)o;
            JSONObject photo = (JSONObject)image.get("photo");
            String imgUrl = (String)photo.get("path");
            result.add(imgUrl);
        }
        paramMap.put("start", 200);
        result2 = HttpUtil.get(url, paramMap);
        map = JSONUtil.toBean(result2, Map.class);
        data = (JSONObject)map.get("data");
        jsonArray = (JSONArray)data.get("object_list");
        for (Object o : jsonArray) {
            JSONObject image = (JSONObject)o;
            JSONObject photo = (JSONObject)image.get("photo");
            String imgUrl = (String)photo.get("path");
            result.add(imgUrl);
        }
        paramMap.put("start", 300);
        result2 = HttpUtil.get(url, paramMap);
        map = JSONUtil.toBean(result2, Map.class);
        data = (JSONObject)map.get("data");
        jsonArray = (JSONArray)data.get("object_list");
        for (Object o : jsonArray) {
            JSONObject image = (JSONObject)o;
            JSONObject photo = (JSONObject)image.get("photo");
            String imgUrl = (String)photo.get("path");
            result.add(imgUrl);
        }
        System.out.println(jsonArray.size());
        System.out.println(result);
        return result;
    }
}