How to crawl a website with multiple pages using java

问题

Following code works fine but it only fetch data from one page , can anyone suggest how to handle pagination so that code can fetch data from the first page then second and continue until the last page number

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

import org.apache.poi.hssf.usermodel.HSSFRow;
import org.apache.poi.hssf.usermodel.HSSFSheet;
import org.apache.poi.hssf.usermodel.HSSFWorkbook;
import org.apache.poi.ss.usermodel.Row;

import com.webscrap4j.WebScrap;
import com.webscrap4j.WebScrapException;


public class okayapower_battery {
    @SuppressWarnings("resource")
    public static void main(String[] args) throws IOException {



        ArrayList<String> al = new ArrayList<String>();
        ArrayList<String> bl = new ArrayList<String>();
        ArrayList<String> cl = new ArrayList<String>();
        WebScrap ws = new WebScrap();


        ws.setUrl("https://www.okayapower.com/product-category/inverter/");
        try


        {

            ws.startWebScrap();
            //al = ws.getImageTagData("img", "title");
            al = ws.getSingleHTMLScriptData("<h3>", "</h3>");
            bl = ws.getSingleHTMLScriptData("<del>", "</del>");
            cl = ws.getSingleHTMLScriptData("<ins>", "</ins>");




            HSSFWorkbook workBook = new HSSFWorkbook();
             FileOutputStream fos = new FileOutputStream("/Users/parthpatil/Documents/Abm Technologies/Crawl/okaya_battery.xls"); {

            // Create the Sheet
            HSSFSheet Sheet = workBook.createSheet("products");

            // Create the first row corresponding to the header
            Row header = Sheet.createRow(0);
            header.createCell(0).setCellValue("Product Name");
            header.createCell(1).setCellValue("Product Price");
            header.createCell(2).setCellValue("Product MRP");

            // Ensure that all the List have the same size otherwise throw an exception
            if (al.size() != bl.size() || al.size() != cl.size())
                throw new IllegalStateException("Some data is missing");

            // Iterate over all the list an create the rows of data
            for(int i = 0; i < al.size(); i++){
                // Create the current starting from 1 to al.size()
                HSSFRow row = Sheet.createRow((short) i + 1);
                // Cell of the Product Name
                row.createCell(0).setCellValue(al.get(i));
                // Cell of the Product Price
                row.createCell(1).setCellValue(cl.get(i));
                // Cell of the Product MRP
                row.createCell(2).setCellValue(bl.get(i));
            }
            // Write the result into the file
            workBook.write(fos);


            for (String adata : al)
            {

                System.out.println("the product are:- " + adata);

            }
            for (String bdata : bl)
            {

                System.out.println("the MRp are:- " + bdata);

            }
            for (String cdata : cl)
            {

                System.out.println("the selling price is:- " + cdata);

            }


        }
             }catch (WebScrapException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        }

}

回答1:

Just add simple for loop like for(int page=1; page<=10; page++) { (where 10 is the last page you want to parse) just before ws.setUrl(... which should be as well changed to ws.setUrl("https://www.okayapower.com/product-category/inver‌​ter/page/" + String.valueOf(page) + "/");

So the resultant code should look like:

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

import org.apache.poi.hssf.usermodel.HSSFRow;
import org.apache.poi.hssf.usermodel.HSSFSheet;
import org.apache.poi.hssf.usermodel.HSSFWorkbook;
import org.apache.poi.ss.usermodel.Row;

import com.webscrap4j.WebScrap;
import com.webscrap4j.WebScrapException;


public class okayapower_battery {
    @SuppressWarnings("resource")
    public static void main(String[] args) throws IOException {

        ArrayList<String> al = new ArrayList<String>();
        ArrayList<String> bl = new ArrayList<String>();
        ArrayList<String> cl = new ArrayList<String>();
        WebScrap ws = new WebScrap();
        for(int page=1; page<=10; page++) {
            ws.setUrl("https://www.okayapower.com/product-category/inverter/page/" + String.valueOf(page) + "/");
            try {
                ws.startWebScrap();
                //al = ws.getImageTagData("img", "title");
                al = ws.getSingleHTMLScriptData("<h3>", "</h3>");
                bl = ws.getSingleHTMLScriptData("<del>", "</del>");
                cl = ws.getSingleHTMLScriptData("<ins>", "</ins>");

                HSSFWorkbook workBook = new HSSFWorkbook();
                FileOutputStream fos = new FileOutputStream("/Users/parthpatil/Documents/Abm Technologies/Crawl/okaya_battery.xls"); {

                    // Create the Sheet
                    HSSFSheet Sheet = workBook.createSheet("products");

                    // Create the first row corresponding to the header
                    Row header = Sheet.createRow(0);
                    header.createCell(0).setCellValue("Product Name");
                    header.createCell(1).setCellValue("Product Price");
                    header.createCell(2).setCellValue("Product MRP");

                    // Ensure that all the List have the same size otherwise throw an exception
                    if (al.size() != bl.size() || al.size() != cl.size())
                        throw new IllegalStateException("Some data is missing");

                    // Iterate over all the list an create the rows of data
                    for(int i = 0; i < al.size(); i++){
                        // Create the current starting from 1 to al.size()
                        HSSFRow row = Sheet.createRow((short) i + 1);
                        // Cell of the Product Name
                        row.createCell(0).setCellValue(al.get(i));
                        // Cell of the Product Price
                        row.createCell(1).setCellValue(cl.get(i));
                        // Cell of the Product MRP
                        row.createCell(2).setCellValue(bl.get(i));
                    }
                    // Write the result into the file
                    workBook.write(fos);

                    for (String adata : al)
                    {
                        System.out.println("the product are:- " + adata);
                    }
                    for (String bdata : bl)
                    {
                        System.out.println("the MRp are:- " + bdata);
                    }
                    for (String cdata : cl)
                    {
                        System.out.println("the selling price is:- " + cdata);
                    }
                }
            } catch (WebScrapException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
    }
}

来源：https://stackoverflow.com/questions/39246136/how-to-crawl-a-website-with-multiple-pages-using-java