使用poi導入導出excel文件方法使用及改進

首先賣個萌，poi~

當然這裏不是什麼夕立啊奇怪的口癖，是指Apache POI。Apache POI提供API給Java程式對Microsoft Office格式檔案讀和寫的功能，這裏我就改進了對excel的讀寫方法，因爲用到了~

下面是正題：

慣例maven項目，加入以下依賴：

        <!-- https://mvnrepository.com/artifact/org.apache.poi/poi -->
        <dependency>
            <groupId>org.apache.poi</groupId>
            <artifactId>poi</artifactId>
            <version>3.14</version>
        </dependency>

        <!-- https://mvnrepository.com/artifact/org.apache.poi/poi-ooxml -->
        <dependency>
            <groupId>org.apache.poi</groupId>
            <artifactId>poi-ooxml</artifactId>
            <version>3.14</version>
        </dependency>

然後是整體代碼，兩個方法，讀和寫。

import org.apache.poi.hssf.usermodel.HSSFDateUtil;
import org.apache.poi.hssf.usermodel.HSSFWorkbook;
import org.apache.poi.ss.usermodel.*;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.*;

/**
 * Created by Dian.N.Wang on 2016/11/9.
 */
public class Functions {

    /**
     * 導入excel
     * @param filepath
     * @param classref
     * @return List
     */
    public List importExcelToList(String filepath,Class classref){
        List list = new ArrayList();
        try {
            //Create the input stream from the xlsx/xls file
            FileInputStream fis = new FileInputStream(filepath);

            //Create Workbook instance for xlsx/xls file input stream
            Workbook workbook = null;
            if(filepath.toLowerCase().endsWith("xlsx")){
                workbook = new XSSFWorkbook(fis);
            }else if(filepath.toLowerCase().endsWith("xls")){
                workbook = new HSSFWorkbook(fis);
            }

            //Get the number of sheets in the xlsx file
            int numberOfSheets = workbook.getNumberOfSheets();

            //loop through each of the sheets
            for(int i=0; i < numberOfSheets; i++){

                //Get the nth sheet from the workbook
                Sheet sheet = workbook.getSheetAt(i);

                //every sheet has rows, iterate over them
                Iterator<Row> rowIterator = sheet.iterator();

                //ignore header
                if (rowIterator.hasNext()) {
                    rowIterator.next();
                }

                //every row
                while (rowIterator.hasNext())
                {
                    Field[] fs = classref.getDeclaredFields();
                    Object obj=classref.newInstance();
                    //Get the row object
                    Row row = rowIterator.next();

                    //Every row has columns, get the column iterator and iterate over them
                    Iterator<Cell> cellIterator = row.cellIterator();

                    //every cell
                    while (cellIterator.hasNext()) {
                        for (Field field : fs) {
                            String fieldname = field.getName();
                            String setname="set"+fieldname.substring(0,1).toUpperCase()+ fieldname.substring(1);
                            Class fieidclazz=field.getType();
                            Method m=classref.getDeclaredMethod(setname,fieidclazz);

                            //Get the Cell object
                            Cell cell = cellIterator.next();

                            //check the cell type and process accordingly
                            switch (cell.getCellType()) {
                                case Cell.CELL_TYPE_STRING:
                                    m.invoke(obj,cell.getStringCellValue().trim());
                                    break;
                                case Cell.CELL_TYPE_NUMERIC:
                                    if (HSSFDateUtil.isCellDateFormatted(cell)) {
                                        Date d = cell.getDateCellValue();
                                        DateFormat formater = new SimpleDateFormat("yyyy-MM-dd");
                                        m.invoke(obj,formater.format(d));
                                    } else {
                                        m.invoke(obj,(int) cell.getNumericCellValue());
                                    }
                                    break;
                                case Cell.CELL_TYPE_BLANK:
                                    m.invoke(obj,null);
                                    break;
                                case Cell.CELL_TYPE_BOOLEAN:
                                    m.invoke(obj, cell.getBooleanCellValue());
                                    break;
                                default:
                                    throw new NoSuchTypeException();
                            }
                        }
                    }//end of cell iterator
                    list.add(obj);
                } //end of rows iterator
            } //end of sheets for loop

            //close file input stream
            fis.close();

        } catch (IOException e) {
            e.printStackTrace();
        } catch (NoSuchTypeException e) {
            e.dealWithException();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InstantiationException e) {
            e.printStackTrace();
        } catch (NoSuchMethodException e) {
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            e.printStackTrace();
        }
        return list;
    }

    /**
     *導出excel
     * @param list
     * @param fileName
     * @throws Exception
     */
    public void exportListToExcel(List list,String fileName,Class classref) throws Exception {
        Workbook workbook = null;
        if(fileName.endsWith("xlsx")){
            workbook = new XSSFWorkbook();
        }else if(fileName.endsWith("xls")){
            workbook = new HSSFWorkbook();
        }else{
            throw new Exception("invalid file name, should be xls or xlsx");
        }

        //create sheet
        Sheet sheet = workbook.createSheet(classref.getName());

        Field[] fs = classref.getDeclaredFields();
        Iterator iterator = list.iterator();

        //create header
        int rowIndex = 0;
        Row row = sheet.createRow(rowIndex++);
        int cellcount=0;
        for(Field field:fs) {
            Cell cell = row.createCell(cellcount);
            cell.setCellValue(field.getName());
            cellcount++;
        }

        //write contents
        while(iterator.hasNext()){
            Object obj = iterator.next();
            row = sheet.createRow(rowIndex++);
            cellcount=0;
            for(Field field:fs) {
                Cell cell = row.createCell(cellcount);
                String fieldname = field.getName();
                String getname="get"+fieldname.substring(0,1).toUpperCase()+ fieldname.substring(1);
                Method m=classref.getDeclaredMethod(getname);
                cell.setCellValue(String.valueOf(m.invoke(obj)));
                cellcount++;
            }

        }

        //lets write the excel data to file now
        FileOutputStream fos = new FileOutputStream(fileName);
        workbook.write(fos);
        fos.close();
        System.out.println(fileName + " written successfully");
    }

    /**
     * 拋出未處理的表格單元格的數據類型
     */
    private class NoSuchTypeException extends Throwable {
        public void dealWithException(){
            System.out.println("未解析的excel表格類型");
        }
    }
}

運用反射機制，這樣就可以不需要考慮究竟是何種具體model對象，只要知道是什麼類就好（好難表述啊，感覺怎麼說都不合適，就是你不需要根據網上找的那些實例爲每一個model都建立讀寫方法了，啊，不知道怎麼說了，用到也許會明白吧）。另外，表頭的部分如果不使用model中屬性的名字的話，可能要自己增加參數或是進行轉化（配置文件的方式），代碼不可能總是一成不變的，需要什麼佐料還是要靠自己添加。

下面是簡單的測試方法，也可以看出是這讀和寫兩個方法是如何調用的：

model類：

public class User {
    private String name;
    private int age;

    public User(){};
    public User(String name,int age){
        this.name=name;
        this.age=age;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public String toString(){
        return "name:"+this.name+"  age:"+this.age;
    }

}

main函數：

public class Test {

    public static void main(String[] args) throws Exception {

        Functions func=new Functions();
        Class<?> clazz = Class.forName("User");

        func.importExcelToList("C:\\Users\\Dian.N.Wang\\Desktop\\aaa.xlsx",clazz);

        User user1=new User("sb",25);
        User user2=new User("sb2",30);
        List users=new ArrayList();
        users.add(user1);
        users.add(user2);
        func.exportListToExcel(users,"C:\\Users\\Dian.N.Wang\\Desktop\\bbb.xlsx",clazz);
    }
}

其實這只是反射的一個小小的應用點，但是你會發現他可以刪減你很多的代碼量（自己感覺，你們能理解就好了，淚目/(ㄒoㄒ)/~~）。

最後，跟着我大聲喊：“poi~”