使用SpringEL功能動態解析模板Excel來生成Excel

SpringEL能夠參考：http://www.javashuo.com/article/p-krauasds-hu.html

本文基於POI 3.1.7，spring 5.1.7編寫。

因爲excel裏的#是數字的關鍵字，全部我使用${}來替換了#字符。

核心幫助類：

package com.longge.util;

import java.io.InputStream;
import java.util.ArrayList;
import java.util.List;

import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.ss.usermodel.CellStyle;
import org.apache.poi.ss.usermodel.CellType;
import org.apache.poi.ss.usermodel.Row;
import org.apache.poi.ss.usermodel.Sheet;
import org.apache.poi.ss.usermodel.Workbook;
import org.apache.poi.ss.usermodel.WorkbookFactory;
import org.springframework.core.io.ClassPathResource;
import org.springframework.expression.EvaluationContext;
import org.springframework.expression.ExpressionParser;
import org.springframework.expression.spel.standard.SpelExpressionParser;
import org.springframework.expression.spel.support.StandardEvaluationContext;
import org.springframework.util.CollectionUtils;

/**
 * @author yangzhilong
 * @date 8/01/2019
 */
public class ExcelTemplateWriteUtils {
    
    /**
     * get excel template Workbook
     * @param templateFilePath  eg: static/excelTemplate/xx.xlsx
     * @return
     */
    public static Workbook getWorkbook(String templateFilePath) {
        try {
            InputStream is;
            if(templateFilePath.startsWith("/")) {
                is = ExcelTemplateWriteUtils.class.getResourceAsStream(templateFilePath);
            } else {
                is = new ClassPathResource(templateFilePath).getInputStream();
            }
            return WorkbookFactory.create(is);
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }
    
    /**
     * @param sheet
     * @param templateRowIndex
     * @param list
     */
    public static void fillDataWithTemplate(Sheet sheet, int templateRowIndex, List<? extends Object> list) {
        int tIndex = templateRowIndex;
        Row templateRow = sheet.getRow(templateRowIndex);
        if(CollectionUtils.isEmpty(list)) {
            sheet.removeRow(templateRow);
        } else {
            List<Object> template = new ArrayList<>(templateRow.getPhysicalNumberOfCells());
            List<CellStyle> sytles = new ArrayList<>(templateRow.getPhysicalNumberOfCells());
            templateRow.forEach(cell -> {
                sytles.add(cell.getCellStyle());
                cell.getCellStyle();
                CellType type = cell.getCellTypeEnum();
                if(CellType.NUMERIC.equals(type)) {
                    template.add(cell.getNumericCellValue());
                } else if(CellType.STRING.equals(type)) {
                    String value = cell.getStringCellValue();
                    if(value.startsWith("${")) {
                        value = formatEl(value);
                    }
                    template.add(value);
                } else if(CellType.BLANK.equals(type)) {
                    template.add(null);
                } else {
                    throw new RuntimeException("can't support cell type:" + type.toString());
                }
            });
            ExpressionParser parser = new SpelExpressionParser();
            for(int i=0,len=list.size(); i<len; i++) {
                Object item = list.get(i);
                
                Row newRow = sheet.createRow(tIndex++);
                EvaluationContext context = new StandardEvaluationContext();
                context.setVariable("item", item);
                
                ForEachUtils.forEach(0, template, (index, value) -> {
                    Cell newCell = newRow.createCell(index);
                    newCell.setCellStyle(sytles.get(index));
                    if(null != value) {
                        if (value instanceof String) {
                            String v = (String)value;
                            if(v.startsWith("#")) {
                                v = parser.parseExpression(v).getValue(context, String.class);
                            }
                            newCell.setCellValue(v);
                        } else if(value instanceof Number) {
                            newCell.setCellValue(((Number)value).doubleValue());
                        }
                    }
                });
            }
        }
    }
    
    private static String formatEl(String el) {
        return el.replace("${", "#").replace("}", "");
    }
}

單元測試類：

package com.longge.util;

import static org.junit.Assert.assertEquals;

import java.io.File;
import java.io.FileOutputStream;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.UUID;

import org.apache.poi.ss.usermodel.Sheet;
import org.apache.poi.ss.usermodel.Workbook;
import org.junit.Test;

import com.longge.dto.CustomerDto;

/**
 * @author yangzhilong
 * @date 8/01/2019
 */
public class ExcelTemplateWriteUtilsTest {
    @Test
    public void test() throws Exception {
        String path = "util/template.xlsx";
        //String path = "/util/template.xlsx";
        Workbook workbook = ExcelTemplateWriteUtils.getWorkbook(path);
        Sheet sheet = workbook.getSheetAt(0);
        
        List<CustomerDto> list = new ArrayList<>(10);
        for(int i=0; i<10; i++) {
            CustomerDto dto = new CustomerDto();
            dto.setChineseName("name:" + i);
            dto.setCustomerCode("code:" + i);
            dto.setOwnerGroup("group:" + i);
            list.add(dto);
        }
        
        ExcelTemplateWriteUtils.fillDataWithTemplate(sheet, 1, list);
        
        assertEquals(sheet.getPhysicalNumberOfRows(), 11);
        
        workbook.write(new FileOutputStream(new File("C:\\Users\\RYan27\\Desktop\\test\\" + UUID.randomUUID().toString() + ".xlsx")));
        workbook.close();
    }
}

模板文件：

最終生成的文件實例：