通过模板(模板有样式)使用导出工具类（基于自定义注解，反射）导出excel

    /**
     * 抽取工具类通过注解、反射，使用模板打印完成报表生成。
     * 通过自定义注解：根据模板列顺序对实体属性
     *                 添加注解，例@ExcelAttribute(sort = 0)
     */
@RequestMapping(value = "/export/{type}", method = RequestMethod.GET)
public void export(@PathVariable String type) throws Exception {
    //1.获取excel报表需要的数据
    List<User> list = userService.findByType(type);
    //2.加载模板
    Resource resource = new ClassPathResource("template/user.xlsx");
    FileInputStream fis = new FileInputStream(resource.getFile());
    //3.通过工具类完成下载
    new ExcelExportUtil(User.class,2,2).export(response,fis,list,"用户报表.xlsx");
}

 

package com.*.poi;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.FIELD)
public @interface ExcelAttribute {
    /** 对应的列名称 */
    String name() default "";

    /** 列序号 */
    int sort();

    /** 字段类型对应的格式 */
    String format() default "";

}

 

package com.*.common.poi.utils;

import com.*.poi.ExcelAttribute;
import lombok.Getter;
import lombok.Setter;
import org.apache.poi.hssf.usermodel.*;
import org.apache.poi.poifs.filesystem.POIFSFileSystem;
import org.apache.poi.ss.formula.functions.T;
import org.apache.poi.ss.usermodel.*;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;

import javax.servlet.http.HttpServletResponse;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.lang.reflect.Field;
import java.net.URLEncoder;
import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;
import java.util.concurrent.atomic.AtomicInteger;

@Getter
@Setter
public class ExcelExportUtil<T> {

    private int rowIndex;
    private int styleIndex;
    private String templatePath;
    private Class clazz;
    private List<Field> fields;

    /**
     * 参数rowIndex为开始写入的行索引
     * 参数styleIndex为需要获取表格的样式所在行的索引
     */
    public ExcelExportUtil(Class clazz,int rowIndex,int styleIndex) {
        this.clazz = clazz;
        this.rowIndex = rowIndex;
        this.styleIndex = styleIndex;
        fields = new ArrayList<>();
        //getDeclaredFields获得当前类的所有声明的字段，即包括public、private和proteced，但是不包括父类的申明字段。
        //fields.addAll(new ArrayList<>(Arrays.asList(clazz.getDeclaredFields())));
        while (clazz!=null){//父类字段也获取
            fields.addAll(new ArrayList<>(Arrays.asList(clazz.getDeclaredFields())));
            clazz = clazz.getSuperclass();
            if(clazz.getName().equals("java.lang.Object")){
                break;
            }
        }
    }

    /**
     * 基于注解导出
     */
    public void export(HttpServletResponse response,InputStream is, List<T> objs,String fileName) throws Exception {

        XSSFWorkbook workbook = new XSSFWorkbook(is);
        Sheet sheet = workbook.getSheetAt(0);

        CellStyle[] styles = getTemplateStyles(sheet.getRow(styleIndex));

        AtomicInteger datasAi = new AtomicInteger(rowIndex);
        for (T t : objs) {
            Row row = sheet.createRow(datasAi.getAndIncrement());
            for(int i=0;i<styles.length;i++) {
                Cell cell = row.createCell(i);
                cell.setCellStyle(styles[i]);
                for (Field field : fields) {
                    if(field.isAnnotationPresent(ExcelAttribute.class)){
                        field.setAccessible(true);
                        ExcelAttribute ea = field.getAnnotation(ExcelAttribute.class);
                        if(i == ea.sort()) {
                            //取出数据，判空处理，否则设置值时空指针
                            Object obj = field.get(t);
                            cell.setCellValue(null==obj?"":obj.toString());
                        }
                    }
                }
            }
        }
        fileName = URLEncoder.encode(fileName, "UTF-8");
        response.setContentType("application/octet-stream");
        response.setHeader("content-disposition", "attachment;filename=" + new String(fileName.getBytes("ISO8859-1")));
        response.setHeader("filename", fileName);
        workbook.write(response.getOutputStream());
    }

    /**
     * 获取模板样式
     */
    public CellStyle[] getTemplateStyles(Row row) {
        CellStyle [] styles = new CellStyle[row.getLastCellNum()];
        for(int i=0;i<row.getLastCellNum();i++) {
            styles[i] = row.getCell(i).getCellStyle();
        }
        return styles;
    }
}