例如：
- 思路 通过自定义注解,标注实体类上并设置列表头，反射获取里面值通过apache.poi 这个jar生成Excel表
提示：默认Dao取出来数据List<T> 这种类型数据
啥也不说直接开搞
实现步骤：
提示：环境 springboot 和maven
例如：
- 使用Maven导入jar包
<dependency>
<groupId>org.apache.poi</groupId>
<artifactId>poi</artifactId>
<version>5.2.2</version>
</dependency>
- 自定义注解
/**
* 通过注解定义Excel的列头
*/
@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.FIELD)
public @interface ExcelHead {
public String value() default "默认设置列头";
}
-
标注实体类后效果
-
封装工具类
@Component
public class ExcelUtil<T> {
/**
* 建立Excel的核心
* @param savePath 输出路径，也就是保存Excel的路径
* @param listName 表名字 这里值打开Excel左下角表名字，并不是文件名字
* @param list dao层里取数据
* @param columnWidth 列宽
* @param rowHeight 行高
* @param target list里装的实体类的class
* @throws Exception
*/
public void createExcel(String savePath, String listName, List<T> list, int columnWidth, int rowHeight, Class target) throws Exception {
FileOutputStream outputStream = null;
HSSFWorkbook workbook = new HSSFWorkbook();
//创建表
HSSFSheet sheet = workbook.createSheet(listName);
//设置列头
setHead(target, sheet, columnWidth, rowHeight);
int i = 1;
//对于list里数据进行遍历
for (T t : list) {
//设置第一行
HSSFRow row = sheet.createRow(i++);
//设置行高度
row.setHeight((short) (rowHeight * 10));
Class<?> aClass = t.getClass();
Field[] declaredFields = aClass.getDeclaredFields();
int j = 0;
for (Field field : declaredFields) {
field.setAccessible(true);
//对于没有标注该注解直接结束本次循环
if (field.getAnnotation(ExcelHead.class) == null){
continue;
}
Object o = field.get(t);
HSSFCell cell = row.createCell(j++);
cell.setCellValue(o.toString());
}
}
try {
outputStream = new FileOutputStream(savePath);
workbook.write(outputStream);
} catch (Exception e) {
e.printStackTrace();
} finally {
close(outputStream);
}
}
/**
* 设置列头 就是通过反射拿到注解里值完后通过 poi设置Excel里值
* @param target dao层理取 比如List<User> target就是user.class
* @param sheet
* @param ColumnWidth 列宽度
* @param rowHeight 行高度
*/
public void setHead(Class target, HSSFSheet sheet, int ColumnWidth, int rowHeight) {
//建立第0行
HSSFRow row = sheet.createRow(0);
//通过反射拿到属性
Field[] fields = target.getDeclaredFields();
int i = 0;
for (Field field : fields) {
//突破private
field.setAccessible(true);
//有些属性没有标注注解那么结束本次循环，没必要继续往下进行操作
if (field.getAnnotation(ExcelHead.class) == null) {
continue;
}
ExcelHead annotation = field.getAnnotation(ExcelHead.class);
//获取注解里值
String value = annotation.value();
//建立0行第i个小单元格
HSSFCell cell = row.createCell(i++);
//设置列宽
sheet.setColumnWidth(i, ColumnWidth * 256);
//设置行高
row.setHeight((short) (rowHeight * 10));
//往一个单元格放值（也就是注解里值）
cell.setCellValue(value);
}
}
public void close(FileOutputStream fileOutputStream) {
if (fileOutputStream != null) {
try {
fileOutputStream.flush();
fileOutputStream.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
public void createExcel(String savePath, String listName, List<T> list, Class target) throws Exception {
this.createExcel(savePath, listName, list, 20, 30, target);
}
}
- 最后完成业务层
@Service
public class CsvServiceImpl implements CsvService{
//通过spring注入工具类
@Autowired
ExcelUtil<LoginLogEntity> excelUtil;
@Override
public void getCSVFile(HttpServletResponse response, HttpSession session) throws Exception{
//通过session取dao里获取数据
List<LoginLogEntity> list = (List<LoginLogEntity>)session.getAttribute("userLog");
//输出路径
String savePath = "./src/main/resources/static/用户日志表.xls";
try {
excelUtil.createExcel(savePath,"用户日志表",list,LoginLogEntity.class);
}catch (Exception e){
e.printStackTrace();
}
//以上完成excel文档（里面已经存入dao里数据）在项目里建立，下面就是取Excel文档了
FileInputStream inputStream = null;
ServletOutputStream stream = null;
try {
//因为中文问题，对中文名解码ios
String filename = "日志表.xls";
String filename1 = new String(filename.getBytes("utf-8"),"ISO-8859-1");
//告诉浏览器下载
response.addHeader("content-type","application/x-msdownload");
response.setContentType("application/octet-stream");
response.addHeader("Content-Disposition","attachment;filename="+filename1);
File file = new File("./src/main/resources/static/用户日志表.xls");
if (!file.exists()){
throw new RuntimeException("文件不存在");
}
inputStream = new FileInputStream(file);
stream = response.getOutputStream();
byte[] bytes = new byte[200];
int len = 0;
while ((len = inputStream.read(bytes)) != -1){
stream.write(bytes,0,len);
}
}finally {
if (stream != null){
stream.flush();
stream.close();
}
if (inputStream != null){
inputStream.close();
}
}
}
}