1. First get the path of the Excel template, this example is placed in the project
String path = request.getSession().getServletContext().getRealPath("/") + File.separator + "WEB-INF" + File.separator + "templetfile" + File.separator;
String filename = "rolledlossData.xlsx";
2. Get the XSSFWorkbook object ( XSSFWorkbook is the version that operates Excel2007, the extension is .xlsx)
XSSFWorkbook workbook = new XSSFWorkbook(new FileInputStream(path+filename));
3. Get the set of objects to be exported (the object properties must be in the same order and fields as in the table)
------------- List<Object> list is used in this example
4. Write the object collection to the excel sheet
Workbook wb =hssfWorkbook;
Sheet sheet = wb.getSheetAt(0);
Row row = null;
Cell cell;
Object data = null;
Object fieldValue = null;
SimpleDateFormat format = new SimpleDateFormat(defaultDateFormatPattern);
/** write data to excel **/
CellStyle dataStyle = createDataCellStyle(wb);
Field[] fields = list.get(0).getClass().getDeclaredFields();
int sums = list.size();
for (int rowIndex = 0; rowIndex < sums; rowIndex++) {
data = list.get(rowIndex);
row = sheet.createRow(rowIndex + 1);
int colums = fields.length;
for (int i=0;i<colums;i++){
cell = row.createCell(i);
cell.setCellStyle(dataStyle);
fieldValue = ReflectiveUtils.getValueByReflectField(data, fields[i]);
cell.setCellValue(convertObjectToString(fieldValue, format));
}
}
Get the value of the attribute through reflection, and convert the attribute value to String type method
public static Object getValueByReflectField(Object data, Field field) {
try {
if(field == null){
return null;
}
field.setAccessible(true);
Object value = field.get(data);
return value;
} catch (SecurityException e) {
logger.error("Failed to obtain class attributes through reflection",e);
throw new RuntimeException("Failed to obtain class attributes through reflection",e);
}catch (IllegalArgumentException e) {
logger.error("Acquired through reflection When the object value is used, the object is invalid",e);
throw new RuntimeException("When the object value is obtained by reflection, the object is invalid",e);
} catch (IllegalAccessException e) {
logger.error("The object value cannot be obtained by reflection , insufficient permissions",e);
throw new RuntimeException("Cannot get the object value through reflection, insufficient permissions",e);
}
}
How to convert object to String
private static String convertObjectToString(Object value, DateFormat format) {
String strValue = null;
if (value instanceof Date) {
strValue = format.format(value);
} else if (value instanceof String) {
strValue = (String) value;
} else {
if (value == null) {
strValue = "";
} else {
strValue = value.toString();
}
}
return strValue;
}
5. Write the table to the stream
ByteArrayOutputStream byteOutput = new ByteArrayOutputStream(); wb.write(byteOutput); InputStream inputStream = new ByteArrayInputStream( byteOutput.toByteArray());
6. Write the file stream to the client (where the response is the client request HttpServletResponse response)
BufferedInputStream bin = null;
BufferedOutputStream bos = null;
GZIPOutputStream gzipOutput = null;
try {
/** Convert the file name here, otherwise Chinese garbled **/
String fileName = new String(displayName.getBytes("GBK"),"ISO-8859-1");
// clear the response
response.reset();
//The client side uses the dialog box to save the file
response.setHeader("Content-disposition", "attachment;filename="+fileName);
response.setHeader("Content-Encoding", "gzip");
response.setContentType("application/octet-stream");
bin = new BufferedInputStream(inputStream);
OutputStream out = response.getOutputStream();
bos = new BufferedOutputStream(out);
/** This uses gizp for compression**/
gzipOutput = new GZIPOutputStream(bos);
byte[] buffer = new byte[512];
int readCount = -1;
while(true){
readCount = bin.read(buffer);
if(readCount == -1){
break;
}
gzipOutput.write(buffer,0,readCount);
}
}finally{
if(bin != null){
bin.close();
}
if(gzipOutput != null){
gzipOutput.close();
}
}