Learn to read excel, write excel, evaluate formula cells and apply custom formatting to the generated excel files using Apache POI library with examples.
If we are building software for the HR or Finance domain, there is usually a requirement for generating excel reports across management levels. Apart from reports, we can also expect some input data for the applications coming in the form of excel sheets and the application is expected to support this requirement.
Apache POI is a well-trusted library among many other open-source libraries to handle such usecases involving excel files. Please note that, in addition, we can read and write MS Word and MS PowerPoint files also using the Apache POI library.
This Apache POI tutorial will discuss some everyday excel operations in real-life applications.
1. Maven
If we are working on a maven project, we can include the Apache POI dependencies in pom.xml
file using this:
<dependency>
<groupId>org.apache.poi</groupId>
<artifactId>poi</artifactId>
<version>5.2.2</version>
</dependency>
<dependency>
<groupId>org.apache.poi</groupId>
<artifactId>poi-ooxml</artifactId>
<version>5.2.2</version>
</dependency>
2. Core Classes in POI Library
HSSF, XSSF and XSSF classes
Apache POI main classes usually start with either HSSF, XSSF or SXSSF.
- HSSF – is the POI Project’s pure Java implementation of the Excel 97(-2007) file format. e.g., HSSFWorkbook, HSSFSheet.
- XSSF – is the POI Project’s pure Java implementation of the Excel 2007 OOXML (.xlsx) file format. e.g., XSSFWorkbook, XSSFSheet.
- SXSSF (since 3.8-beta3) – is an API-compatible streaming extension of XSSF to be used when huge spreadsheets have to be produced and heap space is limited. e.g., SXSSFWorkbook, SXSSFSheet. SXSSF achieves its low memory footprint by limiting access to the rows within a sliding window, while XSSF gives access to all rows in the document.
Row and Cell
Apart from the above classes, Row and Cell interact with a particular row and a particular cell in an excel sheet.
Styling Related Classes
A wide range of classes like CellStyle, BuiltinFormats, ComparisonOperator, ConditionalFormattingRule, FontFormatting, IndexedColors, PatternFormatting, SheetConditionalFormatting etc. are used when you have to add formatting to a sheet, primarily based on some rules.
FormulaEvaluator
Another helpful class FormulaEvaluator is used to evaluate the formula cells in an excel sheet.
3. Write to an Excel File
I am taking this example first so we can reuse the excel sheet created by this code in further examples.
Writing excel using POI is very simple and involves the following steps:
- Create a workbook
- Create a sheet in the workbook
- Create a row in the sheet
- Add cells to the sheet
- Repeat steps 3 and 4 to write more data
It seems very simple, right? Let’s have a look at the code doing these steps.
Java program to write an excel file using Apache POI library.
//Blank workbook
XSSFWorkbook workbook = new XSSFWorkbook();
//Create a blank sheet
XSSFSheet sheet = workbook.createSheet("Employee Data");
//Prepare data to be written as an Object[]
Map<String, Object[]> data = new TreeMap<String, Object[]>();
data.put("1", new Object[] {"ID", "NAME", "LASTNAME"});
data.put("2", new Object[] {1, "Amit", "Shukla"});
data.put("3", new Object[] {2, "Lokesh", "Gupta"});
data.put("4", new Object[] {3, "John", "Adwards"});
data.put("5", new Object[] {4, "Brian", "Schultz"});
//Iterate over data and write to sheet
Set<String> keyset = data.keySet();
int rownum = 0;
for (String key : keyset) {
Row row = sheet.createRow(rownum++);
Object [] objArr = data.get(key);
int cellnum = 0;
for (Object obj : objArr)
{
Cell cell = row.createCell(cellnum++);
if(obj instanceof String)
cell.setCellValue((String)obj);
else if(obj instanceof Integer)
cell.setCellValue((Integer)obj);
}
}
//Write the workbook in file system
try {
FileOutputStream out = new FileOutputStream(new File("howtodoinjava_demo.xlsx"));
workbook.write(out);
out.close();
System.out.println("howtodoinjava_demo.xlsx written successfully on disk.");
}
catch (Exception e) {
e.printStackTrace();
}
See Also: Appending Rows to Excel
4. Reading an Excel File
Reading an excel file using POI is also very simple if we divide this into steps.
- Create a workbook instance from an excel sheet
- Get to the desired sheet
- Increment row number
- Iterate over all cells in a row
- Repeat steps 3 and 4 until all data is read
Let’s see all the above steps in the code. I am writing the code to read the excel file created in the above example. It will read all the column names and the values in it – cell by cell.
Java program to read an excel file using Apache POI library.
FileInputStream file = new FileInputStream(new File("howtodoinjava_demo.xlsx"));
//Create Workbook instance holding reference to .xlsx file
XSSFWorkbook workbook = new XSSFWorkbook(file);
//Get first/desired sheet from the workbook
XSSFSheet sheet = workbook.getSheetAt(0);
//Iterate through each rows one by one
Iterator<Row> rowIterator = sheet.iterator();
while (rowIterator.hasNext()) {
Row row = rowIterator.next();
//For each row, iterate through all the columns
Iterator<Cell> cellIterator = row.cellIterator();
while (cellIterator.hasNext()) {
Cell cell = cellIterator.next();
//Check the cell type and format accordingly
switch (cell.getCellType()) {
case Cell.CELL_TYPE_NUMERIC:
System.out.print(cell.getNumericCellValue() + "t");
break;
case Cell.CELL_TYPE_STRING:
System.out.print(cell.getStringCellValue() + "t");
break;
}
}
System.out.println("");
}
file.close();
Program Output:
ID NAME LASTNAME
1.0 Amit Shukla
2.0 Lokesh Gupta
3.0 John Adwards
4.0 Brian Schultz
5. Add and Evaluate Formula Cells
When working on complex excel sheets, we encounter many cells with formulas to calculate their values. These are formula cells. Apache POI also has excellent support for adding formula cells and evaluating already present formula cells.
Let’s see one example of how to add formula cells in excel?
The sheet has four cells in a row and the fourth one in the multiplication of all the previous 3 rows. So the formula will be: A2*B2*C2 (in the second row)
Java program to add formulas in an excel file using Apache POI library.
XSSFWorkbook workbook = new XSSFWorkbook();
XSSFSheet sheet = workbook.createSheet("Calculate Simple Interest");
Row header = sheet.createRow(0);
header.createCell(0).setCellValue("Pricipal");
header.createCell(1).setCellValue("RoI");
header.createCell(2).setCellValue("T");
header.createCell(3).setCellValue("Interest (P r t)");
Row dataRow = sheet.createRow(1);
dataRow.createCell(0).setCellValue(14500d);
dataRow.createCell(1).setCellValue(9.25);
dataRow.createCell(2).setCellValue(3d);
dataRow.createCell(3).setCellFormula("A2*B2*C2");
try {
FileOutputStream out = new FileOutputStream(new File("formulaDemo.xlsx"));
workbook.write(out);
out.close();
System.out.println("Excel with foumula cells written successfully");
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
Similarly, we want to read a file with formula cells and use the following logic to evaluate formula cells.
Java program to evaluate formulas in an excel file using Apache POI library.
FileInputStream file = new FileInputStream(new File("formulaDemo.xlsx"));
//Create Workbook instance holding reference to .xlsx file
XSSFWorkbook workbook = new XSSFWorkbook(file);
FormulaEvaluator evaluator = workbook.getCreationHelper().createFormulaEvaluator();
//Get first/desired sheet from the workbook
XSSFSheet sheet = workbook.getSheetAt(0);
//Iterate through each rows one by one
Iterator<Row> rowIterator = sheet.iterator();
while (rowIterator.hasNext()) {
Row row = rowIterator.next();
//For each row, iterate through all the columns
Iterator<Cell> cellIterator = row.cellIterator();
while (cellIterator.hasNext()) {
Cell cell = cellIterator.next();
//Check the cell type after eveluating formulae
//If it is formula cell, it will be evaluated otherwise no change will happen
switch (evaluator.evaluateInCell(cell).getCellType()) {
case Cell.CELL_TYPE_NUMERIC:
System.out.print(cell.getNumericCellValue() + "tt");
break;
case Cell.CELL_TYPE_STRING:
System.out.print(cell.getStringCellValue() + "tt");
break;
case Cell.CELL_TYPE_FORMULA:
//Not again
break;
}
}
System.out.println("");
}
file.close();
Program Output:
Pricipal RoI T Interest (P r t)
14500.0 9.25 3.0 402375.0
6. Formatting the Cells
So far we have seen examples of reading/writing and excel files using Apache POI. But, when creating a report in an excel file, it is essential to add formatting on cells that fit into any pre-determined criteria.
This formatting can be a different coloring based on a specific value range, expiry date limit etc.
In the below examples, we are taking a couple of such cell formatting examples for various purposes.
6.1. Cell value in a specific range
This code will color any cell in a range whose value is between a configured range. [e.g., between 50 and 70]
static void basedOnValue(Sheet sheet)
{
//Creating some random values
sheet.createRow(0).createCell(0).setCellValue(84);
sheet.createRow(1).createCell(0).setCellValue(74);
sheet.createRow(2).createCell(0).setCellValue(50);
sheet.createRow(3).createCell(0).setCellValue(51);
sheet.createRow(4).createCell(0).setCellValue(49);
sheet.createRow(5).createCell(0).setCellValue(41);
SheetConditionalFormatting sheetCF = sheet.getSheetConditionalFormatting();
//Condition 1: Cell Value Is greater than 70 (Blue Fill)
ConditionalFormattingRule rule1 = sheetCF.createConditionalFormattingRule(ComparisonOperator.GT, "70");
PatternFormatting fill1 = rule1.createPatternFormatting();
fill1.setFillBackgroundColor(IndexedColors.BLUE.index);
fill1.setFillPattern(PatternFormatting.SOLID_FOREGROUND);
//Condition 2: Cell Value Is less than 50 (Green Fill)
ConditionalFormattingRule rule2 = sheetCF.createConditionalFormattingRule(ComparisonOperator.LT, "50");
PatternFormatting fill2 = rule2.createPatternFormatting();
fill2.setFillBackgroundColor(IndexedColors.GREEN.index);
fill2.setFillPattern(PatternFormatting.SOLID_FOREGROUND);
CellRangeAddress[] regions = {
CellRangeAddress.valueOf("A1:A6")
};
sheetCF.addConditionalFormatting(regions, rule1, rule2);
}
6.2. Highlight Duplicate Values
Highlight all cells which have duplicate values in observed cells.
static void formatDuplicates(Sheet sheet) {
sheet.createRow(0).createCell(0).setCellValue("Code");
sheet.createRow(1).createCell(0).setCellValue(4);
sheet.createRow(2).createCell(0).setCellValue(3);
sheet.createRow(3).createCell(0).setCellValue(6);
sheet.createRow(4).createCell(0).setCellValue(3);
sheet.createRow(5).createCell(0).setCellValue(5);
sheet.createRow(6).createCell(0).setCellValue(8);
sheet.createRow(7).createCell(0).setCellValue(0);
sheet.createRow(8).createCell(0).setCellValue(2);
sheet.createRow(9).createCell(0).setCellValue(8);
sheet.createRow(10).createCell(0).setCellValue(6);
SheetConditionalFormatting sheetCF = sheet.getSheetConditionalFormatting();
// Condition 1: Formula Is =A2=A1 (White Font)
ConditionalFormattingRule rule1 = sheetCF.createConditionalFormattingRule("COUNTIF($A$2:$A$11,A2)>1");
FontFormatting font = rule1.createFontFormatting();
font.setFontStyle(false, true);
font.setFontColorIndex(IndexedColors.BLUE.index);
CellRangeAddress[] regions = {
CellRangeAddress.valueOf("A2:A11")
};
sheetCF.addConditionalFormatting(regions, rule1);
sheet.getRow(2).createCell(1).setCellValue("<== Duplicates numbers in the column are highlighted. " +
"Condition: Formula Is =COUNTIF($A$2:$A$11,A2)>1 (Blue Font)");
}
6.3. Alternate Color Rows in Different Colors
A simple code to color each alternate row in a different color.
static void shadeAlt(Sheet sheet) {
SheetConditionalFormatting sheetCF = sheet.getSheetConditionalFormatting();
// Condition 1: Formula Is =A2=A1 (White Font)
ConditionalFormattingRule rule1 = sheetCF.createConditionalFormattingRule("MOD(ROW(),2)");
PatternFormatting fill1 = rule1.createPatternFormatting();
fill1.setFillBackgroundColor(IndexedColors.LIGHT_GREEN.index);
fill1.setFillPattern(PatternFormatting.SOLID_FOREGROUND);
CellRangeAddress[] regions = {
CellRangeAddress.valueOf("A1:Z100")
};
sheetCF.addConditionalFormatting(regions, rule1);
sheet.createRow(0).createCell(1).setCellValue("Shade Alternating Rows");
sheet.createRow(1).createCell(1).setCellValue("Condition: Formula Is =MOD(ROW(),2) (Light Green Fill)");
}
6.4. Color amounts that are going to expire in the next 30 days
A handy code for financial projects which keeps track of deadlines.
static void expiryInNext30Days(Sheet sheet)
{
CellStyle style = sheet.getWorkbook().createCellStyle();
style.setDataFormat((short)BuiltinFormats.getBuiltinFormat("d-mmm"));
sheet.createRow(0).createCell(0).setCellValue("Date");
sheet.createRow(1).createCell(0).setCellFormula("TODAY()+29");
sheet.createRow(2).createCell(0).setCellFormula("A2+1");
sheet.createRow(3).createCell(0).setCellFormula("A3+1");
for(int rownum = 1; rownum <= 3; rownum++) sheet.getRow(rownum).getCell(0).setCellStyle(style);
SheetConditionalFormatting sheetCF = sheet.getSheetConditionalFormatting();
// Condition 1: Formula Is =A2=A1 (White Font)
ConditionalFormattingRule rule1 = sheetCF.createConditionalFormattingRule("AND(A2-TODAY()>=0,A2-TODAY()<=30)");
FontFormatting font = rule1.createFontFormatting();
font.setFontStyle(false, true);
font.setFontColorIndex(IndexedColors.BLUE.index);
CellRangeAddress[] regions = {
CellRangeAddress.valueOf("A2:A4")
};
sheetCF.addConditionalFormatting(regions, rule1);
sheet.getRow(0).createCell(1).setCellValue("Dates within the next 30 days are highlighted");
}
I am ending this apache poi tutorial here to keep the post within a limit.
7. Conclusion
In this tutorial, we learned to read excel, write excel, set and evaluate formula cells, and format the cells with color codings using the Apache POI library.
Happy Learning !!
Hi,
I am generating an excel file that has formulae that extract data from external files, and when the file is opened, the ‘Enable Updates?’ needs to be set.
Is there any way to automatically enable external updates?
In addition, my organisation requires sensitivity labels to allow updates to the file.
Is there any way to add a sensitivity label?
Never tried such things. Let’s see if someone else can answer it.
How to set confidentiality level in excel
Please elaborate the requirements. Are you trying to password protect a workbook or sheet? Or something else?
Not Password protect, but set a sensitivity label
CELL_TYPE_STRING cannot be resolved or is not a field
CELL_TYPE_NUMERIC cannot be resolved or is not a field
i am getting erorr. thanks in advance
The working code is on Github. Checkout for POI version and class imports.
Hi,
I have excel sheet with columns like this( Asset Name , Asset Type, Asset SubType , Asset Logo Path)… Here I want to read blob data based on Asset Logo Path column(/home/mbytes/yellaiah/asset imgs/pens.png) value to back-end(spring) from front-end extjs grid. I have tested reading file based on asset logo path column value, blob data is reading if client and server both are in same system, but i want to upload excel sheet from system2 by connecting to my server system and read files from local system(based on uploaded system) and insert into db. when i upload excel sheet i am display uploaded data to extjs grid. in grid i have button. when i click on button i need to pass data to back-end.how can i read blob from other system. pls give some suggestions.
Some of the istorm reports are not working correctly in Excel 365.Which version of POI.jar supports excel 365?Kindly help me.
Hi Lokesh, it was very helpful. Thanks for your help. I have a question on your second example;
Reading an excel file:
instead of getting all the cell values, what if want to get an input from an user (getText), lets say : ID – 1 and I need those cell values i.e. Amit and Shukla? Please throw some light on this.
Hi Mr.Lokesh,
Thanks for the helpful work uploaded.
Also, can u plz let me know can i read & write simultaneously from an excel file using Java, keeping the file open ?
Hello,
How can I find user selected cells or active cells?
Thank u
Hi,
I am uploading xl to db using Hibernate and spring i am facing foreign key problem.?please help me.
What problem??
how to pass foreign key to the controller?
Great Work! That too, you have given the source code downloading option! Highly appreciated! Great work!
Hi,
I am abel to write data in excel using above code, but when I open the file I am getting Data like :
3.0 John Adwards
4.0 Brian Schultz
ID NAME LASTNAME
1.0 Amit Shukla
2.0 Lokesh Gupta
any idea?
how can you read the password protected excel file ?
Hi Sachin, first find any tool to crack the password. Then read it. I am not aware of any other way.
Very very helpful post and brilliant tutorial for Excel
Need the suggestion regarding the below..
reading the above created file, howtodoinjava_demo.xlsx.
while parsing by using SAX Parser, the output is differing the output as below.
Employee Data [index=0]:
“ID”,”NAME”,”LASTNAME”,,,
1.0,”Amit”,”Shukla”,,,
2.0,”Lokesh”,”Gupta”,,,
3.0,”John”,”Adwards”,,,
4.0,”Brian”,”Schultz”,,,
Same file just edited in local system and doing the same gives the below output – looks fine.
Employee Data [index=0]:
“ID”,”NAME”,”LASTNAME”,,,
1,”Amit”,”Shukla”,,,
2,”Lokesh”,”Gupta”,,,
3,”John”,”Adwards”,,,
4,”Brian”,”Schultz”,,,
Please advise what can we do to get same results with system generated file?
is Apache POI free if not then what price of this
Its free.
Hi Lokesh,
I am stuck in 1 requirement to upload an read excel and save it in db.
Problem: i have n no. of excel sheets and all have different columns and all sheets would save in different table (having different table structure). And i want to create a common service , which read excel sheets and save accordingly.
In that case, you MUST put some restriction for users who are uploading those files. E.g. File names should include a particular word for each different format, OR column names should match exactly what is specified. There MUST be some rule which could be verified after file is received at server side.
Hi Lokesh, Thanks for the reply. I should elaborate more of my problem, to understand u in clear way:
For Example I have 3 excel tabs A, B & C. A has 5 columns, B has 10 & C has 15 columns. As of now, i am creating 3 different beans with the same no. of attributes (Setter/Getter) , sets every column and finally save the object in db(using hibernate).
But using this concept, i need to create 3 different service for 3 different tabs.
SO, is there any optimize way of doing this.
I will suggest you to stick with 3 services. It is good for future use.
See, it’s more of coding style question. I believe that code should be easy enough to read AND follow these SOLID principles. I will prefer easy maintainable code, rather than optimized code. Choice is yours.