It's a wrapper of Apache POI, with which you can do javabeans <-> spreadsheet conversion even more easily.
<dependencies>
<dependency>
<groupId>com.github.chenjianjx</groupId>
<artifactId>sep4j</artifactId>
<version>2.0.5</version>
</dependency>
..
</dependencies>
Map<String, String> headerMap = new LinkedHashMap<String, String>();
headerMap.put("userId", "User Id"); // "userId" is a property of the javabeans you are going to save.
// "User Id" will be the corresponding column header in the spreadsheet.
headerMap.put("firstName", "First Name");
headerMap.put("lastName", "Last Name");
OutputStream spreadsheetOutputStream = new FileOutputStream("someExcelFile.xlsx");
Ssio.save(headerMap, userList, spreadsheetOutputStream);
//"spreadsheetOutputStream" can be replaced with "spreadsheetOutputFile" (a java.io.File object) or if you use Guava, you can just
Ssio.save(
ImmutableMap.of("userId", "User Id", "firstName","First Name", "lastName", "Last Name"),
userList, spreadsheetOutputStream);You can even let the program generate a header map for you:
Ssio.save(User.class, userList, spreadsheetOutputStream);You will get an spreadsheet file like
| User Id | First Name | Last Name |
|---|---|---|
| 1 | Lei | Li |
| 2 | Jim | Green |
Note: All cells generated will be String-Typed Cells.
Map<String, String> reverseHeaderMap = new HashMap<String,String>();
reverseHeaderMap.put("User Id", "userId"); //"User Id" is a column header in the spreadsheet.
//"userId" is the corresponding property of User class.
reverseHeaderMap.put("First Name", "firstName");
reverseHeaderMap.put("Last Name","lastName");
InputStream spreadsheetInputStream = new FileInputStream("someExcelFile.xlsx");
List<User> users = Ssio.parseIgnoringErrors(reverseHeaderMap, spreadsheetInputStream, User.class);
//"spreadsheetInputStream" can be replaced with "spreadsheetInputFile" (a java.io.File object) or if you use Guava, you can just
List<User> users = Ssio.parse(
ImmutableMap.of("User Id","userId","First Name","firstName","Last Name","lastName"),
spreadsheetInputStream, User.class);You can even let the program guess out a reverseHeaderMap for you
List<User> users = Ssio.parseIgnoringErrors(spreadsheetInputStream, User.class);
List<DatumError> datumErrors = new ArrayList<DatumError>(); //to collect the errors
headerMap.put("fakeProperty", "Fake Property"); //try to write an non-existing property
Ssio.save(headerMap, users, outputStream, "!!ERROR!!", datumErrors);
for (DatumError de : datumErrors) {//here to handle the errors
System.err.println(MessageFormat.format("Error: recordIndex = {0},
propName = \"{1}\", cause = {2}",
de.getRecordIndex(), de.getPropName(), de.getCause()));
}Will then get an spreadsheet file like
| User Id | First Name | Last Name | Fake Property |
|---|---|---|---|
| 1 | Lei | Li | !!ERROR!! |
| 2 | Jim | Green | !!ERROR!! |
List<CellError> cellErrors = new ArrayList<CellError>();
try{
List<User> users = Ssio.parse(reverseHeaderMap, inputStream, cellErrors, User.class);
}catch (InvalidFormatException e) {
System.err.println("Not a valid spreadsheet file");
} catch (InvalidHeaderRowException e) {
System.err.println("The column headers of your spreadsheet file do not match what we need");
}
for (CellError ce : cellErrors) {
System.err.println(MessageFormat.format("failed to parse a cell: rowIndexOneBased = {0},
columnIndexOneBased = {1}, propName = \"{2}\", headerText = \"{3}\", cause = {4} ",
ce.getRowIndexOneBased(),ce.getColumnIndexOneBased(),
ce.getPropName(),ce.getHeaderText(), ce.getCause()));
}Sep4j will call the properties' toString() methods to convert a property value to a String, and then write them to an spreadsheet file as String-typed cells.
- What if I want the property printed another way instead of toString(), for example, to format a date in Chinese style?
- Create a new, String-typed property in your class by adding a getter method.
private static final class User {
...
public String getBirthDayString(){
if(birthDay == null){
return null;
}
return DateFormatUtils.format(birthDay, "yyyy-MM-dd");
}
...
}Also, add it to the header map:
headerMap.put("birthDayString", "Birth Date");- Can I let Sep4j produce Numeric-typed cells or another type others than String ?
- No, you can't. This is how Sep4j keeps itself simple.
- You can use ssio for that purpose, which was made by the same author.
-
Sep4j will only take cells of the following types. Cells of other types such as formula, blank etc. will be parsed as null values.
- String
- Boolean
- Numeric
- Date (Actually it is a Numeric cell type + Date cell style)
-
What if a cell is of String type in the spreadsheet, but its corresponding java property is of double?
- Sep4j will do a guess for you, if the String's format in the cell is a valid number; You don't need another setter. if the String's format in the cell is not a valid number, Sep4j will report a CellError saying "no suitable setter"
-
A property of my class is not of any basic types. For example, it's of List. What to do?
- Add a String-Typed setter to your class
public void setRoles(String rolesString){
String[] roleArray = StringUtils.split(rolesString, ",");
this.setRoles(Arrays.asList(roleArray));
}- Null handling
- Cell with null value will lead to a null property value. However, if the property is of primitive type such as "int", "long", then a CellError will be raised.
In some cases you have a collection of Maps and you don't want to bother creating a class. This can help:
ImmutableMap<String, Object> record1 = ImmutableMap.of("firstName", "Jim", "lastName", "Green");
ImmutableMap<String, Object> record2 = ImmutableMap.of("firstName", "Li", "lastName", "Lei");
List<Map<String,Object>> records = Arrays.asList(record1, record2);
ImmutableMap<String, String> headerMap = ImmutableMap.of("firstName", "First Name", "lastName", "Last Name");
Ssio.saveMaps(headerMap, records, spreadsheetOutputStream);
You can also let sep4j generate a header map for you, by just providing the map's keys
Ssio.saveMaps(Arrays.asList("firstName", "lastName"), records, spreadsheetOutputStream);
Map<String, String> reverseHeaderMap = ImmutableMap.of("User Id", "userId",
"First Name", "firstName", "Last Name", "lastName");
List<Map<String, String>> users = Ssio.parseToMapsIgnoringErrors(reverseHeaderMap, inputStream);
Ssio.appendTo(headerMap, newListToAppend, theFile);
A date column in a spreadsheet may have both String-typed cells and Date-typed cells (common human error). You need to accommodate both.
/**
* if the cell is of Date type
* @param birthDay
*/
public void setBirthDay(Date birthDay) {
this.birthDay = birthDay;
}
/**
* if the cell is of String type
* @param birthDayString
* @throws ParseException
*/
public void setBirthDay(String birthDayString) throws ParseException {
if(birthDayString == null){
return;
}
birthDay = DateUtils.parseDate(birthDayString, new String[]{"yyyy-MM-dd"});
}