How to set value of list<String> in DynamicJasper - list

Question

I need to generate dynamic count of columns in me report. So I set to my JasperPrint the massive of Object:
Object[] obj = new Object[selectedUsers.size()];
//fill the massive
JasperPrint jp = DynamicJasperHelper.generateJasperPrint(dr, new ClassicLayoutManager(), new JRBeanArrayDataSource(obj));
My obj is a class:
public class ResultsDTO {
private String login;
private Integer id;
private List<String> list;
private Object[] results;
public Object[] getResults() {
return results;
}
public void setResults(Object[] results) {
this.results = results;
}
public ResultsDTO(){
}
public ResultsDTO(Integer id,String login) {
super();
this.login = login;
this.id = id;
}
public ResultsDTO(String login, Integer id, List<String> list) {
super();
this.login = login;
this.id = id;
this.list = list;
}
public String getLogin() {
return login;
}
public void setLogin(String login) {
this.login = login;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public List<String> getList() {
return list;
}
public void setList(List<String> list) {
this.list = list;
}
public void addToList(String day_result){
this.list.add(day_result);
}
}
and then I try to create columns:
FastReportBuilder firstReport = new FastReportBuilder();
List<AbstractColumn> column_list = new ArrayList<AbstractColumn>();
AbstractColumn columnId = getColumn("id", Integer.class,"№", 30, headerStyle, detailStyle);
AbstractColumn columnLogin = getColumn("login", String.class,"ФИО", 150, headerStyle, detailStyle);
for (int i = 0; i < header.size(); i++){
AbstractColumn column = getColumn("results", Object.class, header.get(i), 80, headerStyle, detailStyle);
column_list.add(column);
}
Eventually I have an exception:
net.sf.jasperreports.engine.design.JRValidationException: Report
design not valid :
1. Class "java.lang.Object" not supported for text field expression.
Please, help! I don' know how to use jasper and list or array

Answer 1

Jasper Reports does not allow Object as a valid type for its elements. I has to be one of the following:
String
Number (or any subclass of it)
Date
Boolean
You should ask each element in the form for its class and pass proper class to the column builder.