Jasper Reports：Subeport 在主报告中显示空值，数据源是一个 java 列表

Question

WHAT I HAVE

My Main Report shows all values are null from my subreport.

WHAT I WANT

I am passing data to subReport from MainReport through a parameter called subData as shown in the MainReport JRXML snippet below.

NB : Its a List

My subReport snippet in the MainReport is given below, the dataSource expression is clearly "$P{subData}"

My main java class passes an instance of a List (named subData) through a parameter (named subDataOrion) shown below.

public class SubRepoExample {

public static void main(String[] args) throws JRException {
   SubRepoExample repo = new SubRepoExample();
   repo.combineMasterAndSubreport();
}

public void combineMasterAndSubreport() throws JRException{

    JasperReport main = JasperCompileManager.compileReport("src/subrepoexample/masterReport.jrxml");

    JasperReport sub = JasperCompileManager.compileReport("src/subrepoexample/subReport.jrxml");



   //create a list for holding the subreport object

    //SubreportWrapper subDataWrap = new SubreportWrapper();

    List<SubreportObject> subData = new ArrayList();
    //subData.add(subDataWrap.getSubData());
    subData.add(new SubreportObject("Kevin",20));
    subData.add(new SubreportObject("Jane",20));
    subData.add(new SubreportObject("Mike",20));
    subData.add(new SubreportObject("Simon",20)); 
    //subData.add(new SubreportObject("Naomi",25));
    //subData.add(new SubreportObject("Pat",20));


    //SubreportWrapper subDataWrap = new SubreportWrapper();

    //List<SubreportObject> subData = subDataWrap.getSubData();

    Map para = new HashMap();
    //pass the report itself through a parameter
    //para.put("SUBREPORT", sub);
    //pass the list to parameter
    //JRDataSource subx = new JRBeanCollectionDataSource(subData);
    para.put("subDataOrion",subData);

    //JasperPrint jp = JasperFillManager.fillReport(sub, para,new JRBeanCollectionDataSource(subData));      
    //JasperPrint jp = JasperFillManager.fillReport(main, para,new JRTableModelDataSource(createMasterData()));


     JasperCompileManager.compileReportToFile(
            "src/subrepoexample/subReport.jrxml", 
            "src/subrepoexample/subReport.jasper"); 


    JasperPrint jp = JasperFillManager.fillReport(main, para,new JRTableModelDataSource(createMasterData()));
    JasperViewer.viewReport(jp, false);  

}

 public DefaultTableModel createMasterData(){

    String [] cols = {"COL_1","COL_2","COL_3"};
    Object[][] data = {{"Data","Data","Data"},
                       {"Data","Data","Data"},       
                       {"Data","Data","Data"},   
                       {"Data","Data","Data"},   
                       {"Data","Data","Data"},  
                      };
    DefaultTableModel dtm = new DefaultTableModel(data,cols);

return dtm;}

}

SubReport class that creates the subReport objects

public class SubreportObject {
  String name;
  int age;

 public SubreportObject(String name,int age){
     this.name = name;
     this.age = age;  
     }

 public String getName() {
 return name;
     }

 public void setName(String name) {
 this.name = name;
     }

 public int getAge() {
 return age;
     }

 public void setAge(int age) {
 this.age = age;
     }

  }

I am aware there are two issues here, the arrangement issue of the data since the subreport data is mixed. or scrambled with the main report data as shown in the first screen shot. This I think can be fixed by groups, which is not my question here.

MY QUESTION :

I need first to eliminate the 'null' values so that I can go to the next stage of using group expression. Am stuck here and not sure what is wrong? At least I asked this question and at least 'null' values appeared, earlier they were completely not appearing.

Why is the data in the List appearing as 'null', when compiled separately, they compile wonderfully.

EDIT 1:

Sorry for being sloppy on the earlier version of this question. Thank you people.

EDIT 2:

I have added the JRBeanCollection as shown below

Even changed the parameter class to JRDataSource as below

but still shows null values..???

Answer 1

您缺少JRBeanCollectionDatasource ，List 本身不是数据源，除非它实现了 JRDataSource 接口应该由 JRDataSource 包装/改编。