Using POJO's with SelectOneMenu with Generic Converter

Question

Hello How to use List of POJO's with JSF h:selectOneMenu or Primefaces p:selectOneMenu?
I know that there are lot of related questions which suggest to use Converter but no clear build from scratch example.

I want a generic converter code for the above Purpose.

Please suggest any alternatives/point me to the right question if its a duplicate.

Answer 1

here is a complete example of using a POJO with Primefaces p:selectOneMenu.the primfaces select one menu display a list of students.If you press details button after select any student, a primfaces dialog will appear with the full name of this student.

com.model package:

Student class

package com.model;

import java.io.Serializable;

public class Student implements Serializable{


private static final long serialVersionUID = 1L;

private int Id;


public int getId() {
    return Id;
}
public void setId(int id) {
    Id = id;
}

private String lastName;
private String firstName;


public String getLastName() {
    return lastName;
}
public void setLastName(String lastName) {
    this.lastName = lastName;
}
public String getFirstName() {
    return firstName;
}
public void setFirstName(String firstName) {
    this.firstName = firstName;
}

public Student() {
    super();
    }

    public Student(String lastName, String firstName,int Id) {
    super();
    this.lastName = lastName;
    this.firstName = firstName;
    this.Id = Id;


  }}

The converter

   package com.model;

 import java.util.ArrayList;
 import java.util.List;

 import javax.faces.application.FacesMessage;
 import javax.faces.component.UIComponent;
 import javax.faces.context.FacesContext;
 import javax.faces.convert.Converter;
 import javax.faces.convert.ConverterException;
 import javax.faces.convert.FacesConverter;

  @FacesConverter(forClass = com.model.Student.class,value="student")
   public class StudentConverter implements Converter{
 public static List<Student> studentDB;

    static {
        studentDB = new ArrayList<Student>();
        studentDB.add(new Student("William", "Wong", 1));
        studentDB.add(new Student("John", "Smith", 2));
        studentDB.add(new Student("Mari", "Beckley", 3));
        studentDB.add(new Student("Messi", "Leonardo",4));
        studentDB.add(new Student("William", "Astrid", 5));
        studentDB.add(new Student("William", "Banana", 6));

        }

    public Object getAsObject(FacesContext facesContext, UIComponent component, String submittedValue) {
        if (submittedValue.trim().equals("")) {
            return null;
        } else {
            try {
                int number = Integer.parseInt(submittedValue);

                for (Student s : studentDB) {
                    if (s.getId() == number) {
                        return s;
                    }
                }

            } catch(NumberFormatException exception) {
                throw new ConverterException(new FacesMessage(FacesMessage.SEVERITY_ERROR, "Conversion Error", "Not a valid player"));
            }
        }

        return null;
    }

    public String getAsString(FacesContext facesContext, UIComponent component, Object value) {
        if (value == null || value.equals("")) {
            return "";
        } else {
            return String.valueOf(((Student) value).getId());
        }
    }
}

com.managedbean package

   package com.managedbean;

   import java.util.List;
   import javax.annotation.PostConstruct;
   import javax.faces.bean.ManagedBean;
   import javax.faces.bean.ViewScoped;
   import com.model.Student;
   import com.model.StudentConverter;

 @ManagedBean
 @ViewScoped
    public class StudentMB {
    private Student  selectedStudent;
    public Student getSelectedStudent() {
    return selectedStudent;
}


public void setSelectedStudent(Student selectedStudent) {
    this.selectedStudent = selectedStudent;
}


public List<Student> getStudents() {
    return students;
}


public void setStudents(List<Student> students) {
    this.students = students;
}


private List<Student> students;


@PostConstruct
public void init(){
    students=StudentConverter.studentDB;
}

 }

selectMenu.xhtml

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
 <html xmlns="http://www.w3.org/1999/xhtml"
  xmlns:h="http://java.sun.com/jsf/html"
  xmlns:f="http://java.sun.com/jsf/core"
  xmlns:p="http://primefaces.org/ui">
  <h:head>
 </h:head>
 <h:body>
 <h:form> 
 <h:panelGrid columns="2" style="margin-bottom:10px" cellpadding="1">  
 <h:outputText value="Pojo: " />  
     <p:selectOneMenu value="#{studentMB.selectedStudent}"  effect="fade" converter="student">  
        <f:selectItem itemLabel="Select One" itemValue="" />  
        <f:selectItems value="#{studentMB.students}" var="student" itemLabel="#{student.firstName}" itemValue="#{student}"/>  
    </p:selectOneMenu> 
    </h:panelGrid>  
    <p:commandButton value="Details" update="display" oncomplete="dlg.show()" />  

 <p:dialog header="Selected Value" modal="true" showEffect="fade" hideEffect="fade" widgetVar="dlg">
 <h:panelGrid columns="1" id="display">  
  <h:outputText value="#{studentMB.selectedStudent.firstName} #{studentMB.selectedStudent.lastName}" rendered="#{not empty studentMB.selectedStudent}" />
  </h:panelGrid>
  </p:dialog>
  </h:form>


</h:body>
</html>

get the source code

you can download the complete example built using eclipse and deployed to glassfish from here

Answer 2

In h:selectOneMenu it's possible, but yours POJO must implements a interface with a identifier atrribute.

Interface:

public inteface IConvertible {
    public Integer getId();
}

Pojo:

public class POJO implements IConvertible {
    ....
    ....
}

And generic converter:

@SuppressWarnings("unchecked")
public class GenericConverter implements Converter {

    @Override
    public Object getAsObject(FacesContext arg0, UIComponent arg1, String arg2) {
        IConvertible ret = null;
        UIComponent src = arg1;
        if (src != null) {
            List<UIComponent> childs = src.getChildren();
            UISelectItems itens = null;
            if (childs != null) {
                for (UIComponent ui : childs) {
                    if (ui instanceof UISelectItems) {
                        itens = (UISelectItems) ui;
                        break;
                    } else if (ui instanceof UISelectItem) {
                        UISelectItem item = (UISelectItem) ui;
                        try {
                            IConvertible val = (IConvertible) item.getItemValue();
                            if (arg2.equals("" + val.getId())) {
                                ret = val;
                                break;
                            }
                        } catch (Exception e) {
                        }
                    }
                }
            }

            if (itens != null) {
                List<IConvertible> values = (List<IConvertible>) itens.getValue();
                if (values != null) {
                    for (IConvertible val : values) {
                        if (arg2.equals("" + val.getId())) {
                            ret = val;
                            break;
                        }
                    }
                }
            }
        }
        return ret;
    }

    @Override
    public String getAsString(FacesContext arg0, UIComponent arg1, Object arg2) {
        String ret = "";
        if (arg2 != null && arg2 instanceof IConvertible) {
            IConvertible m = (IConvertible) arg2;
            if (m != null) {
                Long id = m.getId();
                if (id != null) {
                    ret = id.toString();
                }
            }
        }
        return ret;
    }
}

JSF page:

<h:selectOneMenu id="combo" value="#{pojoMB.pojo}" converter="genericConverter">
    <f:selectItem itemLabel="-- Select one --" itemValue="" />
    <f:selectItems value="#{pojoMB.pojoList}" var="pj" itemValue="#{pj}" itemLabel="#{pj.labelOfPojo}" />
</h:selectOneMenu>