SAP NetWeaver Cloud - Java - how configure persistent data objects and how can i use them

i want to create a simple project management application at the SAP NetWeaver Cloud (Java) Users can add persons to projects and define the working hours of a person who works on a project.

I created successfully a small application logic. However it's not clear to me how i should define the persistent data objects. And how to store and read the data on the right way.

I created the classes "Project" and "Person" to add data. (see at end person.java & project.java)

How can I create a relation between them and store the working hours of a person. (depending on the project)

On an ERM i know the solution. A 1:n relation between Person and Project and an extra table between them with "projectID","personID" and "workingHours".

So far the app writes data with the function "addNewPerson":

addNewPerson : function( sFirstName, sLastName, oTable ) {  
          var _this = this;  
          _this.odataServiceUrl = personsListOdataServiceUrl;  
          jQuery.ajax({  
             url : _this.odataServiceUrl + "/Person?$format=json",  
             type : 'POST',  
             contentType : 'application/json',  
             data : JSON.stringify({  
                                     firstName : sFirstName,  
                                     lastName : sLastName  
                                  }),  
             success : function(data) {  
               _this.getView().getModel().refresh();  
               oTable.unbindRows().bindRows("/Person");  
      },  
             error : function(jqXHR, textStatus, errorThrown) {  
           sap.ui.commons.MessageBox.alert("Failed to add person: " + textStatus+ "\n" + errorThrown);  
             }  
      }); },  

To read the data i simple bind the rows to the object.

So, how can i create the data objects the right way? And how can i read and write the data to the objects?

Thank you very much,

Martino

Person.java:

package com.sap.netweaver.cloud.sample;
import javax.persistence.*;
@Entity
@Table(name = "T_PERSON")
@NamedQuery(name = "AllPersons", query = "select p from Person p")

public class Person {
@Id
@GeneratedValue
private long id;
@Basic
private String firstName;
@Basic
private String lastName;

public long getId() {
    return id;
}

public void setId(long id) {
    this.id = id;
}

public void setFirstName(String param) {
    this.firstName = param;
}

public String getFirstName() {
    return firstName;
}

public void setLastName(String param) {
    this.lastName = param;
}

public String getLastName() {
    return lastName;
}

}

Project.java:

package com.sap.netweaver.cloud.sample;

import javax.persistence.Basic;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.NamedQuery;
import javax.persistence.Table;

@Entity
@Table(name = "T_PROJECT")
@NamedQuery(name = "AllProjects", query = "select p from Project p")
public class Project {

@Id
@GeneratedValue
private long id;
@Basic
private String projectName;
@Basic
private String projectDesc;
public long getId() {
    return id;
}

public void setId(long id) {
    this.id = id;
}

public void setProjectName(String param) {
    this.projectName = param;
}

public String getProjectName() {
    return projectName;
}

public void setProjectDesc(String param) {
    this.projectDesc = param;
}

public String getProjectDesc() {
    return projectDesc;
}

}