Java – when using Grails sortedset, the first () element cannot be accessed from an empty list

I'm trying to dynamically create some Grails domain objects and then add a sortedset declared in another Grails domain object I created a project class, filled in its values, and checked to make sure it was valid It is valid, so I want to add this item to the employee

My code is basically like this

Employee employee = Employee.get(session.empid)
...
//populate some Project objects
...
//add projects to employee
employee.addToProjects(project)

This could go wrong? If I execute project Validate (), and then check for errors, the only one that indicates that the project does not have a valid employee associated with it – but once I execute employee Addtoprojects should disappear Employee has many project objects. Its declaration is as follows:

class Employee implements Comparable
{
    static hasMany = [projects:Project]

    static constraints = 
    {
    }

    static mapping = {
        projects cascade:"all,delete-orphan",lazy:false
    }

    SortedSet<Project> projects = new TreeSet<Project>();
}


public class Project implements Comparable
{  
    static belongsTo = [employee:Employee]

    static hasMany = [roles:Role]

    static mapping = {
          roles lazy:false,cascade:"all,delete-orphan"
    }

    @XmlElement
    List<Role> roles = new ArrayList<Role>();


    /*
     * return sorted list.  overwriting default getter was causing error upon saving multiple roles.
     *
     */
    def List getSortedRoles(){
        Collections.sort(roles,new RoleComparator());
        return roles;
    }


    String toString()
    {
        return name
    }


    // compare by latest date of roles,then by name + id
    //if this is too intrusive,implement comparator with this logic and sort on rendering page
       int compareTo(obj) {
           if(obj == null){
               return 1;
           }

           def myMaxRole = findMaxRole(roles);
           def rhsMaxRole = findMaxRole(obj.roles);

           def rcomparator = new RoleComparator();

           System.out.println(myMaxRole.title + " " + rhsMaxRole.title + " " + rcomparator.compare(myMaxRole,rhsMaxRole));
           return rcomparator.compare(myMaxRole,rhsMaxRole);
       }

    def List getExpandableRoleList()
    {
        return LazyList.decorate(roles,FactoryUtils.instantiateFactory(Role.class));
    }


    def setExpandableRoleList(List l)
    {
        return roles = l;
    }

        def Role findMaxRole(roles){
            RoleComparator rc = new RoleComparator();

            Role maxRole = roles.first();
            for(role in roles){
                if(rc.compare(maxRole,role) > 0){
                    maxRole = role;
                }
            }

            return maxRole;
        }

public class Role implements Comparable
{

    static belongsTo = [project:Project]
    static hasMany = [roleSkills:RoleSkill,roleTools:RoleTool]

    static mapping = {
        duties type:"text"
        roleSkills cascade:"all,lazy:false
        roleTools cascade:"all,lazy:false

    }

    static contraints = {
        endDate(nullable: true)
    }

    boolean _deleted
    static transients = ['_deleted']

    @XmlElement
    String title = ""
    @XmlElement
    String duties = ""
    @XmlElement
    int levelOfEffort
    @XmlElement
    Date startDate = new Date()
    @XmlElement
    Date endDate = new Date()
    @XmlElement
    Date lastModified = new Date()
    @XmlElement
    LocationType locationType = new LocationType(type: "UnkNown")
    @XmlElement
    String rank
    @XmlElement
    List<RoleSkill> roleSkills = new ArrayList<RoleSkill>()
    @XmlElement
    List<RoleTool> roleTools  = new ArrayList<RoleTool>()

    String toString()
    {   
        return title;
    }

    int compareTo(obj) {

        return title.compareTo(obj.title)
    }

    def skills() {
        return roleSkills.collect{it.skill}
    }
    def tools() {
        return roleTools.collect{it.tool}
    }
}

Solution

Go back to the basics and write an integration test with your object. Everything is normal. You must make an error in how to save the object

Test fragment

void testSomething() {
    def emp = new Employee(first:"Aaron",last:"Saunders")
    emp.save()

    emp =  Employee.get(1)

    emp.addToProjects(new Project(name:"Project 3"))
    emp.addToProjects(new Project(name:"Project 1"))
    emp.addToProjects(new Project(name:"Project 2"))

    emp.save()

    println Employee.get(1)

    println Employee.get(1).projects.first()
}

My object

public class Project implements Comparable
{  
    static belongsTo = [employee:Employee]

    String name;

    static mapping = {
          roles lazy:false,delete-orphan"
    }


    String toString()
    {
        return name
    }


    // compare by latest date of roles,implement comparator with this logic and sort on rendering page
       int compareTo(obj) {
           if(obj == null){
               return 1;
           }


           return this.name.compareTo(obj.name);
       }

}

class Employee implements Comparable
{
    static hasMany = [projects:Project]

    String first,last
    static constraints = 
    {
    }

    static mapping = {
        projects cascade:"all,lazy:false
    }

    SortedSet<Project> projects = new TreeSet<Project>();

    int compareTo(obj) {
        if(obj == null){
            return 1;
        }
           return this.name.compareTo(obj.name);
    }

}