Th:each iterate specific variables from a hashSet Thymeleaf Spring MVC - spring-mvc

Question

So I"m using Thymeleaf and spring MVC and I have a Course object which has a TreeSet of Posts and the set of posts are similar to a reddit post. I'm trying to represent a set of Posts, on a user homepage that I created. I want the posts to come in chronological order, in a newsfeed sort of way, and I already have the user's courses that they are subscribed to on the model.
My problem is that when I try to iterate through each of the posts I can only pull up the post's id, which looks something like this [com.quizbanks.domain.Post#26], and when I try to show the title, which is the variable for the title of the post I always get a spring processor error.
So here's what my thymeleaf code looks like
<table class="table table-bordered">
<tr th:each="course : ${courses}" th:object="${course}">
<td><span th:text="${course.posts}"></span></td>
</tr>
</table>
and then I tried this, but this gives me the spring processor error
<table class="table table-bordered">
<tr th:each="course : ${courses}" th:object="${course}">
<td><span th:text="${course.posts.title}"></span></td>
</tr>
</table>
So I'm not really sure what to do, if anyone can see my issue and help me out that would be great, thanks in advance.
Also if you want to see my controller code or anything else, let me know and I'll post it.
UPDATE
User Class
package com.quizbanks.domain;
import java.util.HashSet;
import java.util.Set;
import javax.persistence.CascadeType;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.JoinTable;
import javax.persistence.ManyToMany;
import javax.persistence.ManyToOne;
import javax.persistence.OneToMany;
import javax.persistence.Table;
import javax.validation.constraints.NotNull;
import org.hibernate.validator.constraints.NotEmpty;
import com.fasterxml.jackson.annotation.JsonIdentityInfo;
import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
import com.fasterxml.jackson.annotation.JsonManagedReference;
import com.fasterxml.jackson.annotation.ObjectIdGenerators;
import com.quizbanks.security.Authorities;
import com.quizbanks.validators.ValidEmail;
#Entity
#Table(name="users")
#JsonIdentityInfo(generator = ObjectIdGenerators.IntSequenceGenerator.class, property = "#id")
public class User
{
private Long id;
#ValidEmail
#NotNull
#NotEmpty
private String email;
private String username;
private String password;
private University university;
private Set<Authorities> authorities = new HashSet<>();
private Set<Course> courses = new HashSet<>();
private Set<Post> posts = new HashSet<>();
private Set<Comment> comments = new HashSet<>();
private Set<StudySet> studySet = new HashSet<>();
private Set<Course> myCourses = new HashSet<Course>();
public User ()
{
}
public User(User user)
{
this.id = user.getId();
this.email = user.getEmail();
this.username = user.getUsername();
this.password = user.getPassword();
this.university = user.getUniversity();
this.authorities = user.getAuthorities();
this.courses = user.getCourses();
this.posts = user.getPosts();
this.comments = user.getComments();
this.studySet = user.getStudySet();
this.myCourses = user.getMyCourses();
}
#Id
#GeneratedValue
public Long getId()
{
return id;
}
public void setId(Long id)
{
this.id = id;
}
#OneToMany(cascade=CascadeType.ALL, fetch=FetchType.EAGER, mappedBy="user", orphanRemoval=true)
public Set<Course> getCourses()
{
return courses;
}
public void setCourses(Set<Course> courses)
{
this.courses = courses;
}
#OneToMany(cascade=CascadeType.ALL, fetch=FetchType.EAGER, mappedBy="user", orphanRemoval=true)
public Set<Post> getPosts() {
return posts;
}
public void setPosts(Set<Post> posts) {
this.posts = posts;
}
public String getEmail()
{
return email;
}
public void setEmail(String email)
{
this.email = email;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getPassword()
{
return password;
}
public void setPassword(String password)
{
this.password = password;
}
#ManyToOne
public University getUniversity() {
return university;
}
public void setUniversity(University university) {
this.university = university;
}
#OneToMany(fetch=FetchType.EAGER, cascade=CascadeType.ALL, mappedBy="user")
#JsonManagedReference
#JsonIgnoreProperties(allowGetters=true, value = "user" )
public Set<Comment> getComments() {
return comments;
}
public void setComments(Set<Comment> comments) {
this.comments = comments;
}
#OneToMany(fetch=FetchType.EAGER, cascade=CascadeType.ALL, mappedBy="user")
public Set<Authorities> getAuthorities()
{
return authorities;
}
public void setAuthorities(Set<Authorities> authorities)
{
this.authorities = authorities;
}
#OneToMany(cascade=CascadeType.ALL, fetch=FetchType.EAGER, mappedBy="user", orphanRemoval=true)
public Set<StudySet> getStudySet() {
return studySet;
}
public void setStudySet(Set<StudySet> studySet) {
this.studySet = studySet;
}
#ManyToMany(cascade={CascadeType.ALL}, fetch=FetchType.EAGER)
#JoinTable(name="user_myCourses")
public Set<Course> getMyCourses()
{
return myCourses;
}
public void setMyCourses(Set<Course> myCourses)
{
this.myCourses = myCourses;
}
}
Post Class
package com.quizbanks.domain;
import java.util.Set;
import java.util.TreeSet;
import javax.persistence.CascadeType;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.ManyToOne;
import javax.persistence.OneToMany;
import javax.validation.constraints.Size;
import com.fasterxml.jackson.annotation.JsonIdentityInfo;
import com.fasterxml.jackson.annotation.ObjectIdGenerators;
#Entity
#JsonIdentityInfo(generator = ObjectIdGenerators.IntSequenceGenerator.class, property = "#id")
public class Course
{
private Long id;
#Size(min=1, max=50)
private String name;
#Size(min=1, max=50)
private String professor;
#Size(min=1, max=50)
private University university;
private Set<Post> posts = new TreeSet<>();
private User user;
#Id
#GeneratedValue
public Long getId()
{
return id;
}
public void setId(Long id)
{
this.id = id;
}
#ManyToOne
public User getUser()
{
return user;
}
public void setUser(User user)
{
this.user = user;
}
public String getName()
{
return name;
}
public void setName(String name)
{
this.name = name;
}
public String getProfessor()
{
return professor;
}
public void setProfessor(String professor)
{
this.professor = professor;
}
#ManyToOne
public University getUniversity() {
return university;
}
public void setUniversity(University university) {
this.university = university;
}
#OneToMany(fetch=FetchType.EAGER, cascade=CascadeType.ALL, mappedBy="course")
public Set<Post> getPosts()
{
return posts;
}
public void setPosts(Set<Post> posts)
{
this.posts = posts;
}
#Override
public int hashCode()
{
final int prime = 31;
int result = 1;
result = prime * result + ((id == null) ? 0 : id.hashCode());
return result;
}
#Override
public boolean equals(Object obj)
{
if (this == obj)
return true;
if (obj == null)
return false;
if (getClass() != obj.getClass())
return false;
Course other = (Course) obj;
if (id == null)
{
if (other.id != null)
return false;
} else if (!id.equals(other.id))
return false;
return true;
}
}
Post
package com.quizbanks.domain;
import java.util.Set;
import java.util.TreeSet;
import javax.persistence.CascadeType;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.ManyToOne;
import javax.persistence.OneToMany;
import javax.validation.constraints.NotNull;
import javax.validation.constraints.Size;
import com.fasterxml.jackson.annotation.JsonIdentityInfo;
import com.fasterxml.jackson.annotation.ObjectIdGenerators;
#Entity
#JsonIdentityInfo(generator = ObjectIdGenerators.IntSequenceGenerator.class, property = "#id")
public class Post
{
private Long id;
#Size(min=1, max=140)
#NotNull
private String title;
#Size(min=1, max=1000)
private String content;
private Course course;
private Set<Comment> comments = new TreeSet<>();
private User user;
#Id
#GeneratedValue
public Long getId()
{
return id;
}
public void setId(Long id)
{
this.id = id;
}
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
public String getContent() {
return content;
}
public void setContent(String content) {
this.content = content;
}
#ManyToOne
public Course getCourse()
{
return course;
}
public void setCourse(Course course)
{
this.course = course;
}
#ManyToOne
public User getUser()
{
return user;
}
public void setUser(User user)
{
this.user = user;
}
#OneToMany(fetch=FetchType.EAGER, cascade=CascadeType.ALL, mappedBy="post")
public Set<Comment> getComments() {
return comments;
}
public void setComments(Set<Comment> comments) {
this.comments = comments;
}
#Override
public int hashCode()
{
final int prime = 31;
int result = 1;
result = prime * result + ((id == null) ? 0 : id.hashCode());
return result;
}
#Override
public boolean equals(Object obj)
{
if (this == obj)
return true;
if (obj == null)
return false;
if (getClass() != obj.getClass())
return false;
Post other = (Post) obj;
if (id == null)
{
if (other.id != null)
return false;
} else if (!id.equals(other.id))
return false;
return true;
}
}
Controller
#RequestMapping(value="{user}", method=RequestMethod.GET)
public String userPageGet (ModelMap model, #AuthenticationPrincipal User user)
{
List<User> usersList = userRepo.findAll();
model.addAttribute("usersList", usersList);
List<StudySet> studySets = studySetRepo.findByUser(user);
model.addAttribute("studySets", studySets);
List<Course> courses = courseRepo.findByUser(user);
model.addAttribute("courses", courses);
return "user";
}

Answer 1

${courses} is a list of Courses with posts set inside.
It seems that the problem is that posts is a TreeSet, so you should iterate for each element inside that set to get actual Posts and then get titles.
UPDATE:
List<Course> courses = courseRepo.findByUser(user); here you get all courses for your user. So, next step is to iterate over that list to get all posts:
Set<Post> posts = new TreeSet<>();
for (Course course : courses) {
posts.addAll(course.getPosts);
}
model.addAttribute("posts", posts);