Hibernate mapping,and database problems

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Java

SQL

Hibernate

Hello ,

I try to make a web application but i have some problem with my databse and mapping.
I used Hibernate Annotation(used field),and made 3 tables (it will be a quiz game) one for the Category's(contains an id and a name) one for the Questions(contains an id aka pk and a foreign key from category; to define from which category is part of),and one for Answers(id aka pk and a foreign key from Questions).
Now my problem is when i test them togtether for exmpl. I make a category,question and answer;save and set them, its ok.But if later i try to set a new question with an answer for an already existing category its add a nother one with the same name....
I tried to make it unique from database but then just throws an exception and rolls back as i handle it.
Can any1 help a bit?

Here are my codes (a bit long) :


Category::

@Entity
@Table(name = "category")
public class Category {

	@Id
	@GeneratedValue(strategy = GenerationType.IDENTITY)
	@Column(name = "ID", nullable = false)
	public int id;

	@Column(name = "NAME")
	public String name;

	@OneToMany(mappedBy = "category", fetch = FetchType.LAZY)
	@Fetch(FetchMode.SELECT)
	public Set<Questions> questions = new HashSet<Questions>();

	public Category() {

	}

	public Category(String name) {
		this.name = name;
	}

	public Category(int id, String name) {
		this.id = id;
		this.name = name;

	}

	public int getId() {
		return id;
	}

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

	public String getName() {
		return name;
	}

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

	public Set<Questions> getQuestions() {
		return questions;
	}

	public void setQuestions(Set<Questions> questions) {
		this.questions = questions;
	}

}

Questions::

@Entity
@Table(name = "questions")
public class Questions implements Serializable {

	@Id
	@GeneratedValue(strategy = GenerationType.IDENTITY)
	@Column(name = "ID")
	private int id;

	@Column(name = "CAT_ID", insertable = false, updatable = false)
	private int cat_id;

	@Column(name = "QUESTION")
	private String question;

	@ManyToOne(fetch = FetchType.LAZY, cascade = CascadeType.ALL)
	@Fetch(FetchMode.SELECT)
	@JoinColumn(name = "CAT_ID", nullable = false)
	private Category category;

	@OneToMany(fetch = FetchType.LAZY)
	@Fetch(FetchMode.SELECT)
	private Set<Answers> answers = new HashSet<Answers>();

	public Questions() {

	}

	public Questions(int cat_id, String question) {
		this.cat_id = cat_id;
		this.question = question;
	}

	public Questions(String question) {
		this.question = question;
	}

	public Questions(int id, int cat_id, String question) {
		this.id = id;
		this.cat_id = cat_id;
		this.question = question;

	}

	public int getId() {
		return id;
	}

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

	public int getCat_id() {
		return cat_id;
	}

	public void setCat_id(int cat_id) {
		this.cat_id = cat_id;
	}

	public String getQuestion() {
		return question;
	}

	public void setQuestion(String question) {
		this.question = question;
	}

	public Category getCategory() {
		return category;
	}

	public void setCategory(Category category) {
		this.category = category;
	}

	public Set<Answers> getAnswers() {
		return answers;
	}

	public void setAnswers(Set<Answers> answers) {
		this.answers = answers;
	}

}

Answers::

package com.finalproject.pojo;

import javax.persistence.*;

import org.hibernate.annotations.Fetch;
import org.hibernate.annotations.FetchMode;

@Entity
@Table(name = "answers")
public class Answers {

	@Id
	@GeneratedValue(strategy = GenerationType.IDENTITY)
	@Column(name = "ID")
	private int id;

	@Column(name = "QUESTION_ID", insertable = false, updatable = false)
	private int question_id;

	@Column(name = "CORRECT_ANSWER")
	private String correct_answer;

	@Column(name = "WA_1")
	private String wa_1;

	@Column(name = "WA_2")
	private String wa_2;

	@Column(name = "WA_3")
	private String wa_3;

	@ManyToOne(fetch = FetchType.LAZY, cascade = CascadeType.ALL)
	@Fetch(FetchMode.SELECT)
	@JoinColumn(name = "QUESTION_ID", nullable = false)
	private Questions questions;

	public Answers() {

	}

	public Answers(String correct_answer, String wa_1, String wa_2, String wa_3) {

		this.correct_answer = correct_answer;
		this.wa_1 = wa_1;
		this.wa_2 = wa_2;
		this.wa_3 = wa_3;
	}

	public Answers(int question_id, String correct_answer, String wa_1,
			String wa_2, String wa_3) {

		this.question_id = question_id;
		this.correct_answer = correct_answer;
		this.wa_1 = wa_1;
		this.wa_2 = wa_2;
		this.wa_3 = wa_3;
	}

	public Answers(int id, int question_id, String correct_answer, String wa_1,
			String wa_2, String wa_3) {

		this.id = id;
		this.question_id = question_id;
		this.correct_answer = correct_answer;
		this.wa_1 = wa_1;
		this.wa_2 = wa_2;
		this.wa_3 = wa_3;
	}

	public int getId() {
		return id;
	}

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

	public int getQuestion_id() {
		return question_id;
	}

	public void setQuestion_id(int question_id) {
		this.question_id = question_id;
	}

	public String getCorrect_answer() {
		return correct_answer;
	}

	public void setCorrect_answer(String correct_answer) {
		this.correct_answer = correct_answer;
	}

	public String getWa_1() {
		return wa_1;
	}

	public void setWa_1(String wa_1) {
		this.wa_1 = wa_1;
	}

	public String getWa_2() {
		return wa_2;
	}

	public void setWa_2(String wa_2) {
		this.wa_2 = wa_2;
	}

	public String getWa_3() {
		return wa_3;
	}

	public void setWa_3(String wa_3) {
		this.wa_3 = wa_3;
	}

	public Questions getQuestions() {
		return questions;
	}

	public void setQuestions(Questions questions) {
		this.questions = questions;
	}

}