Hibernate Basics

.idea/vcs.xml

+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="VcsDirectoryMappings">
+    <mapping directory="$PROJECT_DIR$" vcs="Git" />
+  </component>
+</project>
\ No newline at end of file

src/main/java/org/example/App.java

@@ -6,6 +6,8 @@ import org.example.model.Student;
 import javax.persistence.EntityManager;
 import javax.persistence.EntityManagerFactory;
 import javax.persistence.Persistence;
+import java.util.ArrayList;
+import java.util.List;
 
 /**
  * Hello world!
@@ -16,28 +18,92 @@ public class App
 {
     public static void main( String[] args )
     {
-        EntityManagerFactory entityManagerFactory = Persistence.createEntityManagerFactory("org.hibernate.tutorial.jpa");
+        EntityManagerFactory entityManagerFactory = Persistence.createEntityManagerFactory("student");
+
 
-        Student student = new Student();
-        student.setId(15);
-        student.setName("naveeds");
-        student.setRollNo(114);
-        student.setAge(24);
 
-        Course course = new Course();
-        course.setId(6);
-        course.setName("Arts");
 
 
         EntityManager entityManager = entityManagerFactory.createEntityManager();
+        // transactions begins
         entityManager.getTransaction().begin();
+        // Create student and course objects and add them to db.
 
-        entityManager.persist(student);
-        entityManager.persist(course);
+//        Course course = new Course();
+//        course.setId(3);
+//        course.setName("Art");
+//        entityManager.persist(course);         // use persist() method to add to db
 
-        entityManager.getTransaction().commit();
+//        Student student = new Student();
+//        student.setId(15);
+//        student.setName("naveeds");
+//        student.setRollNo(114);
+//        student.setAge(24);
+
+
+        // Read data from db
+//        Course course = entityManager.find(Course.class, 1); // find() to find tuple by id
+//        System.out.println(course.getName());
+
+//        entityManager.persist(student);
+
+
+//         Delete using id
+//        Course course = entityManager.find(Course.class, 2);
+//        entityManager.remove(course); // remove() after finding the object.
+
+//        Student student = entityManager.find(Student.class, 3);
+//        entityManager.remove(student);
 
+//
+//        Course english = entityManager.find(Course.class, 1);
+//        Course math = entityManager.find(Course.class, 2);
+//        Course art = entityManager.find(Course.class, 3);
+//
+//
+//        Student student = new Student();
+//        List<Course> courseList = new ArrayList<Course>();
+//
+//        student.setName("Jerry");
+//        student.setAge(31);
+//        student.setRollNo(13);
+//
+//        courseList.add(math);
+//        courseList.add(english);
+//        student.setCourse(courseList);
+
+//         get list of courses for a particular student.
+        Student findStudent = entityManager.find(Student.class, 1);
+        List<Course> findCourseList = findStudent.getCourse();
+        System.out.println(findStudent);
+        System.out.println(findCourseList);
+
+
+//        Student student1 = new Student();
+//        student1.setName("Matt");
+//        student1.setAge(22);
+//        student1.setRollNo(12);
+//        student1.getCourse().add(math);
+//        student1.getCourse().add(art);
+//
+//          entityManager.persist(student);
+//        entityManager.persist(student1);
+
+//        // Update student
+//        Student student = entityManager.find(Student.class, 1);
+//        List<Course> courseList = new ArrayList<>();
+//        courseList.add(math);
+//        courseList.add(english);
+//        courseList.add(art);
+//        student.setCourse(courseList);
+//
+//        entityManager.merge(student);
+
+
+        // all the operations are performed here.
+        entityManager.getTransaction().commit();
         entityManager.close();
         System.exit(0);
+
     }
 }

src/main/java/org/example/model/Course.java

@@ -2,6 +2,9 @@ package org.example.model;
 
 import javax.persistence.Entity;
 import javax.persistence.Id;
+import javax.persistence.ManyToMany;
+import java.util.ArrayList;
+import java.util.List;
 
 @Entity
 public class Course {
@@ -27,6 +30,6 @@ public class Course {
 
     @Override
     public String toString() {
-        return "id: " + getId() + "name: " + getName();
+        return "id: " + getId() + " name: " + getName();
     }
 }

src/main/java/org/example/model/Student.java

 package org.example.model;
 
-import javax.persistence.Entity;
-import javax.persistence.GeneratedValue;
-import javax.persistence.Id;
+import javax.persistence.*;
+
 import org.hibernate.annotations.GenericGenerator;
 
+import java.util.ArrayList;
+import java.util.List;
+
 @Entity
 public class Student {
     @Id
+    @GeneratedValue(strategy=GenerationType.AUTO)
     private int id;
     private String name;
+    private int rollNo;
+    private int age;
+
+    @JoinTable
+    @ManyToMany()
+    private List<Course> course = new ArrayList<>();
+
+    public List<Course> getCourse() {
+        return course;
+    }
+
+    public void setCourse(List<Course> course) {
+        this.course = course;
+    }
 
     public int getId() {
         return id;
@@ -43,11 +60,10 @@ public class Student {
         this.age = age;
     }
 
-    private int rollNo;
-    private int age;
+
 
     @Override
     public String toString() {
-        return "id: " + getId() + "name: " + getName() + "rollno: " + getRollNo() + "age: " + getAge();
+        return "id: " + getId() + " name: " + getName() + " rollno: " + getRollNo() + " age: " + getAge();
     }
 }

src/main/java/org/example/services/CourseService.java

-package org.example.services;
-
-public class CourseService {
-
-}

src/main/java/org/example/services/StudentService.java

-package org.example.services;
-
-import org.example.model.Course;
-import org.example.model.Student;
-
-import javax.persistence.EntityManager;
-import javax.persistence.EntityManagerFactory;
-import javax.persistence.Persistence;
-
-public class StudentService {
-    EntityManagerFactory entityManagerFactory = Persistence.createEntityManagerFactory("org.hibernate.tutorial.jpa");
-
-    public Student createStudent(String name, int rollNo, int age) {
-        Student student = new Student();
-        student.setName(name);
-        student.setRollNo(rollNo);
-        student.setAge(age);
-        return student;
-    }
-
-    EntityManager entityManager = entityManagerFactory.createEntityManager();
-        entityManager.getTransaction().begin();
-
-        entityManager.persist(student);
-        entityManager.persist(course);
-
-        entityManager.getTransaction().commit();
-
-        entityManager.close();
-        System.exit(0);
-}

src/main/resources/META-INF/persistence.xml

@@ -3,7 +3,7 @@
              xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
              xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence
              http://xmlns.jcp.org/xml/ns/persistence/persistence_2_1.xsd">
-    <persistence-unit name="org.hibernate.tutorial.jpa">
+    <persistence-unit name="student">
 
         <properties>
             <property name="hibernate.connection.driver_class" value="com.mysql.jdbc.Driver"/>

target/classes/META-INF/persistence.xml

@@ -3,7 +3,7 @@
              xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
              xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence
              http://xmlns.jcp.org/xml/ns/persistence/persistence_2_1.xsd">
-    <persistence-unit name="org.hibernate.tutorial.jpa">
+    <persistence-unit name="student">
 
         <properties>
             <property name="hibernate.connection.driver_class" value="com.mysql.jdbc.Driver"/>