Entity Managers: Create, Find, Update and Delete Student

pom.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+  <modelVersion>4.0.0</modelVersion>
+
+  <groupId>org.tutorial</groupId>
+  <artifactId>jpa</artifactId>
+  <version>1.0-SNAPSHOT</version>
+
+  <name>jpa</name>
+
+  <properties>
+    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+    <maven.compiler.source>1.8</maven.compiler.source>
+    <maven.compiler.target>1.8</maven.compiler.target>
+  </properties>
+
+  <dependencies>
+    <dependency>
+      <groupId>junit</groupId>
+      <artifactId>junit</artifactId>
+      <version>4.11</version>
+      <scope>test</scope>
+    </dependency>
+    <dependency>
+      <groupId>org.hibernate</groupId>
+      <artifactId>hibernate-core</artifactId>
+      <version>5.4.18.Final</version>
+    </dependency>
+    <dependency>
+      <groupId>com.h2database</groupId>
+      <artifactId>h2</artifactId>
+      <version>1.4.200</version>
+    </dependency>
+    <dependency>
+      <groupId>org.postgresql</groupId>
+      <artifactId>postgresql</artifactId>
+      <version>42.2.14</version>
+    </dependency>
+
+  </dependencies>
+
+  <build>
+    <pluginManagement><!-- lock down plugins versions to avoid using Maven defaults (may be moved to parent pom) -->
+      <plugins>
+        <!-- clean lifecycle, see https://maven.apache.org/ref/current/maven-core/lifecycles.html#clean_Lifecycle -->
+        <plugin>
+          <artifactId>maven-clean-plugin</artifactId>
+          <version>3.1.0</version>
+        </plugin>
+        <!-- default lifecycle, jar packaging: see https://maven.apache.org/ref/current/maven-core/default-bindings.html#Plugin_bindings_for_jar_packaging -->
+        <plugin>
+          <artifactId>maven-resources-plugin</artifactId>
+          <version>3.0.2</version>
+        </plugin>
+        <plugin>
+          <artifactId>maven-compiler-plugin</artifactId>
+          <version>3.8.0</version>
+        </plugin>
+        <plugin>
+          <artifactId>maven-surefire-plugin</artifactId>
+          <version>2.22.1</version>
+        </plugin>
+        <plugin>
+          <artifactId>maven-jar-plugin</artifactId>
+          <version>3.0.2</version>
+        </plugin>
+        <plugin>
+          <artifactId>maven-install-plugin</artifactId>
+          <version>2.5.2</version>
+        </plugin>
+        <plugin>
+          <artifactId>maven-deploy-plugin</artifactId>
+          <version>2.8.2</version>
+        </plugin>
+        <!-- site lifecycle, see https://maven.apache.org/ref/current/maven-core/lifecycles.html#site_Lifecycle -->
+        <plugin>
+          <artifactId>maven-site-plugin</artifactId>
+          <version>3.7.1</version>
+        </plugin>
+        <plugin>
+          <artifactId>maven-project-info-reports-plugin</artifactId>
+          <version>3.0.0</version>
+        </plugin>
+      </plugins>
+    </pluginManagement>
+  </build>
+</project>

src/main/java/org/tutorial/App.java

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+package org.tutorial;
+
+/**
+ * Hello world!
+ *
+ */
+public class App 
+{
+    public static void main( String[] args )
+    {
+        System.out.println( "Hello World!" );
+    }
+}

src/main/java/org/tutorial/CreateStudent.java

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+package org.tutorial;
+
+import org.tutorial.model.Student;
+
+import javax.persistence.EntityManager;
+import javax.persistence.EntityManagerFactory;
+import javax.persistence.EntityTransaction;
+import javax.persistence.Persistence;
+
+public class CreateStudent {
+  public static void main(String[] args) {
+      EntityManagerFactory entityManagerFactory = Persistence.createEntityManagerFactory("student_pu");
+      EntityManager entityManager = entityManagerFactory.createEntityManager();
+      EntityTransaction entityTransaction = entityManager.getTransaction();
+
+      entityTransaction.begin();
+
+      Student student = new Student();
+      student.setFirstName("John");
+      student.setLastName("Bell");
+
+      Student student1 = new Student();
+      student1.setFirstName("Alan");
+      student1.setLastName("Conrad");
+
+      entityManager.persist(student);
+
+      entityTransaction.commit();
+
+      entityManager.close();
+      entityManagerFactory.close();
+  }
+}

src/main/java/org/tutorial/DeleteStudent.java

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+package org.tutorial;
+
+import org.tutorial.model.Student;
+
+import javax.persistence.EntityManager;
+import javax.persistence.EntityManagerFactory;
+import javax.persistence.EntityTransaction;
+import javax.persistence.Persistence;
+
+public class DeleteStudent {
+
+  public static void main(String[] args) {
+    EntityManagerFactory entityManagerFactory =
+        Persistence.createEntityManagerFactory("student_pu");
+    EntityManager entityManager = entityManagerFactory.createEntityManager();
+    EntityTransaction entityTransaction = entityManager.getTransaction();
+
+    Student student = entityManager.find(Student.class, 1L);
+
+    System.out.println(student.toString());
+
+    entityTransaction.begin();
+
+    entityManager.remove(student);
+
+    entityTransaction.commit();
+
+    entityManager.close();
+    entityManagerFactory.close();
+  }
+}

src/main/java/org/tutorial/FindStudent.java

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+package org.tutorial;
+
+import org.tutorial.model.Student;
+
+import javax.persistence.EntityManager;
+import javax.persistence.EntityManagerFactory;
+import javax.persistence.Persistence;
+
+public class FindStudent {
+
+  public static void main(String[] args) {
+    EntityManagerFactory entityManagerFactory =
+        Persistence.createEntityManagerFactory("student_pu");
+    EntityManager entityManager = entityManagerFactory.createEntityManager();
+
+    Student student = entityManager.find(Student.class, 1L);
+
+    if (student != null) {
+      System.out.println(student.toString());
+    }
+  }
+}

src/main/java/org/tutorial/UpdateStudent.java

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+package org.tutorial;
+
+import org.tutorial.model.Student;
+
+import javax.persistence.EntityManager;
+import javax.persistence.EntityManagerFactory;
+import javax.persistence.EntityTransaction;
+import javax.persistence.Persistence;
+
+public class UpdateStudent {
+
+  public static void main(String[] args) {
+    EntityManagerFactory entityManagerFactory =
+        Persistence.createEntityManagerFactory("student_pu");
+    EntityManager entityManager = entityManagerFactory.createEntityManager();
+    EntityTransaction entityTransaction = entityManager.getTransaction();
+
+    Student student = entityManager.find(Student.class, 1L);
+    System.out.println("Before update " + student.toString());
+
+    entityTransaction.begin();
+
+    student.setFirstName("Alan");
+    student.setLastName("Bold");
+
+    entityTransaction.commit();
+
+    System.out.println("After update " + student.toString());
+
+    entityManager.close();
+    entityManagerFactory.close();
+  }
+}

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

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+package org.tutorial.model;
+
+import javax.persistence.*;
+
+@Entity
+@Table(name = "student")
+public class Student {
+
+    @Id
+    @GeneratedValue(strategy = GenerationType.AUTO)
+    private Long id;
+
+    @Column(name = "first_name", nullable = false, length = 150)
+    private String firstName;
+
+    @Column(name = "last_name", nullable = false, length = 250)
+    private String lastName;
+
+    public Student() {
+    }
+
+    public Student(Long id, String firstName, String lastName) {
+        this.id = id;
+        this.firstName = firstName;
+        this.lastName = lastName;
+    }
+
+    public Long getId() {
+        return id;
+    }
+
+    public void setId(Long id) {
+        this.id = id;
+    }
+
+    public String getFirstName() {
+        return firstName;
+    }
+
+    public void setFirstName(String firstName) {
+        this.firstName = firstName;
+    }
+
+    public String getLastName() {
+        return lastName;
+    }
+
+    public void setLastName(String lastName) {
+        this.lastName = lastName;
+    }
+
+    @Override
+    public String toString() {
+        return "Student{" +
+                "id=" + id +
+                ", firstName='" + firstName + '\'' +
+                ", lastName='" + lastName + '\'' +
+                '}';
+    }
+}

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

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+<persistence xmlns="http://java.sun.com/xml/ns/persistence" version="2.0">
+    <persistence-unit name="student_pu" transaction-type="RESOURCE_LOCAL">
+        <provider>org.hibernate.jpa.HibernatePersistenceProvider</provider>
+
+        <class>org.tutorial.model.Student</class>
+
+        <properties>
+            <property name="javax.persistence.jdbc.url" value="jdbc:h2:~/test"/>
+            <property name="javax.persistence.jdbc.driver" value="org.h2.Driver"/>
+            <property name="javax.persistence.jdbc.user" value="sa"/>
+            <property name="javax.persistence.jdbc.password" value=""/>
+
+            <property name="hibernate.dialect" value="org.hibernate.dialect.H2Dialect"/>
+            <property name="hibernate.show_sql" value="true"/>
+            <property name="hibernate.format_sql" value="true"/>
+            <!-- <property name="hibernate.hbm2ddl.auto" value="create"/> -->
+        </properties>
+    </persistence-unit>
+</persistence>

src/test/java/org/tutorial/AppTest.java

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+package org.tutorial;
+
+import static org.junit.Assert.assertTrue;
+
+import org.junit.Test;
+
+/**
+ * Unit test for simple App.
+ */
+public class AppTest 
+{
+    /**
+     * Rigorous Test :-)
+     */
+    @Test
+    public void shouldAnswerWithTrue()
+    {
+        assertTrue( true );
+    }
+}