[BAEL-6535] hydration of object examples (#15421)

Co-authored-by: Bhaskar <bhaskar.dastidar@freshworks.com>

libraries-data/pom.xml

@@ -97,6 +97,11 @@
                 </exclusion>
             </exclusions>
         </dependency>
+        <dependency>
+            <groupId>com.h2database</groupId>
+            <artifactId>h2</artifactId>
+            <version>1.3.170</version>
+        </dependency>
         <dependency>
             <groupId>com.fasterxml.jackson.core</groupId>
             <artifactId>jackson-databind</artifactId>
@@ -150,6 +155,16 @@
             <artifactId>xstream</artifactId>
             <version>1.4.16</version>
         </dependency>
+        <dependency>
+            <groupId>org.springframework.data</groupId>
+            <artifactId>spring-data-jpa</artifactId>
+            <version>2.1.5.RELEASE</version>
+        </dependency>
+        <dependency>
+            <groupId>javax.persistence</groupId>
+            <artifactId>javax.persistence-api</artifactId>
+            <version>2.2</version>
+        </dependency>
 
     </dependencies>
 

libraries-data/src/main/java/com/baeldung/objecthydration/User.java

@@ -0,0 +1,75 @@
+package com.baeldung.objecthydration;
+
+import java.io.Serializable;
+import java.util.Objects;
+
+public class User implements Serializable {
+    private String uId;
+    private String firstName;
+    private String lastName;
+    private String alias;
+
+    public User() {
+    }
+
+    public User(String firstName, String uId, String lastName, String alias) {
+        this.firstName = firstName;
+        this.uId = uId;
+        this.lastName = lastName;
+        this.alias = alias;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o)
+            return true;
+        if (o == null || getClass() != o.getClass())
+            return false;
+        User user = (User) o;
+        return Objects.equals(firstName, user.firstName) && Objects.equals(uId, user.uId) && Objects.equals(lastName, user.lastName) && Objects.equals(alias, user.alias);
+    }
+
+    public String getuId() {
+        return uId;
+    }
+
+    public void setuId(String uId) {
+        this.uId = uId;
+    }
+
+    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;
+    }
+
+    public String getAlias() {
+        return alias;
+    }
+
+    public void setAlias(String alias) {
+        this.alias = alias;
+    }
+
+    public void generateMyUser() {
+        this.setAlias("007");
+        this.setFirstName("James");
+        this.setLastName("Bond");
+        this.setuId("JB");
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(firstName, uId, lastName, alias);
+    }
+}

libraries-data/src/main/java/com/baeldung/objecthydration/UserSerialisationDeserialisation.java

@@ -0,0 +1,34 @@
+package com.baeldung.objecthydration;
+
+import java.io.*;
+
+public class UserSerialisationDeserialisation {
+    public void serialisedUser(User user, String outputName) {
+        try {
+            FileOutputStream fileOut = new FileOutputStream(outputName);
+            ObjectOutputStream out = new ObjectOutputStream(fileOut);
+            out.writeObject(user);
+            out.close();
+            fileOut.close();
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
+    }
+
+    public User deserialiseUser(String serialisedFile) {
+        User deserializedUser = null;
+        try {
+            FileInputStream fileIn = new FileInputStream(serialisedFile);
+            ObjectInputStream in = new ObjectInputStream(fileIn);
+            deserializedUser = (User) in.readObject();
+            in.close();
+            fileIn.close();
+        } catch (IOException | ClassNotFoundException e) {
+            e.printStackTrace();
+        } finally {
+            File f = new File(serialisedFile);
+            f.delete();
+        }
+        return deserializedUser;
+    }
+}

libraries-data/src/main/java/com/baeldung/objecthydration/entity/Book.java

@@ -0,0 +1,71 @@
+package com.baeldung.objecthydration.entity;
+
+import javax.persistence.Column;
+import javax.persistence.Entity;
+import javax.persistence.GeneratedValue;
+import javax.persistence.GenerationType;
+import javax.persistence.Id;
+import javax.persistence.Table;
+
+@Entity
+@Table(name = "books")
+public class Book {
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private Long id;
+
+    @Column(name = "name")
+    private String name;
+
+    @Column(name = "author")
+    private String author;
+
+    @Column(name = "isbn")
+    private String isbn;
+
+    // Constructors, getters, and setters
+
+    public Book() {
+        // Default constructor required by Hibernate
+    }
+
+    public Book(String name, String author, String isbn) {
+        this.name = name;
+        this.author = author;
+        this.isbn = isbn;
+    }
+
+    // Getters and setters for all attributes
+
+    public Long getId() {
+        return id;
+    }
+
+    public void setId(Long id) {
+        this.id = id;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public String getAuthor() {
+        return author;
+    }
+
+    public void setAuthor(String author) {
+        this.author = author;
+    }
+
+    public String getIsbn() {
+        return isbn;
+    }
+
+    public void setIsbn(String isbn) {
+        this.isbn = isbn;
+    }
+}

libraries-data/src/main/java/com/baeldung/objecthydration/repository/BookRepository.java

@@ -0,0 +1,7 @@
+package com.baeldung.objecthydration.repository;
+
+import com.baeldung.objecthydration.entity.Book;
+import org.springframework.data.jpa.repository.JpaRepository;
+
+public interface BookRepository extends JpaRepository<Book, Long> {
+}

libraries-data/src/test/java/com/baeldung/objecthydration/HydrationUnitTest.java

@@ -0,0 +1,40 @@
+package com.baeldung.objecthydration;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+public class HydrationUnitTest {
+
+    @Test
+    public void givenEmptyClass_whenLazilyinitialised_thenGiveNullOnGet() {
+        User iamUser = new User();
+        Assert.assertNull(iamUser.getuId());
+    }
+
+    @Test
+    public void givenInitialisedClass_withLazilyInitialised_thenDoesNotGiveNullOnGet() {
+        User iamUser = new User();
+        iamUser.setAlias("007");
+        Assert.assertNotNull(iamUser.getAlias());
+    }
+
+    @Test
+    public void givenEmptyClass_withHydration_thenShouldHaveAllAttributesSet() {
+        User jamesBond = new User();
+        Assert.assertNull(jamesBond.getAlias());
+
+        jamesBond.generateMyUser();
+        Assert.assertEquals("007", jamesBond.getAlias());
+    }
+
+    @Test
+    public void givenUser_thenShouldPerformUserSerialisationDeserialisation() {
+        User iamUser = new User();
+        iamUser.setAlias("007");
+        UserSerialisationDeserialisation usd = new UserSerialisationDeserialisation();
+        usd.serialisedUser(iamUser, "bond.ser");
+        User deserialisedUser = usd.deserialiseUser("bond.ser");
+        Assert.assertEquals(iamUser.getAlias(), deserialisedUser.getAlias());
+
+    }
+}