BAEL-1023 Introduction to Kryo (#2336)

libraries/pom.xml

@@ -453,6 +453,11 @@
             <artifactId>pcollections</artifactId>
             <version>${pcollections.version}</version>
         </dependency>
+        <dependency>
+            <groupId>com.esotericsoftware</groupId>
+            <artifactId>kryo</artifactId>
+            <version>${kryo.version}</version>
+        </dependency>
     </dependencies>
     <properties>
         <multiverse.version>0.7.0</multiverse.version>
@@ -493,5 +498,6 @@
         <hll.version>1.6.0</hll.version>
         <bytebuddy.version>1.7.1</bytebuddy.version>
         <pcollections.version>2.1.2</pcollections.version>
+        <kryo.version>4.0.1</kryo.version>
     </properties>
 </project>

libraries/src/main/java/com/baeldung/kryo/ComplexClass.java

@@ -0,0 +1,16 @@
+package com.baeldung.kryo;
+
+import java.io.Serializable;
+
+public class ComplexClass implements Serializable{
+    private static final long serialVersionUID = 123456L;
+    private String name = "Bael";
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+}

libraries/src/main/java/com/baeldung/kryo/Person.java

@@ -0,0 +1,54 @@
+package com.baeldung.kryo;
+
+import com.esotericsoftware.kryo.DefaultSerializer;
+import com.esotericsoftware.kryo.Kryo;
+import com.esotericsoftware.kryo.KryoSerializable;
+import com.esotericsoftware.kryo.io.Input;
+import com.esotericsoftware.kryo.io.Output;
+import java.util.Date;
+
+@DefaultSerializer(PersonSerializer.class)
+public class Person implements KryoSerializable {
+    private String name = "John Doe";
+    private int age = 18;
+    private Date birthDate = new Date(933191282821L);
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public int getAge() {
+        return age;
+    }
+
+    public void setAge(int age) {
+        this.age = age;
+    }
+
+    public Date getBirthDate() {
+        return birthDate;
+    }
+
+    public void setBirthDate(Date birthDate) {
+        this.birthDate = birthDate;
+    }
+
+    @Override
+    public void write(Kryo kryo, Output output) {
+        output.writeString(name);
+        output.writeLong(birthDate.getTime());
+        output.writeInt(age);
+    }
+
+    @Override
+    public void read(Kryo kryo, Input input) {
+        name = input.readString();
+        birthDate = new Date(input.readLong());
+        age = input.readInt();
+    }
+
+}

libraries/src/main/java/com/baeldung/kryo/PersonSerializer.java

@@ -0,0 +1,33 @@
+package com.baeldung.kryo;
+
+import com.esotericsoftware.kryo.Kryo;
+import com.esotericsoftware.kryo.Serializer;
+import com.esotericsoftware.kryo.io.Input;
+import com.esotericsoftware.kryo.io.Output;
+import java.util.Date;
+
+public class PersonSerializer extends Serializer<Person> {
+
+    @Override
+    public void write(Kryo kryo, Output output, Person object) {
+        output.writeString(object.getName());
+        output.writeLong(object.getBirthDate()
+            .getTime());
+    }
+
+    @Override
+    public Person read(Kryo kryo, Input input, Class<Person> type) {
+        Person person = new Person();
+        person.setName(input.readString());
+        long birthDate = input.readLong();
+        person.setBirthDate(new Date(birthDate));
+        person.setAge(calculateAge(birthDate));
+        return person;
+    }
+
+    private int calculateAge(long birthDate) {
+        // Some custom logic
+        return 18;
+    }
+
+}

libraries/src/test/java/com/baeldung/kryo/KryoUnitTest.java

@@ -0,0 +1,125 @@
+package com.baeldung.kryo;
+
+import static org.junit.Assert.assertEquals;
+
+import java.io.FileInputStream;
+import java.io.FileNotFoundException;
+import java.io.FileOutputStream;
+import java.util.Date;
+import java.util.logging.Level;
+import java.util.logging.Logger;
+
+import org.junit.Before;
+import org.junit.Test;
+
+import com.esotericsoftware.kryo.Kryo;
+import com.esotericsoftware.kryo.io.Input;
+import com.esotericsoftware.kryo.io.Output;
+import com.esotericsoftware.kryo.serializers.JavaSerializer;
+
+public class KryoUnitTest {
+
+    private Kryo kryo;
+    private Output output;
+    private Input input;
+
+    @Before
+    public void init() {
+        kryo = new Kryo();
+        try {
+            output = new Output(new FileOutputStream("file.dat"));
+            input = new Input(new FileInputStream("file.dat"));
+        } catch (FileNotFoundException ex) {
+            Logger.getLogger(KryoUnitTest.class.getName())
+                .log(Level.SEVERE, null, ex);
+        }
+    }
+
+    @Test
+    public void givenObject_whenSerializing_thenReadCorrectly() {
+        Object someObject = "Some string";
+
+        kryo.writeClassAndObject(output, someObject);
+        output.close();
+
+        Object theObject = kryo.readClassAndObject(input);
+        input.close();
+
+        assertEquals(theObject, "Some string");
+    }
+
+    @Test
+    public void givenObjects_whenSerializing_thenReadCorrectly() {
+        String someString = "Multiple Objects";
+        Date someDate = new Date(915170400000L);
+
+        kryo.writeObject(output, someString);
+        kryo.writeObject(output, someDate);
+        output.close();
+
+        String readString = kryo.readObject(input, String.class);
+        Date readDate = kryo.readObject(input, Date.class);
+        input.close();
+
+        assertEquals(readString, "Multiple Objects");
+        assertEquals(readDate.getTime(), 915170400000L);
+    }
+
+    @Test
+    public void givenPerson_whenSerializing_thenReadCorrectly() {
+        Person person = new Person();
+
+        kryo.writeObject(output, person);
+        output.close();
+
+        Person readPerson = kryo.readObject(input, Person.class);
+        input.close();
+
+        assertEquals(readPerson.getName(), "John Doe");
+    }
+
+    @Test
+    public void givenPerson_whenUsingCustomSerializer_thenReadCorrectly() {
+        Person person = new Person();
+        person.setAge(0);
+        kryo.register(Person.class, new PersonSerializer());
+
+        kryo.writeObject(output, person);
+        output.close();
+
+        Person readPerson = kryo.readObject(input, Person.class);
+        input.close();
+
+        assertEquals(readPerson.getName(), "John Doe");
+        assertEquals(readPerson.getAge(), 18);
+    }
+    
+    @Test
+    public void givenPerson_whenCustomSerialization_thenReadCorrectly() {
+        Person person = new Person();
+
+        kryo.writeObject(output, person);
+        output.close();
+
+        Person readPerson = kryo.readObject(input, Person.class);
+        input.close();
+
+        assertEquals(readPerson.getName(), "John Doe");
+        assertEquals(readPerson.getAge(), 18);
+    }
+
+    @Test
+    public void givenJavaSerializable_whenSerializing_thenReadCorrectly() {
+        ComplexClass complexClass = new ComplexClass();
+        kryo.register(ComplexClass.class, new JavaSerializer());
+
+        kryo.writeObject(output, complexClass);
+        output.close();
+
+        ComplexClass readComplexObject = kryo.readObject(input, ComplexClass.class);
+        input.close();
+
+        assertEquals(readComplexObject.getName(), "Bael");
+    }
+
+}