Bael 769 javers (#1543)

* BAEL-769 code for javers article

* BAEL-769 add more examples

libraries/pom.xml

@@ -67,6 +67,11 @@
             <artifactId>jsonassert</artifactId>
             <version>${jsonassert.version}</version>
         </dependency>
+        <dependency>
+            <groupId>org.javers</groupId>
+            <artifactId>javers-core</artifactId>
+            <version>${javers.version}</version>
+        </dependency>
     </dependencies>
 
     <properties>
@@ -78,6 +83,7 @@
         <javaassist.version>3.21.0-GA</javaassist.version>
         <assertj.version>3.6.2</assertj.version>
         <jsonassert.version>1.5.0</jsonassert.version>
+        <javers.version>3.1.0</javers.version>
     </properties>
 
 </project>

libraries/src/main/java/com/baeldung/javers/Address.java

@@ -0,0 +1,11 @@
+package com.baeldung.javers;
+
+
+public class Address {
+    private String country;
+
+    public Address(String country) {
+        this.country = country;
+    }
+
+}

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

@@ -0,0 +1,27 @@
+package com.baeldung.javers;
+
+public class Person {
+    private Integer id;
+    private String name;
+
+    public Person(Integer id, String name) {
+        this.id = id;
+        this.name = name;
+    }
+
+    public Integer getId() {
+        return id;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setId(Integer id) {
+        this.id = id;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+}

libraries/src/main/java/com/baeldung/javers/PersonWithAddress.java

@@ -0,0 +1,40 @@
+package com.baeldung.javers;
+
+
+import java.util.List;
+
+public class PersonWithAddress {
+    private Integer id;
+    private String name;
+    private List<Address> address;
+
+    public PersonWithAddress(Integer id, String name, List<Address> address) {
+        this.id = id;
+        this.name = name;
+        this.address = address;
+    }
+
+    public Integer getId() {
+        return id;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setId(Integer id) {
+        this.id = id;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public List<Address> getAddress() {
+        return address;
+    }
+
+    public void setAddress(List<Address> address) {
+        this.address = address;
+    }
+}

libraries/src/test/java/com/baeldung/javers/JaversTest.java

@@ -0,0 +1,113 @@
+package com.baeldung.javers;
+
+
+import org.javers.common.collections.Lists;
+import org.javers.core.Javers;
+import org.javers.core.JaversBuilder;
+import org.javers.core.diff.Diff;
+import org.javers.core.diff.changetype.NewObject;
+import org.javers.core.diff.changetype.ObjectRemoved;
+import org.javers.core.diff.changetype.ValueChange;
+import org.javers.core.diff.changetype.container.ListChange;
+import org.junit.Test;
+
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class JaversTest {
+
+    @Test
+    public void givenPersonObject_whenApplyModificationOnIt_thenShouldDetectChange() {
+        //given
+        Javers javers = JaversBuilder.javers().build();
+
+        Person person = new Person(1, "Michael Program");
+        Person personAfterModification = new Person(1, "Michael Java");
+
+        //when
+        Diff diff = javers.compare(person, personAfterModification);
+
+        //then
+        ValueChange change = diff.getChangesByType(ValueChange.class).get(0);
+
+        assertThat(diff.getChanges()).hasSize(1);
+        assertThat(change.getPropertyName()).isEqualTo("name");
+        assertThat(change.getLeft()).isEqualTo("Michael Program");
+        assertThat(change.getRight()).isEqualTo("Michael Java");
+    }
+
+
+    @Test
+    public void givenListOfPersons_whenCompare_ThenShouldDetectChanges() {
+        //given
+        Javers javers = JaversBuilder.javers().build();
+        Person personThatWillBeRemoved = new Person(2, "Thomas Link");
+        List<Person> oldList = Lists.asList(new Person(1, "Michael Program"), personThatWillBeRemoved);
+        List<Person> newList = Lists.asList(new Person(1, "Michael Not Program"));
+
+        //when
+        Diff diff = javers.compareCollections(oldList, newList, Person.class);
+
+        //then
+        assertThat(diff.getChanges()).hasSize(3);
+
+
+        ValueChange valueChange = diff.getChangesByType(ValueChange.class).get(0);
+        assertThat(valueChange.getPropertyName()).isEqualTo("name");
+        assertThat(valueChange.getLeft()).isEqualTo("Michael Program");
+        assertThat(valueChange.getRight()).isEqualTo("Michael Not Program");
+
+        ObjectRemoved objectRemoved = diff.getChangesByType(ObjectRemoved.class).get(0);
+        assertThat(objectRemoved.getAffectedObject().get().equals(personThatWillBeRemoved)).isTrue();
+
+        ListChange listChange = diff.getChangesByType(ListChange.class).get(0);
+        assertThat(listChange.getValueRemovedChanges().size()).isEqualTo(1);
+
+    }
+
+    @Test
+    public void givenListOfPerson_whenPersonHasNewAddress_thenDetectThatChange() {
+        //given
+        Javers javers = JaversBuilder.javers().build();
+
+        PersonWithAddress person =
+                new PersonWithAddress(1, "Tom", Arrays.asList(new Address("England")));
+
+        PersonWithAddress personWithNewAddress =
+                new PersonWithAddress(1, "Tom",
+                        Arrays.asList(new Address("England"), new Address("USA")));
+
+
+        //when
+        Diff diff = javers.compare(person, personWithNewAddress);
+        List objectsByChangeType = diff.getObjectsByChangeType(NewObject.class);
+
+        //then
+        assertThat(objectsByChangeType).hasSize(1);
+        assertThat(objectsByChangeType.get(0).equals(new Address("USA")));
+    }
+
+    @Test
+    public void givenListOfPerson_whenPersonRemovedAddress_thenDetectThatChange() {
+        //given
+        Javers javers = JaversBuilder.javers().build();
+
+        PersonWithAddress person =
+                new PersonWithAddress(1, "Tom", Arrays.asList(new Address("England")));
+
+        PersonWithAddress personWithNewAddress =
+                new PersonWithAddress(1, "Tom", Collections.emptyList());
+
+
+        //when
+        Diff diff = javers.compare(person, personWithNewAddress);
+        List objectsByChangeType = diff.getObjectsByChangeType(ObjectRemoved.class);
+
+        //then
+        assertThat(objectsByChangeType).hasSize(1);
+        assertThat(objectsByChangeType.get(0).equals(new Address("England")));
+    }
+}