Merge pull request eugenp#6051 from mchugunov/BAEL-2475-deserialize-immutable-objects

BAEL-2475: Deserialize immutable objects

Author: eric-martin

jackson/src/main/java/com/baeldung/jackson/deserialization/immutable/Employee.java

@@ -0,0 +1,24 @@
+package com.baeldung.jackson.deserialization.immutable;
+
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonProperty;
+
+public class Employee {
+
+    private final long id;
+    private final String name;
+
+    @JsonCreator(mode = JsonCreator.Mode.PROPERTIES)
+    public Employee(@JsonProperty("id") long id, @JsonProperty("name") String name) {
+        this.id = id;
+        this.name = name;
+    }
+
+    public long getId() {
+        return id;
+    }
+
+    public String getName() {
+        return name;
+    }
+}

jackson/src/main/java/com/baeldung/jackson/deserialization/immutable/Person.java

@@ -0,0 +1,44 @@
+package com.baeldung.jackson.deserialization.immutable;
+
+import com.fasterxml.jackson.databind.annotation.JsonDeserialize;
+import com.fasterxml.jackson.databind.annotation.JsonPOJOBuilder;
+
+@JsonDeserialize(builder = Person.Builder.class)
+public class Person {
+
+    private final String name;
+    private final Integer age;
+
+    private Person(String name, Integer age) {
+        this.name = name;
+        this.age = age;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public Integer getAge() {
+        return age;
+    }
+
+    @JsonPOJOBuilder
+    static class Builder {
+        String name;
+        Integer age;
+
+        Builder withName(String name) {
+            this.name = name;
+            return this;
+        }
+
+        Builder withAge(Integer age) {
+            this.age = age;
+            return this;
+        }
+
+        Person build() {
+            return new Person(name, age);
+        }
+    }
+}

jackson/src/test/java/com/baeldung/jackson/deserialization/immutable/ImmutableObjectDeserializationUnitTest.java

@@ -0,0 +1,38 @@
+package com.baeldung.jackson.deserialization.immutable;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+import org.junit.Test;
+
+import java.io.IOException;
+
+import static org.junit.Assert.*;
+
+public class ImmutableObjectDeserializationUnitTest {
+
+    @Test
+    public void whenPublicConstructorIsUsed_thenObjectIsDeserialized() throws IOException {
+        final String json = "{\"name\":\"Frank\",\"id\":5000}";
+        Employee employee = new ObjectMapper().readValue(json, Employee.class);
+
+        assertEquals("Frank", employee.getName());
+        assertEquals(5000, employee.getId());
+    }
+
+    @Test
+    public void whenBuilderIsUsedAndFieldIsNull_thenObjectIsDeserialized() throws IOException {
+        final String json = "{\"name\":\"Frank\"}";
+        Person person = new ObjectMapper().readValue(json, Person.class);
+
+        assertEquals("Frank", person.getName());
+        assertNull(person.getAge());
+    }
+
+    @Test
+    public void whenBuilderIsUsedAndAllFieldsPresent_thenObjectIsDeserialized() throws IOException {
+        final String json = "{\"name\":\"Frank\",\"age\":50}";
+        Person person = new ObjectMapper().readValue(json, Person.class);
+
+        assertEquals("Frank", person.getName());
+        assertEquals(50, (int) person.getAge());
+    }
+}