jackson custom serializer work

jackson/src/test/java/org/baeldung/jackson/dtos/Item.java

@@ -3,12 +3,12 @@ package org.baeldung.jackson.dtos;
 public class Item {
     public final int id;
     public final String itemNr;
-    public final User createdBy;
+    public final User owner;
 
-    public Item(final int id, final String itemNr, final User createdBy) {
+    public Item(final int id, final String itemNr, final User owner) {
         this.id = id;
         this.itemNr = itemNr;
-        this.createdBy = createdBy;
+        this.owner = owner;
     }
 
     // API
@@ -21,8 +21,8 @@ public class Item {
         return itemNr;
     }
 
-    public User getCreatedBy() {
+    public User getOwner() {
-        return createdBy;
+        return owner;
     }
 
 }

jackson/src/test/java/org/baeldung/jackson/dtos/ItemWithSerializer.java

@@ -0,0 +1,33 @@
+package org.baeldung.jackson.dtos;
+
+import org.baeldung.jackson.serialization.ItemSerializerOnClass;
+
+import com.fasterxml.jackson.databind.annotation.JsonSerialize;
+
+@JsonSerialize(using = ItemSerializerOnClass.class)
+public class ItemWithSerializer {
+    public final int id;
+    public final String itemNr;
+    public final User owner;
+
+    public ItemWithSerializer(final int id, final String itemNr, final User owner) {
+        this.id = id;
+        this.itemNr = itemNr;
+        this.owner = owner;
+    }
+
+    // API
+
+    public int getId() {
+        return id;
+    }
+
+    public String getItemNr() {
+        return itemNr;
+    }
+
+    public User getOwner() {
+        return owner;
+    }
+
+}

jackson/src/test/java/org/baeldung/jackson/dtos/ignore/MyDtoIgnoreField.java

@@ -1,4 +1,4 @@
-package org.baeldung.jackson.dtos;
+package org.baeldung.jackson.dtos.ignore;
 
 import com.fasterxml.jackson.annotation.JsonIgnore;
 

jackson/src/test/java/org/baeldung/jackson/dtos/ignore/MyDtoIgnoreFieldByName.java

@@ -1,4 +1,4 @@
-package org.baeldung.jackson.dtos;
+package org.baeldung.jackson.dtos.ignore;
 
 import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
 

jackson/src/test/java/org/baeldung/jackson/dtos/ignore/MyDtoIgnoreNull.java

@@ -1,4 +1,4 @@
-package org.baeldung.jackson.dtos;
+package org.baeldung.jackson.dtos.ignore;
 
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonInclude.Include;

jackson/src/test/java/org/baeldung/jackson/dtos/ignore/MyDtoIgnoreType.java

@@ -1,4 +1,4 @@
-package org.baeldung.jackson.dtos;
+package org.baeldung.jackson.dtos.ignore;
 
 import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
 

jackson/src/test/java/org/baeldung/jackson/dtos/ignore/MyDtoIgnoreUnknown.java

@@ -1,4 +1,4 @@
-package org.baeldung.jackson.dtos;
+package org.baeldung.jackson.dtos.ignore;
 
 import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
 

jackson/src/test/java/org/baeldung/jackson/serialization/ItemSerializer.java

@@ -1,4 +1,4 @@
-package org.baeldung.jackson.try1;
+package org.baeldung.jackson.serialization;
 
 import java.io.IOException;
 
@@ -16,7 +16,7 @@ public class ItemSerializer extends JsonSerializer<Item> {
         jgen.writeStartObject();
         jgen.writeNumberField("id", value.id);
         jgen.writeStringField("itemNr", value.itemNr);
-        jgen.writeNumberField("createdBy", value.createdBy.id);
+        jgen.writeNumberField("createdBy", value.owner.id);
         jgen.writeEndObject();
     }
 

jackson/src/test/java/org/baeldung/jackson/serialization/ItemSerializerOnClass.java

@@ -0,0 +1,23 @@
+package org.baeldung.jackson.serialization;
+
+import java.io.IOException;
+
+import org.baeldung.jackson.dtos.ItemWithSerializer;
+
+import com.fasterxml.jackson.core.JsonGenerator;
+import com.fasterxml.jackson.core.JsonProcessingException;
+import com.fasterxml.jackson.databind.JsonSerializer;
+import com.fasterxml.jackson.databind.SerializerProvider;
+
+public class ItemSerializerOnClass extends JsonSerializer<ItemWithSerializer> {
+
+    @Override
+    public final void serialize(final ItemWithSerializer value, final JsonGenerator jgen, final SerializerProvider provider) throws IOException, JsonProcessingException {
+        jgen.writeStartObject();
+        jgen.writeNumberField("id", value.id);
+        jgen.writeStringField("itemNr", value.itemNr);
+        jgen.writeNumberField("createdBy", value.owner.id);
+        jgen.writeEndObject();
+    }
+
+}

jackson/src/test/java/org/baeldung/jackson/test/JacksonDeserializationUnitTest.java

@@ -7,7 +7,7 @@ import static org.junit.Assert.assertThat;
 import java.io.IOException;
 
 import org.baeldung.jackson.dtos.MyDto;
-import org.baeldung.jackson.dtos.MyDtoIgnoreUnknown;
+import org.baeldung.jackson.dtos.ignore.MyDtoIgnoreUnknown;
 import org.junit.Test;
 
 import com.fasterxml.jackson.core.JsonFactory;

jackson/src/test/java/org/baeldung/jackson/test/JacksonSerializationIgnoreUnitTest.java

@@ -7,12 +7,12 @@ import static org.junit.Assert.assertThat;
 import java.io.IOException;
 
 import org.baeldung.jackson.dtos.MyDto;
-import org.baeldung.jackson.dtos.MyDtoIgnoreField;
-import org.baeldung.jackson.dtos.MyDtoIgnoreFieldByName;
-import org.baeldung.jackson.dtos.MyDtoIgnoreNull;
 import org.baeldung.jackson.dtos.MyDtoIncludeNonDefault;
 import org.baeldung.jackson.dtos.MyDtoWithFilter;
 import org.baeldung.jackson.dtos.MyMixInForString;
+import org.baeldung.jackson.dtos.ignore.MyDtoIgnoreField;
+import org.baeldung.jackson.dtos.ignore.MyDtoIgnoreFieldByName;
+import org.baeldung.jackson.dtos.ignore.MyDtoIgnoreNull;
 import org.junit.Test;
 
 import com.fasterxml.jackson.annotation.JsonInclude.Include;

jackson/src/test/java/org/baeldung/jackson/test/JacksonSerializationUnitTest.java

@@ -1,30 +1,27 @@
 package org.baeldung.jackson.test;
 
-import static org.apache.commons.lang3.RandomStringUtils.randomAlphabetic;
-import static org.apache.commons.lang3.RandomStringUtils.randomNumeric;
 import static org.hamcrest.Matchers.containsString;
 import static org.hamcrest.Matchers.not;
 import static org.hamcrest.Matchers.notNullValue;
 import static org.junit.Assert.assertThat;
 
 import java.io.IOException;
-import java.io.StringWriter;
 import java.util.List;
 
 import org.baeldung.jackson.dtos.Item;
+import org.baeldung.jackson.dtos.ItemWithSerializer;
 import org.baeldung.jackson.dtos.MyDto;
 import org.baeldung.jackson.dtos.MyDtoFieldNameChanged;
 import org.baeldung.jackson.dtos.MyDtoNoAccessors;
 import org.baeldung.jackson.dtos.MyDtoNoAccessorsAndFieldVisibility;
 import org.baeldung.jackson.dtos.User;
-import org.baeldung.jackson.try1.ItemSerializer;
+import org.baeldung.jackson.serialization.ItemSerializer;
 import org.junit.Test;
 
 import com.fasterxml.jackson.annotation.JsonAutoDetect.Visibility;
 import com.fasterxml.jackson.annotation.PropertyAccessor;
 import com.fasterxml.jackson.core.JsonGenerationException;
 import com.fasterxml.jackson.core.JsonParseException;
-import com.fasterxml.jackson.core.Version;
 import com.fasterxml.jackson.databind.JsonMappingException;
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.fasterxml.jackson.databind.module.SimpleModule;
@@ -101,20 +98,32 @@ public class JacksonSerializationUnitTest {
 
     // tests - custom serializer
 
+    @Test
+    public final void whenSerializing_thenNoExceptions() throws JsonGenerationException, JsonMappingException, IOException {
+        final Item myItem = new Item(1, "theItem", new User(2, "theUser"));
+        final String serialized = new ObjectMapper().writeValueAsString(myItem);
+        System.out.println(serialized);
+    }
+
     @Test
     public final void whenSerializingWithCustomSerializer_thenNoExceptions() throws JsonGenerationException, JsonMappingException, IOException {
-        final Item myItem = new Item(Integer.parseInt(randomNumeric(2)), randomAlphabetic(8), new User(Integer.parseInt(randomNumeric(2)), randomAlphabetic(8)));
+        final Item myItem = new Item(1, "theItem", new User(2, "theUser"));
 
         final ObjectMapper mapper = new ObjectMapper();
 
-        final SimpleModule simpleModule = new SimpleModule("SimpleModule", new Version(1, 0, 0, null));
+        final SimpleModule simpleModule = new SimpleModule();
         simpleModule.addSerializer(Item.class, new ItemSerializer());
-        // simpleModule.addSerializer(User.class, new UserSerializer());
         mapper.registerModule(simpleModule);
 
-        final StringWriter writer = new StringWriter();
+        final String serialized = mapper.writeValueAsString(myItem);
-        mapper.writeValue(writer, myItem);
+        System.out.println(serialized);
-        final String serialized = writer.toString();
+    }
+
+    @Test
+    public final void givenSerializerRegisteredOnClass_whenSerializingWithCustomSerializer_thenNoExceptions() throws JsonGenerationException, JsonMappingException, IOException {
+        final ItemWithSerializer myItem = new ItemWithSerializer(1, "theItem", new User(2, "theUser"));
+
+        final String serialized = new ObjectMapper().writeValueAsString(myItem);
         System.out.println(serialized);
     }