Standard Serialization of an Object Graph

@Data
@NoArgsConstructor
@AllArgsConstructor
public class Item {public int id;public String itemName;public User owner;
}

@Data
@NoArgsConstructor
@AllArgsConstructor
public class User {public int id;public String name;
}

Item myItem = new Item(1, "theItem", new User(2, "theUser"));
String serialized = new ObjectMapper().writeValueAsString(myItem);
System.out.println(serialized);结果
{"id":1,"itemName":"theItem","owner":{"id":2,"name":"theUser"}}

Custom Serializer on the ObjectMapper

@Data
@NoArgsConstructor
@AllArgsConstructor
public class Item {public int id;public String itemName;public User owner;
}

@Data
@NoArgsConstructor
@AllArgsConstructor
public class User {public int id;public String name;
}

public class ItemSerializer extends StdSerializer<Item> {public ItemSerializer() {this(null);}public ItemSerializer(Class<Item> t) {super(t);}@Overridepublic void serialize(Item value, JsonGenerator jsonGenerator, SerializerProvider provider) throws IOException {jsonGenerator.writeStartObject();jsonGenerator.writeNumberField("id", value.id);jsonGenerator.writeStringField("itemName", value.itemName);jsonGenerator.writeNumberField("owner", value.owner.id);jsonGenerator.writeEndObject();}
}

ObjectMapper mapper = new ObjectMapper();
SimpleModule module = new SimpleModule();
module.addSerializer(Item.class, new ItemSerializer());
mapper.registerModule(module);Item myItem = new Item(1, "theItem", new User(2, "theUser"));
String serialized = mapper.writeValueAsString(myItem);
System.out.println(serialized);结果
{"id":1,"itemName":"theItem","owner":2}

Custom Serializer on the Class

@Data
@NoArgsConstructor
@AllArgsConstructor
public class User {public int id;public String name;
}

@Data
@NoArgsConstructor
@AllArgsConstructor
@JsonSerialize(using = ItemSerializer.class)
public class Item {public int id;public String itemName;public User owner;
}

Item myItem = new Item(1, "theItem", new User(2, "theUser"));
String serialized = new ObjectMapper().writeValueAsString(myItem);
System.out.println(serialized);结果
{"id":1,"itemName":"theItem","owner":2}

-----------------------------------------------------------------------------读书笔记摘自 文章：Jackson – Custom Serializer