Jackson Serialize Null As Empty String

1 package org. // Written by David Megginson, [email protected] In the case of a count you probably always want some valid number (unless the count is unknown or undefined), but in the case of strings, who knows? The empty string could mean something in your application. The @JsonInclude annotation contains below two values. Return an empty array or collection instead of a null value for methods that return an array or collection. Visual Studio Languages ,. A factory instance can be used to create multiple builder instances with the same configuration. BeanSerializer. I am however, getting empty String values for java. If textual values are used, other settings are also considered. Starting with release 8. This makes it easier to switch to Boon from GSON or Jackson. from airflow. Feature is disabled by default. Jackson is a very popular JSON processor and is widely used. The important thing to remember is that the empty string and the number zero are conceptually distinct from null. The example creates an XmlAttributes object, and sets the XmlIgnore property to false, thereby overriding the XmlIgnoreAttribute. As I've been setting up a JSON-RPC (Remote Procedure Call) API for a ColdFusion project, I've been learning a few little tips and trips about JSON formation. Given an list of user defined objects or POJO and object may contains the empty values (e. I however made it work by providing a custom factory. This means it will be serialized with a value of true or false, depending on whether it is empty or not. // Written by David Megginson, [email protected] I have a JSON string that marks empty lists as "" instead of []. catch only required during debugging response. The following are top voted examples for showing how to use org. Since that record is of type ["string", "null"], we can either set it to a string or leave it null; it is essentially optional. InvalidDefinitionException: No serializer found for class ABC and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationFeature. x provides @JsonInclude annotation to specify the property that should be included during serialization based on its values. An array containing zero values is called an empty null value, the second JSON string saves space. ObjectMapper is the main actor class of Jackson library. Method to use for accessing String values. Json 형식으로 데이터를 주고받을 때 Jackson의 ObjectMapper를 자주 이용한다. The detail of exception is like following. Adding an array element to JSON using Jackson; Jackson Json Mapper: no field or empty field? Converting JSON array to POJO using jackson object mapper; Jackson JSON gives exception on collection of nested class; polymorphic deserialization of JSON with jackson, property type becomes "null" Spring Boot Automatic JSON to Object at Controller. OrderAdded", "com. The Boon ObjectMapper class is designed to have an interface similar to both GSON and the Jackson ObjectMapper classes. 我正在使用Jackson反序列化一个可能包含Map变量空值的JSON。我想要的是如果值为null,我希望地图是一个空的HashMap而不是null。 JSON:. JsonNullSerializer to send empty string instead of null value - Set them to "empty string". The canonical reference for building a production grade API with Spring. This will force Jackson to serialize only those properties which don't have @JsonView annotation at all, or have @JsonView annotations matching specified view. This is for a spring-boot application where I POST a json file into an ArrayList of my class object and then reading a single array element into JsonNode object. You can vote up the examples you like. This is an automated email from the ASF dual-hosted git repository. Thanks for the nice article. NON_NULL) at the class level. Unity seems a bit quicker, but it’s possibly just noise in the testing. JsonParseException, com. Questions: I have a a Map foosMap that I want to serialize through Jackson. Note that if you want to make the output completely non-loaded, then use Empty for class-level annotations in Entity, such as @Json Include (Json Include. JsonPropertyAttribute indicates that a property should be serialized when member serialization is set to opt-in. The canonical reference for building a production grade API with Spring. Jackson: how to exclude null value properties from JSON serialization Posted on January 8, 2016 by Davis Molinari In the comments to a previous article about the Jackson library , it had been raised the question on how to exclude from the JSON serialization of a Java object properties that had a null value. Serialization is the process of writing a Java Object into JSON format (on the web you find references to POJOs (Plain Old Java Objects) but, basically, you only need a class that you want to serialize in your domain to follow some properties and anything can be serialized. There are two common ways of making a plain Java object candidate for JSON deserialization: including an empty constructor or using Jackson annotations. This practice can lead to denial-of-service vulnerabilities when the client code fails to explicitly handle the null return value case. We use cookies for various purposes including analytics. To create a custom serializer, we need to create a class by extending Jackson StdSerializer class and override its serialize method. Basic interface serialization and deserialization of Objects to byte arrays (binary data). Jackson is a very popular and efficient Java-based library to serialize or map Java objects to JSON and vice versa. It includes non-public properties in serialization and deserialization. # 値がnullのプロパティーを出力しない spring. Omitting empty fields. In most cases where your domain-specific POJO model consists of only basic types such as String, Number, Calendar or compound classes having those basic types as well, you won't have any problem in JSON Serialization as Jackson library will handle those basic types automatically. 我正在使用Jackson反序列化一个可能包含Map变量空值的JSON。我想要的是如果值为null,我希望地图是一个空的HashMap而不是null。 JSON:. Note that, by default Java simple objects are assigned as null without enabling this feature. In these two cases the deserializer returns null in all other cases it removes the last letter ('n') and tries to convert the string to a BigInteger respectively a Long. However camel-jackson must be explicit enabled, which is done by setting some options on the CamelContext properties, as shown below:. I have an Issue. 3 seconds with. This page will walk through Jackson custom serializer example. Given an list of user defined objects or POJO and object may contains the empty values (e. The Jackson ObjectMapper can parse JSON from a string, stream or file, and create a Java object or object graph representing the parsed JSON. This makes it easier to switch to Boon from GSON or Jackson. x includes null and empty object fields while serializing to JSON. While using RestController in Spring Rest service at time response automatically converted to JSON using Jackson. To convert a Java object to JSON with Jackson, we need to create an ObjectMapper object and use its writeValueAsString method to serialize any Java value as a String. Default implementation will consider only null values to be empty. We do not want to serialize null values of POJO (setSerializationInclusion of Jackson ObjectMapper - example). The following are top voted examples for showing how to use com. The next two examples cover those scenarios. ordinal() (an integer) will be used as the serialization. There is a switch to change the Jackson default as shown in the code. The following example serializes a class named Group, which contains a member named Comment to which the XmlIgnoreAttribute is applied. Let's assume that You are writing an API which will handle /login requests. Overview In this tutorial, we’ll look at serialization of null values. While the original use case for Jackson. InvalidDefinitionException: No serializer found for class ABC and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationFeature. Toggle JsonNode` serialization does not consider default an override for converting `null` for String values to empty. But when it comes to serialization and deserialization performance, the differences started to show. In addition to item reader and writer based on super-csv library, jberet-support also contains jacksonCsvItemReader and jacksonCsvItemWriter, which implement reading from and writing to CSV using jackson-dataformat-csv library. Jackson is a very popular JSON processor and is widely used. Note that Redis does not accept null keys or values but can return null replies (for non existing keys). [英] How to serialize a null string as a single empty tag? 本文翻译自 Michael 查看原文 2013/06/20 2073 I have tried assigning an empty string:. Note that this feature has precedence over WRITE_ENUMS_USING_TO_STRING, which is only considered if this feature is set to false. This practice can lead to denial-of-service vulnerabilities when the client code fails to explicitly handle the null return value case. ObjectMapper is the main actor class of Jackson library. For Serialization we are going to look at the System. java - serialize an XML document // XMLWriter. JsonObject object = Json. I need jackson json (1. It's been a long wait, but Java EE 8 introduces powerful JSON binding features to the core Java enterprise platform. Feature is disabled by default. Overview In this tutorial, we’ll look at serialization of null values. jackson { # The Jackson JSON serializer will register these modules. While it could be beneficial to do so, I am not sure if that is technically feasible because of complexities wrt coercion of empty String, and how null handling here is handled. jgen - Generator used to output resulting Json content provider - Provider that can be used to get serializers for serializing Objects value contains, if any. catch only required during debugging response. It's good to see this open source library getting integrated into. Lets see how the date object will be displayed in default case. NOTE: various serialize methods are never (to be) called with null values -- caller must handle null values, usually by calling SerializerProvider. The Boon ObjectMapper class is designed to have an interface similar to both GSON and the Jackson ObjectMapper classes. When feature is enabled, conversions from JSON String are allowed, as long as textual value matches (for example, String "true" is allowed as equivalent of JSON boolean token "true"; or String "1. For Java arrays, empty arrays are ones with length of 0 For Java Strings, length() is called, and return value of 0 indicates empty String (note that String. length() returns 0. time with Jackson JSON mapper. Using Jackson, you can easily handle automatic conversion from Java objects to JSON and back. If you want to dig deeper and learn other cool things you can do with the Jackson 2 – head on over to the main Jackson tutorial. Toggle JsonNode` serialization does not consider default an override for converting `null` for String values to empty. findNullValueSerializer(com. Overview In this tutorial, we’ll look at serialization of null values. Introduction. 'Absent' values as defined by JsonInclude. Questions: I have a a Map foosMap that I want to serialize through Jackson. NET, including the brief introduction of JSON, how to serialize and deserialize with ASP. 2 If an empty tag is available in the xml and the respective field in the object is a string, it would be nice to have jackson populate the field with empty string rather than with null value. When adding an item to comparison from ca. For example: public class SomeClass { // what jackson annotation causes jackson to skip over this value if it is null but will. String)' on a null. I need jackson json (1. Unions, as mentioned above, are represented using JSON arrays. serialize in class StdSerializer Parameters: value - Value to serialize; can not be null. For example, ["null", "string"] declares a schema which may be either a null or string. This tutorial will demonstrate how to serialize Java object to JSON and de-serialize it back using Jackson 2. If this feature is enabled, return value of Enum. how to use @JsonPropertyOrder annotation. It includes non-public properties in serialization and deserialization. These examples are extracted from open source projects. Adding an array element to JSON using Jackson; Jackson Json Mapper: no field or empty field? Converting JSON array to POJO using jackson object mapper; Jackson JSON gives exception on collection of nested class; polymorphic deserialization of JSON with jackson, property type becomes "null" Spring Boot Automatic JSON to Object at Controller. In addition, to support per-property annotations (to configure aspects of deserialization on per-property basis), deserializers may want to implement ContextualDeserializer, which allows specialization of deserializers: call to ContextualDeserializer. I'm pretty new to Jackson and Spring-Boot. THE unique Spring Security education if you’re working with Java today. It does not include markup languages used exclusively as document file formats. Optional < String > empty = Optional If you do need to serialize an object that contains an Optional value, the Jackson library provides support for treating Optionals as ordinary objects. When serializing a dictionary, the keys of the dictionary are converted to strings and used as the JSON object property names. The @JsonRawValue annotation can instruct Jackson to serialize a property exactly as is. We can use @JsonFormat with Date properties to decide if date should be serialized in number or string format. jackson serialize null as empty string (2) Since Jackson 2. This write-up focuses on understanding the Jackson ObjectMapper class - and how to serialize Java objects into JSON and deserialize JSON string into Java objects. The @JsonInclude annotation contains below two values. The Map is persisted as flattened properties of the target POJO. We do not want to serialize null values of POJO (setSerializationInclusion of Jackson ObjectMapper - example). The example code below shows how to build an empty JsonObject instance. Configuring ObjectMapper. The Jackson ObjectMapper can parse JSON from a string, stream or file, and create a Java object or object graph representing the parsed JSON. [[ "4", , "6"], <-- note the empty string in the middle (when I say empty string I mean literally that, not two double quotes "" ;-) [[ 7, 8, 9]] Where the JavaScript object in the array will be 'undefined', which is the JavaScript equivalent to a Java null reference which was there on the server side. If you need to serialize an Object to a byte array or deserialize a byte array back into an Object, Spring Integration provides symmetrical serialization transformers. Throws: IOException JsonGenerationException; getSchema. Starting with release 8. The Jackson ObjectMapper class (com. The class comes with a bunch of overloaded parse methods plus some special methods such as parseText , parseFile and others. could you post your serialization and deserialization code here please. jgen - Generator used to output resulting Json content provider - Provider that can be used to get serializers for serializing Objects value contains, if any. Object Serialization. Include#value is specified so that the higher-level defaults can be used. empty() as a POJO, while Gson produces an empty JSON Object. Omitting empty fields. It does not include markup languages used exclusively as document file formats. Jackson is one of the most common Java libraries for processing JSON. The Map is persisted as flattened properties of the target POJO. General data-binding functionality for Jackson: works on core streaming API While the original use case for Jackson was JSON data-binding, it can now be used for other data formats as well, as long as parser and generator implementations exist. Unions, as mentioned above, are represented using JSON arrays. If you don't specify the INCLUDE_NULL_VALUES option, the JSON output doesn't include properties for values that are null in the query results. GsonBuilder class. Your votes will be used in our system to get more good examples. Serialization - Top 25 interview questions Convert JSON string to java Object - using Jackson. Overview In this quick article, we’re going to look at a more advanced use-case of using Jackson – working with Maps that contain null values or null keys. None is serialized to an empty string. So, I decided to dig into Jackson internals and come up with a solution. This is a common task for Java developers to convert JSON to Java objects and vice-versa so I show you how to do that with examples. It provides various utility methods to check the presence or absence of an object, which helps to deal with NullPointerException. 0 is finally out (*) — it took almost 1 full year to get from 2. Ignore Nulls Values in a Map Jackson has a simple but useful way of globally controlling what happens to null values when a Map gets […]. null values or collection of size=0). Jackson is best known for its ability to serialize POJOs into JSON and back, by means of standard conventions and - where necessary - special annotations to give clues to the Jackson library. In today's post I will show You how to deal with custom enum serialization. Lets see how the date object will be displayed in default case. Unity seems a bit quicker, but it’s possibly just noise in the testing. Jackson Modules. jgen - Generator used to output resulting Json content provider - Provider that can be used to get serializers for serializing Objects value contains, if any. This tutorial will give you a better understanding of Jackson Annotations and how they are best used. If some field values are NULL then Jackson will be converted to NULL value by default as like:. default-property-inclusion=NON_NULL # JSON出力時に改行・インデントを入れる spring. You could include other media types, such as xml, and Jersey would automatically use the appropriate media type based on the Accepts header sent by the client. Project is licensed under Apache License 2. In this article, I show you how to how to use Jackson-databind API for binding Java Object to JSON and JSON data to Java Object. APPLICATION_JSON}). JSONObject to json I got the JsonMappingException. The namespace which is used to read and write files is System. A TypeConverter will also support converting a custom string back again when. NON_DEFAULT는 값이 기본 설정과 다른 경우 속성이 serialization한다. JsonObject object = Json. NON_NULL to ignore fields with Null values and Include. For example: public class SomeClass { // what jackson annotation causes jackson to skip over this value if it is null but will. A TypeConverter will also support converting a custom string back again when. While using RestController in Spring Rest service at time response automatically converted to JSON using Jackson. NON_NULL: Indicates that only properties with not null values will be included in JSON. ACCEPT_FLOAT_AS_INT (default: true) (since 2. Following this, we’ll introduce a solution which will get Jackson to treat Optionals as if they were ordinary nullable objects. Beispielsweise: public class SomeClass { // what jackson annotation causes jackson to skip over this value if it is null but will // serialize it otherwise private String someValue; }. You can vote up the examples you like. To understand more about the Jackson library in general, the. How to tell Jackson to ignore empty object during deserialization? At the deserialization process (which as I understand is the process of converting JSON data into a Java Object), how can I tell Jackson that when it reads a object that contains no data, it should be ignored?. I have been using the Jackson recently and came across a situation where I have to send the null values/ empty property. setSerializationInclusion(JsonInclude. It is forbidden to serialize a collection type or a type that implements IXmlSerializable where a non-collection type that is not IXmlSerializable (except for Object) is. // Creating an empty optional Optional empty If you do need to serialize an object that contains an Optional value, the Jackson library provides support for treating Optionals as. Note: Refer How to convert Java object to JSON string? page for dependent libraries. This sample serializes an object to JSON with T:Newtonsoft. null values or collection of size=0). When adding an item to comparison from ca. Lets see how the date object will be displayed in default case.  It’s in production, and therefore changes to it need to be backward compatible. I am using jackson-dataformat-xml:2. This is due to not having an empty constructor that Jackson can use during its deserialization logic (using reflection utils). We will use the setSerializationInclusion feature of jackson’s ObjectMapper to block serialization of empty values. createContextual(com. The code snippet here would check to see if the query string contained a "'document. x and Spring Boot. I don't know if this problem has been encountered or dealt with. build(); The class JsonBuilderFactory also contains methods to create JsonObjectBuilder instances. In this example, we have an Employee class that contains some mixed type of properties namely integer, String and custom Compensation class type. However camel-jackson must be explicit enabled, which is done by setting some options on the CamelContext properties, as shown below:. - Serialize 검증. There is a switch to change the Jackson default as shown in the code. JsonSerialize. NON_NULL) // 允许单引号. Sometimes, it is desirable to ignore such fields. As already mentioned, the XmlMapper object directly replaced ObjectMapper, only it works in terms of XML instead of JSON. I have a JSON string that marks empty lists as "" instead of []. The Map is persisted as flattened properties of the target POJO. Here's the compared performance on my system (30MB object in RAM, a "map of maps"), serialized into an 11MB JSON Numbers below from a profiling in YourKit: - 1. Does NOT do any conversions for non-String value nodes; for non-String values (ones for which JsonNode. Android 高级 Jackson Marshalling(serialize)/Unmarshalling(deserialize) 本文内容 高级 Jackson Marshalling 只序列化符合自定义标准的字段 把 Enums 序列化成 JSON 对象 JsonMappingException(没有找到类的序列化器) Jac. If this feature is enabled, return value of Enum. As to empty String unfortunately empty String is not null in this respect so it will not apply no. I have been using the Jackson recently and came across a situation where I have to send the null values/ empty property. isEmpty(Object), which was deprecated in 2. void serialize (java. 9368198Z' and jackson mapper is convertion iso Date String to date , here am facing the problem it is returin different results, can you please how to convert ISO Date String into Data in java. But you can use a Custom JsonDeserializer to do. Jackson will not serialize or deserialize transient fields. def serialize (value): """ Serializes a python object to a string. Last week, I talked about how struct keys defined using array-notation maintain case during serialization. We can configure the deserializers, like the serializers, globally or locally on a field by field basis. String defaultValue) Method similar to JsonNode. Jackson is one of the most common Java libraries for processing JSON. how to deserialize a blank json string value to null for java. While it could be beneficial to do so, I am not sure if that is technically feasible because of complexities wrt coercion of empty String, and how null handling here is handled. how to use @JsonPropertyOrder annotation. In controller's constructor we define which model attributes should be serialized (using setRenderedAttributes method), and switch serialization view to the Employer. JSONObject to json I got the JsonMappingException. Do not forget that Java Bean specification implies an empty constructor (without parameters). Is there any Jackson annotation or should I just check for the null inside my getter and return empty string if the property is null?. asText() , except that it will return defaultValue in cases where null value would be returned; either for missing nodes (trying to access missing property, or element at invalid item for array) or explicit nulls. Used to allow passing in configuration settings and reusable temporary objects (scrap arrays, containers). Note that Redis does not accept null keys or values but can return null replies (for non existing keys). Ignore Null Fields on the Class Jackson allows controlling this behavior at either the class level:. How to make Jackson serialize null strings differently than null Objects We’ve got an API. Basic interface serialization and deserialization of Objects to byte arrays (binary data). String[] value, JsonGenerator gen, SerializerProvider provider). This tutorial contains a large number of articles/posts which demonstrates the basic and advanced Jackson library API features and their usage with lots of examples. Using Jackson, you can easily handle automatic conversion from Java objects to JSON and back. foo = Collections. [Jackson] json string에서 null인 properties는 보이지 않게 하기 general java 2012. Cheers, Askar. I guess a better way of expressing it would be, when data binding to an instance of Collection, the deserialization mechanism should produce an empty collection rather than a null object if the corresponding key in the JSON being deserialized does not exist or is null (is that possible?). Empty, null int?s should become 0, null bool?s. Jackson will not serialize or deserialize transient fields. It is recommended that implementations are designed to handle null objects/empty arrays on serialization and deserialization side. This converter can be used to bind to typed beans, or untyped HashMap instances. This is due to not having an empty constructor that Jackson can use during its deserialization logic (using reflection utils). I am however, getting empty String values for java. Following one-liner convert JSON string representing a soccer player into a Java class representing player:. This is useful for saving bandwidth: if the defaults are the same on both sides of the serialization, theres no point in serializing that information. Unity seems a bit quicker, but it’s possibly just noise in the testing. asText() , except that it will return defaultValue in cases where null value would be returned; either for missing nodes (trying to access missing property, or element at invalid item for array) or explicit nulls. 经常要为接口响应对象设置属性,序列化的时候是不是包含空值,反序列化的时候是否忽略不认识的字段。所以,必须要手动制定ObjectMapper或者在类上声明. Note that Redis does not accept null keys or values but can return null replies (for non existing keys). [Solved] com. build(); The class JsonBuilderFactory also contains methods to create JsonObjectBuilder instances. acosentino pushed a commit to. It includes non-public properties in serialization and deserialization. NON_NULL to ignore fields with Null values and Include. Let's assume that You are writing an API which will handle /login requests. Yes, it needs to be supported via jdk8 module as handling relies on information serializer provides. DeserializationContext, com. I'm trying to deserialize a collection (let's use order\items for simplicity's sake) and I'm struggling to get the serializer to differentiate between an empty collection (where the element is specified but not populated) and a NULL collection (where the element isn't specified) These are my serialization classes :-MyOrderItems. NullValueHandling set to Ignore so that properties with a default value aren't included in the JSON result. or: why won’t Micronaut serialize my empty lists? Micronaut omits fields which are null or empty in its JSON output. By default, Jackson 2. whitelist-class-prefix = ["com. 6 and as such can not be used by Jackson For other types, non-null values are to be included. Jackson is best known for its ability to serialize POJOs into JSON and back, by means of standard conventions and - where necessary - special annotations to give clues to the Jackson library. How can Jackson be configured to ignore a field value during serialization if that field's value is null. In addition, to support per-property annotations (to configure aspects of deserialization on per-property basis), deserializers may want to implement ContextualDeserializer, which allows specialization of deserializers: call to ContextualDeserializer. I thought my serializer was working just fine until recently I saw empty entries in my db table column and figured out that xml generated contains empty elements. DeserializationConfig; import com. The next two examples cover those scenarios. util; 4 5 import org. Jackson provides Include. So I used the JsonMarshaller> to serialize and de-serialize this field. It includes non-public properties in serialization and deserialization. When adding an item to comparison from ca. FAIL_ON_EMPTY_BEANS) Next Post [Solved] com. The camel-jackson module allows to integrate Jackson as a Type Converter in the Camel registry. NON_NULL) // 允许单引号. Null values and empty Strings should be accepted, as well as the string "NULL"; in most cases, implementations should interpret these inputs has equivalen. jackson serialize getter class Foo {private List < String > fooElements;} If fooElements contains the strings 'one', 'two. Note:Null objects are serialized as empty arrays and vice versa. // Written by David Megginson, [email protected] NON_NULL는 null이 아닐 때만 serialzation한다. C# class property null with serializing. A TypeConverter will also support converting a custom string back again when. 0’s serializer or seserializer strategies by using the 'serializer' and. Gson is just the opposite. I'm trying to deserialize a collection (let's use order\items for simplicity's sake) and I'm struggling to get the serializer to differentiate between an empty collection (where the element is specified but not populated) and a NULL collection (where the element isn't specified) These are my serialization classes :-MyOrderItems. THE unique Spring Security education if you’re working with Java today. RedisSerializer that can read and write JSON using Jackson's and Jackson Databind ObjectMapper. I am using jackson-dataformat-xml:2. Jackson json module does not coerce JSON nulls into String "null" so I am bit surprised by this.  It’s in production, and therefore changes to it need to be backward compatible. How can Jackson be configured to ignore a field value during serialization if that field's value is null. For example: public class SomeClass { // what jackson annotation causes jackson to skip over this value if it is null but will. Jackson serialization: ignore empty values (or null) Inclusion. IgnoreDemoBean. The list can be how to deserialize a blank json string value to null for java. In the previous article we saw how and where to use the Jackson @JsonIgnore annotation to exclude a property of an Java object from the JSON serialization. But you can use a Custom JsonDeserializer to do. Spring uses Jackson internally for serializing and deserializing data in json format. How to ignore json empty or null values using Jackson API in java? In this example you will know how to ignore json empty or null values using jackson API. I thought my serializer was working just fine until recently I saw empty entries in my db table column and figured out that xml generated contains empty elements. null values or collection of size=0), so while converting list of objects to json we do not want to serialize the empty values. @@ -5,8 +5,8 @@ import java. However, serializing an IXmlSerializable type in place of Object results in loss of type information as the result is a JSON string. C# class property null with serializing. I am using jackson-dataformat-xml:2. def serialize (value): """ Serializes a python object to a string. asText() , except that it will return defaultValue in cases where null value would be returned; either for missing nodes (trying to access missing property, or element at invalid item for array) or explicit nulls.  It uses a certain technology to write JSON data, and this certain technology writes null strings as empty string (“”), but writes null objects as ‘null’. The following are Jave code examples for showing how to use disable() of the com. Home; Projects. COMPARABLE for global on/off configurability of whether to serialize null references +1 Jackson for greater configurability of null reference serialization; Versioning Support Jackson currently has no built-in feature similar to Gson's versioning support, though the next release reportedly will have something comparable.