I am looking for an annotation I can use to replace String value to null in Java
There are some #Json annotation that can do customization while serializing a JSON object to POJO,
I want to do something like this:
#JsonFormat(<if incoming value is SOMESTRING>, <set incoming value to null>)
String valueChangedUsingAnnotation;
Use #JsonIgnore annotation. This annotation is used when you want to ignore certain properties of a java class. It will ignore those fields annotated with when reading from json to java object and also, writing java object to json.
If incoming value is SOMETHING, set its value to null. For this you can update the setter method of that particular field in POJO class. Because, when incoming object is deserialized it invokes setter methods of each fields.
Something like below:
class Test{
//constructor, other fields and their getters and setters
private String target;
public void setTarget(String target) {
if(target.equals("abcd"){
this.target=null
}
else {
this.target=target;
}
}
}
There is no need of any JSON annotations.
If I have a class using Lombok:
#RequiredArgsConstructor
#Getter
class Example {
private final String id;
}
And try to deserialize it from
{
“id”: “test”
}
Jackson throws an exception that although at least one creator was provided, it could not deserialize.
If I then add another final String field to that class, and add that field to the JSON, it is deserialized with no complaints.
Does anyone know what’s going on here? Why are you unable to deserialize if you only have one field?
When only way to intialize object properties is through contructor, Jackson needs to be told that deserialization should happen using constructor via #JsonCreator annotation.
Also, all the property names should be provided via #JsonProperty annotation because Jackson needs to know the sequence of attributes passed in contructor to correctly map json values to Java object attributes.
So, if you are not using lombok contructor, then constructor will look like
#JsonCreator
public Example (#JsonProperty("id") String id) {
this.id = id;
}
If you don't want to manually write the contructor, go ahead with #tashkhisi's answer.
Also, I highly doubt following could happen. Could you update the question with code showing this?
If I then add another final String field to that class, and add that field to the JSON, it is deserialized with no complaints.
I have a legacy JSON API class that I'm evolving to remove a certain property. It's currently at a point where the property value is always the same constant, so I would like my Java code to be just a simple getter with no underlying field for it. I want to continue serializing the value until I know that all my clients have migrated off of using the value. The object is only read by my clients, so I don't have to worry about them sending other values across.
public class MyType {
private String value;
public boolean isLegacyValue() {
return true;
}
}
That said, I don't want any test code or the like to fail if I deserialize a full value with the now-constant property. Is there a way I can tell Jackson to serialize a setter method-only property, but ignore it on deserialization? I tried a few different things, but I get a UnrecognizedPropertyException on deserialization. I'd rather not change the global DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES just for this one property.
{"value": "ABC", "legacyValue": true}
Also acceptable would be a way to tell Jackson to include the value without including a Java field for it.
I'm aware I can add a getter in addition to my setter, or make it a field, but both those options feel like they're confusing the Java API, as it's not actually matching the constant constraint:
public void setLegacyValue(boolean legacyValue) {
// No-op; only exists for Jackson deserialization
}
One thing I've found to work through trial and error is making it a final field. For whatever reason, Jackson knows to handle that as a write-only constant in a way that doesn't work with the getter without matching setter. This will be my solution if there's no way to do it with just a getter.
private final boolean legacyValue = true;
public boolean isLegacyValue() {
return legacyValue;
}
Jackson supports "one-way" properties using the access parameter of #JsonProperty. Annotate your property like this:
#JsonProperty(access = READ_ONLY)
public boolean isLegacyValue() {
return true;
}
Does naybody knows a way to use Jersey's GET method to return a JSON that returns only some fields of an entity instead of all?
Does anybody know a way to use Jersey's GET method to return a JSON that returns only some fields of an entity instead of all?
E.g. in the following class I want to receive (with POST) values for 'name' and for 'confidential', buy while returning (with GET) I only need 'name' value, not 'confidential'.
#Entity
#Table(name = "a")
#XmlRootElement
#JsonIgnoreProperties({"confifentialInfo"})
public class A extends B implements Serializable {
private String name;
#Basic(optional = false)
private String confifentialInfo;
// more fields, getters and setters
}
If you are using the JAXB approach, you can mark fields with #XmlTransient to omit them. If you are using POJO mapping or want to exclude fields only for some requests, you should construct the JSON with the low level JSON API.
If you are using Jackson, you can use the annotation #JsonIgnore for methods
Marker annotation similar to javax.xml.bind.annotation.XmlTransient
that indicates that the annotated method is to be ignored by
introspection-based serialization and deserialization functionality.
That is, it should not be consider a "getter", "setter" or "creator".
And #JsonIgnoreProperties for properties
Annotation that can be used to either suppress serialization of
properties (during serialization), or ignore processing of JSON
properties read (during deserialization).
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
// serialize it otherwise
private String someValue;
}
To suppress serializing properties with null values using Jackson >2.0, you can configure the ObjectMapper directly, or make use of the #JsonInclude annotation:
mapper.setSerializationInclusion(Include.NON_NULL);
or:
#JsonInclude(Include.NON_NULL)
class Foo
{
String bar;
}
Alternatively, you could use #JsonInclude in a getter so that the attribute would be shown if the value is not null.
A more complete example is available in my answer to How to prevent null values inside a Map and null fields inside a bean from getting serialized through Jackson.
Just to expand on the other answers - if you need to control the omission of null values on a per-field basis, annotate the field in question (or alternatively annotate the field's 'getter').
example - here only fieldOne will be omitted from the JSON if it is null. fieldTwo will always be included in the JSON regardless of if it is null.
public class Foo {
#JsonInclude(JsonInclude.Include.NON_NULL)
private String fieldOne;
private String fieldTwo;
}
To omit all null values in the class as a default, annotate the class. Per-field/getter annotations can still be used to override this default if necessary.
example - here fieldOne and fieldTwo will be omitted from the JSON if they are null, respectively, because this is the default set by the class annotation. fieldThree however will override the default and will always be included, because of the annotation on the field.
#JsonInclude(JsonInclude.Include.NON_NULL)
public class Foo {
private String fieldOne;
private String fieldTwo;
#JsonInclude(JsonInclude.Include.ALWAYS)
private String fieldThree;
}
UPDATE
The above is for Jackson 2. For earlier versions of Jackson you need to use:
#JsonSerialize(include=JsonSerialize.Inclusion.NON_NULL)
instead of
#JsonInclude(JsonInclude.Include.NON_NULL)
If this update is useful, please upvote ZiglioUK's answer below, it pointed out the newer Jackson 2 annotation long before I updated my answer to use it!
With Jackson > 1.9.11 and < 2.x use #JsonSerialize annotation to do that:
#JsonSerialize(include=JsonSerialize.Inclusion.NON_NULL)
In Jackson 2.x, use:
#JsonInclude(JsonInclude.Include.NON_NULL)
You can use the following mapper configuration:
mapper.getSerializationConfig().setSerializationInclusion(Inclusion.NON_NULL);
Since 2.5 you can user:
mapper.setSerializationInclusion(Include.NON_NULL);
You can set application.properties:
spring.jackson.default-property-inclusion=non_null
or application.yaml:
spring:
jackson:
default-property-inclusion: non_null
http://docs.spring.io/spring-boot/docs/current/reference/html/common-application-properties.html
in my case
#JsonInclude(Include.NON_EMPTY)
made it work.
#JsonInclude(JsonInclude.Include.NON_NULL)
#JsonInclude(JsonInclude.Include.NON_EMPTY)
should work.
Include.NON_EMPTY indicates that property is serialized if its value is not null and not empty.
Include.NON_NULL indicates that property is serialized if its value is not null.
This Will work in Spring boot 2.0.3+ and Jackson 2.0+
import com.fasterxml.jackson.annotation.JsonInclude;
#JsonInclude(JsonInclude.Include.NON_NULL)
public class ApiDTO
{
// your class variable and
// methods
}
If you want to add this rule to all models in Jackson 2.6+ use:
mapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);
If in Spring Boot, you can customize the jackson ObjectMapper directly through property files.
Example application.yml:
spring:
jackson:
default-property-inclusion: non_null # only include props if non-null
Possible values are:
always|non_null|non_absent|non_default|non_empty
More: https://docs.spring.io/spring-boot/docs/current/reference/html/howto-spring-mvc.html#howto-customize-the-jackson-objectmapper
For Jackson 2.5 use :
#JsonInclude(content=Include.NON_NULL)
If you're trying to serialize a list of object and one of them is null you'll end up including the null item in the JSON even with
mapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);
will result in:
[{myObject},null]
to get this:
[{myObject}]
one can do something like:
mapper.getSerializerProvider().setNullValueSerializer(new JsonSerializer<Object>() {
#Override
public void serialize(Object obj, JsonGenerator jsonGen, SerializerProvider unused)
throws IOException
{
//IGNORES NULL VALUES!
}
});
TIP: If you're using DropWizard you can retrieve the ObjectMapper being used by Jersey using environment.getObjectMapper()
This has been troubling me for quite some time and I finally found the issue. The issue was due to a wrong import. Earlier I had been using
com.fasterxml.jackson.databind.annotation.JsonSerialize
Which had been deprecated. Just replace the import by
import org.codehaus.jackson.map.annotate.JsonSerialize;
import org.codehaus.jackson.map.annotate.JsonSerialize.Inclusion;
and use it as
#JsonSerialize(include=Inclusion.NON_NULL)
Global configuration if you use Spring
#Configuration
public class JsonConfigurations {
#Bean
public Jackson2ObjectMapperBuilder objectMapperBuilder() {
Jackson2ObjectMapperBuilder builder = new Jackson2ObjectMapperBuilder();
builder.serializationInclusion(JsonInclude.Include.NON_NULL);
builder.serializationInclusion(JsonInclude.Include.NON_EMPTY);
builder.failOnUnknownProperties(false);
return builder;
}
}
We have lot of answers to this question. This answer may be helpful in some scenarios
If you want to ignore the null values you can use the NOT_NULL in class level.
as below
#JsonInclude(Include.NON_NULL)
class Foo
{
String bar;
}
Some times you may need to ignore the empty values such as you may have initialized the arrayList but there is no elements in that list.In that time using NOT_EMPTY annotation to ignore those empty value fields
#JsonInclude(Include.NON_EMPTY)
class Foo
{
String bar;
}
Case one
#JsonInclude(JsonInclude.Include.NON_NULL)
private String someString;
Case two
#JsonInclude(JsonInclude.Include.NON_EMPTY)
private String someString;
If someString is null, it will be ignored on both of cases.
If someString is "" it just only be ignored on case two.
The same for List = null or List.size() = 0
Try this -
#JsonSerialize(include=JsonSerialize.Inclusion.NON_NULL)
public class XYZ {
protected String field1;
protected String field2;
}
And for non-null values (On getters/class level) -
#JsonSerialize(include=JsonSerialize.Inclusion.NON_EMPTY)
Jackson 2.x+ use
mapper.getSerializationConfig().withSerializationInclusion(JsonInclude.Include.NON_NULL);
Also, you have to change your approach when using Map myVariable as described in the documentation to eleminate nulls:
From documentation:
com.fasterxml.jackson.annotation.JsonInclude
#JacksonAnnotation
#Target(value={ANNOTATION_TYPE, FIELD, METHOD, PARAMETER, TYPE})
#Retention(value=RUNTIME)
Annotation used to indicate when value of the annotated property (when used for a field, method or constructor parameter), or all properties of the annotated class, is to be serialized. Without annotation property values are always included, but by using this annotation one can specify simple exclusion rules to reduce amount of properties to write out.
*Note that the main inclusion criteria (one annotated with value) is checked on Java object level, for the annotated type, and NOT on JSON output -- so even with Include.NON_NULL it is possible that JSON null values are output, if object reference in question is not `null`. An example is java.util.concurrent.atomic.AtomicReference instance constructed to reference null value: such a value would be serialized as JSON null, and not filtered out.
To base inclusion on value of contained value(s), you will typically also need to specify content() annotation; for example, specifying only value as Include.NON_EMPTY for a {link java.util.Map} would exclude Maps with no values, but would include Maps with `null` values. To exclude Map with only `null` value, you would use both annotations like so:
public class Bean {
#JsonInclude(value=Include.NON_EMPTY, content=Include.NON_NULL)
public Map<String,String> entries;
}
Similarly you could Maps that only contain "empty" elements, or "non-default" values (see Include.NON_EMPTY and Include.NON_DEFAULT for more details).
In addition to `Map`s, `content` concept is also supported for referential types (like java.util.concurrent.atomic.AtomicReference). Note that `content` is NOT currently (as of Jackson 2.9) supported for arrays or java.util.Collections, but supported may be added in future versions.
Since:
2.0