JsonProperty annotation on field as well as getter setter

Question

I have inherited a certain bit code that has the  JsonProperty annotation on getter setters  The purpose is so that when the object is serialized using the Jackson library  the fields have that specific name   Current code   private String fileName    JsonProperty  FILENAME   public String getFileName         return fileName      JsonProperty  FILENAME   public void setFileName String fileName        this fileName   fileName      Now for another tool  I need to annotate the field with JsonProperty as well  So this will be my changed code    JsonProperty  FILENAME   private String fileName    JsonProperty  FILENAME   public String getFileName         return fileName      JsonProperty  FILENAME   public void setFileName String fileName        this fileName   fileName      Has anyone used this same annotation on both - the field as well as the getter setters  I looked around on the net but didn t see anything   I have compiled  amp  run the code but I m not sure if this would this cause any problems down the road  Any thoughts on this

User · Accepted Answer

My observations based on a few tests has been that whichever name differs from the property name is one which takes effect:

For eg. consider a slight modification of your case:

@JsonProperty("fileName")
private String fileName;

@JsonProperty("fileName")
public String getFileName()
{
    return fileName;
}

@JsonProperty("fileName1")
public void setFileName(String fileName)
{
    this.fileName = fileName;
}

Both fileName field, and method getFileName, have the correct property name of fileName and setFileName has a different one fileName1, in this case Jackson will look for a fileName1 attribute in json at the point of deserialization and will create a attribute called fileName1 at the point of serialization.

Now, coming to your case, where all the three @JsonProperty differ from the default propertyname of fileName, it would just pick one of them as the attribute(FILENAME), and had any on of the three differed, it would have thrown an exception:

java.lang.IllegalStateException: Conflicting property name definitions

User · Answer

In addition to existing good answers  note that Jackson 1 9 improved handling by adding  property unification   meaning that ALL annotations from difference parts of a logical property are combined  using  hopefully  intuitive precedence   In Jackson 1 8 and prior  only field and getter annotations were used when determining what and how to serialize  writing JSON   and only and setter annotations for deserialization  reading JSON   This sometimes required addition of  extra  annotations  like annotating both getter and setter   With Jackson 1 9 and above these extra annotations are NOT needed  It is still possible to add those  and if different names are used  one can create  split  properties  serializing using one name  deserializing using other   this is occasionally useful for sort of renaming

[java] @JsonProperty annotation on field as well as getter/setter

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