How to bypass #JsonIgnore annotation? - json

Question

I am trying to create a rest end point and using Swagger as UI representation. The pojo which I'm using it has a variable annotated with #JsonIgnore as shown below.
#JsonIgnore
private Map<String, Object> property = new HashMap<String, Object>();
Now, when I'm providing JSON (with property value) to this end point and trying to read its value it is coming out as null (due to #JsonIgnore).
pojoObj.getProperties(); //null
Is there any way if I can get property value without removing the #JsonIgnore annotation?

Answer 1

This can be achieved by utilizing Jackson's Mixin feature, where you create another class that cancels the ignore annotation. You can then "attach" the mixin to the ObjectMapper at run time:
This is the POJO I used:
public class Bean
{
// always deserialized
public String name;
// ignored (unless...)
#JsonIgnore
public Map<String, Object> properties = new HashMap<String, Object>();
}
This is the "other" class. It is just another POJO with the same property name
public class DoNotIgnore
{
#JsonIgnore(false)
public Map<String, Object> properties;
}
a Jackson Module is used to tie the bean to the mixin:
#SuppressWarnings("serial")
public class DoNotIgnoreModule extends SimpleModule
{
public DoNotIgnoreModule() {
super("DoNotIgnoreModule");
}
#Override
public void setupModule(SetupContext context)
{
context.setMixInAnnotations(Bean.class, DoNotIgnore.class);
}
}
Tying it all together:
public static void main(String[] args)
{
String json = "{\"name\": \"MyName\","
+"\"properties\": {\"key1\": \"val1\", \"key2\": \"val2\", \"key3\": \"val3\"}"
+ "}";
try {
ObjectMapper mapper = new ObjectMapper();
// decide at run time whether to ignore properties or not
if ("do-not-ignore".equals(args[0])) {
mapper.registerModule(new DoNotIgnoreModule());
}
Bean bean = mapper.readValue(json, Bean.class);
System.out.println(" Name: " + bean.name + ", properties " + bean.properties);
} catch (IOException e) {
e.printStackTrace();
}
}