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Filtering for your restful webServices

Filters are one of the important features provided by the JAX-RS framework. It is used in various contexts. It may be applied on either request to a resource or the response from a resource, or both.Consider a scenario in which we do not want to show some class members in the response. This process is called filtering. Jackson has two annotations that are used in filtering are: @JsonIgnore and @JsonIgnoreProperties.



@JsonIgnore is used at field level to mark a property or list of properties to be ignored.


import java.io.IOException;
import com.fasterxml.jackson.annotation.JsonIgnore;
import com.fasterxml.jackson.databind.ObjectMapper;

public class JacksonSampleTest {
   public static void main(String args[]){
      ObjectMapper mapper = new ObjectMapper();
      try{
         Student student = new Student(1,11,"LABORATORY","SAMUEL");       
         String jsonString = mapper
            .writerWithDefaultPrettyPrinter()
            .writeValueAsString(student);
         System.out.println(jsonString);
      }
      catch (IOException e) { 
         e.printStackTrace();
      }     
   }
}
class Student { 
   public int id;
   @JsonIgnore
   public String systemId;
   public int rollNo;
   public String name;

   Student(int id, int rollNo, String systemId, String name){
      this.id = id;
      this.systemId = systemId;
      this.rollNo = rollNo;
      this.name = name;
   }
}
{
   "id" : 1,
   "rollNo" : 11,
   "name" : "SAMUEL"
}




@JsonIgnore  is a member or method level annotation. It expects that the properties to be excluded are marked one by one. If we want to eliminate a member from the process of serialization and deserialization, we can annotate the actual property or its setter or getter. 

@JsonIgnoreProperties is a class-level annotation. It ignores the logical properties in JSON serialization and deserialization.

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