Jackson provides an efficient way to bind JSON to POJOs. However, at times, certain properties may need to be ignored while converting a JSON to Java Object or Java Object to JSON. Jackson provides three ways to Ignore fields in JSON.

1. @JsonIgnoreProperties– This annotation can be used at the type level to ignore json properties. In the example below, we ignore the ‘tags’ property from the albums dataset.
2. @JsonIgnore – This annotation can be set at the property level to ignore certain properties.
3. Using Custom filters

The example below shows method 1 and 2. Also, note the use of the @JsonAutoDetect annotation.

Example for how to Ignore fields in JSON using Jackson

Databinding

package com.studytrails.json.jackson;

import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;

import com.fasterxml.jackson.core.JsonParseException;
import com.fasterxml.jackson.databind.DeserializationFeature;
import com.fasterxml.jackson.databind.JsonMappingException;
import com.fasterxml.jackson.databind.ObjectMapper;

public class DataBindingFilter {
	public static void main(String[] args) throws JsonParseException, JsonMappingException, MalformedURLException, IOException {
		String url = "http://freemusicarchive.org/api/get/albums.json?api_key=60BLHNQCAOUFPIBZ&limit=2";
		ObjectMapper mapper = new ObjectMapper();
		mapper.disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES);
		AlbumsFilter albums = mapper.readValue(new URL(url), AlbumsFilter.class);
		System.out.println(albums.getTotal_pages());
		System.out.println(albums.getTitle());
		for (DatasetFilter dataset : albums.getDatasetFilter()) {
			System.out.println(dataset.getAlbum_comments());
			System.out.println(dataset.get("album_images"));
			System.out.println(dataset.get("tags"));
			System.out.println(dataset.get("album_listens"));
			break;
		}
	}

}

The AlbumsFilter class

package com.studytrails.json.jackson;

import com.fasterxml.jackson.annotation.JsonAutoDetect;
import com.fasterxml.jackson.annotation.JsonAutoDetect.Visibility;
import com.fasterxml.jackson.annotation.JsonProperty;

// Do not use fields to autodetect. use the public getter methods to autodetect properties
@JsonAutoDetect(fieldVisibility = Visibility.NONE, getterVisibility = Visibility.PUBLIC_ONLY)
public class AlbumsFilter {

	private String title;
	private DatasetFilter[] datasetFilter;
	public String total_pages;

	protected String getTotal_pages() {
		return total_pages;
	}

	public String getTitle() {
		return title;
	}

	// this getter method is for the 'dataset' property
	@JsonProperty("dataset")
	public DatasetFilter[] getDatasetFilter() {
		return datasetFilter;
	}
}

DatasetFilter class

package com.studytrails.json.jackson;

import java.util.HashMap;
import java.util.Map;

import com.fasterxml.jackson.annotation.JsonAnyGetter;
import com.fasterxml.jackson.annotation.JsonAnySetter;
import com.fasterxml.jackson.annotation.JsonCreator;
import com.fasterxml.jackson.annotation.JsonIgnore;
import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
import com.fasterxml.jackson.annotation.JsonProperty;

// ignore the property with name 'tags'.
@JsonIgnoreProperties({ "tags" })
public class DatasetFilter {
	private String album_id;
	private String album_title;
	private Map<String , Object> otherProperties = new HashMap<String , Object>();
	private String album_comments;

	@JsonCreator
	public DatasetFilter(@JsonProperty("album_id") String album_id, @JsonProperty("album_title") String album_title) {
		this.album_id = album_id;
		this.album_title = album_title;
	}

	// ignore the property specified by this getter.
	@JsonIgnore
	public String getAlbum_comments() {
		return album_comments;
	}

	public String getAlbum_id() {
		return album_id;
	}

	public void setAlbum_id(String album_id) {
		this.album_id = album_id;
	}

	public String getAlbum_title() {
		return album_title;
	}

	public void setAlbum_title(String album_title) {
		this.album_title = album_title;
	}

	public Object get(String name) {
		return otherProperties.get(name);
	}

	// this method is used to get all properties not specified earlier.
	@JsonAnyGetter
	public Map<String , Object> any() {
		return otherProperties;
	}

	@JsonAnySetter
	public void set(String name, Object value) {
		otherProperties.put(name, value);
	}
}