Jackson Parser example in android

Jackson parser’s ObjectMapper for reading value and transforms it into a Java object.

ObjectMapper mapper = new ObjectMapper();
Person person1, person2, person3;
//read from an url
person1 = mapper.readValue(new URL("https://api.myjson.com/bins/hoh4j"), Person.class);

//read from a string
String personJsonStr = "{\"firstname\":\"John\",\"lastname\":\"Doe\"}";
person2 = mapper.readValue(personJsonStr, Person.class);

//read from a file
person3 = mapper.readValue(new File("/a/path/to/person.json"), Person.class);

Jackson parser’s ObjectMapper for writing to json string from Java object.

ObjectMapper mapper = new ObjectMapper();
Person person = new Person();

mapper.writeValue(new File("/a/path/to/person.json"), person);  // write to file
String jsonStr = mapper.writeValueAsString(person);            // write to string

1. Jackson parser dependencies to be included in the gradle file.

compile 'com.fasterxml.jackson.core:jackson-databind:2.8.5'
compile 'com.fasterxml.jackson.core:jackson-core:2.8.5'
compile 'com.fasterxml.jackson.core:jackson-annotations:2.8.5'

2. Exclude META-INF/LICENSE in the android tag in the gradle file to avoid dup license file error in Android studio

packagingOptions {
    exclude 'META-INF/LICENSE'
}

3. Sample json string, https://api.myjson.com/bins/hoh4j

{
  "firstname": "John",
  "lastname": "Doe"
}

4. Sample model class with Jackson annotations for the above json string.

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.JsonIgnore;
import com.fasterxml.jackson.annotation.JsonInclude;
import com.fasterxml.jackson.annotation.JsonProperty;
import com.fasterxml.jackson.annotation.JsonPropertyOrder;

@JsonInclude(JsonInclude.Include.NON_NULL)
@JsonPropertyOrder({
        "firstname",
        "lastname"
})
public class Person {
    @JsonProperty("firstname")
    private String firstname;
    @JsonProperty("lastname")
    private String lastname;
    @JsonIgnore
    private Map additionalProperties = new HashMap();

    @JsonProperty("firstname")
    public String getFirstname() {
        return firstname;
    }

    @JsonProperty("firstname")
    public void setFirstname(String firstname) {
        this.firstname = firstname;
    }

    @JsonProperty("lastname")
    public String getLastname() {
        return lastname;
    }

    @JsonProperty("lastname")
    public void setLastname(String lastname) {
        this.lastname = lastname;
    }

    @JsonAnyGetter
    public Map getAdditionalProperties() {
        return this.additionalProperties;
    }

    @JsonAnySetter
    public void setAdditionalProperty(String name, Object value) {
        this.additionalProperties.put(name, value);
    }
}

5. Json string to Java object using Jackson parser

private void jsonToObject() {
    final ObjectMapper mapper = new ObjectMapper();
    try {
        String personJsonStr = "{\"firstname\":\"John\",\"lastname\":\"Doe\"}";
        //Person person = mapper.readValue(new File(getFilesDir(), "person.json"), Person.class);    // read from file
        Person person = mapper.readValue(personJsonStr, Person.class);                               // read from json string
        tvDisplay.setText("json string -> object\n" + person.getFirstname() + " " + person.getLastname());
    } catch (IOException e) {
        e.printStackTrace();
        tvDisplay.setText(e.getMessage());
        progressBar.setVisibility(View.GONE);
    }
}

6. Json string from an url to Java object using Jackson parser in Android, since there is network involved, the INTERNET use-permission needs to be enabled in the manifest file and it has to run in a background thread.

private void jsonToObjectUrl() {
    final ObjectMapper mapper = new ObjectMapper();
    final Handler handler = new Handler();
    new Thread(new Runnable() {
        @Override
        public void run() {
            try {
                Person person = mapper.readValue(new URL("https://api.myjson.com/bins/hoh4j"), Person.class);                                 // read from url
                handler.post(new Runnable() {
                    @Override
                    public void run() {
                        tvDisplay.setText("json string -> object\n" + person.getFirstname() + " " + person.getLastname());
                    }
                });
            } catch (MalformedURLException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }).start();
}

7. Java object to Json string using Jackson parser.

private void objectToJson() {
    ObjectMapper mapper = new ObjectMapper();
    try {
        //mapper.writeValue(new File(getFilesDir(), "person.json"), person);  // write to file
        String jsonStr = mapper.writeValueAsString(person);                   // write to string
        tvDisplay.setText("object -> json string\n" + jsonStr);
    } catch (JsonProcessingException e) {
        e.printStackTrace();
        tvDisplay.setText(e.getMessage());
    } catch (IOException e) {
        e.printStackTrace();
        tvDisplay.setText(e.getMessage());
    }
}

Complete example in Github