Summary - Serialization

Combine ObjectMapper and @JsonProperty to write a config file.

Summary - Serialization

In this group you learned structured text serialization with Jackson. ObjectMapper is the central class; writeValueAsString goes from object to text, readValue from text to object. With @JsonProperty you set key names; with the null-skipping annotation you controlled empty fields. TypeReference was used for List and Map.

This summary will serialize a User record and read it back.

Exercise Serialize and read back a User

Define record User(String name, int age) {}. Add throws Exception to main. Create an ObjectMapper mapper = new ObjectMapper();, build a user with User u = new User("Ayşe", 30);, serialize with String text = mapper.writeValueAsString(u);, read back with User u2 = mapper.readValue(text, User.class); and print System.out.println(u2.name() + " " + u2.age());.

Show example solution

import com.fasterxml.jackson.databind.ObjectMapper;

record User(String name, int age) {}

public class Main {
    public static void main(String[] args) throws Exception {
        ObjectMapper mapper = new ObjectMapper();
        User u = new User("Ayşe", 30);
        String text = mapper.writeValueAsString(u);
        User u2 = mapper.readValue(text, User.class);
        System.out.println(u2.name() + " " + u2.age());
    }
}

Test yourself

Which method converts text to an object?
- getProperty
- writeValueAsString
- readValue
- toText
Show answer

readValue — readValue converts structured text into a Java object.

Annotation that customizes the key

@____("user_name") String userName

Show answer

@JsonProperty("user_name") String userName

Match the serialization summary

ObjectMapper

Central converter
writeValueAsString

Object to text
readValue

Text to object
@JsonProperty

Text key name

Next lesson: Generic class

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