pojo.example_2.md

Overview

1. Example of "idiomatic" Jackson compatible Java 8-17 POJO
2. See also, detailed explanation
3. See also, non-Jackson POJO example
4. See also, Lombok POJO examples

POJO Example

/**
 * TODO: add a BRIEF description of purpose
 * TODO: if this POJO aligns with a DB table, mention that here
 */
@JsonDeserialize(builder = Employee.Builder.class)
@JsonPropertyOrder(alphabetic = true)
public final class Employee {

  private final boolean active;

  /**
   * [16, 100]
   */
  private final int age;

  /**
   * [a-zA-Z-]{2,64}
   * eg. "Wil"
   */
  private final String name;

  @JsonProperty("firstDayOnTheJob")
  private final LocalDate startDate;

  private Employee(Builder builder) {

    // Example of default value
    active = Optional.ofNullable(builder.active).orElse(true);
    age = builder.age;
    name = builder.name;
    startDate = builder.startDate;

    // -- Validations
    checkArgument(age <= 100, "age is too high: " + age);
    checkArgument(age >= 16, "age is too low: " + age);

    checkArgument(isNotBlank(name), "name is required");

    requireNonNull(startDate, "startDate is required and missing.");
    //TODO: other validations go here
  }

  // NOTE: Generated getters, hashcode, equals, toString appear around here

  // (Almost) Everything below is generated by Innerbuilder plugin ...

  public static Builder newBuilder() {
    return new Builder();
  }

  public static Builder newBuilder(Employee copy) {
    Builder builder = new Builder();
    builder.active = copy.active;
    builder.age = copy.age;
    builder.name = copy.name;
    builder.startDate = copy.startDate;
    return builder;
  }

  // NOTE: Notice the annotations below
  @JsonIgnoreProperties({"\u0024schema", "\u0024id"})
  @JsonPOJOBuilder(withPrefix = "")
  public static final class Builder {
    // notice the object type allows defaulting active to true
    private Boolean active;
    private int age;
    private String name;

    // NOTE: Notice the annotation below
    @JsonProperty("firstDayOnTheJob")
    private LocalDate startDate;

    private Builder() {
    }

    public Builder active(boolean active) {
      this.active = active;
      return this;
    }

    public Builder age(int age) {
      this.age = age;
      return this;
    }

    public Employee build() {
      return new Employee(this);
    }

    public Builder name(String name) {
      this.name = name;
      return this;
    }

    public Builder startDate(LocalDate startDate) {
      this.startDate = startDate;
      return this;
    }
  }
}

Usage Example

    ObjectMapper objectMapper = ...

    Employee wil = Employee.newBuilder()
      .age(35)
      .name("Wil C")
      .startDate(LocalDate.of(2020, 01, 31))
      .build();

    // NOTE: wil.active is defaulted to true

    System.out.println(
      objectMapper.writeValueAsString(wil));