如何在 Spring 引导中对 List<> 中的月份进行排序 - 使用 Java 8

Question

I have list of months, I am setting in the POJO class, While I am setting it, order is not getting sorted. I want to sort it. Sample data looks like -

My POJO Class -

public class SamplePojo {
   private static final long serialVersionUID = 1L;
   private String type;
   private String name;
   private Integer January;
   private Integer February;
   private Integer March;
   private Integer April;
   private Integer May;
   private Integer June;
}

ServiceImpl -

List<SamplePojo> sp = new ArrayList<SamplePojo>();
SamplePojo tp1 = new SamplePojo ();
        
        tp1.type("type");
        tp1.name("name");
        tp1.setJanuary(12);
        tp1.setFebruary(2);
        tp1.setMarch(33);
        tp1.setApril(0);
        tp1.setMay(0);
        tp1.setJune(0);
        tp1.setTotal(122);
        sp.add(tp1);

Unsorted data -

[
    {
        "type": "LLB",
        "name": "Working",
        "total": 0,
        "march": 33,
        "april": 0,
        "may": 0,
        "june": 0,
        "february": 2,
        "january": 12
    },
    {
        "type": "Engineer",
        "name": "Not Working",
        "total": 0,
        "march": 33,
        "april": 0,
        "may": 0,
        "june": 0,
        "february": 2,
        "january": 12
    }
]

Wanted to sort -

[
    {
        "type": "LLB",
        "name": "Working",
        "january": 11,
        "february": 2,
        "march": 3,
        "april": 3,
        "may": 0,
        "june": 0,
        "total": 0
    },
    {
        "type": "Engineer",
        "name": "Not Working",
        "january": 12,
        "february": 2,
        "march": 33,
        "april": 0,
        "may": 0,
        "june": 0,
        "total": 0
    }
]

How can I do this using Spring boot. I am new to this Spring boot and New to this stackoverflow. Can you please help me out.

Answer 1

If you want to sort the JSON payload, you can use @JsonPropertyOrder annotation

@JsonPropertyOrder({
  "type",
  "name",
  "January",
  "February",
  "March"
})
public class SamplePojo {
  private static final long serialVersionUID = 1 L;
  private String type;
  private String name;
  private Integer January;
  private Integer February;
  private Integer March;
  private Integer April;
  private Integer May;
  private Integer June;
}

Answer 2

The best way to do this is sorting from the repository by using Spring Data Repository query keywords by find all SampleEntity by following code.

@Repository
public interface SampleEntityRepository extends JpaRepository<SampleEntity, Long> {
    List<SampleEntity> findAllByOrderByJanuaryAsc();
}

But if you want to sort on the last layer to showing List of SamplePojo you can use stream and sorted by some criteria.

List<SamplePojo> lastList = sampleService.findAll();
lastList
    .stream()
    .sorted((sPojo1, sPojo2) -> sPojo1.getJanuary().compareTo(sPojo2.getJanuary()));