Spring Data Repository: "find" method with orderBy gets the wrong order

Question

I have a Spring Boot application with some JPA repositories. I defined the following method inside one of the repository interfaces:

    public List<Post> findAllByOrderByPublishedOnDesc();

Quite obviously, I would like to retrive the list of all the Posts sorted by publishOn DESC. Strangely, I get the order wrong when two or more of the posts have a value of publishedOn that differs only for the minute component of the LocalDateTime class (see the comments in the code below). What Am I doing wrong?

Here's the example code. The test is executed with the H2 database:

Entity:

    @Entity
    public class Post
    {
        @Id
        @GeneratedValue(strategy = GenerationType.AUTO)
        Long id;

        @Column(unique = true, nullable = false)
        String sourceUrl;

        @Column
        String title;

        @Column
        LocalDateTime publishedOn;

        @LastModifiedDate
        LocalDateTime editedOn;

        @OneToOne(fetch = FetchType.LAZY, cascade = CascadeType.ALL)
        Text text;
    }

Repository:

    public interface PostRepository extends JpaRepository<Post, Long>
    {
        public Post findBySourceUrl(String sourceUrl);
        public List<Post> findAllByOrderByPublishedOnDesc();
    }

Test:

    public class OrderByJPATest
    {
    @Autowired
    PostRepository postRepo;

    public OrderByJPATest()
    {
    }

    @Test
    public void testOrderByDays()
    {
            // First try: older by 1 day
            Post newer = insertTestEntity("newer", LocalDateTime.of(2016, 11, 13, 0, 0));
            Post older = insertTestEntity("older", LocalDateTime.of(2016, 11, 12, 0, 0));

            List<Post> ordered = postRepo.findAllByOrderByPublishedOnDesc();

            ordered.stream().forEach((post) -> log.info("{} => {}", post.getSourceUrl(), post.getPublishedOn()));

            /*
            output:
            newer => 2016-11-13T00:00
            older => 2016-11-12T00:00
            */

            assertTrue(ordered.get(0).getPublishedOn()
                    .isAfter(ordered.get(1).getPublishedOn()));

            postRepo.deleteAll();
            postRepo.flush();

            // Second try: older by 1 minute
            newer = insertTestEntity("newerBy1Min", LocalDateTime.of(2016, 11, 13, 01, 02));
            older = insertTestEntity("olderBy1Min", LocalDateTime.of(2016, 11, 13, 01, 01));

            ordered = postRepo.findAllByOrderByPublishedOnDesc();

            ordered.stream().forEach((post) -> log.info("{} => {}", post.getSourceUrl(), post.getPublishedOn()));

            /* 
            output:
            olderBy1Min => 2016-11-13T01:01
            newerBy1Min => 2016-11-13T01:02
            */

            // this assert fails!
            assertTrue(ordered.get(0).getPublishedOn()
                    .isAfter(ordered.get(1).getPublishedOn()));
    }

    private Post insertTestEntity(String url, LocalDateTime publishDate)
    {
            Text text = new Text();
            text.setValue("Testing...");
            Post post = new Post();
            post.setPublishedOn(publishDate);
            post.setSourceUrl(url);
            post.setText(text);

            return postRepo.save(post);
    }
    }

POM (dependencies):

   <dependencies>

        <dependency>
            <groupId>com.atlassian.commonmark</groupId>
            <artifactId>commonmark</artifactId>
            <version>0.6.0</version>
        </dependency>
        <dependency>
            <groupId>commons-io</groupId>
            <artifactId>commons-io</artifactId>
            <version>2.4</version>
        </dependency>
        <dependency>
            <groupId>commons-lang</groupId>
            <artifactId>commons-lang</artifactId>
            <version>2.6</version>
        </dependency>
        <!--Additional dependencies -end-->

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-rest</artifactId>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-security</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-thymeleaf</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-logging</artifactId>
        </dependency>

        <dependency>
            <groupId>org.thymeleaf.extras</groupId>
            <artifactId>thymeleaf-extras-java8time</artifactId>
        </dependency>

        <dependency>
            <groupId>com.h2database</groupId>
            <artifactId>h2</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.security</groupId>
            <artifactId>spring-security-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

Answer 1

JPA by default will map Java's LocalDateTime to a BLOB instead of a DateTime or Timestamp.

The database doesn't understand how to perform a date/time sort on a BLOB.

1. Make sure you create your schema with the appropriate data type (either using the @Column annotation or with a SQL script).
2. Add the hibernate-java8 dependency to your project

After performing the above steps, the correct ordering will take place.