[FIXED] Java 8 date time types serialized as object with Spring Boot

Issue

I have an entity with fields of Java 8 date time types. The issue is that these fields are serialized as object. I added the jackson-datatype-jsr310 dependency, so Spring Boot 1.5.7 would auto configure the JavaTimeModule that handles Java 8 date time types. It seems that the module is not registered (I put a breakpoint in JavaTimeModule constructor). I know I don't need a custom ObjectMapper. I spent hours reading about that issue and the solution is always to add the jackson-datatype-jsr310 dependency but it does not work in my case.

The entity:

@Entity
public class DateTimeEntity {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    private LocalDate localDate;

    private LocalDateTime localDateTime;

    private Instant instant;

    private OffsetDateTime offsetDateTime;

    private ZonedDateTime zonedDateTime;

}

The RestController method:

@GetMapping("/datetimes/{id}")
public ResponseEntity<DateTimeEntity> getById(@PathVariable Long id) {
    DateTimeEntity dateTimeEntity = dateTimeRepository.findOne(id);
    return new ResponseEntity<DateTimeEntity>(dateTimeEntity, HttpStatus.OK);

}

The JSON object returned:

    {
    "id": 1,
    "localDate": null,
    "localDateTime": null,
    "instant": {
        "epochSecond": 1508772600,
        "nano": 0
    },
    "offsetDateTime": {
        "offset": {
            "totalSeconds": 0,
            "id": "Z",
            "rules": {
                "fixedOffset": true,
                "transitionRules": [],
                "transitions": []
            }
        },
        "dayOfMonth": 23,
        "dayOfWeek": "MONDAY",
        "dayOfYear": 296,
        "month": "OCTOBER",
        "monthValue": 10,
        "year": 2017,
        "hour": 15,
        "minute": 30,
        "nano": 0,
        "second": 0
    },
    "zonedDateTime": {
        "offset": {
            "totalSeconds": 0,
            "id": "Z",
            "rules": {
                "fixedOffset": true,
                "transitionRules": [],
                "transitions": []
            }
        },
        "zone": {
            "totalSeconds": 0,
            "id": "Z",
            "rules": {
                "fixedOffset": true,
                "transitionRules": [],
                "transitions": []
            }
        },
        "dayOfMonth": 23,
        "dayOfWeek": "MONDAY",
        "dayOfYear": 296,
        "month": "OCTOBER",
        "monthValue": 10,
        "year": 2017,
        "hour": 15,
        "minute": 30,
        "nano": 0,
        "second": 0,
        "chronology": {
            "id": "ISO",
            "calendarType": "iso8601"
        }
    }
}

The POM file:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.example</groupId>
    <artifactId>framework-demo</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.5.7.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <java.version>1.8</java.version>
        <mockito.version>2.11.0</mockito.version>
        <org.mapstruct.version>1.2.0.Final</org.mapstruct.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.mapstruct</groupId>
            <artifactId>mapstruct-jdk8</artifactId>
            <version>${org.mapstruct.version}</version>
        </dependency>
        <dependency>
            <groupId>com.fasterxml.jackson.datatype</groupId>
            <artifactId>jackson-datatype-jsr310</artifactId>
        </dependency>

        <dependency>
            <groupId>com.h2database</groupId>
            <artifactId>h2</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.postgresql</groupId>
            <artifactId>postgresql</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>com.fasterxml.jackson.datatype</groupId>
            <artifactId>jackson-datatype-jsr310</artifactId>
            <version>${jackson.version}</version>
            <scope>test</scope>
        </dependency>

    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.5.1</version>
                <configuration>
                    <source>${java.version}</source>
                    <target>${java.version}</target>
                    <annotationProcessorPaths>
                        <path>
                            <groupId>org.mapstruct</groupId>
                            <artifactId>mapstruct-processor</artifactId>
                            <version>${org.mapstruct.version}</version>
                        </path>
                    </annotationProcessorPaths>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.asciidoctor</groupId>
                <artifactId>asciidoctor-maven-plugin</artifactId>
                <version>1.5.5</version>
                <executions>
                    <execution>
                        <id>output-html</id>
                        <phase>generate-resources</phase>
                        <goals>
                            <goal>process-asciidoc</goal>
                        </goals>
                        <configuration>
                            <backend>html</backend>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>

</project>

Solution

The solution was to add the dependency to the classpath. For some reason, it was not in the IDE.

Even though the dependency is deprecated, it's still used by spring-boot-autoconfigure module. See Spring Boot Code

<dependency>
    <groupId>com.fasterxml.jackson.datatype</groupId>
    <artifactId>jackson-datatype-jsr310</artifactId>
</dependency>

when it's in the classpath, Java 8 date and time objects are serialized as a timestamp.

Answered By - Sydney