Use java.time.Instant to represent DateTime instead of OffsetDateTime

Question

I'm using the openApi maven plugin to generate java request/responses for a REST api.

The request has a DateTime property, when I run the generator I get the DateTime property of the attribute represented as java.time.OffsetDateTime. The problem is I have a requirement to represent the property as java.time.Instant.

This is the openApi specification for the request:

"DocumentDto" : {
      "type" : "object",
      "properties" : {
        "uuid" : {
          "type" : "string",
          "format" : "uuid"
        },
        "creationDate" : {
          "type" : "string",
          "format" : "date-time"
        }
      }
    }

The generated java request:

@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen", date = "2019-05-21T13:07:21.639+02:00[Europe/Zurich]")
public class DocumentDto {
  public static final String SERIALIZED_NAME_UUID = "uuid";
  @SerializedName(SERIALIZED_NAME_UUID)
  private UUID uuid;


  public static final String SERIALIZED_NAME_TEST = "creationDate";
  @SerializedName(SERIALIZED_NAME_TEST)
  private OffsetDateTime creationDate;
}

The maven plugin setup:

<plugin>
    <groupId>org.openapitools</groupId>
    <artifactId>openapi-generator-maven-plugin</artifactId>
    <version>3.3.4</version>
    <executions>
        <execution>
            <id>test-service</id>
            <phase>validate</phase>
            <goals>
                <goal>generate</goal>
            </goals>
            <configuration>
                <inputSpec>
                    ${project.build.directory}/open-api/swagger.json
                </inputSpec>
                <generatorName>java</generatorName>
                <validateSpec>false</validateSpec>
                <generateApis>false</generateApis>
                <groupId>com.test</groupId>
                <artifactId>test-service</artifactId>
                <modelPackage>test.model</modelPackage>
                <apiPackage>test.api</apiPackage>
                <configOptions>
                    <sourceFolder>src/gen/java/main</sourceFolder>
                    <dateLibrary>java8</dateLibrary>
                    <java8>true</java8>
                </configOptions>
            </configuration>
        </execution>              
    </executions>
</plugin>

I've already tried the typeMappings and importMappings as follow but it had no affect on the generated code:

<typeMappings>DateTime=Instant</typeMappings>
<importMappings>Instant=java.time.Instant</importMappings>

Did you manage to get this working in the end? I still can't get Instant to work with openApiGenerator and I'm looking for a solution. — BarbetNL
– BarbetNL, Commented Jul 27, 2022 at 13:33
The following helped me in my case (generator spring 7.5 + gradle): typeMappings.set(["string+date-time": "Instant"]) importMappings.set([Instant: "java.time.Instant"]) — tarasnn
– tarasnn, Commented May 19, 2024 at 8:23

President James K. Polk · Accepted Answer · 2025-01-23 04:22:18Z

40

I had the same problem but wanted to use LocalDateTime instead of Instant. Adding the following works, at least for entities:

<configuration>
    <typeMappings>
        <typeMapping>OffsetDateTime=LocalDateTime</typeMapping>
    </typeMappings>
    <importMappings>
        <importMapping>java.time.OffsetDateTime=java.time.LocalDateTime</importMapping>
    </importMappings>
</configuration>

i.e. an import for LocalDateTime is added, and any entity fields in the yaml with type format: date-time are mapped to LocalDateTime.

However, for api parameters, no import was added with those settings. After a while I gave up and instead used fully qualified types so that no import is required. Just change the above typeMapping to:

<typeMapping>OffsetDateTime=java.time.LocalDateTime</typeMapping>

Your generated methods afterwards looked like:

default ResponseEntity<List<SomeDto>> someMethodGet(
            @ApiParam(value = "") @Valid @RequestParam(value = "changeDateFrom",
                required = false) @org.springframework.format.annotation.DateTimeFormat(
                    iso = org.springframework.format.annotation.DateTimeFormat.ISO.DATE_TIME) java.time.LocalDateTime changeDateFrom,
        {
            return getDelegate().someMethodGet(..., changeDateFrom, ...);
        }

PS1 Make sure you use the most recent version of the plugin.

PS2 I used the delegate pattern.

PS3 I used the spring model.

edited Jan 23 at 4:22

President James K. Polk

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answered Feb 20, 2020 at 12:43

zmeeagain

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4 Comments

BarbetNL Over a year ago

Just <dateLibrary>java8-localdatetime</dateLibrary> will be enough to make it LocalDateTime (openapi-generator.tech/docs/generators/java). I still can't get it to work with Instant.

Dani Over a year ago

@BarbetNL did you have any luck getting it to work with Instant?

BarbetNL Over a year ago

No, eventually I gave up, and had to convert it in the java code manually.

Undertaker Over a year ago

For Gradle with Kotlin: typeMappings.set( mapOf( "OffsetDateTime" to "LocalDateTime" ) ) importMappings.set( mapOf( "java.time.OffsetDateTime" to "java.time.LocalDateTime" ) )

Maksim Yakidovich · Accepted Answer · 2019-09-18 12:39:36Z

35

just add to the configuration of openapi-generator-maven-plugin

<typeMappings>
     <typeMapping>OffsetDateTime=Instant</typeMapping>
</typeMappings>
<importMappings>                                
     <importMapping>java.time.OffsetDateTime=java.time.Instant</importMapping>
</importMappings>

answered Sep 18, 2019 at 12:39

Maksim Yakidovich

4605 silver badges7 bronze badges

Comments

tsachev · Accepted Answer · 2020-03-11 17:03:07Z

Your changes are overridden by the dateLibrary configuration for the generator. To override date or date-time format types you better disable the dateLibrary by specifying value which is not recognized by the java generators.

Add this to you plugin's <configuration> to achieve this:

  <configOptions>
    <java8>true</java8>
    <dateLibrary>custom</dateLibrary>
  </configOptions>
  <typeMappings>
    <typeMapping>DateTime=Instant</typeMapping>
    <typeMapping>Date=LocalDate</typeMapping>
  </typeMappings>
  <importMappings>
    <importMapping>Instant=java.time.Instant</importMapping>
    <importMapping>LocalDate=java.time.LocalDate</importMapping>
  </importMappings>

You may also want to add <jsr310>true</jsr310> config option, since it is auto enabled when dateLibrary is java8 (but this is used mostly when generating clients as far as I can see).

Daniel Plucenio · Accepted Answer · 2021-11-18 10:36:59Z

13

I know the question was about openapi-generator-maven-plugin, but since looking for the same configuration for org.openapi.generator gradle plugin brought me here, I guess this could be useful for someone else:

The equivalent for org.openapi.generator gradle plugin would be:

openApiGenerate {
    // ...
    typeMappings = [
        OffsetDateTime: "Instant"
    ]
    importMappings = [
        "java.time.OffsetDateTime": "java.time.Instant"
    ]
}

edited Nov 18, 2021 at 10:36

answered Nov 18, 2021 at 10:29

Daniel Plucenio

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3 Comments

Martin Mansour Over a year ago

Having a problem with the import not being changed. Any ideas?

Demigod Over a year ago

Doesn't work for me at all...

Semaphor Over a year ago

Since 5.4.0 of the gradle plugin, the importMappings do not work as one might expect, see: github.com/OpenAPITools/openapi-generator/issues/11506. A workaround would be to remove the importMappings and use OffsetDateTime: "java.time.Instant" in typeMappings.

petronius · Accepted Answer · 2019-11-15 15:54:36Z

2

You indeed have to add the mappings as @MaksimYakidovich says, but also change your spec with "format" : "offset-date-time" instead of date-time

answered Nov 15, 2019 at 15:54

petronius

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