How to use Lombok Builder + Jackson + Graal?

[altaiezior]

I am trying to use an immutable type like

@Value
@Builder
@Jacksonized
@Introspected(builder = @IntrospectionBuilder(builderClass = GitProperties.GitPropertiesBuilder.class))
public class GitProperties {
    @JsonProperty("git.branch")
    String branchName;

    @JsonProperty("git.commit.id.abbrev")
    String commitAbbrev;

    @JsonProperty("git.commit.id.full")
    String commitId;

    @JsonProperty("git.commit.message.short")
    String commitMessage;

    @JsonProperty("git.commit.time")
    String commitTime;

    @JsonProperty("git.commit.user.email")
    String committerEmail;

    @JsonProperty("git.commit.user.name")
    String commitUser;

    @JsonProperty("git.build.user.email")
    String buildUserEmail;

    @JsonProperty("git.build.user.name")
    String buildUser;

    @JsonProperty("git.build.time")
    String buildTime;
}

But when deserialising the value in graal vm I get the error that the build method is not found.

[altaiezior]

After deep diving in the code I think I identified the issue, so I am using module-scan which means that BeanIntrospectionModule is installed.

So what BeanIntrospectionModule does is that it makes Jackson use BeanIntrospection rather than reflection to get the setters / getters / builders and other properties.

In the above case the code will flow as follows:

• Jackson knows there exists a builder class because of the annotation
• It has discovered the @JsonProperty over these fields as well and creates a base list of properties given by me
• now it has a empty builder instance which it gives bean introspection module to enrich (and not use its own reflection)
• bean introspection module tries to find the revelant builder setters from its introspection and enriches the builder
• this enriched builder is given back to jackson and then it finally tries to complete the builder setup

For the properties defined and used by the IntrospectionModule has been discovered by Graal and added in the native image

But it doesn't set / enrich the build method in the builder which is a bug.

Before giving the builder to BeanIntrospectionModule Jackson tries to find the build method via reflection, but since the method was not seemd to be used during graal static analysis it was removed.

When jackson finally does a check for the _buildMethod to be present here it doesn't find any and throws exception.

[TatyOko28]

Solution : Complete @introspected configuration (Recommended)

Add the missing static builder method to the introspection configuration.

import com.fasterxml.jackson.annotation.JsonProperty;
import io.micronaut.core.annotation.Introspected;
import lombok.Builder;
import lombok.Value;
import lombok.jackson.Jacksonized;

@Value
@Builder
@Jacksonized
@Introspected(
    builder = @Introspected.IntrospectionBuilder(
        builderClass = GitProperties.GitPropertiesBuilder.class,
        buildMethod = "build"  // Explicitly specify build method
    ),
    accessKind = {Introspected.AccessKind.METHOD, Introspected.AccessKind.FIELD},
    classes = {@Introspected.Classed(type = GitProperties.GitPropertiesBuilder.class)}
)
public class GitProperties {
    
    @JsonProperty("git.branch")
    String branchName;

    @JsonProperty("git.commit.id.abbrev")
    String commitAbbrev;

    @JsonProperty("git.commit.id.full")
    String commitId;

    @JsonProperty("git.commit.message.short")
    String commitMessage;

    @JsonProperty("git.commit.time")
    String commitTime;

    @JsonProperty("git.commit.user.email")
    String committerEmail;

    @JsonProperty("git.commit.user.name")
    String commitUser;

    @JsonProperty("git.build.user.email")
    String buildUserEmail;

    @JsonProperty("git.build.user.name")
    String buildUser;

    @JsonProperty("git.build.time")
    String buildTime;
    
    // Explicit builder method for GraalVM
    public static GitPropertiesBuilder builder() {
        return new GitPropertiesBuilder();
    }
}

[altaiezior]

I will test this, so do we still use reflection here to discover and call the build method?

From the jackson code, I guess there was no way to specify the build method cleanly like we can specify the setters.

Also do we need to add this boilerplate to every POJO or can we add a simple annotation to handle this boilerplate code?