micronaut reactive-mongo setup Internal Server Error

Question

I'm trying to setup the mongo reactive client in a micronaut project based in java and I'm getting the following error:

"Internal Server Error: An exception occurred when decoding using the AutomaticPojoCodec.\nDecoding into a 'Member' failed with the following exception:\n\nCannot find a public constructor for 'Member'.\n\nA custom Codec or PojoCodec may need to be explicitly configured and registered to handle this type."

my project setup is looing as follows:

├── Application.java
├── config
│   └── MongoConfiguration.java
├── controller
│   └── MemberController.java
├── model
│   └── Member.java
└── service
    └── MemberService.java

The app is launching but if I am calling the http endpoint to list all members it throws an Error as listed here in the post.

My Member is looking quite simple for the beginning:

import com.fasterxml.jackson.annotation.JsonProperty;

public class Member {
    private final String firstname;
    private final String lastname;

    public Member( @JsonProperty("firstname") String firstname, @JsonProperty("lastname") String lastname) {
        this.firstname = firstname;
        this.lastname = lastname;
    }

   ....

}

// And my service, has this method where I'm calling mongo
    private MongoCollection<Member> getCollection() {
        configuration.setCollectionName("members");
        return mongoClient.getDatabase(configuration.getDatabaseName())
                .getCollection(configuration.getCollectionName(), Member.class);
    }

Any I idea whats wrong in the setup or do need more information?

thx for the help

Answer 1

Your constrictor should be annotated with @JsonCreator, because Member doesn't have default construcor and have custom constructor with arguments annotated @JsonProperty

Constructor/factory method where every argument is annotated with either JsonProperty or JacksonInject, to indicate name of property to bind to

public class Member {
    private final String firstname;
    private final String lastname;

    @JsonCreator
    public Member(@JsonProperty("firstname") String firstname, 
                  @JsonProperty("lastname") String lastname) {
        this.firstname = firstname;
        this.lastname = lastname;
    }

   ....

}