Java classes generated by the openapi-generator maven plugin exhibit a notable issue:

Non-standard annotations such as @javax.annotation.Nonnull or @javax.annotation.Nullable from com.google.code.findbugs:jsr305:3.0.2 are used.

Steps to reproduce:

• Write the OpenApi spec for your model
• Generate java class using openapi-generator-maven-plugin version 7.5.0

OpenAPI declaration file:

{
  "openapi": "3.1.0",
  "info": {
    "title": "Sample contract",
    "version": "1.0.0"
  },
  "paths": {},
  "components": {
    "schemas": {
      "Request": {
        "type": "object",
        "required": ["token"],
        "properties": {
          "token": {
            "type": "string"
          }
        }
      }
    }
  }
}

Generated java class:

package com.sample;

import java.net.URLEncoder;
import java.nio.charset.StandardCharsets;
import java.util.StringJoiner;
import java.util.Objects;
import java.util.Map;
import java.util.HashMap;
import com.fasterxml.jackson.annotation.JsonInclude;
import com.fasterxml.jackson.annotation.JsonProperty;
import com.fasterxml.jackson.annotation.JsonCreator;
import com.fasterxml.jackson.annotation.JsonTypeName;
import com.fasterxml.jackson.annotation.JsonValue;
import java.util.Arrays;
import com.fasterxml.jackson.annotation.JsonPropertyOrder;
import javax.validation.constraints.*;
import javax.validation.Valid;


/**
 * Request
 */
@JsonPropertyOrder({
  Request.JSON_PROPERTY_TOKEN
})
@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen", date = "2024-04-23T12:47:19.320030+02:00[Europe/Madrid]", comments = "Generator version: 7.5.0")
public class Request {
  public static final String JSON_PROPERTY_TOKEN = "token";
  private String token;

  public Request() { 
  }

  public Request token(String token) {
    this.token = token;
    return this;
  }

   /**
   * Get token
   * @return token
  **/
  @javax.annotation.Nonnull
  @NotNull

  @JsonProperty(JSON_PROPERTY_TOKEN)
  @JsonInclude(value = JsonInclude.Include.ALWAYS)

  public String getToken() {
    return token;
  }


  @JsonProperty(JSON_PROPERTY_TOKEN)
  @JsonInclude(value = JsonInclude.Include.ALWAYS)
  public void setToken(String token) {
    this.token = token;
  }

  
}

As you can see, the generated class makes use of @javax.annotation.Nonnull which is a non-standard class that must be brought using a non-standard dependency like:

<dependency>
  <groupId>com.google.code.findbugs</groupId>
  <artifactId>jsr305</artifactId>
  <version>3.0.2</version>
</dependency>

Ideally, the class should not contain that annotation or use an standard one.