[RESOLVE] Added Spring JPA annotations support to SpringCodegen

Created by: MarkusBansky

REQUEST #2972 (closed)

Added Spring JPA annotations support to SpringCodegen.

Added additionalAnnotations to CodegenModel, CodegenProperty. Added isJpaEntity to CodegenModel. Added useSpringJpa config option to SpringCodegen.

Example:

User:
  type: object
  x-java-jpa-entity: true
  x-java-jpa-table: users
  properties:
    id:
      type: integer
      format: int64
      x-java-jpa-annotations:
        - "@Id"
        - "@GeneratedValue(strategy = GenerationType.IDENTITY)"
    firstName:
      type: string
    lastName:
      type: string
    username:
      type: string
    passwordHash:
      type: string

Would generate this class for you:

/**
 * User
 */
@javax.annotation.Generated(value = "org.openapitools.codegen.languages.SpringCodegen", date = "2020-02-13T21:44:31.102132Z[Europe/London]")

@Entity // <---- makes this an Entity
@Table(name = "users") // <---- applies table name
public class User   {

  @Id // <---- adds annotations
  @GeneratedValue(strategy = GenerationType.IDENTITY)
  @JsonProperty("id")
  private Long id;


  @JsonProperty("firstName")
  private String firstName;


  @JsonProperty("lastName")
  private String lastName;


  @JsonProperty("username")
  private String username;


  @JsonProperty("passwordHash")
  private String passwordHash;

  public User id(Long id) {
    this.id = id;
    return this;
  }

  /**
   * Get id
   * @return id
  */
  @ApiModelProperty(value = "")


  public Long getId() {
    return id;
  }

  public void setId(Long id) {
    this.id = id;
  }

/// the rest of the file there

PR checklist

• Read the contribution guidelines.
• If contributing template-only or documentation-only changes which will change sample output, build the project before.
• Run the shell script(s) under ./bin/ (or Windows batch scripts under.\bin\windows) to update Petstore samples related to your fix. This is important, as CI jobs will verify all generator outputs of your HEAD commit, and these must match the expectations made by your contribution. You only need to run ./bin/{LANG}-petstore.sh, ./bin/openapi3/{LANG}-petstore.sh if updating the code or mustache templates for a language ({LANG}) (e.g. php, ruby, python, etc).
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