JHipster Domain Language (JDL) - Entities Permalink to " JHipster Domain Language (JDL) - Entities"

Summary Permalink to "Summary"

  1. Syntax
  2. Examples
    1. Basic example
    2. With a custom table name
    3. With fields
    4. With field validations
    5. Blob declaration
    6. Regular expressions
    7. Commenting
  3. Field types and validations

Syntax Permalink to "Syntax"

The entity declaration is done as follows:

[<entity javadoc>]
[<entity annotation>*]
entity <entity name> [(<table name>)] {
  [<field javadoc>]
  [<field annotation>*]
  <field name> <field type> [<validation>*]
  • <entity name> the name of the entity,
  • <field name> the name of one field of the entity,
  • <field type> the JHipster supported type of the field,
  • and as an option:
    • <entity javadoc> the documentation of the entity,
    • <entity annotation> the options for the entity (see OptionsEntity for a complete list of available options),
    • <table name> the database table name (if you want to specify something different that the name automatically computed from the entity name),
    • <field javadoc> the documentation of the field,
    • <field annotation> the options for the field (see OptionsField for a complete list of available options),
    • <validation> the validations for the field.

Examples Permalink to "Examples"

Basic example Permalink to "Basic example"

entity A

This is equivalent to:

entity A(a) {}

The former the simpler form, without specifying a “body” (braces for fields) and a table name.

With a custom table name Permalink to "With a custom table name"

Specifying a custom table name is possible too:

 entity A(my_super_entity)

With fields Permalink to "With fields"

entity A {
  name String required
  age Integer

With field validations Permalink to "With field validations"

entity A {
  name String required
  age Integer min(42) max(42)

Blob declaration Permalink to "Blob declaration"

JHipster gives a great choice as one can choose between an image type or any binary type. JDL lets you do the same. Create a custom type (see DataType) with the editor, name it according to these conventions:

  • AnyBlob or Blob to create a field of the “any” binary type;
  • ImageBlob to create a field meant to be an image.
  • TextBlob to create a field for a CLOB (long text).

And you can create as many DataTypes as you like.

Regular expressions Permalink to "Regular expressions"

This is a certain validation (only available to String types), and its syntax is:

entity A {
  name String pattern(/^[A-Z][a-z]+\d$/)

Let’s break it down:

  • pattern is the keyword to declare a regex validation (with the normal parentheses)
  • /.../ the pattern is declared inside two slashes
  • \ anti-slashes needn’t be escaped

Commenting Permalink to "Commenting"

Commenting is possible in the JDL for entities and fields, and will generate documentation (Javadoc or JSDoc, depending on the backend).

 * This is a comment
 * about a class
 * @author Someone
entity A {
   * This comment will also be used!
   * @type...
   name String
   age Integer // this is yet another comment

These comments will later be added as Javadoc comments by JHipster. The JDL possesses its own kind of comment:

  • // an ignored comment
  • /** not an ignored comment */

Therefore, anything that starts with // is considered an internal comment for JDL, and will not be counted as Javadoc. Please note that the JDL Studio directives that start with # will be ignored during parsing.

Another form of comments are the following comments:

entity A {
  name String /** My super field */
  count Integer /** My other super field */

Here A’s name will be commented with My super field, B with My other super field.

Yes, commas are not mandatory but it’s wiser to have them so as not to make mistakes in the code. If you want to mix commas and following comments, beware!

entity A {
  name String, /** My comment */
  count Integer

A’s name won’t have the comment, because the count will.

Field types and validations Permalink to "Field types and validations"

Each field type has its own validation list. Here are the types supported in the JDL:

JDL type Validations
String required, minlength, maxlength, pattern, unique
Integer required, min, max, unique
Long required, min, max, unique
BigDecimal required, min, max, unique
Float required, min, max, unique
Double required, min, max, unique
Enum required, unique
Boolean required, unique
LocalDate required, unique
ZonedDateTime required, unique
Instant required, unique
Duration required, unique
UUID required, unique
Blob required, minbytes, maxbytes, unique
AnyBlob required, minbytes, maxbytes, unique
ImageBlob required, minbytes, maxbytes, unique
TextBlob required, unique