- Syntax
- Examples
- Basic example
- With a custom table name
- With fields
- With field validations
- Blob declaration
- Regular expressions
- Commenting
- Field types and validations
The entity declaration is done as follows:
```
[]
[*]
entity [(<table name>)] {
[]
[*]
[*]
}
```
- `` the name of the entity,
- `` the name of one field of the entity,
- `` the JHipster supported type of the field,
- and as an option:
- `` the documentation of the entity,
- `` the options for the entity (see [Options][] for a complete list of available options),
- `` the database table name (if you want to specify something different that the name automatically computed from the entity name),
- `` the documentation of the field,
- `` the options for the field,
- `` the validations for the field.
---
### Examples
#### Basic example
```jdl
entity A
```
This is equivalent to:
```jdl
entity A(a) {}
```
The former the simpler form, without specifying a "body" (braces for fields) and a table name.
---
#### With a custom table name
Specifying a custom table name is possible too:
```jdl
entity A(my_super_entity)
```
---
#### With fields
```jdl
entity A {
name String required
age Integer
}
```
---
#### With field validations
```jdl
entity A {
name String required
age Integer min(42) max(42)
}
```
---
#### 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
This is a certain validation (only available to String types), and its syntax is:
```jdl
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 parenthesises)
- `/.../` the pattern is declared inside two slashes
- `\` anti-slashes needn't be escaped
---
#### Commenting
Commenting is possible in the JDL for entities and fields, and will generate documentation (Javadoc or JSDoc, depending
on the backend).
```jdl
/**
* 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
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 |
[Options]: options#available-options "Options"