### Grails command examples

Source: https://grails.apache.org/docs/4.0.12/guide/single.html

Common examples of running commands with environments or creating new applications.

```bash
$ grails dev run-app
$ grails create-app books
```

--------------------------------

### YAML Configuration Example

Source: https://grails.apache.org/docs/4.0.12/guide/single.html

Example of a YAML configuration file used for structuring the Grails user guide. Each key maps to a specific Asciidoc template, and nesting defines the hierarchy in the Table of Contents.

```yaml
introduction:
  title: Introduction
  whatsNew:
    title: What's new in Grails 3.2?
  ...

```

--------------------------------

### create-service Command Usage Examples

Source: https://grails.apache.org/docs/4.0.12/ref/Command%20Line/create-service.html

Examples of invoking the create-service command with and without arguments.

```bash
grails create-service
```

```bash
grails create-service book
```

```bash
grails create-service org.bookstore.Book
```

--------------------------------

### Run Application

Source: https://grails.apache.org/docs/4.0.12/guide/gettingStarted.html

Start the embedded server to host the application.

```text
grails> run-app
```

--------------------------------

### Example URL Mapping Script

Source: https://grails.apache.org/docs/4.0.12/api/org/grails/web/mapping/DefaultUrlMappingEvaluator.html

A Groovy script example demonstrating how to define URL mappings with controller, action, and constraints.

```groovy
 mappings {
    /$post/$year?/$month?/$day?" {
       controller = "blog"
       action = "show"
       constraints {
           year(matches:/\d{4}/)
           month(matches:/\d{2}/)
       }
    }
 }
```

--------------------------------

### Generate Project Documentation

Source: https://grails.apache.org/docs/4.0.12/ref/Command%20Line/docs.html

Execute the `gradle docs` command to generate user guides and API documentation. This command creates HTML and PDF outputs for the user guide, and Javadoc/Groovydoc for the API.

```bash
gradle docs
```

--------------------------------

### Grails Setup Method Transaction Persistence

Source: https://grails.apache.org/docs/4.0.12/guide/testing.html

Illustrates how data persisted in the `setup()` method using `save(flush: true)` will persist to the database because `setup()` runs in a separate transaction that is not rolled back.

```groovy
import grails.testing.mixin.integration.Integration
import grails.gorm.transactions.*
import spock.lang.*

@Integration
@Rollback
class BookSpec extends Specification {

    void setup() {
        // Below line would persist and not roll back
        new Book(name: 'Grails in Action').save(flush: true)
    }

    void "test something"() {
        expect:
        Book.count() == 1
    }
}
```

--------------------------------

### Generate-all Command Usage Examples

Source: https://grails.apache.org/docs/4.0.12/ref/Command%20Line/generate-all.html

Examples of invoking the generate-all command with different arguments to scaffold domain classes.

```bash
grails generate-all
grails generate-all org.bookstore.Book
grails generate-all "*"
```

--------------------------------

### Accept Header Examples

Source: https://grails.apache.org/docs/4.0.12/guide/single.html

Examples of common HTTP Accept header values sent by browsers and non-browser clients.

```text
*/*
```

```text
text/xml, application/xml, application/xhtml+xml, text/html;q=0.9, \
    text/plain;q=0.8, image/png, */*;q=0.5
```

```text
application/json
```

--------------------------------

### Install Grails using SDKMAN

Source: https://grails.apache.org/docs/4.0.12/guide/single.html

Install the latest version of Grails using the SDKMAN package manager.

```bash
sdk install grails
```

--------------------------------

### Container Renderer Example

Source: https://grails.apache.org/docs/4.0.12/guide/REST.html

Example of implementing a ContainerRenderer for lists of objects, specifying target and component types, and MIME types.

```groovy
class BookListRenderer implements ContainerRenderer<List, Book> {
    Class<List> getTargetType() { List }
    Class<Book> getComponentType() { Book }
    MimeType[] getMimeTypes() { [ MimeType.XML] as MimeType[] }
    void render(List object, RenderContext context) {
        ....
    }
}
```

--------------------------------

### Build Grails Installation from Source

Source: https://grails.apache.org/docs/4.0.12/guide/contributing.html

Build a Grails installation from the cloned source code using Gradle. This command fetches dependencies and builds the necessary files. It skips extensive test class collection.

```bash
./gradlew install
```

--------------------------------

### GET /plugin/instance

Source: https://grails.apache.org/docs/4.0.12/api/index-all.html

Methods for retrieving plugin instances and configuration.

```APIDOC
## GET /plugin/instance

### Description
Retrieves the wrapped plugin instance and configuration details for Grails plugins.

### Methods
- getInstance() - Retrieves the wrapped plugin instance.
- getLoadAfterNames() - Returns names of plugins that should be loaded after this one.

### Response
- **instance** (GrailsPlugin) - The plugin instance object.
```

--------------------------------

### Grails Domain Class Example

Source: https://grails.apache.org/docs/4.0.12/ref/Plug-ins/hibernate.html

An example of a Grails domain class. Refer to the GORM section of the Grails user guide for more details on creating domain classes.

```groovy
class Book {
    String title
    Date releaseDate
    Author author
}
```

--------------------------------

### Pagination and Caching with findAll

Source: https://grails.apache.org/docs/4.0.12/ref/Domain%20Classes/findAll.html

Examples showing how to apply pagination and enable the 2nd level cache during queries.

```Groovy
Book.findAll("from Book as b where b.author=:author",
             [author: 'Dan Brown'], [max: 10, offset: 5])
```

```Groovy
Book.findAll("from Book as b where b.author=:author",
             [author:'Dan Brown'], [max: 10, offset: 5, cache: true])
```

--------------------------------

### Create unit test command examples

Source: https://grails.apache.org/docs/4.0.12/ref/Command%20Line/create-unit-test.html

Demonstrates various ways to invoke the create-unit-test command with and without specific class names or packages.

```bash
grails create-unit-test
grails create-unit-test book
grails create-unit-test org.bookstore.Book
```

--------------------------------

### Clone Grails Core Repository

Source: https://grails.apache.org/docs/4.0.12/guide/contributing.html

Clone the Grails core framework repository from GitHub to start contributing. Ensure you have a Git client installed.

```bash
git clone http://github.com/grails/grails-core.git
```

--------------------------------

### Run create-domain-class command

Source: https://grails.apache.org/docs/4.0.12/ref/Command%20Line/create-domain-class.html

Examples of executing the create-domain-class command with different naming conventions.

```bash
grails create-domain-class
grails create-domain-class Book
grails create-domain-class org.bookstore.Book
```

--------------------------------

### Basic RestfulController Implementation

Source: https://grails.apache.org/docs/4.0.12/guide/REST.html

Extends the RestfulController super class to create a basic RESTful resource controller. This provides a quick way to get started with REST APIs.

```Groovy
class BookController extends RestfulController<Book> {
    static responseFormats = ['json', 'xml']
    BookController() {
        super(Book)
    }
}
```

--------------------------------

### Create Grails Criteria Query

Source: https://grails.apache.org/docs/4.0.12/ref/Domain%20Classes/createCriteria.html

Use `createCriteria()` to get an instance of HibernateCriteriaBuilder for constructing criteria queries. Criterion methods can be statically imported or called directly on the criteria instance. This example demonstrates filtering by name, balance, and branch, with ordering and limiting results.

```groovy
def c = Account.createCriteria()
def results = c.list {
    like("holderFirstName", "Fred%")
    and {
        between("balance", 500, 1000)
        eq("branch", "London")
    }
    maxResults(10)
    order("holderLastName", "desc")
}
```

--------------------------------

### Packaging and Running Application

Source: https://grails.apache.org/docs/4.0.12/guide/conf.html

Package the application into a WAR file and execute it using the java command.

```bash
$ grails package
$ java -jar build/libs/myapp-0.1.war
```

--------------------------------

### Verify Grails Installation

Source: https://grails.apache.org/docs/4.0.12/guide/gettingStarted.html

Check if Grails is installed correctly by running the `grails -version` command in your terminal. This should display the installed Grails version.

```bash
grails -version
```

--------------------------------

### Install Grails Development Version with SDKMAN

Source: https://grails.apache.org/docs/4.0.12/guide/contributing.html

Use SDKMAN to install a local Grails development version from a specified path. This is useful for managing multiple Grails installations.

```bash
sdk install grails dev /path/to/grails-core
```

--------------------------------

### Initialize Grails Project

Source: https://grails.apache.org/docs/4.0.12/guide/gettingStarted.html

Navigate to the project directory and launch the Grails interactive console.

```bash
$ cd helloworld
$ grails
```

--------------------------------

### onStartup Method

Source: https://grails.apache.org/docs/4.0.12/api/org/grails/plugins/web/servlet/context/BootStrapClassRunner.html

Executes the BootStrap startup logic for the Grails application.

```APIDOC
## void onStartup(Map<String, Object> event)

### Description
Triggers the startup sequence for BootStrap classes within the Grails application.

### Parameters
#### Request Body
- **event** (Map<String, Object>) - Required - A map containing event-related data for the startup process.
```

--------------------------------

### Trim start of string

Source: https://grails.apache.org/docs/4.0.12/api/grails/util/GrailsStringUtils.html

Removes the specified prefix from the start of the string.

```java
static java.lang.String trimStart(java.lang.String str, java.lang.String start)
```

--------------------------------

### Create a standard Grails application

Source: https://grails.apache.org/docs/4.0.12/ref/Command%20Line/create-app.html

Initializes a new application in a subdirectory named after the project.

```bash
$ grails create-app bookstore
$ cd bookstore
```

--------------------------------

### Set Post-Creation Instructions

Source: https://grails.apache.org/docs/4.0.12/guide/profiles.html

Define text to display after application creation.

```yaml
instructions: Here are some instructions
```

--------------------------------

### JSON View Output Example

Source: https://grails.apache.org/docs/4.0.12/guide/REST.html

The output generated by the basic JSON view example.

```json
{"person":{"name":"bob"}}
```

--------------------------------

### generate-controller command usage examples

Source: https://grails.apache.org/docs/4.0.12/ref/Command%20Line/generate-controller.html

Examples of invoking the generate-controller command with different arguments.

```bash
grails generate-controller
grails generate-controller org.bookstore.Book
grails generate-controller "*"
```

--------------------------------

### Create Tag Library Command Examples

Source: https://grails.apache.org/docs/4.0.12/ref/Command%20Line/create-taglib.html

Demonstrates various ways to invoke the create-taglib command, including interactive mode, simple naming, and package-qualified naming.

```bash
grails create-taglib
```

```bash
grails create-taglib book
```

```bash
grails create-taglib org.bookstore.Book
```

--------------------------------

### Basic Script Implementation

Source: https://grails.apache.org/docs/4.0.12/guide/commandLine.html

A simple script example that prints output to the console.

```groovy
description "Example description", "grails hello-world"

println "Hello World"
```

--------------------------------

### Define Configuration Properties

Source: https://grails.apache.org/docs/4.0.12/guide/spring.html

Example entries for application.groovy or externalized configuration files.

```groovy
database.driver="com.mysql.jdbc.Driver"
database.dbname="mysql:mydb"
```

--------------------------------

### Criteria Method Examples

Source: https://grails.apache.org/docs/4.0.12/ref/Domain%20Classes/createCriteria.html

Examples of various criteria methods used to filter and order database results.

```Groovy
between("balance", 500, 1000)
```

```Groovy
eq("branch", "London")
```

```Groovy
eq("branch", "london", [ignoreCase: true])
```

```Groovy
eqProperty("lastTx", "firstTx")
```

```Groovy
gt("balance",1000)
```

```Groovy
gtProperty("balance", "overdraft")
```

```Groovy
ge("balance", 1000)
```

```Groovy
geProperty("balance", "overdraft")
```

```Groovy
idEq(1)
```

```Groovy
ilike("holderFirstName", "Steph%")
```

```Groovy
'in'("age",[18..65]) or not {'in'("age",[18..65])}
```

```Groovy
isEmpty("transactions")
```

```Groovy
isNotEmpty("transactions")
```

```Groovy
isNull("holderGender")
```

```Groovy
isNotNull("holderGender")
```

```Groovy
lt("balance", 1000)
```

```Groovy
ltProperty("balance", "overdraft")
```

```Groovy
le("balance", 1000)
```

```Groovy
leProperty("balance", "overdraft")
```

```Groovy
like("holderFirstName", "Steph%")
```

```Groovy
ne("branch", "London")
```

```Groovy
neProperty("lastTx", "firstTx")
```

```Groovy
order("holderLastName", "desc")
```

```Groovy
rlike("holderFirstName", /Steph.+/)
```

```Groovy
sizeEq("transactions", 10)
```

```Groovy
sizeGt("transactions", 10)
```

```Groovy
sizeGe("transactions", 10)
```

```Groovy
sizeLt("transactions", 10)
```

```Groovy
sizeLe("transactions", 10)
```

```Groovy
sizeNe("transactions", 10)
```

```Groovy
sqlRestriction "char_length(first_name) = 4"
```

--------------------------------

### Implement Show Action with Respond

Source: https://grails.apache.org/docs/4.0.12/guide/REST.html

A concise implementation of the 'show' action that uses 'respond' to handle domain instance lookup and rendering.

```Groovy
def show(Book book) {
    respond book
}
```

--------------------------------

### Example XML Request Body

Source: https://grails.apache.org/docs/4.0.12/guide/REST.html

An example XML structure used for binding to a Book domain object.

```xml
<?xml version="1.0" encoding="UTF-8"?>
<book>
    <title>The Stand</title>
    <authorName>Stephen King</authorName>
</book>
```

--------------------------------

### Generate documentation

Source: https://grails.apache.org/docs/4.0.12/guide/contributing.html

Build the documentation using the Gradle wrapper, skipping API documentation for faster execution.

```bash
$ ./gradlew publishGuide -x apiDocs
```

--------------------------------

### Querying Domain Instances with findAll

Source: https://grails.apache.org/docs/4.0.12/ref/Domain%20Classes/findAll.html

Demonstrates various HQL, positional, named parameter, and query-by-example patterns for retrieving domain objects.

```Groovy
// everything
Book.findAll()

// with a positional parameter
Book.findAll("from Book as b where b.author=?", ['Dan Brown'])

// 10 books from Dan Brown staring from 5th book ordered by release date
Book.findAll("from Book as b where b.author=? order by b.releaseDate",
             ['Dan Brown'], [max: 10, offset: 5])

// examples with max/offset usage
def query = "from Book as b where b.author='Dan Brown' order by b.releaseDate"

// first 10 books
Book.findAll(query, [max: 10])

// 10 books starting from 5th
Book.findAll(query, [max: 10, offset: 5])

// examples with named parameters
Book.findAll("from Book as b where b.author=:author",
             [author: 'Dan Brown'])
Book.findAll("from Book as b where b.author=:author",
             [author: 'Dan Brown'], [max: 10, offset: 5])
Book.findAll("from Book as b where b.author in (:authors)",
             [authors: ['Dan Brown', 'Jack London']])

// examples with tables join
Book.findAll("from Book as b where not exists " +
                "(from Borrow as br where br.book = b)")

// query by example
def example = new Book(author: "Dan Brown")
Book.findAll(example)

// Use where criteria (since Grails 2.0)
def results = Person.findAll {
     lastName == "Simpson"
}
def results = Person.findAll(sort:"firstName") {
     lastName == "Simpson"
}
```

--------------------------------

### Install Specific Grails Version using SDKMAN

Source: https://grails.apache.org/docs/4.0.12/guide/single.html

Install a specific version of Grails, such as 4.0.12, using SDKMAN.

```bash
sdk install grails 4.0.12
```

--------------------------------

### Publish profile to local repository

Source: https://grails.apache.org/docs/4.0.12/guide/profiles.html

After configuring your profile, use the `gradle install` command to publish it to your local repository, making it available for use.

```bash
$ gradle install
```

--------------------------------

### Vnd.Error JSON Response Example

Source: https://grails.apache.org/docs/4.0.12/guide/REST.html

This is an example of a Vnd.Error JSON response when the client accepts `application/vnd.error+json` and validation errors occur.

```shell
$ curl -i -H "Accept: application/vnd.error+json,application/json" -H "Content-Type: application/json" -X POST -d "" http://localhost:8080/books
HTTP/1.1 200 OK
Server: Apache-Coyote/1.1
Content-Type: application/vnd.error+json;charset=ISO-8859-1

[
    {
        "logref": "book.nullable,
        "message": "Property [title] of class [class rest.test.Book] cannot be null",
        "_links": {
            "resource": {
                "href": "http://localhost:8080/rest-test/books"
            }
        }
    }
]
```

--------------------------------

### Using the respond method

Source: https://grails.apache.org/docs/4.0.12/ref/Controllers/respond.html

Demonstrates basic usage of the respond method to return content based on negotiation, including restricting output formats.

```Groovy
// pick the best content type to respond with
respond Book.get(1)

// pick the best content type to respond with from the given formats
respond Book.get(1), formats: ['xml', 'json']
```

--------------------------------

### Grails 3.0 Multi-Project Setup

Source: https://grails.apache.org/docs/4.0.12/guide/single.html

Commands and configuration for setting up inline-style plugins in Grails 3.x.

```bash
$ grails create-app myapp
$ grails create-plugin myplugin
```

```gradle
include 'myapp', 'myplugin'
```

```gradle
compile project(':myplugin')
```

--------------------------------

### External Bean Definition Script Example

Source: https://grails.apache.org/docs/4.0.12/guide/spring.html

An example of a Groovy script file containing bean definitions to be loaded by BeanBuilder.

```groovy
import org.apache.commons.dbcp.BasicDataSource
import org.grails.orm.hibernate.ConfigurableLocalSessionFactoryBean

beans {

    dataSource(BasicDataSource) {
        driverClassName = "org.h2.Driver"
        url = "jdbc:h2:mem:grailsDB"
        username = "sa"
        password = ""
    }

    sessionFactory(ConfigurableLocalSessionFactoryBean) {
        dataSource = dataSource
        hibernateProperties = ["hibernate.hbm2ddl.auto": "create-drop",
                               "hibernate.show_sql":     "true"]
    }
}
```

--------------------------------

### Grails Build Output Example

Source: https://grails.apache.org/docs/4.0.12/guide/plugins.html

This output demonstrates the Gradle build process, including the compilation and processing steps for both the plugin and the application. It confirms that plugin sources are being built and placed on the application's classpath.

```text
:myplugin:compileAstJava UP-TO-DATE
:myplugin:compileAstGroovy UP-TO-DATE
:myplugin:processAstResources UP-TO-DATE
:myplugin:astClasses UP-TO-DATE
:myplugin:compileJava UP-TO-DATE
:myplugin:configScript UP-TO-DATE
:myplugin:compileGroovy
:myplugin:copyAssets UP-TO-DATE
:myplugin:copyCommands UP-TO-DATE
:myplugin:copyTemplates UP-TO-DATE
:myplugin:processResources
:myapp:compileJava UP-TO-DATE
:myapp:compileGroovy
:myapp:processResources UP-TO-DATE
:myapp:classes
:myapp:findMainClass
:myapp:bootRun
Grails application running at http://localhost:8080 in environment: development
```

--------------------------------

### Install Local Grails Plugin

Source: https://grails.apache.org/docs/4.0.12/guide/plugins.html

Use this command to install a Grails plugin into your local Maven cache, making it available for use in other projects.

```bash
grails install
```

--------------------------------

### List available Grails plugins

Source: https://grails.apache.org/docs/4.0.12/ref/Command%20Line/list-plugins.html

Executes the command to list installable plugins. Note that execution time depends on internet connectivity.

```bash
grails list-plugins
```

```bash
grails list-plugins
grails list-plugins -repository=myRepository
```

--------------------------------

### Example script content

Source: https://grails.apache.org/docs/4.0.12/ref/Command%20Line/create-script.html

The generated Groovy script file structure for custom commands.

```groovy
description "Example description", "grails example-usage"

println "Example Script"
```

--------------------------------

### Interactive Grails Application Mode

Source: https://grails.apache.org/docs/4.0.12/guide/gettingStarted.html

Start the application in interactive mode to quickly restart the server. Use `run-app` to start and `stop-app` to shut down.

```bash
$ grails
grails> run-app
| Grails application running at http://localhost:8080 in environment: development
grails> stop-app
| Shutting down application...
| Application shutdown.
grails> run-app
| Grails application running at http://localhost:8080 in environment: development
```

--------------------------------

### FileSystemResource Constructors

Source: https://grails.apache.org/docs/4.0.12/api/org/grails/io/support/FileSystemResource.html

Details on how to instantiate a FileSystemResource.

```APIDOC
## FileSystemResource Constructors

### Constructor Summary

Constructors and their descriptions:

*   `FileSystemResource(java.io.File file)`
    Create a new FileSystemResource from a File handle.

*   `FileSystemResource(java.lang.String path)`
    Create a new FileSystemResource from a file path.

### Constructor Detail

*   #### public **FileSystemResource**(java.io.File file)
    Create a new FileSystemResource from a File handle.

    **Parameters:**
        *   `file` (java.io.File) - a File handle

*   #### public **FileSystemResource**(java.lang.String path)
    Create a new FileSystemResource from a file path.

    **Parameters:**
        *   `path` (java.lang.String) - a file path
```

--------------------------------

### Message Bundle Property Example

Source: https://grails.apache.org/docs/4.0.12/guide/i18n.html

Example of a message bundle property file entry. The key 'my.localized.content' maps to the specified localized string.

```properties
my.localized.content=Hola, me llamo John. Hoy es domingo.
```

--------------------------------

### Grails Factories File Example

Source: https://grails.apache.org/docs/4.0.12/guide/plugins.html

Example of a `META-INF/grails.factories` descriptor file that lists trait injectors. This file is automatically generated but can be manually defined if needed.

```properties
#Grails Factories File
grails.compiler.traits.TraitInjector=
myplugin.ControllerTraitInjector,myplugin.DateTraitTraitInjector
```

--------------------------------

### static void main(java.lang.String[] args)

Source: https://grails.apache.org/docs/4.0.12/api/grails/ui/command/GrailsApplicationContextCommandRunner.html

Main method to run an existing Application class.

```APIDOC
## static void main(java.lang.String[] args)

### Description
Main method to run an existing Application class.

### Parameters
#### Query Parameters
- **args** (String[]) - Required - The first argument is the Command name, the last argument is the Application class name
```

--------------------------------

### Retrieve domain instances using getAll

Source: https://grails.apache.org/docs/4.0.12/ref/Domain%20Classes/getAll.html

Demonstrates retrieving domain instances using variable arguments, a list of IDs, or no arguments to fetch all instances.

```groovy
// get a list which contains Book instances with ids 2, 1, 3 respectively
def bookList = Book.getAll(2, 1, 3)

// can take a list of ids as only argument, very
// useful when the ids list is calculated in code
def bookList = Book.getAll([1, 2, 3])

// when called without arguments returns list of all objects
def bookList = Book.getAll()
```

--------------------------------

### Example Grails command class

Source: https://grails.apache.org/docs/4.0.12/ref/Command%20Line/create-command.html

This is an example of a generated Grails command class. It implements the ApplicationCommand interface and can access application beans like DataSource.

```groovy
import grails.dev.commands.*

class MyExampleCommand implements ApplicationCommand {

  boolean handle(ExecutionContext ctx) {
      def dataSource = applicationContext.getBean(DataSource)
      return true
  }
}
```

--------------------------------

### Publish Local Grails Installation to Maven

Source: https://grails.apache.org/docs/4.0.12/guide/contributing.html

Publish your local Grails development installation to your local Maven repository. This allows your local build to be used by other projects.

```bash
./gradlew pTML
```

--------------------------------

### Configure SSL via command-line

Source: https://grails.apache.org/docs/4.0.12/guide/deployment.html

Use system properties to override or set SSL configuration during application startup.

```bash
-Dserver.ssl.enabled=true -Dserver.ssl.key-store=/path/to/keystore
```

--------------------------------

### Create an application with a custom profile

Source: https://grails.apache.org/docs/4.0.12/guide/single.html

Uses the custom profile to scaffold a new application.

```bash
$ grails create-app myapp --profile mycompany
```

```bash
$ grails create-app myapp --profile com.mycompany:mycompany:1.0.1
```

--------------------------------

### Basic JSON View Example

Source: https://grails.apache.org/docs/4.0.12/guide/REST.html

Create a .gson file in grails-app/views to define a JSON structure. This example creates a simple JSON object with a 'name' property.

```groovy
json.person {
    name "bob"
}
```

--------------------------------

### Create Controller and Unit Test

Source: https://grails.apache.org/docs/4.0.12/guide/testing.html

Use the `create-controller` command to generate a controller and its corresponding unit test file.

```bash
grails create-controller com.acme.app.simple
```

--------------------------------

### Install Grails with SDKMAN

Source: https://grails.apache.org/docs/4.0.12/guide/gettingStarted.html

Use SDKMAN to install the latest version of Grails or a specific version like 4.0.12. SDKMAN simplifies managing multiple Grails versions.

```bash
sdk install grails
```

```bash
sdk install grails 4.0.12
```

--------------------------------

### Rendered Scaffolding Tag Example

Source: https://grails.apache.org/docs/4.0.12/ref/Constraints/attributes.html

Illustrates how custom attributes are rendered in a GSP tag for scaffolding. The example shows a `g:datePicker` tag with a limited year range.

```HTML
<g:datePicker name="birthDate" ... years="2000..2011" ... />
```

--------------------------------

### Groovy Configuration Example

Source: https://grails.apache.org/docs/4.0.12/guide/conf.html

Example of using Groovy's ConfigSlurper syntax for Grails configuration. The `userHome`, `grailsHome`, `appName`, and `appVersion` variables are available within the configuration script.

```groovy
my.tmp.dir = "${userHome}/.grails/tmp"
```

--------------------------------

### General Initialization Methods

Source: https://grails.apache.org/docs/4.0.12/api/index-all.html

Miscellaneous initialization methods.

```APIDOC
## initialize() AbstractProfile

### Description
Initializes the profile.

### Method
N/A (Method implementation)

### Endpoint
N/A

### Parameters
None

### Request Example
None

### Response
None
```

```APIDOC
## initialize() ClosureValueInitializer

### Description
Initializes the closure value initializer.

### Method
N/A (Method implementation)

### Endpoint
N/A

### Parameters
None

### Request Example
None

### Response
None
```

```APIDOC
## initialize() DefaultDataBindingSourceRegistry

### Description
Initializes the default data binding source registry.

### Method
N/A (Method implementation)

### Endpoint
N/A

### Parameters
None

### Request Example
None

### Response
None
```

```APIDOC
## initialize(Object) DefaultProxyHandler

### Description
Initializes the default proxy handler.

### Method
N/A (Method implementation)

### Endpoint
N/A

### Parameters
- **target** (Object) - The target object to initialize the proxy for.

### Request Example
None

### Response
None
```

```APIDOC
## initialize() DefaultRendererRegistry

### Description
Initializes the default renderer registry.

### Method
N/A (Method implementation)

### Endpoint
N/A

### Parameters
None

### Request Example
None

### Response
None
```

```APIDOC
## initialize() DefaultUrlMappingsHolder

### Description
Initializes the default URL mappings holder.

### Method
N/A (Method implementation)

### Endpoint
N/A

### Parameters
None

### Request Example
None

### Response
None
```

```APIDOC
## initialize() DocPublisher

### Description
Initializes the documentation publisher.

### Method
N/A (Method implementation)

### Endpoint
N/A

### Parameters
None

### Request Example
None

### Response
None
```

```APIDOC
## initialize(GrailsApplication) FilteringCodecsByContentTypeSettings

### Description
Initializes the filtering codecs by content type settings.

### Method
N/A (Method implementation)

### Endpoint
N/A

### Parameters
- **grailsApplication** (GrailsApplication) - The Grails application instance.

### Request Example
None

### Response
None
```

```APIDOC
## initialize() GradleStep

### Description
Initializes the Gradle step.

### Method
N/A (Method implementation)

### Endpoint
N/A

### Parameters
None

### Request Example
None

### Response
None
```

```APIDOC
## initialize(InputStream, PrintStream, PrintStream) GrailsConsole

### Description
Initializes the Grails console with input and output streams.

### Method
N/A (Method implementation)

### Endpoint
N/A

### Parameters
- **inputStream** (InputStream) - The input stream.
- **outputStream** (PrintStream) - The standard output stream.
- **errorStream** (PrintStream) - The error output stream.

### Request Example
None

### Response
None
```

```APIDOC
## initialize() HalJsonRenderer

### Description
Initializes the HAL JSON renderer.

### Method
N/A (Method implementation)

### Endpoint
N/A

### Parameters
None

### Request Example
None

### Response
None
```

```APIDOC
## initialize(Object) ProxyHandler

### Description
Initializes an existing uninitialized proxy instance.

### Method
N/A (Interface method)

### Endpoint
N/A

### Parameters
- **proxy** (Object) - The proxy instance to initialize.

### Request Example
None

### Response
None
```

```APIDOC
## initialize() ValueInitializer

### Description
Initializes the value initializer.

### Method
N/A (Interface method)

### Endpoint
N/A

### Parameters
None

### Request Example
None

### Response
None
```

```APIDOC
## initializeResourcePath() DefaultLinkGenerator

### Description
Initializes the resource path for the link generator.

### Method
N/A (Method implementation)

### Endpoint
N/A

### Parameters
None

### Request Example
None

### Response
None
```

```APIDOC
## initializeSpringConfig() BeanBuilder

### Description
Initializes the Spring configuration for the bean builder.

### Method
N/A (Method implementation)

### Endpoint
N/A

### Parameters
None

### Request Example
None

### Response
None
```

```APIDOC
## initializeBeanBuilderForClassLoader(ClassLoader) BeanBuilder

### Description
Initializes the bean builder for a specific class loader.

### Method
N/A (Method implementation)

### Endpoint
N/A

### Parameters
- **classLoader** (ClassLoader) - The class loader to use.

### Request Example
None

### Response
None
```

```APIDOC
## initializeFromPropertySources(PropertySources) PropertySourcesConfig

### Description
Initializes the configuration from property sources.

### Method
N/A (Method implementation)

### Endpoint
N/A

### Parameters
- **propertySources** (PropertySources) - The property sources to load configuration from.

### Request Example
None

### Response
None
```

```APIDOC
## initializeGrailsApplication(ApplicationContext) GrailsApplicationPostProcessor

### Description
Initializes the Grails application using the provided ApplicationContext.

### Method
N/A (Method implementation)

### Endpoint
N/A

### Parameters
- **applicationContext** (ApplicationContext) - The Grails application context.

### Request Example
None

### Response
None
```

```APIDOC
## initializeGroupAndName(String, boolean) CreateAppCommand

### Description
Initializes the group and name for the create-app command.

### Method
N/A (Method implementation)

### Endpoint
N/A

### Parameters
- **appName** (String) - The name of the application.
- **force** (boolean) - Whether to force initialization.

### Request Example
None

### Response
None
```

```APIDOC
## initializeMultiple(StreamCharBuffer, boolean) StreamCharBuffer.LazyInitializingMultipleWriter

### Description
Initializes the underlying writer for the lazy initializing multiple writer.

### Method
N/A (Method implementation)

### Endpoint
N/A

### Parameters
- **buffer** (StreamCharBuffer) - The character buffer.
- **flush** (boolean) - Whether to flush after initialization.

### Request Example
None

### Response
None
```

```APIDOC
## initializeActionParameters(ClassNode, ASTNode, String, Parameter, SourceUnit, GeneratorContext) ControllerActionTransformer

### Description
Initializes action parameters within the controller action transformation.

### Method
N/A (Method implementation)

### Endpoint
N/A

### Parameters
- **classNode** (ClassNode) - The class node.
- **astNode** (ASTNode) - The AST node.
- **methodName** (String) - The name of the method.
- **parameter** (Parameter) - The parameter to initialize.
- **sourceUnit** (SourceUnit) - The source unit.
- **generatorContext** (GeneratorContext) - The generator context.

### Request Example
None

### Response
None
```

```APIDOC
## initializeAndValidateCommandObjectParameter(BlockStatement, ClassNode, ClassNode, ASTNode, String, String, SourceUnit, GeneratorContext) ControllerActionTransformer

### Description
Initializes and validates command object parameters.

### Method
N/A (Method implementation)

### Endpoint
N/A

### Parameters
- **blockStatement** (BlockStatement) - The block statement.
- **classNode** (ClassNode) - The class node.
- **commandObjectNode** (ClassNode) - The command object node.
- **astNode** (ASTNode) - The AST node.
- **methodName** (String) - The name of the method.
- **parameterName** (String) - The name of the parameter.
- **sourceUnit** (SourceUnit) - The source unit.
- **generatorContext** (GeneratorContext) - The generator context.

### Request Example
None

### Response
None
```

```APIDOC
## initializeCommandObjectParameter(BlockStatement, ClassNode, String, SourceUnit) ControllerActionTransformer

### Description
Initializes command object parameters.

### Method
N/A (Method implementation)

### Endpoint
N/A

### Parameters
- **blockStatement** (BlockStatement) - The block statement.
- **classNode** (ClassNode) - The class node.
- **parameterName** (String) - The name of the parameter.
- **sourceUnit** (SourceUnit) - The source unit.

### Request Example
None

### Response
None
```

```APIDOC
## initializeMethodParameter(ClassNode, BlockStatement, ASTNode, String, Parameter, SourceUnit, GeneratorContext) ControllerActionTransformer

### Description
Initializes method parameters.

### Method
N/A (Method implementation)

### Endpoint
N/A

### Parameters
- **classNode** (ClassNode) - The class node.
- **blockStatement** (BlockStatement) - The block statement.
- **astNode** (ASTNode) - The AST node.
- **methodName** (String) - The name of the method.
- **parameter** (Parameter) - The parameter to initialize.
- **sourceUnit** (SourceUnit) - The source unit.
- **generatorContext** (GeneratorContext) - The generator context.

### Request Example
None

### Response
None
```

```APIDOC
## initializePrimitiveOrTypeWrapperParameter(ClassNode, BlockStatement, Parameter, String) ControllerActionTransformer

### Description
Initializes primitive or type wrapper parameters.

### Method
N/A (Method implementation)

### Endpoint
N/A

### Parameters
- **classNode** (ClassNode) - The class node.
- **blockStatement** (BlockStatement) - The block statement.
- **parameter** (Parameter) - The parameter to initialize.
- **parameterName** (String) - The name of the parameter.

### Request Example
None

### Response
None
```

```APIDOC
## initializeStringParameter(ClassNode, BlockStatement, Parameter, String) ControllerActionTransformer

### Description
Initializes string parameters.

### Method
N/A (Method implementation)

### Endpoint
N/A

### Parameters
- **classNode** (ClassNode) - The class node.
- **blockStatement** (BlockStatement) - The block statement.
- **parameter** (Parameter) - The parameter to initialize.
- **parameterName** (String) - The name of the parameter.

### Request Example
None

### Response
None
```

--------------------------------

### Generate Controller, Test, and Views

Source: https://grails.apache.org/docs/4.0.12/guide/gettingStarted.html

Use the 'generate-all' command to quickly generate the skeleton of an application, including a controller, its unit test, and associated views for a given domain class.

```bash
grails generate-all helloworld.Book
```

--------------------------------

### Grails Plugin Descriptor Example

Source: https://grails.apache.org/docs/4.0.12/guide/plugins.html

This is a basic example of a Grails plugin descriptor class. All plugins must have such a class to be recognized. It defines metadata and hooks into plugin extension points.

```groovy
import grails.plugins.*

class ExampleGrailsPlugin extends Plugin {
   ... 
}
```

--------------------------------

### Create unit test command usage syntax

Source: https://grails.apache.org/docs/4.0.12/ref/Command%20Line/create-unit-test.html

Shows the standard syntax for the create-unit-test command.

```bash
grails create-unit-test <<name>>
```

--------------------------------

### init() Method

Source: https://grails.apache.org/docs/4.0.12/api/org/grails/spring/context/annotation/GrailsContextNamespaceHandler.html

Initializes the namespace handler configuration.

```APIDOC
## init()

### Description
Initializes the namespace handler, setting up the custom component-scan behavior that ignores Groovy closures.

### Method
void

### Response
- **void** - This method does not return a value.
```

--------------------------------

### Grails JSON View Example

Source: https://grails.apache.org/docs/4.0.12/guide/theWebLayer.html

Example of a Grails JSON view (`.gson`) that iterates over a list of `Book` objects and outputs their titles. It demonstrates how to access the model variable `bookList` passed from the controller.

```groovy
@Field List<Book> bookList = []

json bookList, { Book book ->
    title book.title
}
```

--------------------------------

### Find Book by Example

Source: https://grails.apache.org/docs/4.0.12/ref/Domain%20Classes/find.html

Query for a book by creating an instance of the Book class and setting properties to match. This simplifies queries where you are matching exact values.

```groovy
// query by example
def example = new Book(author: "Dan Brown")
Book.find(example)
```

--------------------------------

### Grails Controller Example

Source: https://grails.apache.org/docs/4.0.12/ref/Plug-ins/controllers.html

A basic Grails controller demonstrating how to list books. Ensure the Book domain class is defined.

```groovy
class BookController {
    def list() {
        [books:Book.list()]
    }
}
```

--------------------------------

### getExpandoMetaClass

Source: https://grails.apache.org/docs/4.0.12/api/grails/util/GrailsClassUtils.html

Gets the ExpandoMetaClass for a given class.

```APIDOC
## @java.lang.SuppressWarnings("rawtypes") public static groovy.lang.MetaClass getExpandoMetaClass(java.lang.Class clazz)

### Description
Gets the ExpandoMetaClass for a given class.

### Parameters
- **clazz** (java.lang.Class) - Required - The class to get the ExpandoMetaClass for.

### Returns
The ExpandoMetaClass for the given class.
```

--------------------------------

### Configure YML and System Properties

Source: https://grails.apache.org/docs/4.0.12/guide/conf.html

Examples for referencing system properties in YAML and configuring build tasks to pass system properties.

```YAML
production:
    dataSource:
        url: '${JDBC_CONNECTION_STRING}'
```

```Groovy
bootRun {
    systemProperties = System.properties
}
```

```Groovy
test {
    systemProperties = System.properties
}
```

--------------------------------

### trimStart

Source: https://grails.apache.org/docs/4.0.12/api/grails/util/GrailsStringUtils.html

Trims the specified start sequence from a string.

```APIDOC
## static java.lang.String trimStart(java.lang.String str, java.lang.String start)

### Description
Trims the start of the string.

### Parameters
- **str** (java.lang.String) - Required - The string to trim.
- **start** (java.lang.String) - Required - The start to trim.

### Response
- **java.lang.String** - The trimmed string.
```

--------------------------------

### GET /restful/index

Source: https://grails.apache.org/docs/4.0.12/api/index-all.html

Lists all resources up to the given maximum.

```APIDOC
## GET /restful/index

### Description
Lists all resources up to the given maximum.

### Method
GET

### Parameters
#### Query Parameters
- **max** (Integer) - Required - The maximum number of resources to list.
```

--------------------------------

### Command usage syntax

Source: https://grails.apache.org/docs/4.0.12/ref/Command%20Line/create-domain-class.html

The standard syntax for invoking the create-domain-class command.

```bash
grails create-domain-class <<name>>
```

--------------------------------

### Basic chain usage

Source: https://grails.apache.org/docs/4.0.12/ref/Controllers/chain.html

Demonstrates how to initiate a chain to another action with a model.

```Groovy
def shawshankRedemption = new Book(title: 'The Shawshank Redemption')
chain(action: "details", model: [book: shawshankRedemption])
```

--------------------------------

### GET /datasource/config

Source: https://grails.apache.org/docs/4.0.12/api/index-all.html

Retrieves the database creation configuration.

```APIDOC
## GET /datasource/config

### Description
Returns whether to generate the database with HBM 2 DDL, values can be "create", "create-drop" or "update".

### Method
GET

### Endpoint
/datasource/config
```

--------------------------------

### Create Grails Application and Domain Class

Source: https://grails.apache.org/docs/4.0.12/guide/gettingStarted.html

Use Grails convenience targets to create a new application and a domain class. This example creates an application named 'helloworld' and a domain class 'Book'.

```bash
grails create-app helloworld
cd helloworld
grails create-domain-class book
```

--------------------------------

### GET /application/metadata

Source: https://grails.apache.org/docs/4.0.12/api/index-all.html

Retrieves metadata for the current application.

```APIDOC
## GET /application/metadata

### Description
Returns the metadata for the current application.

### Method
GET

### Endpoint
/application/metadata
```

--------------------------------

### Configure Profile Publishing

Source: https://grails.apache.org/docs/4.0.12/guide/profiles.html

Set up your Bintray credentials and repository details in build.gradle.

```groovy
grailsPublish {
  user = 'YOUR USERNAME'
  key = 'YOUR KEY'
  githubSlug = 'your-repo/your-profile'
  license = 'Apache-2.0'
}
```

--------------------------------

### GET /JSONArray/length

Source: https://grails.apache.org/docs/4.0.12/api/org/grails/web/json/JSONArray.html

Returns the number of elements in the JSONArray.

```APIDOC
## GET /JSONArray/length

### Description
Get the number of elements in the JSONArray, included nulls.

### Response
#### Success Response (200)
- **length** (int) - The length (or size).
```