Esta es la guía para desarrolladores de AWS CDK v2. La primera versión del CDK pasó a la etapa de mantenimiento el 1.° de junio de 2022 y no cuenta con soporte desde el 1.° de junio de 2023.
Las traducciones son generadas a través de traducción automática. En caso de conflicto entre la traducción y la version original de inglés, prevalecerá la version en inglés.
# Token y AWS CDK
En AWS Cloud Development Kit (AWS CDK), los *tokens* son marcadores de posición para los valores que no se conocen al definir constructos o sintetizar pilas. Estos valores se resolverán por completo en el momento de la implementación, cuando se cree la infraestructura real. Al desarrollar aplicaciones de AWS CDK, trabajará con tokens para administrar estos valores en toda la aplicación.
## Ejemplo de token
A continuación, se muestra un ejemplo de una pila de CDK que define un constructo para un bucket de Amazon Simple Storage Service (Amazon S3). Como aún no se conoce el nombre de nuestro bucket, el valor de `bucketName` se almacena como un token:
**Example**
```
import * as cdk from 'aws-cdk-lib';
import { Construct } from 'constructs';
import * as s3 from 'aws-cdk-lib/aws-s3';
export class CdkDemoAppStack extends cdk.Stack {
constructor(scope: Construct, id: string, props?: cdk.StackProps) {
super(scope, id, props);
// Define an S3 bucket
const myBucket = new s3.Bucket(this, 'myBucket');
// Store value of the S3 bucket name
const myBucketName = myBucket.bucketName;
// Print the current value for the S3 bucket name at synthesis
console.log("myBucketName: " + myBucketName);
}
}
```
```
const { Stack, Duration } = require('aws-cdk-lib');
const s3 = require('aws-cdk-lib/aws-s3');
class CdkDemoAppStack extends Stack {
constructor(scope, id, props) {
super(scope, id, props);
// Define an S3 bucket
const myBucket = new s3.Bucket(this, 'myBucket');
// Store value of the S3 bucket name
const myBucketName = myBucket.bucketName;
// Print the current value for the S3 bucket name at synthesis
console.log("myBucketName: " + myBucketName);
}
}
module.exports = { CdkDemoAppStack }
```
```
from aws_cdk import (
Stack
)
from constructs import Construct
from aws_cdk import aws_s3 as s3
class CdkDemoAppStack(Stack):
def __init__(self, scope: Construct, construct_id: str, **kwargs) -> None:
super().__init__(scope, construct_id, **kwargs)
# Define an S3 bucket
my_bucket = s3.Bucket(self, "myBucket")
# Store the value of the S3 bucket name
my_bucket_name = my_bucket.bucket_name
# Print the current value for the S3 bucket name at synthesis
print(f"myBucketName: {my_bucket_name}")
```
```
package com.myorg;
import software.constructs.Construct;
import software.amazon.awscdk.Stack;
import software.amazon.awscdk.StackProps;
import software.amazon.awscdk.services.s3.Bucket;
import java.util.Map;
public class CdkDemoAppStack extends Stack {
public CdkDemoAppStack(final Construct scope, final String id) {
this(scope, id, null);
}
public CdkDemoAppStack(final Construct scope, final String id, final StackProps props) {
super(scope, id, props);
// Define an S3 bucket
Bucket myBucket = Bucket.Builder.create(this, "myBucket")
.build();
// Store the token for the bucket name
String myBucketName = myBucket.getBucketName();
// Print the token at synthesis
System.out.println("myBucketName: " + myBucketName);
}
}
```
```
using Amazon.CDK;
using Constructs;
using Amazon.CDK.AWS.S3;
namespace CdkDemoApp
{
public class CdkDemoAppStack : Stack
{
internal CdkDemoAppStack(Construct scope, string id, IStackProps props = null) : base(scope, id, props)
{
// Define an S3 bucket
var myBucket = new Bucket(this, "myBucket");
// Store the token for the bucket name
var myBucketName = myBucket.BucketName;
// Print the token at synthesis
System.Console.WriteLine($"myBucketName: {myBucketName}");
}
}
}
```
```
package main
import (
"fmt"
"github.com/aws/aws-cdk-go/awscdk/v2"
"github.com/aws/aws-cdk-go/awscdk/v2/awss3"
"github.com/aws/constructs-go/constructs/v10"
"github.com/aws/jsii-runtime-go"
)
type CdkDemoAppStackProps struct {
awscdk.StackProps
}
func NewCdkDemoAppStack(scope constructs.Construct, id string, props *CdkDemoAppStackProps) awscdk.Stack {
var sprops awscdk.StackProps
if props != nil {
sprops = props.StackProps
}
stack := awscdk.NewStack(scope, &id, &sprops)
// Define an S3 bucket
myBucket := awss3.NewBucket(stack, jsii.String("myBucket"), &awss3.BucketProps{})
// Store the token for the bucket name
myBucketName := myBucket.BucketName()
// Print the token at synthesis
fmt.Println("myBucketName: ", *myBucketName)
return stack
}
// ...
```
Cuando ejecutamos `cdk synth` para sintetizar nuestra pila, el valor de `myBucketName` aparecerá en el formato de token como `${Token[TOKEN.<1234>]}`. Este formato de token es el resultado de cómo AWS CDK codifica los tokens. En este ejemplo, el token está codificado como una cadena:
```
$ cdk synth --quiet
myBucketName: ${Token[TOKEN.21]}
```
Como el valor del nombre de nuestro bucket no se conoce en el momento de la síntesis, el token se representa como `myBucket`. Nuestra plantilla de AWS CloudFormation utiliza la función intrínseca `Ref` como referencia a su valor, que se conocerá en el momento de la implementación:
```
Resources:
myBucket<5AF9C99B>:
# ...
Outputs:
bucketNameOutput:
Description: The name of the S3 bucket
Value:
Ref: myBucket<5AF9C99B>
```
Consulte [ID lógicos generados en su plantilla de AWS CloudFormation](configure-synth.md#how-synth-default-logical-ids) para obtener más información sobre cómo se genera el hash único.
## Transferencia de tokens
Los tokens se pueden transferir como si fueran el valor real que representan. A continuación, se muestra un ejemplo en el que se transfiere el token del nombre del bucket a un constructo de una función de AWS Lambda:
**Example**
```
import * as cdk from 'aws-cdk-lib';
import { Construct } from 'constructs';
import * as s3 from 'aws-cdk-lib/aws-s3';
import * as lambda from 'aws-cdk-lib/aws-lambda';
export class CdkDemoAppStack extends cdk.Stack {
constructor(scope: Construct, id: string, props?: cdk.StackProps) {
super(scope, id, props);
// Define an S3 bucket
const myBucket = new s3.Bucket(this, 'myBucket');
// ...
// Define a Lambda function
const myFunction = new lambda.Function(this, "myFunction", {
runtime: lambda.Runtime.NODEJS_20_X,
handler: "index.handler",
code: lambda.Code.fromInline(`
exports.handler = async function(event) {
return {
statusCode: 200,
body: JSON.stringify('Hello World!'),
};
};
`),
functionName: myBucketName + "Function", // Pass token for the S3 bucket name
environment: {
BUCKET_NAME: myBucketName, // Pass token for the S3 bucket name
}
});
}
}
```
```
const { Stack, Duration } = require('aws-cdk-lib');
const s3 = require('aws-cdk-lib/aws-s3');
const lambda = require('aws-cdk-lib/aws-lambda');
class CdkDemoAppStack extends Stack {
constructor(scope, id, props) {
super(scope, id, props);
// Define an S3 bucket
const myBucket = new s3.Bucket(this, 'myBucket');
// ...
// Define a Lambda function
const myFunction = new lambda.Function(this, 'myFunction', {
runtime: lambda.Runtime.NODEJS_20_X,
handler: 'index.handler',
code: lambda.Code.fromInline(`
exports.handler = async function(event) {
return {
statusCode: 200,
body: JSON.stringify('Hello World!'),
};
};
`),
functionName: myBucketName + 'Function', // Pass token for the S3 bucket name
environment: {
BUCKET_NAME: myBucketName, // Pass token for the S3 bucket name
}
});
}
}
module.exports = { CdkDemoAppStack }
```
```
from aws_cdk import (
Stack
)
from constructs import Construct
from aws_cdk import aws_s3 as s3
from aws_cdk import aws_lambda as _lambda
class CdkDemoAppStack(Stack):
def __init__(self, scope: Construct, construct_id: str, **kwargs) -> None:
super().__init__(scope, construct_id, **kwargs)
# Define an S3 bucket
my_bucket = s3.Bucket(self, "myBucket")
# ...
# Define a Lambda function
my_function = _lambda.Function(self, "myFunction",
runtime=_lambda.Runtime.NODEJS_20_X,
handler="index.handler",
code=_lambda.Code.from_inline("""
exports.handler = async function(event) {
return {
statusCode: 200,
body: JSON.stringify('Hello World!'),
};
};
"""),
function_name=f"{my_bucket_name}Function", # Pass token for the S3 bucket name
environment={
"BUCKET_NAME": my_bucket_name # Pass token for the S3 bucket name
}
)
```
```
package com.myorg;
import software.constructs.Construct;
import software.amazon.awscdk.Stack;
import software.amazon.awscdk.StackProps;
import software.amazon.awscdk.services.s3.Bucket;
import software.amazon.awscdk.services.lambda.Code;
import software.amazon.awscdk.services.lambda.Function;
import software.amazon.awscdk.services.lambda.Runtime;
import java.util.Map;
public class CdkDemoAppStack extends Stack {
public CdkDemoAppStack(final Construct scope, final String id) {
this(scope, id, null);
}
public CdkDemoAppStack(final Construct scope, final String id, final StackProps props) {
super(scope, id, props);
// Define an S3 bucket
Bucket myBucket = Bucket.Builder.create(this, "myBucket")
.build();
// ...
// Define a Lambda function
Function myFunction = Function.Builder.create(this, "myFunction")
.runtime(Runtime.NODEJS_20_X)
.handler("index.handler")
.code(Code.fromInline(
"exports.handler = async function(event) {" +
"return {" +
"statusCode: 200," +
"body: JSON.stringify('Hello World!')," +
"};" +
"};"
))
.functionName(myBucketName + "Function") // Pass the token for the s3 bucket to the function construct
.environment(Map.of("BUCKET_NAME", myBucketName)) // Pass the bucket name as environment variable
.build();
}
}
```
```
using Amazon.CDK;
using Constructs;
using Amazon.CDK.AWS.S3;
using Amazon.CDK.AWS.Lambda;
using System;
using System.Collections.Generic;
namespace CdkDemoApp
{
public class CdkDemoAppStack : Stack
{
internal CdkDemoAppStack(Construct scope, string id, IStackProps props = null) : base(scope, id, props)
{
// Define an S3 bucket
var myBucket = new Bucket(this, "myBucket");
// ...
// Define a Lambda function
var myFunction = new Function(this, "myFunction", new FunctionProps
{
Runtime = Runtime.NODEJS_20_X,
Handler = "index.handler",
Code = Code.FromInline(@"
exports.handler = async function(event) {
return {
statusCode: 200,
body: JSON.stringify('Hello World!'),
};
};
"),
// Pass the token for the S3 bucket name
Environment = new Dictionary
{
{ "BUCKET_NAME", myBucketName }
},
FunctionName = $"{myBucketName}Function" // Pass the token for the s3 bucket to the function construct
});
}
}
}
```
```
package main
import (
"fmt"
"github.com/aws/aws-cdk-go/awscdk/v2"
"github.com/aws/aws-cdk-go/awscdk/v2/awslambda"
"github.com/aws/aws-cdk-go/awscdk/v2/awss3"
"github.com/aws/constructs-go/constructs/v10"
"github.com/aws/jsii-runtime-go"
)
type CdkDemoAppStackProps struct {
awscdk.StackProps
}
func NewCdkDemoAppStack(scope constructs.Construct, id string, props *CdkDemoAppStackProps) awscdk.Stack {
var sprops awscdk.StackProps
if props != nil {
sprops = props.StackProps
}
stack := awscdk.NewStack(scope, &id, &sprops)
// Define an S3 bucket
myBucket := awss3.NewBucket(stack, jsii.String("myBucket"), &awss3.BucketProps{})
// ...
// Define a Lambda function
myFunction := awslambda.NewFunction(stack, jsii.String("myFunction"), &awslambda.FunctionProps{
Runtime: awslambda.Runtime_NODEJS_20_X(),
Handler: jsii.String("index.handler"),
Code: awslambda.Code_FromInline(jsii.String(`
exports.handler = async function(event) {
return {
statusCode: 200,
body: JSON.stringify('Hello World!'),
};
};
`)),
FunctionName: jsii.String(fmt.Sprintf("%sFunction", *myBucketName)), // Pass the token for the S3 bucket to the function name
Environment: &map[string]*string{
"BUCKET_NAME": myBucketName,
},
})
return stack
}
// ...
```
Cuando sintetizamos nuestra plantilla, las funciones intrínsecas `Ref` y `Fn::Join` se utilizan para especificar los valores, que se conocerán en el momento de la implementación:
```
Resources:
myBucket<5AF9C99B>:
Type: AWS::S3::Bucket
# ...
myFunction<884E1557>:
Type: AWS::Lambda::Function
Properties:
# ...
Environment:
Variables:
BUCKET_NAME:
Ref: myBucket<5AF9C99B>
FunctionName:
Fn::Join:
- ""
- - Ref: myBucket<5AF9C99B>
- Function
# ...
```
## Cómo funcionan las codificaciones de tokens
Los tokens son objetos que implementan la interfaz [https://docs.aws.amazon.com/cdk/api/v2/docs/aws-cdk-lib.IResolvable.html](https://docs.aws.amazon.com/cdk/api/v2/docs/aws-cdk-lib.IResolvable.html) , que contiene un único método `resolve`. Durante la síntesis, AWS CDK llama a este método para generar el valor final de los tokens de la plantilla de CloudFormation.
**nota**
En raras ocasiones trabajará con la interfaz `IResolvable`. Lo más probable es que solo vea las versiones de los tokens codificadas en cadenas.
### Tipos de codificación de token
Los tokens participan en el proceso de síntesis para producir valores arbitrarios de cualquier tipo. Por lo general, otras funciones solo aceptan argumentos de tipos básicos, como `string` o `number`. Para utilizar tokens en estos casos, puede codificarlos en uno de los tres tipos mediante métodos estáticos de la clase [https://docs.aws.amazon.com/cdk/api/v2/docs/aws-cdk-lib.Token.html](https://docs.aws.amazon.com/cdk/api/v2/docs/aws-cdk-lib.Token.html).
+ [https://docs.aws.amazon.com/cdk/api/v2/docs/aws-cdk-lib.Token.html#static-aswbrstringvalue-options](https://docs.aws.amazon.com/cdk/api/v2/docs/aws-cdk-lib.Token.html#static-aswbrstringvalue-options) para generar una codificación de cadena (o llamar a `.toString()` en el objeto token).
+ [https://docs.aws.amazon.com/cdk/api/v2/docs/aws-cdk-lib.Token.html#static-aswbrlistvalue-options](https://docs.aws.amazon.com/cdk/api/v2/docs/aws-cdk-lib.Token.html#static-aswbrlistvalue-options) para generar una codificación de lista.
+ [https://docs.aws.amazon.com/cdk/api/v2/docs/aws-cdk-lib.Token.html#static-aswbrnumbervalue](https://docs.aws.amazon.com/cdk/api/v2/docs/aws-cdk-lib.Token.html#static-aswbrnumbervalue) para generar una codificación numérica.
Estos tipos toman un valor arbitrario, que puede ser `IResolvable`, y lo codifican en un valor primitivo del tipo indicado.
**importante**
Como cualquiera de los tipos anteriores puede ser un token codificado, tenga cuidado al analizar o intentar leer su contenido. Por ejemplo, si intenta analizar una cadena para extraer un valor de ella y la cadena es un token codificado, el análisis no se realizará correctamente. Del mismo modo, si intenta consultar la longitud de una matriz o realizar operaciones matemáticas con un número, primero debe comprobar que no sean tokens codificados.
## Cómo comprobar si hay tokens en la aplicación
Para comprobar si un valor contiene un token sin resolver, debe llamar al método [https://docs.aws.amazon.com/cdk/api/v2/docs/aws-cdk-lib.Token.html#static-iswbrunresolvedobj](https://docs.aws.amazon.com/cdk/api/v2/docs/aws-cdk-lib.Token.html#static-iswbrunresolvedobj) (Python: `is_unresolved`). A continuación, se muestra un ejemplo que comprueba si el valor del nombre del bucket de Amazon S3 es un token. Si no es un token, entonces se valida la longitud del nombre del bucket:
**Example**
```
// ...
export class CdkDemoAppStack extends cdk.Stack {
constructor(scope: Construct, id: string, props?: cdk.StackProps) {
super(scope, id, props);
// Define an S3 bucket
const myBucket = new s3.Bucket(this, 'myBucket');
// ...
// Check if bucket name is a token. If not, check if length is less than 10 characters
if (cdk.Token.isUnresolved(myBucketName)) {
console.log("Token identified.");
} else if (!cdk.Token.isUnresolved(myBucketName) && myBucketName.length > 10) {
throw new Error('Maximum length for name is 10 characters.');
};
// ...
}
}
```
```
const { Stack, Duration, Token, CfnOutput } = require('aws-cdk-lib');
// ...
class CdkDemoAppStack extends Stack {
constructor(scope, id, props) {
super(scope, id, props);
// Define an S3 bucket
const myBucket = new s3.Bucket(this, 'myBucket');
// ...
// Check if bucket name is a token. If not, check if length is less than 10 characters
if (Token.isUnresolved(myBucketName)) {
console.log("Token identified.");
} else if (!Token.isUnresolved(myBucketName) && myBucketName.length > 10) {
throw new Error('Maximum length for name is 10 characters.');
};
// ...
}
}
```
```
from aws_cdk import (
Stack,
Token
)
# ...
class CdkDemoAppStack(Stack):
def __init__(self, scope: Construct, construct_id: str, **kwargs) -> None:
super().__init__(scope, construct_id, **kwargs)
# Define an S3 bucket
my_bucket = s3.Bucket(self, "myBucket")
# ...
# Check if bucket name is a token. If not, check if length is less than 10 characters
if Token.is_unresolved(my_bucket_name):
print("Token identified.")
elif not Token.is_unresolved(my_bucket_name) and len(my_bucket_name) < 10:
raise ValueError("Maximum length for name is 10 characters.")
# ...
```
```
// ...
import software.amazon.awscdk.Token;
import software.amazon.awscdk.services.s3.Bucket;
// ...
public class CdkDemoAppStack extends Stack {
public CdkDemoAppStack(final Construct scope, final String id) {
this(scope, id, null);
}
public CdkDemoAppStack(final Construct scope, final String id, final StackProps props) {
super(scope, id, props);
// Define an S3 bucket
Bucket myBucket = Bucket.Builder.create(this, "myBucket")
.build();
// ...
// Get the bucket name
String myBucketName = myBucket.getBucketName();
// Check if the bucket name is a token. If not, check if length is less than 10 characters
if (Token.isUnresolved(myBucketName)) {
System.out.println("Token identified.");
} else if (!Token.isUnresolved(myBucketName) && myBucketName.length() > 10) {
throw new IllegalArgumentException("Maximum length for name is 10 characters.");
}
// ...
}
}
}
```
```
using Amazon.CDK;
using Constructs;
using Amazon.CDK.AWS.S3;
using Amazon.CDK.AWS.Lambda;
using System;
using System.Collections.Generic;
namespace CdkDemoApp
{
public class CdkDemoAppStack : Stack
{
internal CdkDemoAppStack(Construct scope, string id, IStackProps props = null) : base(scope, id, props)
{
// Define an S3 bucket
var myBucket = new Bucket(this, "myBucket");
// ...
// Get the bucket name
var myBucketName = myBucket.BucketName;
// Check if bucket name is a token. If not, check if length is less than 10 characters
if (Token.IsUnresolved(myBucketName))
{
System.Console.WriteLine("Token identified.");
}
else if (!Token.IsUnresolved(myBucketName) && myBucketName.Length > 10)
{
throw new System.Exception("Maximum length for name is 10 characters.");
}
// ...
}
}
}
```
```
// ...
func NewCdkDemoAppStack(scope constructs.Construct, id string, props *CdkDemoAppStackProps) awscdk.Stack {
var sprops awscdk.StackProps
if props != nil {
sprops = props.StackProps
}
stack := awscdk.NewStack(scope, &id, &sprops)
// Define an S3 bucket
myBucket := awss3.NewBucket(stack, jsii.String("myBucket"), &awss3.BucketProps{})
// ...
// Check if the bucket name is unresolved (a token)
if tokenUnresolved := awscdk.Token_IsUnresolved(myBucketName); tokenUnresolved != nil && *tokenUnresolved {
fmt.Println("Token identified.")
} else if tokenUnresolved != nil && !*tokenUnresolved && len(*myBucketName) > 10 {
panic("Maximum length for name is 10 characters.")
}
// ...
}
```
Cuando ejecutamos `cdk synth`, `myBucketName` se identifica como un token:
```
$ cdk synth --quiet
Token identified.
```
**nota**
Puede utilizar codificaciones de token para escapar del sistema de tipos. Por ejemplo, puede codificar en cadena un token que produce un valor numérico en el momento de la síntesis. Si utiliza estas funciones, es su responsabilidad asegurarse de que la plantilla se resuelve a un estado utilizable después de la síntesis.
## Cómo trabajar con tokens codificados en cadena
Así se ven los tokens codificados en cadena.
```
${TOKEN[Bucket.Name.1234]}
```
Se pueden transferir como cadenas normales y se pueden concatenar, como se muestra en el siguiente ejemplo.
**Example**
```
const functionName = bucket.bucketName + 'Function';
```
```
const functionName = bucket.bucketName + 'Function';
```
```
function_name = bucket.bucket_name + "Function"
```
```
String functionName = bucket.getBucketName().concat("Function");
```
```
string functionName = bucket.BucketName + "Function";
```
```
functionName := *bucket.BucketName() + "Function"
```
Si el idioma lo admite, también puede utilizar la interpolación de cadenas como se muestra en el siguiente ejemplo.
**Example**
```
const functionName = `${bucket.bucketName}Function`;
```
```
const functionName = `${bucket.bucketName}Function`;
```
```
function_name = f"{bucket.bucket_name}Function"
```
```
String functionName = String.format("%sFunction". bucket.getBucketName());
```
```
string functionName = $"${bucket.bucketName}Function";
```
Utilice `fmt.Sprintf` para una funcionalidad similar:
```
functionName := fmt.Sprintf("%sFunction", *bucket.BucketName())
```
Evite manipular la cadena de otras formas. Por ejemplo, si se toma una subcadena, es probable que se rompa el token de la cadena.
## Cómo trabajar con tokens codificados en lista
Así se ven los tokens codificados en lista:
```
["#{TOKEN[Stack.NotificationArns.1234]}"]
```
Lo único seguro que se puede hacer con estas listas es transferirlas directamente a otros constructos. Los tokens en lista de cadenas no se pueden concatenar, así como tampoco se puede extraer ningún elemento del token. La única forma segura de manipularlos es mediante el uso de funciones intrínsecas de AWS CloudFormation como [https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/intrinsic-function-reference-select.html](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/intrinsic-function-reference-select.html).
## Cómo trabajar con tokens codificados en números
Los tokens codificados en números son un conjunto de pequeños números negativos de coma flotante con el siguiente aspecto.
```
-1.8881545897087626e+289
```
Al igual que ocurre con los tokens en lista, no se puede modificar el valor numérico, ya que es probable que se rompa el token numérico.
A continuación, se muestra un ejemplo de un constructo que contiene un token codificado como un número:
**Example**
```
import { Stack, Duration, StackProps } from 'aws-cdk-lib';
import { Construct } from 'constructs';
import * as rds from 'aws-cdk-lib/aws-rds';
import * as ec2 from 'aws-cdk-lib/aws-ec2';
export class CdkDemoAppStack extends Stack {
constructor(scope: Construct, id: string, props?: StackProps) {
super(scope, id, props);
// Define a new VPC
const vpc = new ec2.Vpc(this, 'MyVpc', {
maxAzs: 3, // Maximum number of availability zones to use
});
// Define an RDS database cluster
const dbCluster = new rds.DatabaseCluster(this, 'MyRDSCluster', {
engine: rds.DatabaseClusterEngine.AURORA,
instanceProps: {
vpc,
},
});
// Get the port token (this is a token encoded as a number)
const portToken = dbCluster.clusterEndpoint.port;
// Print the value for our token at synthesis
console.log("portToken: " + portToken);
}
}
```
```
const { Stack, Duration } = require('aws-cdk-lib');
const lambda = require('aws-cdk-lib/aws-lambda');
const rds = require('aws-cdk-lib/aws-rds');
const ec2 = require('aws-cdk-lib/aws-ec2');
class CdkDemoAppStack extends Stack {
constructor(scope, id, props) {
super(scope, id, props);
// Define a new VPC
const vpc = new ec2.Vpc(this, 'MyVpc', {
maxAzs: 3, // Maximum number of availability zones to use
});
// Define an RDS database cluster
const dbCluster = new rds.DatabaseCluster(this, 'MyRDSCluster', {
engine: rds.DatabaseClusterEngine.AURORA,
instanceProps: {
vpc,
},
});
// Get the port token (this is a token encoded as a number)
const portToken = dbCluster.clusterEndpoint.port;
// Print the value for our token at synthesis
console.log("portToken: " + portToken);
}
}
module.exports = { CdkDemoAppStack }
```
```
from aws_cdk import (
Duration,
Stack,
)
from aws_cdk import aws_rds as rds
from aws_cdk import aws_ec2 as ec2
from constructs import Construct
class CdkDemoAppStack(Stack):
def __init__(self, scope: Construct, construct_id: str, **kwargs) -> None:
super().__init__(scope, construct_id, **kwargs)
# Define a new VPC
vpc = ec2.Vpc(self, 'MyVpc',
max_azs=3 # Maximum number of availability zones to use
)
# Define an RDS database cluster
db_cluster = rds.DatabaseCluster(self, 'MyRDSCluster',
engine=rds.DatabaseClusterEngine.AURORA,
instance_props=rds.InstanceProps(
vpc=vpc
)
)
# Get the port token (this is a token encoded as a number)
port_token = db_cluster.cluster_endpoint.port
# Print the value for our token at synthesis
print(f"portToken: {port_token}")
```
```
package com.myorg;
import software.constructs.Construct;
import software.amazon.awscdk.Stack;
import software.amazon.awscdk.StackProps;
import software.amazon.awscdk.services.ec2.Vpc;
import software.amazon.awscdk.services.rds.DatabaseCluster;
import software.amazon.awscdk.services.rds.DatabaseClusterEngine;
import software.amazon.awscdk.services.rds.InstanceProps;
public class CdkDemoAppStack extends Stack {
public CdkDemoAppStack(final Construct scope, final String id) {
this(scope, id, null);
}
public CdkDemoAppStack(final Construct scope, final String id, final StackProps props) {
super(scope, id, props);
// Define a new VPC
Vpc vpc = Vpc.Builder.create(this, "MyVpc")
.maxAzs(3) // Maximum number of availability zones to use
.build();
// Define an RDS database cluster
DatabaseCluster dbCluster = DatabaseCluster.Builder.create(this, "MyRDSCluster")
.engine(DatabaseClusterEngine.AURORA)
.instanceProps(InstanceProps.builder()
.vpc(vpc)
.build())
.build();
// Get the port token (this is a token encoded as a number)
Number portToken = dbCluster.getClusterEndpoint().getPort();
// Print the value for our token at synthesis
System.out.println("portToken: " + portToken);
}
}
```
```
using Amazon.CDK;
using Constructs;
using Amazon.CDK.AWS.EC2;
using Amazon.CDK.AWS.RDS;
using System;
using System.Collections.Generic;
namespace CdkDemoApp
{
public class CdkDemoAppStack : Stack
{
internal CdkDemoAppStack(Construct scope, string id, IStackProps props = null) : base(scope, id, props)
{
// Define a new VPC
var vpc = new Vpc(this, "MyVpc", new VpcProps
{
MaxAzs = 3 // Maximum number of availability zones to use
});
// Define an RDS database cluster
var dbCluster = new DatabaseCluster(this, "MyRDSCluster", new DatabaseClusterProps
{
Engine = DatabaseClusterEngine.AURORA, // Remove parentheses
InstanceProps = new Amazon.CDK.AWS.RDS.InstanceProps // Specify RDS InstanceProps
{
Vpc = vpc
}
});
// Get the port token (this is a token encoded as a number)
var portToken = dbCluster.ClusterEndpoint.Port;
// Print the value for our token at synthesis
System.Console.WriteLine($"portToken: {portToken}");
}
}
}
```
```
package main
import (
"fmt"
"github.com/aws/aws-cdk-go/awscdk/v2"
"github.com/aws/aws-cdk-go/awscdk/v2/awsec2"
"github.com/aws/aws-cdk-go/awscdk/v2/awsrds"
"github.com/aws/constructs-go/constructs/v10"
"github.com/aws/jsii-runtime-go"
)
type CdkDemoAppStackProps struct {
awscdk.StackProps
}
func NewCdkDemoAppStack(scope constructs.Construct, id string, props *CdkDemoAppStackProps) awscdk.Stack {
var sprops awscdk.StackProps
if props != nil {
sprops = props.StackProps
}
stack := awscdk.NewStack(scope, &id, &sprops)
// Define a new VPC
vpc := awsec2.NewVpc(stack, jsii.String("MyVpc"), &awsec2.VpcProps{
MaxAzs: jsii.Number(3), // Maximum number of availability zones to use
})
// Define an RDS database cluster
dbCluster := awsrds.NewDatabaseCluster(stack, jsii.String("MyRDSCluster"), &awsrds.DatabaseClusterProps{
Engine: awsrds.DatabaseClusterEngine_AURORA(),
InstanceProps: &awsrds.InstanceProps{
Vpc: vpc,
},
})
// Get the port token (this is a token encoded as a number)
portToken := dbCluster.ClusterEndpoint().Port()
// Print the value for our token at synthesis
fmt.Println("portToken: ", portToken)
return stack
}
// ...
```
Cuando ejecutamos `cdk synth`, el valor de `portToken` se muestra como un token codificado en números:
```
$ cdk synth --quiet
portToken: -1.8881545897087968e+289
```
### Transferencia de tokens codificados en números
Al transferir tokens codificados en números a otros constructos, puede que tenga sentido convertirlos primero en cadenas. Por ejemplo, si desea utilizar el valor de una cadena codificada en números como parte de una cadena concatenada, su conversión mejora la legibilidad.
En el siguiente ejemplo, `portToken` es un token codificado en números que queremos transferir a nuestra función de Lambda como parte de `connectionString`:
**Example**
```
import { Stack, Duration, CfnOutput, StackProps } from 'aws-cdk-lib';
// ...
import * as lambda from 'aws-cdk-lib/aws-lambda';
export class CdkDemoAppStack extends Stack {
constructor(scope: Construct, id: string, props?: StackProps) {
super(scope, id, props);
// Define a new VPC
// ...
// Define an RDS database cluster
// ...
// Get the port token (this is a token encoded as a number)
const portToken = dbCluster.clusterEndpoint.port;
// ...
// Example connection string with the port token as a number
const connectionString = `jdbc:mysql://mydb.cluster.amazonaws.com:${portToken}/mydatabase`;
// Use the connection string as an environment variable in a Lambda function
const myFunction = new lambda.Function(this, 'MyLambdaFunction', {
runtime: lambda.Runtime.NODEJS_20_X,
handler: 'index.handler',
code: lambda.Code.fromInline(`
exports.handler = async function(event) {
return {
statusCode: 200,
body: JSON.stringify('Hello World!'),
};
};
`),
environment: {
DATABASE_CONNECTION_STRING: connectionString, // Using the port token as part of the string
},
});
// Output the value of our connection string at synthesis
console.log("connectionString: " + connectionString);
// Output the connection string
new CfnOutput(this, 'ConnectionString', {
value: connectionString,
});
}
}
```
```
const { Stack, Duration, CfnOutput } = require('aws-cdk-lib');
// ...
const lambda = require('aws-cdk-lib/aws-lambda');
class CdkDemoAppStack extends Stack {
constructor(scope, id, props) {
super(scope, id, props);
// Define a new VPC
// ...
// Define an RDS database cluster
// ...
// Get the port token (this is a token encoded as a number)
const portToken = dbCluster.clusterEndpoint.port;
// ...
// Example connection string with the port token as a number
const connectionString = `jdbc:mysql://mydb.cluster.amazonaws.com:${portToken}/mydatabase`;
// Use the connection string as an environment variable in a Lambda function
const myFunction = new lambda.Function(this, 'MyLambdaFunction', {
runtime: lambda.Runtime.NODEJS_20_X,
handler: 'index.handler',
code: lambda.Code.fromInline(`
exports.handler = async function(event) {
return {
statusCode: 200,
body: JSON.stringify('Hello World!'),
};
};
`),
environment: {
DATABASE_CONNECTION_STRING: connectionString, // Using the port token as part of the string
},
});
// Output the value of our connection string at synthesis
console.log("connectionString: " + connectionString);
// Output the connection string
new CfnOutput(this, 'ConnectionString', {
value: connectionString,
});
}
}
module.exports = { CdkDemoAppStack }
```
```
from aws_cdk import (
Duration,
Stack,
CfnOutput,
)
from aws_cdk import aws_lambda as _lambda
# ...
class CdkDemoAppStack(Stack):
def __init__(self, scope: Construct, construct_id: str, **kwargs) -> None:
super().__init__(scope, construct_id, **kwargs)
# Define a new VPC
# ...
# Define an RDS database cluster
# ...
# Get the port token (this is a token encoded as a number)
port_token = db_cluster.cluster_endpoint.port
# ...
# Example connection string with the port token as a number
connection_string = f"jdbc:mysql://mydb.cluster.amazonaws.com:{port_token}/mydatabase"
# Use the connection string as an environment variable in a Lambda function
my_function = _lambda.Function(self, 'MyLambdaFunction',
runtime=_lambda.Runtime.NODEJS_20_X,
handler='index.handler',
code=_lambda.Code.from_inline("""
exports.handler = async function(event) {
return {
statusCode: 200,
body: JSON.stringify('Hello World!'),
};
};
"""),
environment={
'DATABASE_CONNECTION_STRING': connection_string # Using the port token as part of the string
}
)
# Output the value of our connection string at synthesis
print(f"connectionString: {connection_string}")
# Output the connection string
CfnOutput(self, 'ConnectionString',
value=connection_string
)
```
```
// ...
import software.amazon.awscdk.CfnOutput;
import software.amazon.awscdk.services.lambda.Function;
import software.amazon.awscdk.services.lambda.Runtime;
import software.amazon.awscdk.services.lambda.Code;
import java.util.Map;
public class CdkDemoAppStack extends Stack {
public CdkDemoAppStack(final Construct scope, final String id) {
this(scope, id, null);
}
public CdkDemoAppStack(final Construct scope, final String id, final StackProps props) {
super(scope, id, props);
// Define a new VPC
// ...
// Define an RDS database cluster
// ...
// Get the port token (this is a token encoded as a number)
Number portToken = dbCluster.getClusterEndpoint().getPort();
// ...
// Example connection string with the port token as a number
String connectionString = "jdbc:mysql://mydb.cluster.amazonaws.com:" + portToken + "/mydatabase";
// Use the connection string as an environment variable in a Lambda function
Function myFunction = Function.Builder.create(this, "MyLambdaFunction")
.runtime(Runtime.NODEJS_20_X)
.handler("index.handler")
.code(Code.fromInline(
"exports.handler = async function(event) {\n" +
" return {\n" +
" statusCode: 200,\n" +
" body: JSON.stringify('Hello World!'),\n" +
" };\n" +
"};"))
.environment(Map.of(
"DATABASE_CONNECTION_STRING", connectionString // Using the port token as part of the string
))
.build();
// Output the value of our connection string at synthesis
System.out.println("connectionString: " + connectionString);
// Output the connection string
CfnOutput.Builder.create(this, "ConnectionString")
.value(connectionString)
.build();
}
}
```
```
// ...
using Amazon.CDK.AWS.Lambda;
using Amazon.CDK.AWS.RDS;
using Amazon.CDK;
using Constructs;
using System;
using System.Collections.Generic;
namespace CdkDemoApp
{
public class CdkDemoAppStack : Stack
{
internal CdkDemoAppStack(Construct scope, string id, IStackProps props = null) : base(scope, id, props)
{
// Define a new VPC
// ...
// Define an RDS database cluster
var dbCluster = new DatabaseCluster(this, "MyRDSCluster", new DatabaseClusterProps
{
// ... properties would go here
});
// Get the port token (this is a token encoded as a number)
var portToken = dbCluster.ClusterEndpoint.Port;
// ...
// Example connection string with the port token as a number
var connectionString = $"jdbc:mysql://mydb.cluster.amazonaws.com:{portToken}/mydatabase";
// Use the connection string as an environment variable in a Lambda function
var myFunction = new Function(this, "MyLambdaFunction", new FunctionProps
{
Runtime = Runtime.NODEJS_20_X,
Handler = "index.handler",
Code = Code.FromInline(@"
exports.handler = async function(event) {
return {
statusCode: 200,
body: JSON.stringify('Hello World!'),
};
};
"),
Environment = new Dictionary
{
{ "DATABASE_CONNECTION_STRING", connectionString } // Using the port token as part of the string
}
});
// Output the value of our connection string at synthesis
Console.WriteLine($"connectionString: {connectionString}");
// Output the connection string
new CfnOutput(this, "ConnectionString", new CfnOutputProps
{
Value = connectionString
});
}
}
}
```
```
// ...
"github.com/aws/aws-cdk-go/awscdk/v2/awslambda"
)
type CdkDemoAppStackProps struct {
awscdk.StackProps
}
func NewCdkDemoAppStack(scope constructs.Construct, id string, props *CdkDemoAppStackProps) awscdk.Stack {
var sprops awscdk.StackProps
if props != nil {
sprops = props.StackProps
}
stack := awscdk.NewStack(scope, &id, &sprops)
// Define a new VPC
// ...
// Define an RDS database cluster
// ...
// Get the port token (this is a token encoded as a number)
portToken := dbCluster.ClusterEndpoint().Port()
// ...
// Example connection string with the port token as a number
connectionString := fmt.Sprintf("jdbc:mysql://mydb.cluster.amazonaws.com:%s/mydatabase", portToken)
// Use the connection string as an environment variable in a Lambda function
myFunction := awslambda.NewFunction(stack, jsii.String("MyLambdaFunction"), &awslambda.FunctionProps{
Runtime: awslambda.Runtime_NODEJS_20_X(),
Handler: jsii.String("index.handler"),
Code: awslambda.Code_FromInline(jsii.String(`
exports.handler = async function(event) {
return {
statusCode: 200,
body: JSON.stringify('Hello World!'),
};
};
`)),
Environment: &map[string]*string{
"DATABASE_CONNECTION_STRING": jsii.String(connectionString), // Using the port token as part of the string
},
})
// Output the value of our connection string at synthesis
fmt.Println("connectionString: ", connectionString)
// Output the connection string
awscdk.NewCfnOutput(stack, jsii.String("ConnectionString"), &awscdk.CfnOutputProps{
Value: jsii.String(connectionString),
})
return stack
}
// ...
```
Si transferimos este valor a `connectionString`, el valor de salida al ejecutar `cdk synth` puede resultar confuso debido a la cadena codificada en números:
```
$ cdk synth --quiet
connectionString: jdbc:mysql://mydb.cluster.amazonaws.com:-1.888154589708796e+289/mydatabase
```
Para convertir un token codificado en números en una cadena, utilice [https://docs.aws.amazon.com/cdk/api/v2/docs/aws-cdk-lib.Tokenization.html#static-stringifywbrnumberx](https://docs.aws.amazon.com/cdk/api/v2/docs/aws-cdk-lib.Tokenization.html#static-stringifywbrnumberx). En el siguiente ejemplo, convertimos el token codificado en números en una cadena antes de definir nuestra cadena de conexión:
**Example**
```
import { Stack, Duration, Tokenization, CfnOutput, StackProps } from 'aws-cdk-lib';
// ...
export class CdkDemoAppStack extends Stack {
constructor(scope: Construct, id: string, props?: StackProps) {
super(scope, id, props);
// Define a new VPC
// ...
// Define an RDS database cluster
// ...
// Get the port token (this is a token encoded as a number)
const portToken = dbCluster.clusterEndpoint.port;
// ...
// Convert the encoded number to an encoded string for use in the connection string
const portAsString = Tokenization.stringifyNumber(portToken);
// Example connection string with the port token as a string
const connectionString = `jdbc:mysql://mydb.cluster.amazonaws.com:${portAsString}/mydatabase`;
// Use the connection string as an environment variable in a Lambda function
const myFunction = new lambda.Function(this, 'MyLambdaFunction', {
// ...
environment: {
DATABASE_CONNECTION_STRING: connectionString, // Using the port token as part of the string
},
});
// Output the value of our connection string at synthesis
console.log("connectionString: " + connectionString);
// Output the connection string
new CfnOutput(this, 'ConnectionString', {
value: connectionString,
});
}
}
```
```
const { Stack, Duration, Tokenization, CfnOutput } = require('aws-cdk-lib');
// ...
class CdkDemoAppStack extends Stack {
constructor(scope, id, props) {
super(scope, id, props);
// Define a new VPC
// ...
// Define an RDS database cluster
// ...
// Get the port token (this is a token encoded as a number)
const portToken = dbCluster.clusterEndpoint.port;
// ...
// Convert the encoded number to an encoded string for use in the connection string
const portAsString = Tokenization.stringifyNumber(portToken);
// Example connection string with the port token as a string
const connectionString = `jdbc:mysql://mydb.cluster.amazonaws.com:${portAsString}/mydatabase`;
// Use the connection string as an environment variable in a Lambda function
const myFunction = new lambda.Function(this, 'MyLambdaFunction', {
// ...
environment: {
DATABASE_CONNECTION_STRING: connectionString, // Using the port token as part of the string
},
});
// Output the value of our connection string at synthesis
console.log("connectionString: " + connectionString);
// Output the connection string
new CfnOutput(this, 'ConnectionString', {
value: connectionString,
});
}
}
module.exports = { CdkDemoAppStack }
```
```
from aws_cdk import (
Duration,
Stack,
Tokenization,
CfnOutput,
)
# ...
class CdkDemoAppStack(Stack):
def __init__(self, scope: Construct, construct_id: str, **kwargs) -> None:
super().__init__(scope, construct_id, **kwargs)
# Define a new VPC
# ...
# Define an RDS database cluster
# ...
# Get the port token (this is a token encoded as a number)
port_token = db_cluster.cluster_endpoint.port
# Convert the encoded number to an encoded string for use in the connection string
port_as_string = Tokenization.stringify_number(port_token)
# Example connection string with the port token as a string
connection_string = f"jdbc:mysql://mydb.cluster.amazonaws.com:{port_as_string}/mydatabase"
# Use the connection string as an environment variable in a Lambda function
my_function = _lambda.Function(self, 'MyLambdaFunction',
# ...
environment={
'DATABASE_CONNECTION_STRING': connection_string # Using the port token as part of the string
}
)
# Output the value of our connection string at synthesis
print(f"connectionString: {connection_string}")
# Output the connection string
CfnOutput(self, 'ConnectionString',
value=connection_string
)
```
```
// ...
import software.amazon.awscdk.Tokenization;
public class CdkDemoAppStack extends Stack {
public CdkDemoAppStack(final Construct scope, final String id) {
this(scope, id, null);
}
public CdkDemoAppStack(final Construct scope, final String id, final StackProps props) {
super(scope, id, props);
// Define a new VPC
// ...
// Define an RDS database cluster
// ...
// Get the port token (this is a token encoded as a number)
Number portToken = dbCluster.getClusterEndpoint().getPort();
// ...
// Convert the encoded number to an encoded string for use in the connection string
String portAsString = Tokenization.stringifyNumber(portToken);
// Example connection string with the port token as a string
String connectionString = "jdbc:mysql://mydb.cluster.amazonaws.com:" + portAsString + "/mydatabase";
// Use the connection string as an environment variable in a Lambda function
Function myFunction = Function.Builder.create(this, "MyLambdaFunction")
// ...
.environment(Map.of(
"DATABASE_CONNECTION_STRING", connectionString // Using the port token as part of the string
))
.build();
// Output the value of our connection string at synthesis
System.out.println("connectionString: " + connectionString);
// Output the connection string
CfnOutput.Builder.create(this, "ConnectionString")
.value(connectionString)
.build();
}
}
```
```
// ...
namespace CdkDemoApp
{
public class CdkDemoAppStack : Stack
{
internal CdkDemoAppStack(Construct scope, string id, IStackProps props = null) : base(scope, id, props)
{
// Define a new VPC
// ...
// Define an RDS database cluster
// ...
// Get the port token (this is a token encoded as a number)
var portToken = dbCluster.ClusterEndpoint.Port;
// ...
// Convert the encoded number to an encoded string for use in the connection string
var portAsString = Tokenization.StringifyNumber(portToken);
// Example connection string with the port token as a string
var connectionString = $"jdbc:mysql://mydb.cluster.amazonaws.com:{portAsString}/mydatabase";
// Use the connection string as an environment variable in a Lambda function
var myFunction = new Function(this, "MyLambdaFunction", new FunctionProps
{
// ...
Environment = new Dictionary
{
{ "DATABASE_CONNECTION_STRING", connectionString } // Using the port token as part of the string
}
});
// Output the value of our connection string at synthesis
Console.WriteLine($"connectionString: {connectionString}");
// Output the connection string
new CfnOutput(this, "ConnectionString", new CfnOutputProps
{
Value = connectionString
});
}
}
}
```
```
// ...
func NewCdkDemoAppStack(scope constructs.Construct, id string, props *CdkDemoAppStackProps) awscdk.Stack {
var sprops awscdk.StackProps
if props != nil {
sprops = props.StackProps
}
stack := awscdk.NewStack(scope, &id, &sprops)
// Define a new VPC
// ...
// Define an RDS database cluster
// ...
// Get the port token (this is a token encoded as a number)
portToken := dbCluster.ClusterEndpoint().Port()
// ...
// Convert the encoded number to an encoded string for use in the connection string
portAsString := awscdk.Tokenization_StringifyNumber(portToken)
// Example connection string with the port token as a string
connectionString := fmt.Sprintf("jdbc:mysql://mydb.cluster.amazonaws.com:%s/mydatabase", portAsString)
// Use the connection string as an environment variable in a Lambda function
myFunction := awslambda.NewFunction(stack, jsii.String("MyLambdaFunction"), &awslambda.FunctionProps{
// ...
Environment: &map[string]*string{
"DATABASE_CONNECTION_STRING": jsii.String(connectionString), // Using the port token as part of the string
},
})
// Output the value of our connection string at synthesis
fmt.Println("connectionString: ", connectionString)
// Output the connection string
awscdk.NewCfnOutput(stack, jsii.String("ConnectionString"), &awscdk.CfnOutputProps{
Value: jsii.String(connectionString),
})
fmt.Println(myFunction)
return stack
}
// ...
```
Cuando ejecutamos `cdk synth`, el valor de nuestra cadena de conexión se representa en un formato más limpio y claro:
```
$ cdk synth --quiet
connectionString: jdbc:mysql://mydb.cluster.amazonaws.com:${Token[TOKEN.242]}/mydatabase
```
## Valores diferidos
Además de representar los valores del tiempo de implementación, como los [parámetros](parameters.md) de AWS CloudFormation, los tokens también se utilizan habitualmente para representar los valores diferidos del tiempo de síntesis. Estos son valores para los que el valor final se determinará antes de que se complete la síntesis, pero no en el punto en el que se crea el valor. Utilice tokens para pasar una cadena literal o un valor numérico a otro constructo, mientras que el valor real en el momento de la síntesis podría depender de algún cálculo que aún no se ha producido.
Puede crear tokens que representen valores diferidos en el momento de la síntesis utilizando los métodos estáticos de la clase `Lazy`, como [https://docs.aws.amazon.com/cdk/api/v2/docs/aws-cdk-lib.Lazy.html#static-stringproducer-options](https://docs.aws.amazon.com/cdk/api/v2/docs/aws-cdk-lib.Lazy.html#static-stringproducer-options) y [https://docs.aws.amazon.com/cdk/api/v2/docs/aws-cdk-lib.Lazy.html#static-numberproducer](https://docs.aws.amazon.com/cdk/api/v2/docs/aws-cdk-lib.Lazy.html#static-numberproducer). Estos métodos aceptan un objeto cuya propiedad `produce` es una función que acepta un argumento de contexto y devuelve el valor final cuando se llama.
El siguiente ejemplo crea un grupo de escalado automático cuya capacidad se determina después de su creación.
**Example**
```
let actualValue: number;
new AutoScalingGroup(this, 'Group', {
desiredCapacity: Lazy.numberValue({
produce(context) {
return actualValue;
}
})
});
// At some later point
actualValue = 10;
```
```
let actualValue;
new AutoScalingGroup(this, 'Group', {
desiredCapacity: Lazy.numberValue({
produce(context) {
return (actualValue);
}
})
});
// At some later point
actualValue = 10;
```
```
class Producer:
def __init__(self, func):
self.produce = func
actual_value = None
AutoScalingGroup(self, "Group",
desired_capacity=Lazy.number_value(Producer(lambda context: actual_value))
)
# At some later point
actual_value = 10
```
```
double actualValue = 0;
class ProduceActualValue implements INumberProducer {
@Override
public Number produce(IResolveContext context) {
return actualValue;
}
}
AutoScalingGroup.Builder.create(this, "Group")
.desiredCapacity(Lazy.numberValue(new ProduceActualValue())).build();
// At some later point
actualValue = 10;
```
```
public class NumberProducer : INumberProducer
{
Func function;
public NumberProducer(Func function)
{
this.function = function;
}
public Double Produce(IResolveContext context)
{
return function();
}
}
double actualValue = 0;
new AutoScalingGroup(this, "Group", new AutoScalingGroupProps
{
DesiredCapacity = Lazy.NumberValue(new NumberProducer(() => actualValue))
});
// At some later point
actualValue = 10;
```
## Conversión a JSON
A veces, desea generar una cadena JSON de datos arbitrarios y es posible que no sepa si los datos contienen tokens. Para codificar correctamente en JSON cualquier estructura de datos, independientemente de si contiene o no tokens, utilice el método [https://docs.aws.amazon.com/cdk/api/v2/docs/aws-cdk-lib.Stack.html#towbrjsonwbrstringobj-space](https://docs.aws.amazon.com/cdk/api/v2/docs/aws-cdk-lib.Stack.html#towbrjsonwbrstringobj-space) como se muestra en el siguiente ejemplo.
**Example**
```
const stack = Stack.of(this);
const str = stack.toJsonString({
value: bucket.bucketName
});
```
```
const stack = Stack.of(this);
const str = stack.toJsonString({
value: bucket.bucketName
});
```
```
stack = Stack.of(self)
string = stack.to_json_string(dict(value=bucket.bucket_name))
```
```
Stack stack = Stack.of(this);
String stringVal = stack.toJsonString(java.util.Map.of( // Map.of requires Java 9+
put("value", bucket.getBucketName())));
```
```
var stack = Stack.Of(this);
var stringVal = stack.ToJsonString(new Dictionary
{
["value"] = bucket.BucketName
});
```