Chapter 122. Google Mail Stream Component

Available as of Camel version 2.22

The Google Mail component provides access to Gmail via the Google Mail Web APIs.

Google Mail uses the OAuth 2.0 protocol for authenticating a Google account and authorizing access to user data. Before you can use this component, you will need to create an account and generate OAuth credentials. Credentials comprise of a clientId, clientSecret, and a refreshToken. A handy resource for generating a long-lived refreshToken is the OAuth playground.

Maven users will need to add the following dependency to their pom.xml for this component:

    <dependency>
            <groupId>org.apache.camel</groupId>
            <artifactId>camel-google-mail</artifactId>
            <version>2.22-SNAPSHOT</version>
    </dependency>

122.1. URI Format

The GoogleMail Component uses the following URI format:

        google-mail-stream://index?[options]

122.2. GoogleMailStreamComponent

The Google Mail Stream component supports 3 options, which are listed below.

NameDescriptionDefaultType

configuration (advanced)

The configuration

 

GoogleMailStream Configuration

clientFactory (advanced)

The client Factory

 

GoogleMailClient Factory

resolveProperty Placeholders (advanced)

Whether the component should resolve property placeholders on itself when starting. Only properties which are of String type can use property placeholders.

true

boolean

The Google Mail Stream endpoint is configured using URI syntax:

google-mail-stream:index

with the following path and query parameters:

122.2.1. Path Parameters (1 parameters):

NameDescriptionDefaultType

index

Specifies an index for the endpoint

 

String

122.2.2. Query Parameters (28 parameters):

NameDescriptionDefaultType

accessToken (consumer)

OAuth 2 access token. This typically expires after an hour so refreshToken is recommended for long term usage.

 

String

applicationName (consumer)

Google mail application name. Example would be camel-google-mail/1.0

 

String

bridgeErrorHandler (consumer)

Allows for bridging the consumer to the Camel routing Error Handler, which mean any exceptions occurred while the consumer is trying to pickup incoming messages, or the likes, will now be processed as a message and handled by the routing Error Handler. By default the consumer will use the org.apache.camel.spi.ExceptionHandler to deal with exceptions, that will be logged at WARN or ERROR level and ignored.

false

boolean

clientId (consumer)

Client ID of the mail application

 

String

clientSecret (consumer)

Client secret of the mail application

 

String

labels (consumer)

Comma separated list of labels to take into account

 

String

markAsRead (consumer)

Mark the message as read once it has been consumed

false

boolean

maxResults (consumer)

Max results to be returned

10

long

query (consumer)

The query to execute on gmail box

is:unread

String

refreshToken (consumer)

OAuth 2 refresh token. Using this, the Google Calendar component can obtain a new accessToken whenever the current one expires - a necessity if the application is long-lived.

 

String

sendEmptyMessageWhenIdle (consumer)

If the polling consumer did not poll any files, you can enable this option to send an empty message (no body) instead.

false

boolean

exceptionHandler (consumer)

To let the consumer use a custom ExceptionHandler. Notice if the option bridgeErrorHandler is enabled then this option is not in use. By default the consumer will deal with exceptions, that will be logged at WARN or ERROR level and ignored.

 

ExceptionHandler

exchangePattern (consumer)

Sets the exchange pattern when the consumer creates an exchange.

 

ExchangePattern

pollStrategy (consumer)

A pluggable org.apache.camel.PollingConsumerPollingStrategy allowing you to provide your custom implementation to control error handling usually occurred during the poll operation before an Exchange have been created and being routed in Camel.

 

PollingConsumerPoll Strategy

synchronous (advanced)

Sets whether synchronous processing should be strictly used, or Camel is allowed to use asynchronous processing (if supported).

false

boolean

backoffErrorThreshold (scheduler)

The number of subsequent error polls (failed due some error) that should happen before the backoffMultipler should kick-in.

 

int

backoffIdleThreshold (scheduler)

The number of subsequent idle polls that should happen before the backoffMultipler should kick-in.

 

int

backoffMultiplier (scheduler)

To let the scheduled polling consumer backoff if there has been a number of subsequent idles/errors in a row. The multiplier is then the number of polls that will be skipped before the next actual attempt is happening again. When this option is in use then backoffIdleThreshold and/or backoffErrorThreshold must also be configured.

 

int

delay (scheduler)

Milliseconds before the next poll. You can also specify time values using units, such as 60s (60 seconds), 5m30s (5 minutes and 30 seconds), and 1h (1 hour).

500

long

greedy (scheduler)

If greedy is enabled, then the ScheduledPollConsumer will run immediately again, if the previous run polled 1 or more messages.

false

boolean

initialDelay (scheduler)

Milliseconds before the first poll starts. You can also specify time values using units, such as 60s (60 seconds), 5m30s (5 minutes and 30 seconds), and 1h (1 hour).

1000

long

runLoggingLevel (scheduler)

The consumer logs a start/complete log line when it polls. This option allows you to configure the logging level for that.

TRACE

LoggingLevel

scheduledExecutorService (scheduler)

Allows for configuring a custom/shared thread pool to use for the consumer. By default each consumer has its own single threaded thread pool.

 

ScheduledExecutor Service

scheduler (scheduler)

To use a cron scheduler from either camel-spring or camel-quartz2 component

none

ScheduledPollConsumer Scheduler

schedulerProperties (scheduler)

To configure additional properties when using a custom scheduler or any of the Quartz2, Spring based scheduler.

 

Map

startScheduler (scheduler)

Whether the scheduler should be auto started.

true

boolean

timeUnit (scheduler)

Time unit for initialDelay and delay options.

MILLISECONDS

TimeUnit

useFixedDelay (scheduler)

Controls if fixed delay or fixed rate is used. See ScheduledExecutorService in JDK for details.

true

boolean

122.3. Spring Boot Auto-Configuration

The component supports 13 options, which are listed below.

NameDescriptionDefaultType

camel.component.google-mail-stream.client-factory

The client Factory. The option is a org.apache.camel.component.google.mail.GoogleMailClientFactory type.

 

String

camel.component.google-mail-stream.configuration.access-token

OAuth 2 access token. This typically expires after an hour so refreshToken is recommended for long term usage.

 

String

camel.component.google-mail-stream.configuration.application-name

Google mail application name. Example would be camel-google-mail/1.0

 

String

camel.component.google-mail-stream.configuration.client-id

Client ID of the mail application

 

String

camel.component.google-mail-stream.configuration.client-secret

Client secret of the mail application

 

String

camel.component.google-mail-stream.configuration.index

Specifies an index for the endpoint

 

String

camel.component.google-mail-stream.configuration.labels

Comma separated list of labels to take into account

 

String

camel.component.google-mail-stream.configuration.mark-as-read

Mark the message as read once it has been consumed

false

Boolean

camel.component.google-mail-stream.configuration.max-results

Max results to be returned

10

Long

camel.component.google-mail-stream.configuration.query

The query to execute on gmail box

is:unread

String

camel.component.google-mail-stream.configuration.refresh-token

OAuth 2 refresh token. Using this, the Google Calendar component can obtain a new accessToken whenever the current one expires - a necessity if the application is long-lived.

 

String

camel.component.google-mail-stream.enabled

Whether to enable auto configuration of the google-mail-stream component. This is enabled by default.

 

Boolean

camel.component.google-mail-stream.resolve-property-placeholders

Whether the component should resolve property placeholders on itself when starting. Only properties which are of String type can use property placeholders.

true

Boolean

122.4. Consumer

The consumer will poll by default with the query "is:unread" and maxResults equals to 10.

For example

from("google-mail-stream://test?markAsRead=true&delay=5000&maxResults=5&labels=GitHub,Apache").to("mock:result");

This route will consume unread messages with labels Github and Apache and it will mark the messages as read.