ElSQL Component

Available as of Camel version 2.16

The ELSQL component is an extension to the existing SQL Component that uses ElSql to define the SQL queries.

This component uses spring-jdbc behind the scenes for the actual SQL handling.

This component can be used as a Transactional Client.

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

<dependency>
    <groupId>org.apache.camel</groupId>
    <artifactId>camel-elsql</artifactId>
    <version>x.x.x</version>
    <!-- use the same version as your Camel core version -->
</dependency>

The SQL component uses the following endpoint URI notation:

sql:elSqlName:resourceUri[?options]

You can append query options to the URI in the following format, ?option=value&option=value&…​

The parameters to the SQL queries are named parameters in the elsql mapping files, and maps to corresponding keys from the Camel message, in the given precedence:

  1. from message body if Simple expression.

  2. from message body if its a java.util.Map

  3. from message headers

If a named parameter cannot be resolved, then an exception is thrown.

Options

The ElSQL component supports 5 options, which are listed below.

Name Description Default Type

databaseVendor (common)

To use a vendor specific com.opengamma.elsql.ElSqlConfig

ElSqlDatabaseVendor

dataSource (common)

Sets the DataSource to use to communicate with the database.

DataSource

elSqlConfig (advanced)

To use a specific configured ElSqlConfig. It may be better to use the databaseVendor option instead.

ElSqlConfig

resourceUri (common)

The resource file which contains the elsql SQL statements to use. You can specify multiple resources separated by comma. The resources are loaded on the classpath by default, you can prefix with file: to load from file system. Notice you can set this option on the component and then you do not have to configure this on the endpoint.

String

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 ElSQL endpoint is configured using URI syntax:

elsql:elsqlName:resourceUri

with the following path and query parameters:

Path Parameters (2 parameters):

Name Description Default Type

elsqlName

Required The name of the elsql to use (is NAMED in the elsql file)

String

resourceUri

The resource file which contains the elsql SQL statements to use. You can specify multiple resources separated by comma. The resources are loaded on the classpath by default, you can prefix with file: to load from file system. Notice you can set this option on the component and then you do not have to configure this on the endpoint.

String

Query Parameters (47 parameters):

Name Description Default Type

allowNamedParameters (common)

Whether to allow using named parameters in the queries.

true

boolean

databaseVendor (common)

To use a vendor specific com.opengamma.elsql.ElSqlConfig

ElSqlDatabaseVendor

dataSource (common)

Sets the DataSource to use to communicate with the database.

DataSource

dataSourceRef (common)

Deprecated Sets the reference to a DataSource to lookup from the registry, to use for communicating with the database.

String

outputClass (common)

Specify the full package and class name to use as conversion when outputType=SelectOne.

String

outputHeader (common)

Store the query result in a header instead of the message body. By default, outputHeader == null and the query result is stored in the message body, any existing content in the message body is discarded. If outputHeader is set, the value is used as the name of the header to store the query result and the original message body is preserved.

String

outputType (common)

Make the output of consumer or producer to SelectList as List of Map, or SelectOne as single Java object in the following way:a) If the query has only single column, then that JDBC Column object is returned. (such as SELECT COUNT( ) FROM PROJECT will return a Long object.b) If the query has more than one column, then it will return a Map of that result.c) If the outputClass is set, then it will convert the query result into an Java bean object by calling all the setters that match the column names.It will assume your class has a default constructor to create instance with.d) If the query resulted in more than one rows, it throws an non-unique result exception.StreamList streams the result of the query using an Iterator. This can be used with the Splitter EIP in streaming mode to process the ResultSet in streaming fashion.

SelectList

SqlOutputType

separator (common)

The separator to use when parameter values is taken from message body (if the body is a String type), to be inserted at # placeholders.Notice if you use named parameters, then a Map type is used instead. The default value is comma

,

char

breakBatchOnConsumeFail (consumer)

Sets whether to break batch if onConsume failed.

false

boolean

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

expectedUpdateCount (consumer)

Sets an expected update count to validate when using onConsume.

-1

int

maxMessagesPerPoll (consumer)

Sets the maximum number of messages to poll

int

onConsume (consumer)

After processing each row then this query can be executed, if the Exchange was processed successfully, for example to mark the row as processed. The query can have parameter.

String

onConsumeBatchComplete (consumer)

After processing the entire batch, this query can be executed to bulk update rows etc. The query cannot have parameters.

String

onConsumeFailed (consumer)

After processing each row then this query can be executed, if the Exchange failed, for example to mark the row as failed. The query can have parameter.

String

routeEmptyResultSet (consumer)

Sets whether empty resultset should be allowed to be sent to the next hop. Defaults to false. So the empty resultset will be filtered out.

false

boolean

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

transacted (consumer)

Enables or disables transaction. If enabled then if processing an exchange failed then the consumerbreak out processing any further exchanges to cause a rollback eager.

false

boolean

useIterator (consumer)

Sets how resultset should be delivered to route. Indicates delivery as either a list or individual object. defaults to true.

true

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

processingStrategy (consumer)

Allows to plugin to use a custom org.apache.camel.component.sql.SqlProcessingStrategy to execute queries when the consumer has processed the rows/batch.

SqlProcessingStrategy

batch (producer)

Enables or disables batch mode

false

boolean

noop (producer)

If set, will ignore the results of the SQL query and use the existing IN message as the OUT message for the continuation of processing

false

boolean

useMessageBodyForSql (producer)

Whether to use the message body as the SQL and then headers for parameters. If this option is enabled then the SQL in the uri is not used.

false

boolean

alwaysPopulateStatement (advanced)

If enabled then the populateStatement method from org.apache.camel.component.sql.SqlPrepareStatementStrategy is always invoked, also if there is no expected parameters to be prepared. When this is false then the populateStatement is only invoked if there is 1 or more expected parameters to be set; for example this avoids reading the message body/headers for SQL queries with no parameters.

false

boolean

elSqlConfig (advanced)

To use a specific configured ElSqlConfig. It may be better to use the databaseVendor option instead.

ElSqlConfig

parametersCount (advanced)

If set greater than zero, then Camel will use this count value of parameters to replace instead of querying via JDBC metadata API. This is useful if the JDBC vendor could not return correct parameters count, then user may override instead.

int

placeholder (advanced)

Specifies a character that will be replaced to in SQL query. Notice, that it is simple String.replaceAll() operation and no SQL parsing is involved (quoted strings will also change).

#

String

prepareStatementStrategy (advanced)

Allows to plugin to use a custom org.apache.camel.component.sql.SqlPrepareStatementStrategy to control preparation of the query and prepared statement.

SqlPrepareStatement Strategy

synchronous (advanced)

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

false

boolean

templateOptions (advanced)

Configures the Spring JdbcTemplate with the key/values from the Map

Map

usePlaceholder (advanced)

Sets whether to use placeholder and replace all placeholder characters with sign in the SQL queries.

true

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

Spring Boot Auto-Configuration

When using Spring Boot make sure to use the following Maven dependency to have support for auto configuration:

<dependency>
  <groupId>org.apache.camel</groupId>
  <artifactId>camel-elsql-starter</artifactId>
  <version>x.x.x</version>
  <!-- use the same version as your Camel core version -->
</dependency>

The component supports 6 options, which are listed below.

Name Description Default Type

camel.component.elsql.data-source

Sets the DataSource to use to communicate with the database. The option is a javax.sql.DataSource type.

String

camel.component.elsql.database-vendor

To use a vendor specific com.opengamma.elsql.ElSqlConfig

ElSqlDatabaseVendor

camel.component.elsql.el-sql-config

To use a specific configured ElSqlConfig. It may be better to use the databaseVendor option instead. The option is a com.opengamma.elsql.ElSqlConfig type.

String

camel.component.elsql.enabled

Enable elsql component

true

Boolean

camel.component.elsql.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

camel.component.elsql.resource-uri

The resource file which contains the elsql SQL statements to use. You can specify multiple resources separated by comma. The resources are loaded on the classpath by default, you can prefix with file: to load from file system. Notice you can set this option on the component and then you do not have to configure this on the endpoint.

String

Result of the query

For select operations, the result is an instance of List<Map<String, Object>> type, as returned by the JdbcTemplate.queryForList() method. For update operations, the result is the number of updated rows, returned as an Integer.

By default, the result is placed in the message body. If the outputHeader parameter is set, the result is placed in the header. This is an alternative to using a full message enrichment pattern to add headers, it provides a concise syntax for querying a sequence or some other small value into a header. It is convenient to use outputHeader and outputType together:

Header values

When performing update operations, the SQL Component stores the update count in the following message headers:

Header Description

CamelSqlUpdateCount

The number of rows updated for update operations, returned as an Integer object.

CamelSqlRowCount

The number of rows returned for select operations, returned as an Integer object.

Sample

In the given route below, we want to get all the projects from the projects table. Notice the SQL query has 2 named parameters, :#lic and :#min.

Camel will then lookup for these parameters from the message body or message headers. Notice in the example above we set two headers with constant value

for the named parameters:
   from("direct:projects")
     .setHeader("lic", constant("ASF"))
     .setHeader("min", constant(123))
     .to("elsql:projects:com/foo/orders.elsql")

And the elsql mapping file

@NAME(projects)
  SELECT *
  FROM projects
  WHERE license = :lic AND id > :min
  ORDER BY id

Though if the message body is a java.util.Map then the named parameters will be taken from the body.

   from("direct:projects")
     .to("elsql:projects:com/foo/orders.elsql")

Using expression parameters in producers

In from Camel 2.16.1 onwards you can use Simple expressions as well, which allows to use an OGNL like notation on the message body, where it assumes to have getLicense and getMinimum methods:

@NAME(projects)
  SELECT *
  FROM projects
  WHERE license = :${body.license} AND id > :${body.minimum}
  ORDER BY id

Using expression parameters in consumers

Available as of Camel 2.23

When using the ElSql component as consumer, you can now also use expression parameters (simple language) to build dynamic query parameters, such as calling a method on a bean to retrieve an id, date or something.

For example in the sample below we call the nextId method on the bean myIdGenerator:

@NAME(projectsByIdBean)
  SELECT *
  FROM projects
  WHERE id = :${bean#myIdGenerator.nextId}
Notice in the bean syntax above, we must use # instead of : in the simple expression. This is because Spring query parameter parser is in-use which will separate parameters on colon. Also pay attention that Spring query parser will invoke the bean twice for each query.

And the bean has the following method:

public static class MyIdGenerator {

    private int id = 1;

    public int nextId() {
        // spring will call this twice, one for initializing query and 2nd for actual value
        id++;
        return id / 2;
    }

Notice that there is no existing Exchange with message body and headers, so the simple expression you can use in the consumer are most useable for calling bean methods as in this example.