ElSql Component
Available as of Camel 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.
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. Camel 2.16.1: 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
Option | Type | Default | Description |
|---|
resourceUri | String | null | Required 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. |
elSqlConfig | | null | To use a specific configured ElSqlConfig. It may be better to use the databaseVendor option instead. |
databaseVendor | | Default | To use a vendor specific ElSqlConfig. The possible values are: Default, Postgres, HSql, MySql, Oracle, SqlServer2008, Veritca |
batch
| boolean
| false
| Execute SQL batch update statements. See notes below on how the treatment of the inbound message body changes if this is set to true. |
dataSource
| String
| null
| Reference to a DataSource to look up in the registry. |
template.<xxx>
| | null
| Sets additional options on the Spring NamedParameterJdbcTemplate that is used behind the scenes to execute the queries. For instance, template.maxRows=10. For detailed documentation, see the NamedParameterJdbcTemplate javadoc documentation. |
consumer.delay
| long
| 500
| Delay in milliseconds between each poll. |
consumer.initialDelay
| long
| 1000
| Milliseconds before polling starts. |
consumer.useFixedDelay
| boolean
| false
| Set to true to use fixed delay between polls, otherwise fixed rate is used. See ScheduledExecutorService in JDK for details. |
maxMessagesPerPoll
| int
| 0
| An integer value to define the maximum number of messages to gather per poll. By default, no maximum is set. |
consumer.useIterator
| boolean
| true
| If true each row returned when polling will be processed individually. If false the entire java.util.List of data is set as the IN body. |
consumer.routeEmptyResultSet
| boolean
| false
| Whether to route a single empty Exchange if there was no data to poll. |
consumer.onConsume
| String
| null
| 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. |
consumer.onConsumeFailed
| String
| null
| 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. |
consumer.onConsumeBatchComplete
| String
| null
| After processing the entire batch, this query can be executed to bulk update rows etc. The query cannot have parameters. |
consumer.breakBatchOnConsumeFail
| boolean
| false
| If using consumer.onConsume and it fails, then this option controls whether to break out of the batch or continue processing the next row from the batch. |
outputType
| String
| SelectList
| 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. Tthe SelectList also supports mapping each row to a Java object as the SelectOne does (only step c). From Camel 2.18 onwards there is a new StreamList outputType that streams the result of the query using an Iterator. It can be used with the Splitter EIP in streaming mode to process the ResultSet in streaming fashion. This StreamList do not support batch mode, but you can use outputClass to map each row to a class. |
outputClass
| String
| null
| Specify the full package and class name to use as conversion when outputType=SelectOne. |
outputHeader
| String | null | To store the result as a header instead of the message body. This allows to preserve the existing message body as-is. |
noop
| boolean
| false
| 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 |
transacted | boolean | false | Camel 2.16.2: SQL consumer only:Enables or disables transaction. If enabled then if processing an exchange failed then the consumer break out processing any further exchanges to cause a rollback eager |
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:
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. This header is not provided when using outputType=StreamList. |
CamelSqlRowCount
| The number of rows returned for select operations, returned as an Integer object. This header is not provided when using outputType=StreamList. |
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/projects.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/projects.elsql")
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 StreamList
From Camel 2.18 onwards the producer supports outputType=StreamList that uses an iterator to stream the output of the query. This allows to process the data in a streaming fashion which for example can be used by the Splitter EIP to process each row one at a time, and load data from the database as needed.
from("direct:withSplitModel")
.to("elsql:allProjects:com/foo/projects.elsql?outputType=StreamList&outputClass=org.apache.camel.component.elsql.Project")
.to("log:stream")
.split(body()).streaming()
.to("log:row")
.to("mock:result")
.end();
And the elsql mapping for allProjects
@NAME(allProjects)
SELECT *
FROM projects
ORDER BY id
