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Chapter 235. MyBatis Component

Available as of Camel version 2.7

The mybatis: component allows you to query, poll, insert, update and delete data in a relational database using MyBatis.

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

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

235.1. URI format

mybatis:statementName[?options]

Where statementName is the statement name in the MyBatis XML mapping file which maps to the query, insert, update or delete operation you wish to evaluate.

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

This component will by default load the MyBatis SqlMapConfig file from the root of the classpath with the expected name of SqlMapConfig.xml.
If the file is located in another location, you will need to configure the configurationUri option on the MyBatisComponent component.

235.2. Options

The MyBatis component supports 3 options, which are listed below.

NameDescriptionDefaultType

sqlSessionFactory (advanced)

To use the SqlSessionFactory

 

SqlSessionFactory

configurationUri (common)

Location of MyBatis xml configuration file. The default value is: SqlMapConfig.xml loaded from the classpath

SqlMapConfig.xml

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 MyBatis endpoint is configured using URI syntax: 

mybatis:statement

with the following path and query parameters:

235.2.1. Path Parameters (1 parameters):

NameDescriptionDefaultType

statement

Required The statement name in the MyBatis XML mapping file which maps to the query, insert, update or delete operation you wish to evaluate.

 

String

235.2.2. Query Parameters (29 parameters):

NameDescriptionDefaultType

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

maxMessagesPerPoll (consumer)

This option is intended to split results returned by the database pool into the batches and deliver them in multiple exchanges. This integer defines the maximum messages to deliver in single exchange. By default, no maximum is set. Can be used to set a limit of e.g. 1000 to avoid when starting up the server that there are thousands of files. Set a value of 0 or negative to disable it.

0

int

onConsume (consumer)

Statement to run after data has been processed in the route

 

String

routeEmptyResultSet (consumer)

Whether allow empty resultset to be routed to the next hop

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 consumer break out processing any further exchanges to cause a rollback eager

false

boolean

useIterator (consumer)

Process resultset individually or as a list

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)

To use a custom MyBatisProcessingStrategy

 

MyBatisProcessing Strategy

executorType (producer)

The executor type to be used while executing statements. simple - executor does nothing special. reuse - executor reuses prepared statements. batch - executor reuses statements and batches updates.

SIMPLE

ExecutorType

inputHeader (producer)

User the header value for input parameters instead of the message body. By default, inputHeader == null and the input parameters are taken from the message body. If outputHeader is set, the value is used and query parameters will be taken from the header instead of the body.

 

String

outputHeader (producer)

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. Setting outputHeader will also omit populating the default CamelMyBatisResult header since it would be the same as outputHeader all the time.

 

String

statementType (producer)

Mandatory to specify for the producer to control which kind of operation to invoke.

 

StatementType

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

235.3. Spring Boot Auto-Configuration

The component supports 4 options, which are listed below.

NameDescriptionDefaultType

camel.component.mybatis.configuration-uri

Location of MyBatis xml configuration file. The default value is: SqlMapConfig.xml loaded from the classpath

SqlMapConfig.xml

String

camel.component.mybatis.enabled

Enable mybatis component

true

Boolean

camel.component.mybatis.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.mybatis.sql-session-factory

To use the SqlSessionFactory. The option is a org.apache.ibatis.session.SqlSessionFactory type.

 

String

235.4. Message Headers

Camel will populate the result message, either IN or OUT with a header with the statement used:

HeaderTypeDescription

CamelMyBatisStatementName

String

The statementName used (for example: insertAccount).

CamelMyBatisResult

Object

The response returned from MtBatis in any of the operations. For instance an INSERT could return the auto-generated key, or number of rows etc.

235.5. Message Body

The response from MyBatis will only be set as the body if it’s a SELECT statement. That means, for example, for INSERT statements Camel will not replace the body. This allows you to continue routing and keep the original body. The response from MyBatis is always stored in the header with the key CamelMyBatisResult.

235.6. Samples

For example if you wish to consume beans from a JMS queue and insert them into a database you could do the following: 

from("activemq:queue:newAccount")
  .to("mybatis:insertAccount?statementType=Insert");

Notice we have to specify the statementType, as we need to instruct Camel which kind of operation to invoke.

Where insertAccount is the MyBatis ID in the SQL mapping file: 

  <!-- Insert example, using the Account parameter class -->
  <insert id="insertAccount" parameterType="Account">
    insert into ACCOUNT (
      ACC_ID,
      ACC_FIRST_NAME,
      ACC_LAST_NAME,
      ACC_EMAIL
    )
    values (
      #{id}, #{firstName}, #{lastName}, #{emailAddress}
    )
  </insert>

235.7. Using StatementType for better control of MyBatis

When routing to an MyBatis endpoint you will want more fine grained control so you can control whether the SQL statement to be executed is a SELECT, UPDATE, DELETE or INSERT etc. So for instance if we want to route to an MyBatis endpoint in which the IN body contains parameters to a SELECT statement we can do:

In the code above we can invoke the MyBatis statement selectAccountById and the IN body should contain the account id we want to retrieve, such as an Integer type.

We can do the same for some of the other operations, such as SelectList:

And the same for UPDATE, where we can send an Account object as the IN body to MyBatis:

235.7.1. Using InsertList StatementType

Available as of Camel 2.10

MyBatis allows you to insert multiple rows using its for-each batch driver. To use this, you need to use the <foreach> in the mapper XML file. For example as shown below:

Then you can insert multiple rows, by sending a Camel message to the mybatis endpoint which uses the InsertList statement type, as shown below:

235.7.2. Using UpdateList StatementType

Available as of Camel 2.11

MyBatis allows you to update multiple rows using its for-each batch driver. To use this, you need to use the <foreach> in the mapper XML file. For example as shown below: 

<update id="batchUpdateAccount" parameterType="java.util.Map">
    update ACCOUNT set
    ACC_EMAIL = #{emailAddress}
    where
    ACC_ID in
    <foreach item="Account" collection="list" open="(" close=")" separator=",">
        #{Account.id}
    </foreach>
</update>

Then you can update multiple rows, by sending a Camel message to the mybatis endpoint which uses the UpdateList statement type, as shown below: 

from("direct:start")
    .to("mybatis:batchUpdateAccount?statementType=UpdateList")
    .to("mock:result");

235.7.3. Using DeleteList StatementType

Available as of Camel 2.11

MyBatis allows you to delete multiple rows using its for-each batch driver. To use this, you need to use the <foreach> in the mapper XML file. For example as shown below: 

<delete id="batchDeleteAccountById" parameterType="java.util.List">
    delete from ACCOUNT
    where
    ACC_ID in
    <foreach item="AccountID" collection="list" open="(" close=")" separator=",">
        #{AccountID}
    </foreach>
</delete>

Then you can delete multiple rows, by sending a Camel message to the mybatis endpoint which uses the DeleteList statement type, as shown below: 

from("direct:start")
    .to("mybatis:batchDeleteAccount?statementType=DeleteList")
    .to("mock:result");

235.7.4. Notice on InsertList, UpdateList and DeleteList StatementTypes

Parameter of any type (List, Map, etc.) can be passed to mybatis and an end user is responsible for handling it as required
with the help of mybatis dynamic queries capabilities.

235.7.5. Scheduled polling example

This component supports scheduled polling and can therefore be used as a Polling Consumer. For example to poll the database every minute: 

from("mybatis:selectAllAccounts?delay=60000")
  .to("activemq:queue:allAccounts");

See "ScheduledPollConsumer Options" on Polling Consumer for more options.

Alternatively you can use another mechanism for triggering the scheduled polls, such as the Timer or Quartz components. In the sample below we poll the database, every 30 seconds using the Timer component and send the data to the JMS queue: 

from("timer://pollTheDatabase?delay=30000")
  .to("mybatis:selectAllAccounts")
  .to("activemq:queue:allAccounts");

And the MyBatis SQL mapping file used: 

  <!-- Select with no parameters using the result map for Account class. -->
  <select id="selectAllAccounts" resultMap="AccountResult">
    select * from ACCOUNT
  </select>

235.7.6. Using onConsume

This component supports executing statements after data have been consumed and processed by Camel. This allows you to do post updates in the database. Notice all statements must be UPDATE statements. Camel supports executing multiple statements whose names should be separated by commas.

The route below illustrates we execute the consumeAccount statement data is processed. This allows us to change the status of the row in the database to processed, so we avoid consuming it twice or more.

And the statements in the sqlmap file:

235.7.7. Participating in transactions

Setting up a transaction manager under camel-mybatis can be a little bit fiddly, as it involves externalising the database configuration outside the standard MyBatis SqlMapConfig.xml file.

The first part requires the setup of a DataSource. This is typically a pool (either DBCP, or c3p0), which needs to be wrapped in a Spring proxy. This proxy enables non-Spring use of the DataSource to participate in Spring transactions (the MyBatis SqlSessionFactory does just this). 

<bean id="dataSource" class="org.springframework.jdbc.datasource.TransactionAwareDataSourceProxy">
    <constructor-arg>
        <bean class="com.mchange.v2.c3p0.ComboPooledDataSource">
            <property name="driverClass" value="org.postgresql.Driver"/>
            <property name="jdbcUrl" value="jdbc:postgresql://localhost:5432/myDatabase"/>
            <property name="user" value="myUser"/>
            <property name="password" value="myPassword"/>
        </bean>
    </constructor-arg>
</bean>

This has the additional benefit of enabling the database configuration to be externalised using property placeholders.

A transaction manager is then configured to manage the outermost DataSource: 

<bean id="txManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
    <property name="dataSource" ref="dataSource"/>
</bean>

A mybatis-springSqlSessionFactoryBean then wraps that same DataSource: 

<bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
    <property name="dataSource" ref="dataSource"/>
    <!-- standard mybatis config file -->
<property name="configLocation" value="/META-INF/SqlMapConfig.xml"/>
    <!-- externalised mappers -->
<property name="mapperLocations" value="classpath*:META-INF/mappers/**/*.xml"/>
</bean>

The camel-mybatis component is then configured with that factory: 

<bean id="mybatis" class="org.apache.camel.component.mybatis.MyBatisComponent">
    <property name="sqlSessionFactory" ref="sqlSessionFactory"/>
</bean>

Finally, a transaction policy is defined over the top of the transaction manager, which can then be used as usual: 

<bean id="PROPAGATION_REQUIRED" class="org.apache.camel.spring.spi.SpringTransactionPolicy">
    <property name="transactionManager" ref="txManager"/>
    <property name="propagationBehaviorName" value="PROPAGATION_REQUIRED"/>
</bean>

<camelContext id="my-model-context" xmlns="http://camel.apache.org/schema/spring">
    <route id="insertModel">
        <from uri="direct:insert"/>
        <transacted ref="PROPAGATION_REQUIRED"/>
        <to uri="mybatis:myModel.insert?statementType=Insert"/>
    </route>
</camelContext>
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