# R2DBC Support
## R2DBC Support
Spring Integration provides channel adapters for receiving and sending messages by using reactive access to databases via [R2DBC](https://r2dbc.io/) drivers.
You need to include this dependency into your project:
Maven
```
org.springframework.integration
spring-integration-r2dbc
5.5.9
```
Gradle
```
compile "org.springframework.integration:spring-integration-r2dbc:5.5.9"
```
### R2DBC Inbound Channel Adapter
The `R2dbcMessageSource` is a pollable `MessageSource` implementation based on the `R2dbcEntityOperations` and produces messages with a `Flux` or `Mono` as a payload for data fetched from database according an `expectSingleResult` option.
The query to `SELECT` can be statically provided or based on a SpEL expression which is evaluated on every `receive()` call.
The `R2dbcMessageSource.SelectCreator` is present as a root object for evaluation context to allow to use a `StatementMapper.SelectSpec` fluent API.
By default this channel adapter maps records from the select into a `LinkedCaseInsensitiveMap` instances.
It can be customized providing a `payloadType` options which is used underneath by the `EntityRowMapper` based on the `this.r2dbcEntityOperations.getConverter()`.
The `updateSql` is optional and used to mark read records in the databased for skipping from the subsequent polls.
The `UPDATE` operation can be supplied with a `BiFunction` to bind values into an `UPDATE` based on records in the `SELECT` result.
A typical configuration for this channel adapter might look like this:
```
@Bean
@InboundChannelAdapter("fromR2dbcChannel")
public R2dbcMessageSource r2dbcMessageSourceSelectMany() {
R2dbcMessageSource r2dbcMessageSource = new R2dbcMessageSource(this.r2dbcEntityTemplate,
"SELECT * FROM person WHERE name='Name'");
r2dbcMessageSource.setPayloadType(Person.class);
r2dbcMessageSource.setUpdateSql("UPDATE Person SET name='SomeOtherName' WHERE id = :id");
r2dbcMessageSource.setBindFunction(
(DatabaseClient.GenericExecuteSpec bindSpec, Person o) -> bindSpec.bind("id", o.getId()));}
return r2dbcMessageSource;
}
```
With Java DSL a configuration for this channel adapter is like this:
```
@Bean
IntegrationFlow r2dbcDslFlow(R2dbcEntityTemplate r2dbcEntityTemplate) {
return IntegrationFlows
.from(R2dbc.inboundChannelAdapter(r2dbcEntityTemplate,
(selectCreator) ->
selectCreator.createSelect("person")
.withProjection("*")
.withCriteria(Criteria.where("id").is(1)))
.expectSingleResult(true)
.payloadType(Person.class)
.updateSql("UPDATE Person SET id='2' where id = :id")
.bindFunction((DatabaseClient.GenericExecuteSpec bindSpec, Person o) ->
bindSpec.bind("id", o.getId())),
e -> e.poller(p -> p.fixedDelay(100)))
.>handle((p, h) -> p, e -> e.async(true))
.channel(MessageChannels.flux())
.get();
}
```
### R2DBC Outbound Channel Adapter
The `R2dbcMessageHandler` is a `ReactiveMessageHandler` implementation to perform an `INSERT` (default), `UPDATE` or `DELETE` query in database using a provided `R2dbcEntityOperations`.
The `R2dbcMessageHandler.Type` can be configured statically or via a SpEL expression against request message.
The query to execute can be based on the `tableName`, `values` and `criteria` expression options or (if `tableName` is not provided) the whole message payload is treated as an `org.springframework.data.relational.core.mapping.Table` entity to perform SQL against.
The package `org.springframework.data.relational.core.query` is registered as an import into a SpEL evaluation context for direct access to the `Criteria` fluent API which is used for `UPDATE` and `DELETE` queries.
The `valuesExpression` is used in the `INSERT` and `UPDATE` and must be evaluated to the `Map` for column-value pairs to perform a change in the target table against request message.
A typical configuration for this channel adapter might look like this:
```
@Bean
@ServiceActivator(inputChannel = "toR2dbcChannel")
public R2dbcMessageHandler r2dbcMessageHandler(R2dbcEntityTemplate r2dbcEntityTemplate) {
R2dbcMessageHandler messageHandler = new R2dbcMessageHandler(r2dbcEntityTemplate)
messageHandler.setValuesExpression(new FunctionExpression>(Message::getPayload));
messageHandler.setQueryType(R2dbcMessageHandler.Type.UPDATE);
messageHandler.setCriteriaExpression(
EXPRESSION_PARSER.parseExpression("T(Criteria).where('id).is(headers.personId)));
return messageHandler;
}
```
With Java DSL a configuration for this channel adapter is like this:
```
.handle(R2dbc.outboundChannelAdapter(r2dbcEntityTemplate)
.queryType(R2dbcMessageHandler.Type.UPDATE)
.tableNameExpression("payload.class.simpleName")
.criteria((message) -> Criteria.where("id").is(message.getHeaders().get("personId")))
.values("{age:36}"))
```