INT-4308: Document JdbcMetadataStore

JIRA: https://jira.spring.io/browse/INT-4308

* Document `JdbcMetadataStore`
* Remove unnecessary context DERBY config for the `PersistentAcceptOnceFileListFilterExternalStoreTests`
* Rework the `testFileSystemWithJdbcMetadataStore()` to use `EmbeddedDatabase` directly, without context

src/reference/asciidoc/jdbc.adoc

@@ -988,3 +988,52 @@ Therefore `prefix` property must be used on the `DefaultLockRepository` bean def
 Sometimes it happens that one application has moved to the state when it can't release distributed lock - remove the particular record in the data base.
 For this purpose such dead locks can be expired by the other application on the next locking invocation.
 The `timeToLive` (TTL) option on the `DefaultLockRepository` is provided for this purpose.
+
+[[jdbc-metadata-store]]
+=== JDBC Metadata Store
+
+Starting with _version 5.0_, the JDBC `MetadataStore` (<<metadata-store>>) implementation is available.
+The `JdbcMetadataStore` can be used to maintain metadata state across application restarts.
+This `MetadataStore` implementation can be used with adapters such as:
+
+* <<twitter-inbound>>
+* <<feed-inbound-channel-adapter>>
+* <<file-reading>>
+* <<ftp-inbound>>
+* <<sftp-inbound>>
+
+In order to configure these adapters to use the `JdbcMetadataStore`, simply declare a Spring bean using the
+bean name *metadataStore*. The _Twitter Inbound Channel Adapter_ and the _Feed Inbound Channel Adapter_ will both
+automatically pick up and use the declared `JdbcMetadataStore`:
+
+[source,java]
+----
+@Bean
+public MetadataStore metadataStore(DataSource dataSource) {
+    return new JdbcMetadataStore(dataSource);
+}
+----
+
+Data base schema scripts for several RDMBS vendors are located in the `org.springframework.integration.jdbc` package.
+For example the H2 DDL for metadata table looks like:
+
+[source,sql]
+----
+CREATE TABLE INT_METADATA_STORE  (
+	METADATA_KEY VARCHAR(255) NOT NULL,
+	METADATA_VALUE VARCHAR(4000),
+	REGION VARCHAR(100) NOT NULL,
+	constraint METADATA_STORE primary key (METADATA_KEY, REGION)
+);
+----
+
+The `INT_` prefix can be changed according to the target data base design requirements and the `JdbcMetadataStore` can be configured to use the custom prefix.
+
+The `JdbcMetadataStore` implements `ConcurrentMetadataStore`, allowing it to be reliably shared across multiple
+application instances where only one instance will be allowed to store or modify a key's value.
+All of these operations are _atomic_ via transaction guarantees.
+
+Transaction management is required to use `JdbcMetadataStore`.
+Inbound Channel Adapters can be supplied with a reference to the `TransactionManager` in the poller configuration.
+Unlike non-transactional `MetadataStore` implementations, with `JdbcMetadataStore`, the entry appears in the target table only after the transaction commits.
+When a rollback occurs, no entries is added to the `INT_METADATA_STORE` table.

src/reference/asciidoc/meta-data-store.adoc

@@ -14,9 +14,10 @@ If you need to persist metadata between Application Context restarts, these pers
 the framework:
 
 * `PropertiesPersistingMetadataStore`
-* <<redis-metadata-store>>
 * <<gemfire-metadata-store>>
+* <<jdbc-metadata-store>>
 * <<mongodb-metadata-store>>
+* <<redis-metadata-store>>
 * <<zk-metadata-store>>
 
 

src/reference/asciidoc/whats-new.adoc

@@ -47,6 +47,13 @@ The `ErrorMessagePublisher` and the `ErrorMessageStrategy` are provided for crea
 
 See <<namespace-errorhandler>> for more information.
 
+==== JDBC Metadata Store
+
+A JDBC implementation of `MetadataStore` implementation is now provided.
+This is useful when it is necessary to ensure transactional boundaries for metadata.
+
+See <<jdbc-metadata-store>> for more information.
+
 [[x5.0-general]]
 === General Changes