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About Oracle R2DBC

The Oracle R2DBC Driver is a Java library that supports reactive programming with Oracle Database.

Oracle R2DBC implements the R2DBC Service Provider Interface (SPI) as specified by the Reactive Relational Database Connectivity (R2DBC) project. The R2DBC SPI exposes Reactive Streams as an abstraction for remote database operations. Reactive Streams is a well defined standard for asynchronous, non-blocking, and back-pressured communication. This standard allows an R2DBC driver to interoperate with other reactive libraries and frameworks, such as Spring, Project Reactor, RxJava, and Akka Streams.

Learn More About R2DBC:

R2DBC Project Home Page

R2DBC Javadocs v1.0.0.RELEASE

R2DBC Specification v1.0.0.RELEASE

Learn More About Reactive Streams:

Reactive Streams Project Home Page

Reactive Streams Javadocs v1.0.3

Reactive Streams Specification v1.0.3

About This Version

The 1.0.0 release Oracle R2DBC implements version 1.0.0.RELEASE of the R2DBC SPI.

Changes in this release:

  • Added support for long valued update counts
  • New OracleR2dbcOptions constants for V$SESSION tracing

Integration with Spring and Other Libraries

Oracle R2DBC can interoperate with other libraries that support the 1.0.0.RELEASE version of the R2DBC SPI. When using libraries like Spring and r2dbc-pool, be sure to use a version which supports the 1.0.0.RELEASE of the SPI.

Oracle R2DBC depends on the JDK 11 build of Oracle JDBC 21.5.0.0. Other libraries may depend on a different version of Oracle JDBC which is incompatible. To resolve this incompatibility, it may be necessary to explicitly declare the dependency in your project, ie:

<dependency>
    <groupId>com.oracle.database.jdbc</groupId>
    <artifactId>ojdbc11</artifactId>
    <version>21.5.0.0</version>
</dependency>

Installation

Oracle R2DBC can be obtained from Maven Central.

<dependency>
  <groupId>com.oracle.database.r2dbc</groupId>
  <artifactId>oracle-r2dbc</artifactId>
  <version>1.0.0</version>
</dependency>

Oracle R2DBC can also be built from source using Maven: mvn clean install -DskipTests=true

If -DskipTests=true is omitted from the command above, then it will execute end-to-end tests which connect to an Oracle Database. Tests read the connection configuration from src/test/resources/config.properties.

Oracle R2DBC is compatible with JDK 11 (or newer), and has the following runtime dependencies:

  • R2DBC SPI 1.0.0.RELEASE
  • Reactive Streams 1.0.3
  • Project Reactor 3.4.18
  • Oracle JDBC 21.5.0.0 for JDK 11 (ojdbc11.jar)

The Oracle R2DBC Driver has been verified with Oracle Database versions 18, 19, and 21.

Code Examples

The following method returns an Oracle R2DBC ConnectionFactory

  static ConnectionFactory getConnectionFactory() {
    String user = getUser();
    char[] password = getPassword();
    try {
      return ConnectionFactories.get(
        ConnectionFactoryOptions.builder()
          .option(ConnectionFactoryOptions.DRIVER, "oracle")
          .option(ConnectionFactoryOptions.HOST, "db.host.example.com")
          .option(ConnectionFactoryOptions.PORT, 1521)
          .option(ConnectionFactoryOptions.DATABASE, "db.service.name")
          .option(ConnectionFactoryOptions.USER, user)
          .option(ConnectionFactoryOptions.PASSWORD, CharBuffer.wrap(password))
          .build());
    }
    finally {
      Arrays.fill(password, (char)0);
    }
  }

The following method uses Project Reactor's Flux to open a connection, execute a SQL query, and then close the connection:

Flux.usingWhen(
  getConnectionFactory().create(),
  connection ->
    Flux.from(connection.createStatement(
      "SELECT 'Hello, Oracle' FROM sys.dual")
      .execute())
      .flatMap(result ->
        result.map(row -> row.get(0, String.class))),
  Connection::close)
  .doOnNext(System.out::println)
  .doOnError(Throwable::printStackTrace)
  .subscribe();

When executed, the code above will asynchronously print the result of the SQL query.

The next example uses a named parameter marker, :locale_name, in the SQL command:

Flux.usingWhen(
  getConnectionFactory().create(),
  connection ->
    Flux.from(connection.createStatement(
      "SELECT greeting FROM locale WHERE locale_name = :locale_name")
      .bind("locale_name", "France")
      .execute())
      .flatMap(result ->
        result.map(row ->
          String.format("%s, Oracle", row.get("greeting", String.class)))),
  Connection::close)
  .doOnNext(System.out::println)
  .doOnError(Throwable::printStackTrace)
  .subscribe();

Like the previous example, executing the code above will asynchronously print a greeting message. "France" is set as the bind value for locale_name, so the query should return a greeting like "Bonjour" when row.get("greeting") is called.

Additional code examples can be found here.

Help

For help programming with Oracle R2DBC, ask questions on Stack Overflow tagged with [oracle] and [r2dbc]. The development team monitors Stack Overflow regularly.

Issues may be opened as described in our contribution guide.

Contributing

This project welcomes contributions from the community. Before submitting a pull request, please review our contribution guide.

Security

Please consult the security guide for our responsible security vulnerability disclosure process.

License

Copyright (c) 2021 Oracle and/or its affiliates.

This software is dual-licensed to you under the Universal Permissive License (UPL) 1.0 as shown at https://oss.oracle.com/licenses/upl or Apache License 2.0 as shown at http://www.apache.org/licenses/LICENSE-2.0. You may choose either license.

Documentation

This document specifies the behavior of the R2DBC SPI as implemented for the Oracle Database. This SPI implementation is referred to as the "Oracle R2DBC Driver" or "Oracle R2DBC" throughout the remainder of this document.

The Oracle R2DBC Driver implements behavior specified by the R2DBC 1.0.0.RELEASE Specification and Javadoc

Publisher objects created by Oracle R2DBC implement behavior specified by the Reactive Streams 1.0.3 Specification and Javadoc

The R2DBC and Reactive Streams specifications include requirements that are optional for a compliant implementation. The remainder of this document specifies the Oracle R2DBC Driver's implementation of these optional requirements.

Connection Creation

The Oracle R2DBC Driver is identified by the name "oracle". The driver implements a ConnectionFactoryProvider located by an R2DBC URL identifing "oracle" as a driver, or by a DRIVER ConnectionFactoryOption with the value of "oracle".

Support for Standard R2DBC Options

The following standard ConnectionFactoryOptions are supported by Oracle R2DBC:

  • DRIVER
  • HOST
  • PORT
  • DATABASE
  • USER
  • PASSWORD
  • SSL
  • CONNECT_TIMEOUT
  • STATEMENT_TIMEOUT.

Oracle R2DBC interprets the DATABASE option as the service name of an Oracle Database instance. System Identifiers (SID) are not recognized.

Support for Extended R2DBC Options

Oracle R2DBC extends the standard set of R2DBC options to offer functionality that is specific to Oracle Database and the Oracle JDBC Driver. Extended options are declared in the OracleR2dbcOptions class.

Configuring an Oracle Net Descriptor

The oracle.r2dbc.OracleR2dbcOptions.DESCRIPTOR option may be used to configure an Oracle Net Descriptor of the form (DESCRIPTION=...). If this option is used to configure a descriptor, then it is invalid to specify any other option that conflicts with information in the descriptor. Conflicting options include HOST, PORT, DATABASE, and SSL. These options all conflict with information that appears in a descriptor.

The DESCRIPTOR option has the name oracle.r2dbc.descriptor. This name can be used to configure a descriptor in the query section of an R2DBC URL:

r2dbc:oracle://?oracle.r2dbc.descriptor=(DESCRIPTION=...)

The DESCRIPTOR constant may also be used to configure a descriptor programmatically:

ConnectionFactoryOptions.builder()
  .option(OracleR2dbcOptions.DESCRIPTOR, "(DESCRIPTION=...)")

The DESCRIPTOR option may be set to an aliased entry of a tnsnames.ora file. Use the TNS_ADMIN option to specify the directory where tnsnames.ora is located:

r2dbc:oracle://?oracle.r2dbc.descriptor=myAlias&TNS_ADMIN=/path/to/tnsnames/

Configuring a java.util.concurrent.Executor

The oracle.r2dbc.OracleR2dbcOptions.EXECUTOR option configures a java.util.concurrent.Executor for executing asynchronous callbacks. The EXECUTOR option may be used to configure an Executor programmatically:

ConnectionFactoryOptions.builder()
  .option(OracleR2dbcOptions.EXECUTOR, getExecutor())

There is no way to configure an executor with a URL query parameter

If this option is not configured, then the common java.util.concurrent.ForkJoinPool is used as a default.

Configuring Oracle JDBC Connection Properties

A subset of Oracle JDBC's connection properties are also supported by Oracle R2DBC. These connection properties may be configured as options having the same name as the Oracle JDBC connection property, and may have CharSequence value types.

For example, the following URL configures the oracle.net.wallet_location connection property:

r2dbcs:oracle://db.host.example.com:1522/db.service.name?oracle.net.wallet_location=/path/to/wallet/

The same property can also be configured programmatically:

 ConnectionFactoryOptions.builder()
  .option(OracleR2dbcOptions.TLS_WALLET_LOCATION, "/path/to/wallet")

The following is a list of all Oracle JDBC connection properties that are supported by Oracle R2DBC:

Thread Safety and Parallel Execution

Oracle R2DBC's ConnectionFactory and ConnectionFactoryProvider are the only classes that have a thread safe implementation. All other classes implemented by Oracle R2DBC are not thread safe. For instance, it is not safe for multiple threads to concurrently access a single instance of Result.

It is recommended to use a Reactive Streams library such as Project Reactor or RxJava to manage the consumption of non-thread safe objects

Oracle Database does not allow multiple database calls to execute in parallel over a single Connection. If an attempt is made to execute a database call before a previous call has completed, then Oracle R2DBC will enqueue that call and only execute it after the previous call has completed.

To illustrate, the following code attempts to execute two statements in parallel:

Flux.merge(
  connection.createStatement(
    "INSERT INTO example (id, value) VALUES (0, 'x')")
    .execute(),
  connection.createStatement(
    "INSERT INTO example (id, value) VALUES (1, 'y')")
    .execute())

When the publisher of the second statement is subscribed to, Oracle R2DBC will enqueue a task for sending that statement to the database. The enqueued task will only be executed after the publisher of the first statement has completed.

Reactive Streams

Every method implemented by Oracle R2DBC that returns a Publisher has a JavaDoc which specifies the Publisher's behavior with regard to deferred execution and support for multiple Subscribers.

Oracle R2DBC's implementation of Publishers that emit one or zero items will typically defer execution until a Subscriber subscribes, support multiple Subscribers, and cache the result of a database call (the same result of the same call is emitted to each Subscriber).

Oracle R2DBC's implementation of Publishers that emit multiple items will typically defer execution until a Subscriber signals demand, and not support multiple subscribers.

Errors

Oracle R2DBC creates R2dbcExceptions having the same ORA-XXXXX error codes used by Oracle Database and Oracle JDBC.

A reference for the ORA-XXXXX error codes can be found here

Transactions

Oracle R2DBC uses READ COMMITTED as the default transaction isolation level.

Oracle R2DBC also supports the SERIALIZABLE isolation level. If SERIALIZABLE isolation is configured, then the oracle.r2dbc.OracleR2dbcOptions.ENABLE_QUERY_RESULT_CACHE option must also be configured as false to avoid phantom reads.

READ COMMITTED and SERIALIZABLE are the only isolation levels supported by Oracle Database

Oracle Database does not support a lock wait timeout that is configurable within the scope of a transaction or session. Oracle R2DBC implements SPI methods that configure a lock wait timeout to throw UnsupportedOperationException.

Statements

Oracle R2DBC supports SQL execution with the Statement SPI.

Parameter Markers

A SQL command passed to Connection.createStatement(String) may include named parameter markers, unnamed parameter markers, or both.

Unnamed parameter markers may appear in SQL as a question mark (?):

connection.createStatement(
  "SELECT value FROM example WHERE id=?")
  .bind(0, 99)

The bind method must be called with a zero-based index to set the value of an unnamed parameter.

Named parameter markers may appear in SQL as a colon character (:) followed by an alpha-numeric name:

connection.createStatement(
  "SELECT value FROM example WHERE id=:id")
  .bind("id", 99)

The bind method may be called with a String valued name, or with zero-based index, to set the value of a named parameter. Parameter names are case-sensitive.

Batch Execution

The Statement.add() method may be used execute a DML command multiple times with a batch of different bind values. Oracle Database only supports batch execution for DML type SQL commands (INSERT/UPDATE/DELETE). Attempting to execute a SELECT query with a batch of bind values will result in an error.

Returning Generated Values

The Statement.returnGeneratedValues(String...) method may be called to return generated values from basic forms of INSERT and UPDATE statements.

If an empty set of column names is passed to returnGeneratedValues, the Statement will return the ROWID of each row affected by an INSERT or UPDATE.

Programmers are advised not to use the ROWID as if it were a primary key. The ROWID of a row change, or be reassigned to a different row. See https://asktom.oracle.com/pls/apex/asktom.search?tag=is-it-safe-to-use-rowid-to-locate-a-row for more information.

Returning generated values is only supported for INSERT and UPDATE commands in which a RETURNING INTO clause would be valid. For example, if a table is declared as:

CREATE TABLE example (
  id NUMBER PRIMARY KEY GENERATED ALWAYS AS IDENTITY,
  value VARCAHR(100))

Returning generated values is supported for the following statement:

connection.createStatement(
  "INSERT INTO example(value) VALUES (:value)")
  .bind("value", "x")
  .returningGeneratedValues("id")

This statement is supported because the INSERT could be written to include a RETURNING INTO clause:

INSERT INTO example(value) VALUES (:value) RETURING id INTO :id

As a counter example, returning generated values is not supported for the following statement:

connection.createStatement(
  "INSERT INTO example (value) SELECT 'y' FROM sys.dual")
  .returningGeneratedValues("id")

This statement is not supported because it can not be written to include a RETURNING INTO clause.

The Oracle Database SQL Language Reference specifies the INSERT and UPDATE commands for which a RETURNING INTO clause is supported.

For the INSERT syntax, see: https://docs.oracle.com/en/database/oracle/oracle-database/21/sqlrf/INSERT.html

For the UPDATE syntax, see: https://docs.oracle.com/en/database/oracle/oracle-database/21/sqlrf/UPDATE.html

Procedural Calls

The SQL string passed to Connection.createStatement(String) may execute a PL/SQL call:

connection.createStatement("BEGIN sayHello(:name_in, :greeting_out); END;")

OUT parameters are registered by invoking Statement.bind(int, Object) or Statement.bind(String, Object) with an instance of io.r2dbc.spi.Parameter implementing the io.r2dbc.spi.Parameter.Out marker interface:

statement.bind("greeting_out", Parameters.out(R2dbcType.VARCHAR))

Likewise, an IN OUT parameter would be registered by invoking Statement.bind(int, Object) or Statement.bind(String, Object) with an instance of io.r2dbc.spi.Parameter implementing both the io.r2dbc.spi.Parameter.Out and io.r2dbc.spi.Parameter.In marker interfaces.

OUT parameters are consumed by invoking Result.map(Function):

result.map(outParameters -> outParameters.get("greeting_out", String.class))

If a procedural call returns multiple results, the publisher returned by Statement.execute() emits one Result for each cursor returned by DBMS_SQL.RETURN_RESULT in the procedure. The order in which each Result is emitted corresponds to the order in which the procedure returns each cursor.

If a procedure returns cursors, and also has out parameters, then the Result for the out parameters is emitted last, after the Result for each cursor.

Type Mappings

Oracle R2DBC supports type mappings between Java and SQL for non-standard data types of Oracle Database.

Oracle SQL Type Java Type
JSON javax.json.JsonObject or oracle.sql.json.OracleJsonObject
DATE java.time.LocalDateTime
INTERVAL DAY TO SECOND java.time.Duration
INTERVAL YEAR TO MONTH java.time.Period

Unlike the standard SQL type named "DATE", the Oracle Database type named "DATE" stores values for year, month, day, hour, minute, and second. The standard SQL type only stores year, month, and day. LocalDateTime objects are able to store the same values as a DATE in Oracle Database.

BLOB, CLOB, and NCLOB

Oracle R2DBC allows large objects (LOBs) to be read and written as a reactive stream, or as a fully materialized value.

Prefetched LOB Data

When a SQL query returns a LOB column, only a portion of the LOB's content is received in the response from Oracle Database. The portion received in the SQL query response is referred to as "prefetched data". Any content remaining after the prefetched portion must be fetched with additional database calls.

For example, if a SQL query returns a LOB that is 100MB in size, then the response might prefetch only the first 1MB of the LOB's content. Additional database calls would be required to fetch the remaining 99MB of content.

By default, Oracle R2DBC attempts to prefetch the entire content of a LOB. Oracle R2DBC will request up to 1GB of prefetched data from Oracle Database when executing a SQL query.

Materialzed Type Mapping

The Row.get(...) method allows LOB values to be mapped into materialized types like ByteBuffer and String. If the entire LOB has been prefetched, then Row.get(...) can return a ByteBuffer/String without any additional database calls. However, if the LOB value is larger than the prefetch size, then Row.get(...) must execute a blocking database call to fetch the remainder of that value.

Streamed Type Mapping

In a system that consumes very large LOBs, a very large amount of memory will be consumed if the entire LOB is prefetched. When a LOB is too large to be prefetched entirely, a smaller prefetch size can be configured using the oracle.jdbc.defaultLobPrefetchSize option, and the LOB can be consumed as a stream. By mapping LOB columns to Blob or Clob objects, the content can be consumed as a reactive stream.

Secure Programming Guidelines

The following security related guidelines should be adhered to when programming with the Oracle R2DBC Driver.

Defend Against SQL Injection Attacks

  • Always specify the parameters of a SQL command using the bind methods of io.r2dbc.spi.Statement.
    • Do not use String concatenation to specify parameters of a SQL command.
    • Do not use format Strings to specify parameters of a SQL command.

Protect Passwords

  • Do not hard code passwords in your source code.
  • Avoid hard coding passwords in the R2DBC URL.
    • When handling URL strings in code, be aware that a clear text password may appear in the user info section.
  • Use a sensitive io.r2dbc.spi.Option to specify passwords.
    • If possible, specify the Option's value as an instance of java.nio.CharBuffer or java.lang.StringBuffer and clear the contents immediately after ConnectionFactories.get(ConnectionFactoryOptions) has returned. Oracle R2DBC's implementation of ConnectionFactory does not retain a reference to the clear text password.

Protect Network Communications

  • Use SSL/TLS if possible. Use any of the following methods to enable SSL/TLS:
    • Specify the boolean value of true for io.r2dbc.spi.ConnectionFactoryOptions.SSL
    • Specify "r2dbcs:" as the R2DBC URL schema.
    • Specify "ssl=true" in the query section of the R2DBC URL.
  • Use Option.sensitiveValueOf(String) when creating an Option that specifies a password.
    • Option.sensitiveValueOf(OracleConnection.CONNECTION_PROPERTY_WALLET_PASSWORD)
      • An SSO wallet does not require a password.
    • Option.sensitiveValueOf(OracleConnection.CONNECTION_PROPERTY_THIN_JAVAX_NET_SSL_KEYSTOREPASSWORD)
    • Option.sensitiveValueOf(OracleConnection.CONNECTION_PROPERTY_THIN_JAVAX_NET_SSL_TRUSTSTOREPASSWORD)

Defend Against Denial-of-Service Attacks

  • Use a connection pool and configure a maximum size to limit the number of database sessions created by ConnectionFactory.create()
  • Enforce a maximum batch size to limit invocations of Statement.add() or Batch.add(String).
  • Enforce a maximum fetch size to limit values supplied to Statement.fetchSize(int).
  • Enforce a maximum buffer size to limit memory usage when reading Blob and Clob objects.

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