JarCastingReactive Relational Database Connectivity MySQL Implementation
This project contains the MySQL implementation of the R2DBC SPI. This implementation is not intended to be used directly, but rather to be used as the backing implementation for a humane client library to delegate to. See R2DBC Homepage.
This driver provides the following features:
- Unix domain socket.
- Execution of simple or batch statements without bindings.
- Execution of prepared statements with bindings.
- Reactive LOB types (e.g. BLOB, CLOB)
- All charsets from MySQL, like
utf8mb4_0900_ai_ci,latin1_general_ci,utf32_unicode_520_ci, etc. - All authentication types for MySQL, like
caching_sha2_password,mysql_native_password, etc. - General exceptions with error code and standard SQL state mappings.
- Secure connection with verification (SSL/TLS), auto-select TLS version for community and enterprise editions.
- SSL tunnel for proxy protocol of MySQL.
- Transactions with savepoint.
- Native ping command that can be verifying when argument is
ValidationDepth.REMOTE - Extensible, e.g. extend built-in
Codec(s).
Version compatibility / Integration tests states
In fact, it supports lower versions, in the theory, such as 4.1, 4.0, etc.
However, Docker-certified images do not have these versions lower than 5.5.0, so tests are not integrated on these versions.
Maven
<dependency>
<groupId>dev.miku</groupId>
<artifactId>r2dbc-mysql</artifactId>
<version>0.8.2.RELEASE</version>
</dependency>
If you'd rather like the latest snapshots of the upcoming major version, use SonaType Maven snapshot repository and declare the appropriate dependency version.
<dependency>
<groupId>dev.miku</groupId>
<artifactId>r2dbc-mysql</artifactId>
<version>${r2dbc-mysql.version}.BUILD-SNAPSHOT</version>
</dependency>
<repository>
<id>sonatype-snapshots</id>
<name>SonaType Snapshots</name>
<url>https://oss.sonatype.org/content/repositories/snapshots</url>
<snapshots>
<enabled>true</enabled>
</snapshots>
</repository>
Gradle
Groovy DSL
dependencies {
implementation 'dev.miku:r2dbc-mysql:0.8.2.RELEASE'
}
Kotlin DSL
dependencies {
// Maybe should to use `compile` instead of `implementation` on the lower version of Gradle.
implementation("dev.miku:r2dbc-mysql:0.8.2.RELEASE")
}
Getting Started
Here is a quick teaser of how to use R2DBC MySQL in Java:
URL Connection Factory Discovery
// Notice: the query string must be URL encoded
ConnectionFactory connectionFactory = ConnectionFactories.get(
"r2dbcs:mysql://root:[email protected]:3306/r2dbc?" +
"zeroDate=use_round&" +
"sslMode=verify_identity&" +
"useServerPrepareStatement=true&" +
"tlsVersion=TLSv1.3%2CTLSv1.2%2CTLSv1.1&" +
"sslCa=%2Fpath%2Fto%2Fmysql%2Fca.pem&" +
"sslKey=%2Fpath%2Fto%2Fmysql%2Fclient-key.pem&" +
"sslCert=%2Fpath%2Fto%2Fmysql%2Fclient-cert.pem&" +
"sslKeyPassword=key-pem-password-in-here"
)
// Creating a Mono using Project Reactor
Mono<Connection> connectionMono = Mono.from(connectionFactory.create());
It is just example, see also Programmatic Connection Factory Discovery for more options.
Or use unix domain socket like following:
// Minimum configuration for unix domain socket
ConnectionFactory connectionFactory = ConnectionFactories.get("r2dbc:mysql://root@unix?unixSocket=%2Fpath%2Fto%2Fmysql.sock")
Mono<Connection> connectionMono = Mono.from(connectionFactory.create());
Programmatic Connection Factory Discovery
ConnectionFactoryOptions options = ConnectionFactoryOptions.builder()
.option(DRIVER, "mysql")
.option(HOST, "127.0.0.1")
.option(USER, "root")
.option(PORT, 3306) // optional, default 3306
.option(PASSWORD, "database-password-in-here") // optional, default null, null means has no password
.option(DATABASE, "r2dbc") // optional, default null, null means not specifying the database
.option(CONNECT_TIMEOUT, Duration.ofSeconds(3)) // optional, default null, null means no timeout
.option(SSL, true) // optional, default sslMode is "preferred", it will be ignore if sslMode is set
.option(Option.valueOf("sslMode"), "verify_identity") // optional, default "preferred"
.option(Option.valueOf("sslCa"), "/path/to/mysql/ca.pem") // required when sslMode is verify_ca or verify_identity, default null, null means has no server CA cert
.option(Option.valueOf("sslCert"), "/path/to/mysql/client-cert.pem") // optional, default null, null means has no client cert
.option(Option.valueOf("sslKey"), "/path/to/mysql/client-key.pem") // optional, default null, null means has no client key
.option(Option.valueOf("sslKeyPassword"), "key-pem-password-in-here") // optional, default null, null means has no password for client key (i.e. "sslKey")
.option(Option.valueOf("tlsVersion"), "TLSv1.3,TLSv1.2,TLSv1.1") // optional, default is auto-selected by the server
.option(Option.valueOf("sslHostnameVerifier"), "com.example.demo.MyVerifier") // optional, default is null, null means use standard verifier
.option(Option.valueOf("sslContextBuilderCustomizer"), "com.example.demo.MyCustomizer") // optional, default is no-op customizer
.option(Option.valueOf("zeroDate"), "use_null") // optional, default "use_null"
.option(Option.valueOf("useServerPrepareStatement"), true) // optional, default false
.option(Option.valueOf("tcpKeepAlive"), true) // optional, default false
.option(Option.valueOf("tcpNoDelay"), true) // optional, default false
.option(Option.valueOf("autodetectExtensions"), false) // optional, default false
.build();
ConnectionFactory connectionFactory = ConnectionFactories.get(options);
// Creating a Mono using Project Reactor
Mono<Connection> connectionMono = Mono.from(connectionFactory.create());
Or use unix domain socket like following:
// Minimum configuration for unix domain socket
ConnectionFactoryOptions options = ConnectionFactoryOptions.builder()
.option(DRIVER, "mysql")
.option(Option.valueOf("unixSocket"), "/path/to/mysql.sock")
.option(USER, "root")
.build();
ConnectionFactory connectionFactory = ConnectionFactories.get(options);
Mono<Connection> connectionMono = Mono.from(connectionFactory.create());
Programmatic Configuration
MySqlConnectionConfiguration configuration = MySqlConnectionConfiguration.builder()
.host("127.0.0.1")
.user("root")
.port(3306) // optional, default 3306
.password("database-password-in-here") // optional, default null, null means has no password
.database("r2dbc") // optional, default null, null means not specifying the database
.serverZoneId(ZoneId.of("Continent/City")) // optional, default null, null means query server time zone when connection init
.connectTimeout(Duration.ofSeconds(3)) // optional, default null, null means no timeout
.sslMode(SslMode.VERIFY_IDENTITY) // optional, default SslMode.PREFERRED
.sslCa("/path/to/mysql/ca.pem") // required when sslMode is VERIFY_CA or VERIFY_IDENTITY, default null, null means has no server CA cert
.sslCert("/path/to/mysql/client-cert.pem") // optional, default has no client SSL certificate
.sslKey("/path/to/mysql/client-key.pem") // optional, default has no client SSL key
.sslKeyPassword("key-pem-password-in-here") // optional, default has no client SSL key password
.tlsVersion(TlsVersions.TLS1_3, TlsVersions.TLS1_2, TlsVersions.TLS1_1) // optional, default is auto-selected by the server
.sslHostnameVerifier(MyVerifier.INSTANCE) // optional, default is null, null means use standard verifier
.sslContextBuilderCustomizer(MyCustomizer.INSTANCE) // optional, default is no-op customizer
.zeroDateOption(ZeroDateOption.USE_NULL) // optional, default ZeroDateOption.USE_NULL
.useServerPrepareStatement() // Use server-preparing statements, default use client-preparing statements
.tcpKeepAlive(true) // optional, controls TCP Keep Alive, default is false
.tcpNoDelay(true) // optional, controls TCP No Delay, default is false
.autodetectExtensions(false) // optional, controls extension auto-detect, default is true
.extendWith(MyExtension.INSTANCE) // optional, manual extend an extension into extensions, default using auto-detect
.build();
ConnectionFactory connectionFactory = MySqlConnectionFactory.from(configuration);
// Creating a Mono using Project Reactor
Mono<Connection> connectionMono = Mono.from(connectionFactory.create());
Or use unix domain socket like following:
// Minimum configuration for unix domain socket
MySqlConnectionConfiguration configuration = MySqlConnectionConfiguration.builder()
.unixSocket("/path/to/mysql.sock")
.user("root")
.build();
ConnectionFactory connectionFactory = MySqlConnectionFactory.from(configuration);
Mono<Connection> connectionMono = Mono.from(connectionFactory.create());
Configuration items
| name | valid values | required | description |
|---|---|---|---|
| driver | A constant "mysql" | Required in R2DBC discovery | This driver needs to be discovered by name in R2DBC |
| host | A hostname or IP | Required when unixSocket does not exists |
The host of MySQL database server |
| unixSocket | An absolute or relative path | Required when host does not exists |
The .sock file of Unix Domain Socket |
| port | A positive integer less than 65536 | Optional, default 3306 | The port of MySQL database server |
| user | A valid MySQL username and not be empty | Required | Who wants to connect to the MySQL database |
| password | Any printable string | Optional, default no password | The password of the MySQL database user |
| database | A valid MySQL database name | Optional, default does not initialize database | Database used by the MySQL connection |
| connectTimeout | A Duration which must be positive duration |
Optional, default has no timeout | TCP connect timeout |
| serverZoneId | An id of ZoneId |
Optional, default query time zone when connection init | Server time zone id |
| tcpKeepAlive | true or false |
Optional, default disabled | Controls TCP KeepAlive |
| tcpNoDelay | true or false |
Optional, default disabled | Controls TCP NoDelay |
| sslMode | A value of SslMode |
Optional, default PREFERRED when using hosting connection, DISABLED when using Unix Domain Socket |
SSL mode, see following notice |
| sslCa | A path of local file which type is PEM |
Required when sslMode is VERIFY_CA or VERIFY_IDENTITY |
The CA cert of MySQL database server |
| sslCert | A path of local file which type is PEM |
Required when sslKey exists |
The SSL cert of client |
| sslKey | A path of local file which type is PEM |
Required when sslCert exists |
The SSL key of client |
| sslKeyPassword | Any valid password for PEM file |
Optional, default sslKey has no password |
The password for client SSL key (i.e. sslKey) |
| tlsVersion | Any value list of TlsVersions |
Optional, default is auto-selected by the server | The TLS version for SSL, see following notice |
| sslHostnameVerifier | A HostnameVerifier |
Optional, default use RFC standard | Used only if SslMode is VERIFY_CA or higher |
| sslContextBuilderCustomizer | A Function<SslContextBuilder, SslContextBuilder> |
Optional, default is NO-OP function | Used only if SslMode is not DISABLED |
| zeroDateOption | Any value of ZeroDateOption |
Optional, default USE_NULL |
The option indicates "zero date" handling, see following notice |
| autodetectExtensions | true or false |
Optional, default is true |
Controls auto-detect Extensions |
| useServerPrepareStatement | true, false or Predicate<String> |
Optional, default is false |
See following notice |
SslModeConsiders security level and verification for SSL, make sure the database server supports SSL before you want change SSL mode toREQUIREDor higher. The Unix Domain Socket only offers "DISABLED" availableDISABLEDI don't care about security and don't want to pay the overhead for encryptionPREFERREDI don't care about encryption but will pay the overhead of encryption if the server supports it. Unavailable on Unix Domain SocketREQUIREDI want my data to be encrypted, and I accept the overhead. I trust that the network will make sure I always connect to the server I want. Unavailable on Unix Domain SocketVERIFY_CAI want my data encrypted, and I accept the overhead. I want to be sure I connect to a server that I trust. Unavailable on Unix Domain SocketVERIFY_IDENTITY(the highest level, most like web browser): I want my data encrypted, and I accept the overhead. I want to be sure I connect to a server I trust, and that it's the one I specify. Unavailable on Unix Domain SocketTUNNELUse SSL tunnel to connect to MySQL, it may be useful for some RDS that's using SSL proxy Unavailable on Unix Domain Socket
TlsVersionsConsiders TLS version names for SSL, can be multi-values in the configuration, make sure the database server supports selected TLS versions. Usually sorted from higher to lower. Unavailable on Unix Domain SocketTLS1(i.e. "TLSv1") Under generic circumstances, MySQL database supports it if database supports SSLTLS1_1(i.e. "TLSv1.1") Under generic circumstances, MySQL database supports it if database supports SSLTLS1_2(i.e. "TLSv1.2") Supported only in Community Edition8.0.4or higher, and Enterprise Edition5.6.0or higherTLS1_3(i.e. "TLSv1.3") Supported only available as of MySQL8.0.16or higher, and requires compiling MySQL using OpenSSL1.1.1or higher
ZeroDateOptionConsiders special handling when MySQL database server returning "zero date" (i.e.0000-00-00 00:00:00)EXCEPTIONJust throw an exception when MySQL database server return "zero date"USE_NULLUsenullwhen MySQL database server return "zero date"USE_ROUNDNOT RECOMMENDED, only for compatibility. Use "round" date (i.e.0001-01-01 00:00:00) when MySQL database server return "zero date"
- Prepare Statement: Considers based on server-preparing or client-preparing, some database server maybe not support server-preparing binary-query, such as Vitess
useClientPrepareStatement()default preparing mode, use client-preparing text-query for parametrized statementsuseServerPrepareStatement()use server-preparing binary-query for parametrized statementsuseServerPrepareStatement(Predicate<String>)use server-preparing binary-query for parametrized statements, and enforce server-preparing usage for simple query (not parametrized statements). The usage is judged byPredicate, it's parameter is the simple SQL statement, enforce server-preparing if returntrue
extendWithManual extendExtension, only available in programmatic configuration- It is NOT RECOMMENDED, enable the
autodetectExtensionsis the best way for extensions - The
Extensionswill not remove duplicates, make sure it would be not extended twice or more - The auto-detected
Extensions will not affect manual extends and will not remove duplicates
- It is NOT RECOMMENDED, enable the
Should use enum in Programmatic configuration that not like discovery configurations, except TlsVersions (All elements of TlsVersions will be always String which is case-sensitive).
Pooling
See r2dbc-pool.
Simple statement
connection.createStatement("INSERT INTO `person` (`first_name`, `last_name`) VALUES ('who', 'how')")
.execute(); // return a Publisher include one Result
Parametrized statement
connection.createStatement("INSERT INTO `person` (`birth`, `nickname`, `show_name`) VALUES (?, ?name, ?name)")
.bind(0, LocalDateTime.of(2019, 6, 25, 12, 12, 12))
.bind("name", "Some one") // Not one-to-one binding, call twice of native index-bindings, or call once of name-bindings.
.add()
.bind(0, LocalDateTime.of(2009, 6, 25, 12, 12, 12))
.bind(1, "My Nickname")
.bind(2, "Naming show")
.returnGeneratedValues("generated_id")
.execute(); // return a Publisher include two Results.
- All parameters must be bound before execute, even parameter is
null(usebindNullto bindnull). - It will be using client-preparing by default, see
useServerPrepareStatementin configuration. - In one-to-one binding, because native MySQL prepared statements use index-based parameters, index-bindings will have better performance than name-bindings.
Batch statement
connection.createBatch()
.add("INSERT INTO `person` (`first_name`, `last_name`) VALUES ('who', 'how')")
.add("UPDATE `earth` SET `count` = `count` + 1 WHERE `id` = 'human'")
.execute(); // return a Publisher include two Results.
The last
;will be removed if and only if last statement contains ';', and statement has only whitespace follow the last;.
Transactions
connection.beginTransaction()
.then(Mono.from(connection.createStatement("INSERT INTO `person` (`first_name`, `last_name`) VALUES ('who', 'how')").execute()))
.flatMap(Result::getRowsUpdated)
.thenMany(connection.createStatement("INSERT INTO `person` (`birth`, `nickname`, `show_name`) VALUES (?, ?name, ?name)")
.bind(0, LocalDateTime.of(2019, 6, 25, 12, 12, 12))
.bind("name", "Some one")
.add()
.bind(0, LocalDateTime.of(2009, 6, 25, 12, 12, 12))
.bind(1, "My Nickname")
.bind(2, "Naming show")
.returnGeneratedValues("generated_id")
.execute())
.flatMap(Result::getRowsUpdated)
.then(connection.commitTransaction());
Data Type Mapping
The default built-in Codecs reference table shows the type mapping between MySQL and Java data types:
| MySQL Type | Unsigned | Support Data Type |
|---|---|---|
INT |
UNSIGNED |
Long, BigInteger |
INT |
SIGNED |
Integer, Long, BigInteger |
TINYINT |
UNSIGNED |
Short, Integer, Long, BigInteger, Boolean (Size is 1) |
TINYINT |
SIGNED |
Byte, Short, Integer, Long, BigInteger, Boolean (Size is 1) |
SMALLINT |
UNSIGNED |
Integer, Long, BigInteger |
SMALLINT |
SIGNED |
Short, Integer, Long, BigInteger |
MEDIUMINT |
SIGNED/UNSIGNED |
Integer, Long, BigInteger |
BIGINT |
UNSIGNED |
BigInteger, Long (Not check overflow) |
BIGINT |
SIGNED |
Long, BigInteger |
FLOAT |
SIGNED / UNSIGNED |
Float, BigDecimal |
DOUBLE |
SIGNED / UNSIGNED |
Double, BigDecimal |
DECIMAL |
SIGNED / UNSIGNED |
BigDecimal, Float (Size less than 7), Double (Size less than 16) |
BIT |
- | ByteBuffer, BitSet, Boolean (Size is 1), byte[] |
DATETIME / TIMESTAMP |
- | LocalDateTime, ZonedDateTime, OffsetDateTime, Instant |
DATE |
- | LocalDate |
TIME |
- | LocalTime, Duration, OffsetTime |
YEAR |
- | Short, Integer, Long, BigInteger, Year |
VARCHAR / NVARCHAR |
- | String |
VARBINARY |
- | ByteBuffer, Blob, byte[] |
CHAR / NCHAR |
- | String |
ENUM |
- | String, Enum<?> |
SET |
- | String[], String, Set<String> and Set<Enum<?>> (Set<T> need use ParameterizedType) |
BLOBs (LONGBLOB, etc.) |
- | ByteBuffer, Blob, byte[] |
TEXTs (LONGTEXT, etc.) |
- | String, Clob |
JSON |
- | String, Clob |
GEOMETRY |
- | byte[], Blob |
Add a Codec
This is an extension of a highly customized driver behavior of encoding parameter or decoding field data.
Example for an extending Codec of JSON based-on Jackson.
First, implement a Codec, ParametrizedCodec, MassiveCodec or MassiveParametrizedCodec.
Codecthe normal codec- Data type is
Class<?> - Data buffer size is less than or equal to
Integer.MAX_VALUE
- Data type is
ParametrizedCodec- Data type is
Class<?>orParametrizedType - Data buffer size is less than or equal to
Integer.MAX_VALUE
- Data type is
MassiveCodec- Data type is
Class<?> - Data buffer size is less than or equal to
UnsignedInteger.MAX_VALUE(Java does not have unsigned integers, it just only represents the range)
- Data type is
MassiveParametrizedCodec- Data type is
Class<?>orParametrizedType - Data buffer size is less than or equal to
UnsignedInteger.MAX_VALUE
- Data type is
Actually, JSON can store large json data, and its byte size can be UnsignedInteger.MAX_VALUE. However, this is just an example.
public final class JacksonCodec implements Codec<Object> {
/**
* JUST for example, should configure it in real applications.
*/
private static final ObjectMapper MAPPER = new ObjectMapper();
private final ByteBufAllocator allocator;
/**
* Used for encoding/decoding mode, see also registrar in second step.
*/
private final boolean encoding;
public JacksonCodec(ByteBufAllocator allocator, boolean encoding) {
this.allocator = allocator;
this.encoding = encoding;
}
@Override
public Object decode(ByteBuf value, FieldInformation info, Class<?> target, boolean binary, CodecContext context) {
// If you ensure server is using UTF-8, you can just use InputStream
try (Reader r = new InputStreamReader(new ByteBufInputStream(value), CharCollation.fromId(info.getCollationId(), context.getServerVersion()).getCharset())) {
return MAPPER.readValue(r, target);
} catch (IOException e) {
throw new RuntimeException(e);
}
}
@Override
public Parameter encode(Object value, CodecContext context) {
return new JacksonParameter(allocator, value, context);
}
@Override
public boolean canDecode(FieldInformation info, Class<?> target) {
return !encoding && info.getType() == DataTypes.JSON && info.getCollationId() != CharCollation.BINARY_ID;
}
@Override
public boolean canEncode(Object value) {
return encoding;
}
private static final class JacksonParameter implements Parameter {
private final ByteBufAllocator allocator;
private final Object value;
private final CodecContext context;
private JacksonParameter(ByteBufAllocator allocator, Object value, CodecContext context) {
this.allocator = allocator;
this.value = value;
this.context = context;
}
@Override
public Mono<ByteBuf> publishBinary() {
// JSON in binary protocol should be a var-integer sized encoded string.
// That means we should write a var-integer as a size of following content
// bytes firstly, then write the encoded string as content.
//
// Binary protocol may be different for each type of encoding, so if do not
// use binary protocol, just return a Mono.error() instead.
return Mono.fromSupplier(() -> {
Charset charset = context.getClientCollation().getCharset();
ByteBuf content = allocator.buffer();
// Encode and calculate content bytes first, we should know bytes size.
try (Writer w = new OutputStreamWriter(new ByteBufOutputStream(content), charset)) {
MAPPER.writeValue(w, value);
} catch (IOException e) {
content.release();
throw new CustomRuntimeException(e);
} catch (Throwable e) {
content.release();
throw e;
}
ByteBuf buf = null;
try {
buf = allocator.buffer();
// VarIntUtils is an unstable, internal utility.
VarIntUtils.writeVarInt(buf, content.readableBytes());
return buf.writeBytes(content);
} catch (Throwable e) {
if (buf != null) {
buf.release();
}
throw e;
} finally {
content.release();
}
});
}
@Override
public Mono<Void> publishText(ParameterWriter writer) {
return Mono.fromRunnable(() -> {
try {
MAPPER.writeValue(writer, value);
} catch (IOException e) {
throw new CustomRuntimeException(e);
}
});
}
@Override
public short getType() {
return DataTypes.VARCHAR;
}
}
}
Second, implement a CodecRegistrar.
// It is just an example of package name and does not represent any company, individual or organization.
package org.example.demo.json;
// Some imports...
public final class JacksonCodecRegistrar implements CodecRegistrar {
@Override
public void register(ByteBufAllocator allocator, CodecRegistry registry) {
// Decoding JSON by highest priority, encoding anything by lowest priority.
registry.addFirst(new JacksonCodec(allocator, false))
.addLast(new JacksonCodec(allocator, true));
}
}
Finally, create a file in META-INF/services, which file name is dev.miku.r2dbc.mysql.extension.Extension, it contains this line:
org.example.demo.json.JacksonCodecRegistrar
Reporting Issues
The R2DBC MySQL Implementation uses GitHub as issue tracking system to record bugs and feature requests. If you want to raise an issue, please follow the recommendations below:
- Before log a bug, please search the issue tracker to see if someone has already reported the problem.
- If the issue doesn't already exist, create a new issue.
- Please provide as much information as possible with the issue report, we like to know the version of R2DBC MySQL that you are using and JVM version.
- If you need to paste code, or include a stack trace use Markdown ``` escapes before and after your text.
- If possible try to create a test-case or project that replicates the issue. Attach a link to your code or a compressed file containing your code.
Before use
- The MySQL data fields encoded by index-based natively, get fields by an index will have better performance than get by column name.
- Each
Resultshould be used (callgetRowsUpdatedormap, even table definition), can NOT just ignore anyResult, otherwise inbound stream is unable to align. (likeResultSet.closein jdbc,Resultauto-close after used by once) - The MySQL server does not actively return time zone when query
DATETIMEorTIMESTAMP, this driver does not attempt time zone conversion. That means should always useLocalDateTimefor SQL typeDATETIMEorTIMESTAMP. ExecuteSHOW VARIABLES LIKE '%time_zone%'to get more information. - Should not turn-on the
tracelog level unless debugging. Otherwise, the security information may be exposed throughByteBufdump. - If
StatementboundreturnGeneratedValues, theResultof theStatementcan be called both:getRowsUpdatedto get affected rows, andmapto get last inserted ID. - The MySQL may be not support search rows by a binary field, like
BIT,BLOBandJSON, because those data fields maybe just an address of reference in MySQL server, or maybe need strict bit-aligned. (butVARBINARYis OK)
License
This project is released under version 2.0 of the Apache License.