3. 深入理解r2dbc-mysql
简介
mysql应该是我们在日常工作中使用到的一个非常普遍的数据库，虽然mysql现在是oracle公司的，但是它是开源的，市场占有率还是非常高的。
今天我们将会介绍r2dbc在mysql中的使用。
r2dbc-mysql的maven依赖
要想使用r2dbc-mysql，我们需要添加如下的maven依赖：
<dependency>
<groupId>dev.miku</groupId>
<artifactId>r2dbc-mysql</artifactId>
<version>0.8.2.RELEASE</version>
</dependency>
当然，如果你想使用snapshot版本的话，可以这样：
<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>
创建connectionFactory
创建connectionFactory的代码实际上使用的r2dbc的标准接口，所以和之前 讲到的h2的创建代码基本上是一样的：
// Notice: the query string must be URL encoded
ConnectionFactory connectionFactory = ConnectionFactories.get(
"r2dbcs:mysql://root:database-password-in-here@127.0.0.1:3306/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());
不同的是ConnectionFactories传入的参数不同。
我们也支持unix domain socket的格式：
// 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());
同样的，我们也支持从ConnectionFactoryOptions中创建ConnectionFactory：
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());
或者下面的unix domain socket格式：
// 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());
使用MySqlConnectionFactory创建connection
上面的例子中，我们使用的是通用的r2dbc api来创建connection，同样的，我们也可以使用特有的MySqlConnectionFactory来创建connection：
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());
或者下面的unix domain socket方式：
// 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());
执行statement
首先看一个简单的不带参数的statement:
connection.createStatement("INSERT INTO `person` (`first_name`, `last_name`) VALUES ('who', 'how')")
.execute(); // return a Publisher include one Result
然后看一个带参数的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.
注意，如果参数是null的话，可以使用bindNull来进行null值的绑定。
接下来我们看一个批量执行的操作：
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.
执行事务
我们看一个执行事务的例子：
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());
使用线程池
为了提升数据库的执行效率，减少建立连接的开销，一般数据 库连接都会有连接池的概念，同样的r2dbc也有一个叫做r2dbc-pool的连接池。
r2dbc-pool的依赖：
<dependency>
<groupId>io.r2dbc</groupId>
<artifactId>r2dbc-pool</artifactId>
<version>${version}</version>
</dependency>
如果你想使用snapshot版本，也可以这样指定：
<dependency>
<groupId>io.r2dbc</groupId>
<artifactId>r2dbc-pool</artifactId>
<version>${version}.BUILD-SNAPSHOT</version>
</dependency>
<repository>
<id>spring-libs-snapshot</id>
<name>Spring Snapshot Repository</name>
<url>https://repo.spring.io/libs-snapshot</url>
</repository>
看一下怎么指定数据库连接池：
ConnectionFactory connectionFactory = ConnectionFactories.get("r2dbc:pool:<my-driver>://<host>:<port>/<database>[?maxIdleTime=PT60S[&…]");
Publisher<? extends Connection> connectionPublisher = connectionFactory.create();
可以看到，我们只需要在连接URL上面添加pool这个driver即可。
同样的，我们也可以通过ConnectionFactoryOptions来创建：
ConnectionFactory connectionFactory = ConnectionFactories.get(ConnectionFactoryOptions.builder()
.option(DRIVER, "pool")
.option(PROTOCOL, "postgresql") // driver identifier, PROTOCOL is delegated as DRIVER by the pool.
.option(HOST, "…")
.option(PORT, "…")
.option(USER, "…")
.option(PASSWORD, "…")
.option(DATABASE, "…")
.build());
Publisher<? extends Connection> connectionPublisher = connectionFactory.create();
// Alternative: Creating a Mono using Project Reactor
Mono<Connection> connectionMono = Mono.from(connectionFactory.create());
最后， 你也可以直接通过创建ConnectionPoolConfiguration来使用线程池：
ConnectionFactory connectionFactory = …;
ConnectionPoolConfiguration configuration = ConnectionPoolConfiguration.builder(connectionFactory)
.maxIdleTime(Duration.ofMillis(1000))
.maxSize(20)
.build();
ConnectionPool pool = new ConnectionPool(configuration);
Mono<Connection> connectionMono = pool.create();
// later
Connection connection = …;
Mono<Void> release = connection.close(); // released the connection back to the pool
// application shutdown
pool.dispose();
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