深刻理解r2dbc-mysql

簡介

mysql應該是咱們在平常工做中使用到的一個很是廣泛的數據庫，雖然mysql如今是oracle公司的，可是它是開源的，市場佔有率仍是很是高的。

今天咱們將會介紹r2dbc在mysql中的使用。

r2dbc-mysql的maven依賴

要想使用r2dbc-mysql，咱們須要添加以下的maven依賴：

<dependency>
    <groupId>dev.miku</groupId>
    <artifactId>r2dbc-mysql</artifactId>
    <version>0.8.2.RELEASE</version>
</dependency>

固然，若是你想使用snapshot版本的話，能夠這樣：

<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>

建立connectionFactory

建立connectionFactory的代碼實際上使用的r2dbc的標準接口，因此和以前講到的h2的建立代碼基本上是同樣的：

// 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());

不一樣的是ConnectionFactories傳入的參數不一樣。

咱們也支持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());

一樣的，咱們也支持從ConnectionFactoryOptions中建立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建立connection

上面的例子中，咱們使用的是通用的r2dbc api來建立connection，一樣的，咱們也可使用特有的MySqlConnectionFactory來建立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());

執行statement

首先看一個簡單的不帶參數的statement:

connection.createStatement("INSERT INTO `person` (`first_name`, `last_name`) VALUES ('who', 'how')")
    .execute(); // return a Publisher include one Result

而後看一個帶參數的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，若是參數是null的話，可使用bindNull來進行null值的綁定。

接下來咱們看一個批量執行的操做：

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.

執行事務

咱們看一個執行事務的例子：

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());

使用線程池

爲了提高數據庫的執行效率，減小創建鏈接的開銷，通常數據庫鏈接都會有鏈接池的概念，一樣的r2dbc也有一個叫作r2dbc-pool的鏈接池。

r2dbc-pool的依賴：

<dependency>
  <groupId>io.r2dbc</groupId>
  <artifactId>r2dbc-pool</artifactId>
  <version>${version}</version>
</dependency>

若是你想使用snapshot版本，也能夠這樣指定：

<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>

看一下怎麼指定數據庫鏈接池：

ConnectionFactory connectionFactory = ConnectionFactories.get("r2dbc:pool:<my-driver>://<host>:<port>/<database>[?maxIdleTime=PT60S[&…]");

Publisher<? extends Connection> connectionPublisher = connectionFactory.create();

能夠看到，咱們只須要在鏈接URL上面添加pool這個driver便可。

一樣的，咱們也能夠經過ConnectionFactoryOptions來建立：

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());

最後， 你也能夠直接經過建立ConnectionPoolConfiguration來使用線程池：

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();

本文做者：flydean程序那些事

本文連接：http://www.flydean.com/r2dbc-mysql-in-depth/

本文來源：flydean的博客

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