java17省流版

新开发环境记得设置language level：

 对应的pom中依赖版本需要同步升级：

<properties>
    <maven.compiler.release>17</maven.compiler.release>
    <flink.version>1.19.0</flink.version>
    <logback.version>1.4.14</logback.version>
    <junit.version>5.10.2</junit.version>
    <assertj.version>3.25.3</assertj.version>
    <testcontainers.version>1.19.7</testcontainers.version>
    <mockito.version>5.11.0</mockito.version>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
</properties>

<dependencies>
    <!-- Flink 核心 -->
    <dependency>
        <groupId>org.apache.flink</groupId>
        <artifactId>flink-streaming-java</artifactId>
        <version>${flink.version}</version>
        <scope>provided</scope>
    </dependency>
    <dependency>
        <groupId>org.apache.flink</groupId>
        <artifactId>flink-clients</artifactId>
        <version>${flink.version}</version>
        <scope>provided</scope>
    </dependency>
    <dependency>
        <groupId>org.apache.flink</groupId>
        <artifactId>flink-connector-kafka</artifactId>
        <version>${flink.version}</version>
    </dependency>

    <!-- 日志：官方默认 logback -->
    <dependency>
        <groupId>ch.qos.logback</groupId>
        <artifactId>logback-classic</artifactId>
        <version>${logback.version}</version>
    </dependency>

    <!-- 测试全家桶 -->
    <dependency>
        <groupId>org.junit.jupiter</groupId>
        <artifactId>junit-jupiter</artifactId>
        <version>${junit.version}</version>
        <scope>test</scope>
    </dependency>
    <dependency>
        <groupId>org.assertj</groupId>
        <artifactId>assertj-core</artifactId>
        <version>${assertj.version}</version>
        <scope>test</scope>
    </dependency>
    <dependency>
        <groupId>org.testcontainers</groupId>
        <artifactId>kafka</artifactId>
        <version>${testcontainers.version}</version>
        <scope>test</scope>
    </dependency>
    <dependency>
        <groupId>org.mockito</groupId>
        <artifactId>mockito-core</artifactId>
        <version>${mockito.version}</version>
        <scope>test</scope>
    </dependency>
</dependencies>

<build>
    <plugins>
        <!-- 编译 17 + 预览特性 -->
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-compiler-plugin</artifactId>
            <version>3.12.0</version>
            <configuration>
                <release>17</release>
                <compilerArgs>
                    <arg>--enable-preview</arg>
                </compilerArgs>
            </configuration>
        </plugin>

        <!-- 测试运行 -->
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-surefire-plugin</artifactId>
            <version>3.2.5</version>
            <configuration>
                <argLine>--enable-preview</argLine>
            </configuration>
        </plugin>

        <!-- 打包 fat-jar -->
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-shade-plugin</artifactId>
            <version>3.5.1</version>
            <executions>
                <execution>
                    <phase>package</phase>
                    <goals><goal>shade</goal></goals>
                    <configuration>
                        <transformers>
                            <!-- 解决 SPI 合并 -->
                            <transformer implementation="org.apache.maven.plugins.shade.resource.ServicesResourceTransformer"/>
                            <!-- 解决 Manifest -->
                            <transformer implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
                                <mainClass>com.yourcompany.JobMain</mainClass>
                            </transformer>
                        </transformers>
                    </configuration>
                </execution>
            </executions>
        </plugin>
    </plugins>
</build>

 

文本块：Text Blocks

尤其对SQL：

String ddl = """
CREATE TABLE kafka_source (
user_id STRING,
amount DOUBLE,
ts TIMESTAMP(3),
WATERMARK FOR ts AS ts - INTERVAL '5' SECOND
) WITH (
'connector' = 'kafka',
'topic' = 'user_log',
'properties.bootstrap.servers' = '%s',
'format' = 'json'
)
""".formatted("localhost:9092");
tableEnv.executeSql(ddl);

JSON：

String payload = """
{
"jobName": "%s",
"vertices": [
{
"id": "%s",
"parallelism": %d
}
]
}
""".formatted(jobName, vertexId, parallelism);

 

记录类record

public record UserCategory(String category,int score) {
}

• 私有 final 字段：name 和 age
• 公共构造函数：Person(String name, int age)
• 访问器方法（Getter）：name() 和 age()（注意：不是 getName()，直接用字段名）
• equals() 和 hashCode()：基于所有组件字段的值进行比较
• toString()：格式为 Person[name=Alice, age=25]

在flink中的使用：

// 定义一个 record 作为数据模型
public record User(Long id, String name, String email, LocalDateTime createdAt) {}

// 在 Flink 程序中使用
DataStream<User> users = env.fromElements(
new User(1L, "Alice", "alice@example.com", LocalDateTime.now()),
new User(2L, "Bob", "bob@example.com", LocalDateTime.now())
);

// Flink1.18 可以自动序列化/反序列化这个 record（基于反射或 Kryo）
users
.keyBy(User::id) // 按 id 分组
.window(TumblingProcessingTimeWindows.of(Time.seconds(5)))
.sum("id") // 可以使用字段名，Flink 会通过反射找到对应的访问器方法
.print();

 

switch：

可以灵活通用的使用switch了！支持 enum | String | int 等

public static void main(String[] args) {
    String connector = "kakfa";
    int code = switch (connector){
        case "kafka" -> 1;
        case "jdbc" -> 2;
        default -> 3;
    };
    System.out.println(code);
}

toList代替collect:（注意返回的是不可变的List）

List<String> a = List.of("a", "b", "c");
List<String> list = a.stream().map(String::toUpperCase).toList();

密封类：sealed class / interface

public sealed interface Event
permits OrderEvent, PaymentEvent, LoginEvent {
long timestamp();
}

 

模式匹配：

老写法：

@Override
public void processElement(Event e, Context ctx, Collector<String> out) {
if (e instanceof OrderEvent) {
OrderEvent oe = (OrderEvent) e;
out.collect("order:" + oe.userId());
} else if (e instanceof PaymentEvent) {
PaymentEvent pe = (PaymentEvent) e;
out.collect("payment:" + pe.payId());
}
}

新写法：

@Override
public void processElement(Event e, Context ctx, Collector<String> out) {
if (e instanceof OrderEvent(var userId, var amount)) {
out.collect("order:" + userId);
} else if (e instanceof PaymentEvent(var payId, var amt)) {
out.collect("payment:" + payId);
}
}