如何在Apache Flink中消费来自Kafka的消息？

<dependency>
    <groupId>org.apache.flink</groupId>
    <artifactId>flink-connector-kafka_2.11</artifactId>
    <version>${flink.version}</version>
</dependency>

Properties properties = new Properties();
properties.setProperty("bootstrap.servers", "kafka-broker1:9092,kafka-broker2:9092");
properties.setProperty("group.id", "flink-consumer-group");

FlinkKafkaConsumer<String> kafkaConsumer = new FlinkKafkaConsumer<>(
    "kafka-topic",
    new SimpleStringSchema(),
    properties
);

StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();
env.addSource(kafkaConsumer).print();