how to read table by jdbc as stream in apache flink

To read a table by JDBC as a stream in Apache Flink, you can follow these steps:

1. Add the JDBC dependency to your Flink project:

<dependency>
  <groupId>org.apache.flink</groupId>
  <artifactId>flink-jdbc_${scala.binary.version}</artifactId>
  <version>${flink.version}</version>
</dependency>

2. Define a JDBCInputFormat using the Flink JDBC library. This format provides a way to read data from a JDBC database.

JDBCInputFormat jdbcInputFormat = JDBCInputFormat.buildJDBCInputFormat()
    .setDrivername("com.mysql.jdbc.Driver")
    .setDBUrl("jdbc:mysql://localhost:3306/mydatabase")
    .setUsername("myuser")
    .setPassword("mypassword")
    .setQuery("SELECT * FROM mytable")
    .setRowTypeInfo(rowTypeInfo) // define the schema of the table
    .finish();

3. Create a DataStream using the createInput() method from the JDBCInputFormat.

DataStream<MyRecord> stream = env.createInput(jdbcInputFormat);

4. You can then process the stream using Flink operations like map, filter, and reduce.

DataStream<MyResult> resultStream = stream
    .filter(record -> record.getSomeField() > 0)
    .map(record -> new MyResult(record.getSomeOtherField()));

Note: You may need to adjust the code for your specific database and table schema.