Spark MySQL使用 （java）

<dependency>
            <groupId>org.apache.spark</groupId>
            <artifactId>spark-core_2.12</artifactId>
            <version>2.4.4</version>
        </dependency>
 
        <!-- https://mvnrepository.com/artifact/org.apache.spark/spark-sql -->
        <dependency>
            <groupId>org.apache.spark</groupId>
            <artifactId>spark-sql_2.12</artifactId>
            <version>2.4.4</version>
        </dependency>
 
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.16</version>
        </dependency>

import org.apache.spark.sql.Dataset;
import org.apache.spark.sql.Row;
import org.apache.spark.sql.SparkSession;
 
public class JavaSparkSqlDemo {
    public static void main(String[] args){
        SparkSession sparkSession = SparkSession
                .builder()
                .appName("JavaSparkSqlDemo")  //Sets a name for the application
                .master("local")    //Sets the Spark master URL to connect to
                .getOrCreate();     //获取或者新建一个 sparkSession
        //设置sparkSession数据连接
        Dataset userDataset = sparkSession.read()
                .format("jdbc")
                .option("url","jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=utf-8")
                .option("dbtable","user")
                .option("driver","com.mysql.cj.jdbc.Driver")
                .option("user","root")
                .option("password","root")
                .load();
        Dataset roleDataset = sparkSession.read()
                .format("jdbc")
                .option("url","jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=utf-8")
                .option("dbtable","role")
                .option("driver","com.mysql.cj.jdbc.Driver")
                .option("user","root")
                .option("password","root")
                .load();
        //注册临时表后才能进行select等操作，必需，否则not found in database ‘default‘
        userDataset.registerTempTable("user");
        roleDataset.registerTempTable("role");
        //SQL查询操作
        //注意：1.所有用到的表需要在option和registerTempTable注册
        Dataset<Row> sqlDF = sparkSession.sql("SELECT t1.id,t1.name,t2.role FROM USER t1 LEFT JOIN role t2 ON t1.id = t2.id ");
        sqlDF.show();
       
    }
}