如何将自定义 Java 类转换为 Spark 数据集

2022-01-21 00:00:00 apache-spark dataset java

我不知道如何将测试对象列表转换为 Spark 中的数据集这是我的课:

I can't figure out a way to convert a List of Test objects to a Dataset in Spark This is my class:

public class Test {
    public String a;
    public String b;
    public Test(String a, String b){
        this.a = a;
        this.b = b;
    }

    public List getList(){
        List l = new ArrayList();
        l.add(this.a);
        l.add(this.b);

        return l;
    }
}

推荐答案

您在注释中创建 DataFrame 的代码是正确的.但是，您定义 Test 的方式存在问题.您只能使用来自 Java Bean 的代码创建 DataFrame.您的 Test 类不是 Java Bean.修复该问题后，您可以使用以下代码创建 DataFrame:

Your code in the comments to create a DataFrame is correct. However, there is a problem with the way you define Test. You can create DataFrames using your code only from Java Beans. Your Test class is not a Java Bean. Once you fix that, you can use the following code to create a DataFrame:

Dataset<Row> dataFrame = spark.createDataFrame(listOfTestClasses, Test.class);

这些行来创建一个类型化的数据集:

and these lines to create a typed Dataset:

Encoder<Test> encoder = Encoders.bean(Test.class);
Dataset<Test> dataset = spark.createDataset(listOfTestClasses, encoder);

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