How to use

to

method

in

org.apache.beam.sdk.schemas.transforms.Convert

/**
 * Convert a {@link PCollection}{@literal <Row>} into a {@link PCollection}{@literal <OutputT>}.
 *
 * <p>The output schema will be inferred using the schema registry. A schema must be registered
 * for this type, or the conversion will fail.
 */
public static <OutputT> PTransform<PCollection<Row>, PCollection<OutputT>> fromRows(
  Class<OutputT> clazz) {
 return to(clazz);
}

/**
 * Convert a {@link PCollection}{@literal <Row>} into a {@link PCollection}{@literal <Row>}.
 *
 * <p>The output schema will be inferred using the schema registry. A schema must be registered
 * for this type, or the conversion will fail.
 */
public static <OutputT> PTransform<PCollection<Row>, PCollection<OutputT>> fromRows(
  TypeDescriptor<OutputT> typeDescriptor) {
 return to(typeDescriptor);
}

/**
 * Convert a {@link PCollection}{@literal <InputT>} into a {@link PCollection}{@literal <Row>}.
 *
 * <p>The input {@link PCollection} must have a schema attached. The output collection will have
 * the same schema as the iput.
 */
public static <InputT> PTransform<PCollection<InputT>, PCollection<Row>> toRows() {
 return to(Row.class);
}

/**
 * Convert a {@link PCollection}{@literal <InputT>} to a {@link PCollection}{@literal <OutputT>}.
 *
 * <p>This function allows converting between two types as long as the two types have
 * <i>compatible</i> schemas. Two schemas are said to be <i>compatible</i> if they recursively
 * have fields with the same names, but possibly different orders.
 */
public static <InputT, OutputT> PTransform<PCollection<InputT>, PCollection<OutputT>> to(
  Class<OutputT> clazz) {
 return to(TypeDescriptor.of(clazz));
}

 @Test
 @Category(NeedsRunner.class)
 public void testGeneralConvert() {
  PCollection<POJO2> pojos =
    pipeline.apply(Create.of(new POJO1())).apply(Convert.to(POJO2.class));
  PAssert.that(pojos).containsInAnyOrder(new POJO2());
  pipeline.run();
 }
}

@Test
@Category(NeedsRunner.class)
public void testSelectAll() {
 PCollection<POJO1> pojos =
   pipeline
     .apply(Create.of(new POJO1()))
     .apply(Select.fieldAccess(FieldAccessDescriptor.withAllFields()))
     .apply(Convert.to(POJO1.class));
 PAssert.that(pojos).containsInAnyOrder(new POJO1());
 pipeline.run();
}

@Test
@Category(NeedsRunner.class)
public void testSimpleSelect() {
 PCollection<POJO1Selected> pojos =
   pipeline
     .apply(Create.of(new POJO1()))
     .apply(Select.fieldNames("field1", "field3"))
     .apply(Convert.to(POJO1Selected.class));
 PAssert.that(pojos).containsInAnyOrder(new POJO1Selected());
 pipeline.run();
}

@Test
@Category(NeedsRunner.class)
public void testComplexCast() throws Exception {
 Schema outputSchema = pipeline.getSchemaRegistry().getSchema(All2.class);
 PCollection<All2> pojos =
   pipeline
     .apply(Create.of(new All1()))
     .apply(Cast.narrowing(outputSchema))
     .apply(Convert.to(All2.class));
 PAssert.that(pojos).containsInAnyOrder(new All2());
 pipeline.run();
}

@Test
@Category(NeedsRunner.class)
public void testTypeNarrow() throws Exception {
 // narrowing is the opposite of widening
 Schema outputSchema = pipeline.getSchemaRegistry().getSchema(TypeWiden1.class);
 PCollection<TypeWiden1> pojos =
   pipeline
     .apply(Create.of(new TypeWiden2()))
     .apply(Cast.narrowing(outputSchema))
     .apply(Convert.to(TypeWiden1.class));
 PAssert.that(pojos).containsInAnyOrder(new TypeWiden1());
 pipeline.run();
}

@Test
@Category(NeedsRunner.class)
public void testTypeWiden() throws Exception {
 Schema outputSchema = pipeline.getSchemaRegistry().getSchema(TypeWiden2.class);
 PCollection<TypeWiden2> pojos =
   pipeline
     .apply(Create.of(new TypeWiden1()))
     .apply(Cast.widening(outputSchema))
     .apply(Convert.to(TypeWiden2.class));
 PAssert.that(pojos).containsInAnyOrder(new TypeWiden2());
 pipeline.run();
}

@Test
@Category(NeedsRunner.class)
public void testWeakedNullable() throws Exception {
 Schema outputSchema = pipeline.getSchemaRegistry().getSchema(Nullable2.class);
 PCollection<Nullable2> pojos =
   pipeline
     .apply(Create.of(new Nullable1()))
     .apply(Cast.narrowing(outputSchema))
     .apply(Convert.to(Nullable2.class));
 PAssert.that(pojos).containsInAnyOrder(new Nullable2());
 pipeline.run();
}

@Test
@Category(NeedsRunner.class)
public void testProjection() throws Exception {
 Schema outputSchema = pipeline.getSchemaRegistry().getSchema(Projection2.class);
 PCollection<Projection2> pojos =
   pipeline
     .apply(Create.of(new Projection1()))
     .apply(Cast.widening(outputSchema))
     .apply(Convert.to(Projection2.class));
 PAssert.that(pojos).containsInAnyOrder(new Projection2());
 pipeline.run();
}

@Test
@Category(NeedsRunner.class)
public void testIgnoreNullable() throws Exception {
 // ignoring nullable is opposite of weakening
 Schema outputSchema = pipeline.getSchemaRegistry().getSchema(Nullable1.class);
 PCollection<Nullable1> pojos =
   pipeline
     .apply(Create.of(new Nullable2()))
     .apply(Cast.narrowing(outputSchema))
     .apply(Convert.to(Nullable1.class));
 PAssert.that(pojos).containsInAnyOrder(new Nullable1());
 pipeline.run();
}

 @Test
 @Category(NeedsRunner.class)
 public void testSelectNestedPartial() {
  PCollection<POJO2NestedPartial> pojos =
    pipeline
      .apply(Create.of(new POJO2()))
      .apply(
        Select.fieldAccess(
          FieldAccessDescriptor.create()
            .withNestedField(
              "field2", FieldAccessDescriptor.withFieldNames("field1", "field3"))))
      .apply(Convert.to(POJO2NestedPartial.class));
  PAssert.that(pojos).containsInAnyOrder(new POJO2NestedPartial());
  pipeline.run();
 }
}

@Test
@Category(NeedsRunner.class)
public void testSelectNestedAll() {
 PCollection<POJO2NestedAll> pojos =
   pipeline
     .apply(Create.of(new POJO2()))
     .apply(
       Select.fieldAccess(
         FieldAccessDescriptor.create()
           .withNestedField("field2", FieldAccessDescriptor.withAllFields())))
     .apply(Convert.to(POJO2NestedAll.class));
 PAssert.that(pojos).containsInAnyOrder(new POJO2NestedAll());
 pipeline.run();
}