How do you customize the java JSON serialization done by Google Cloud Endpoints? - google-cloud-endpoints

Question

Below is the relevant method. One of the properties is of LocalDate (Joda).
#ApiMethod(
name = "taxforms.get",
path = "tax-forms",
httpMethod = ApiMethod.HttpMethod.GET
)
public TaxDataList retrieveTaxDataList(
HttpServletRequest httpServletRequest
) {
TaxDataList taxDataList = new TaxDataList( );
TaxData taxData = SampleTax.sampleTaxData( "Tax1098" );
taxDataList.addFormsItem( taxData );
return taxDataList;
}
If I do my own serialization, my code includes this:
ObjectMapper objectMapper = new ObjectMapper( );
// Special handling for dates
objectMapper.registerModule( new JodaModule( ) );
objectMapper.disable( SerializationFeature.WRITE_DATES_AS_TIMESTAMPS );
objectMapper.writeValue( sw, data );
json = sw.toString( );
How can I customize the way the framework does the serialization?

Answer 1

This is a close sample code to what you want and which uses transforms java LocalDate and Instant classes into strings and numbers:
package com.company.example;
import com.google.api.server.spi.config.Api;
import com.google.api.server.spi.config.ApiMethod;
import com.google.api.server.spi.config.Transformer;
import java.time.Instant;
import java.time.LocalDate;
import java.time.format.DateTimeFormatter;
#Api(
name="myApi",
version="v1",
transformers={
MyApi.MyInstantTransformer.class,
MyApi.MyLocalDateTransformer.class,
}
)
public class MyApi {
#ApiMethod(name="getStuff")
public MyStuff getStuff() {
return new MyStuff();
}
public static class MyStuff {
private final LocalDate date;
private final Instant instant;
MyStuff() {
date = LocalDate.now();
instant = Instant.now();
}
public LocalDate getDate() { return date; }
public Instant getInstant() { return instant; }
}
public static class MyInstantTransformer implements Transformer<Instant, Long> {
public Instant transformFrom(Long input) {
return Instant.ofEpochMilli(input);
}
public Long transformTo(Instant input) {
return input.toEpochMilli();
}
}
public static class MyLocalDateTransformer implements Transformer<LocalDate, String> {
public LocalDate transformFrom(String input) {
return LocalDate.parse(input, DateTimeFormatter.ISO_LOCAL_DATE);
}
public String transformTo(LocalDate input) {
return input.format(DateTimeFormatter.ISO_LOCAL_DATE);
}
}
}