Spring Data REST #Idclass not recognized - spring

Question

I have an entity named EmployeeDepartment as below
#IdClass(EmployeeDepartmentPK.class) //EmployeeDepartmentPK is a serializeable object
#Entity
EmployeeDepartment{
#Id
private String employeeID;
#Id
private String departmentCode;
---- Getters, Setters and other props/columns
}
and I have a Spring Data Repository defined as as below
#RepositoryRestResource(....)
public interface IEmployeeDepartmentRepository extends PagingAndSortingRepository<EmployeeDepartment, EmployeeDepartmentPK> {
}
Further, I have a converter registered to convert from String to EmployeeDepartmentPK.
Now, for an entity, qualified by ID employeeID="abc123" and departmentCode="JBG", I expect the ID to use when SDR interface is called is abc123_JBG.
For example http://localhost/EmployeeDepartment/abc123_JBG should fetch me the result and indeed it does.
But, when I try to save an entity using PUT, the ID property available in BasicPersistentEntity class of Spring Data Commons is having a value of
abc123_JBG for departmentCode. This is wrong. I'm not sure if this is an expected behaviour.
Please help.
Thanks!

Answer 1

Currently Spring Data REST only supports compound keys that are represented as by a single field. That effectively means only #EmbeddedId is supported. I've filed DATAJPA-770 to fix that.
If you can switch to #EmbeddedId you still need to teach Spring Data REST the way you'd like to represent your complex identifier in the URI and how to transform the path segment back into an instance of your id type. To achieve that, implement a BackendIdConverter and register it as Spring bean.
#Component
class CustomBackendIdConverter implements BackendIdConverter {
#Override
public Serializable fromRequestId(String id, Class<?> entityType) {
// Make sure you validate the input
String[] parts = id.split("_");
return new YourEmbeddedIdType(parts[0], parts[1]);
}
#Override
public String toRequestId(Serializable source, Class<?> entityType) {
YourIdType id = (YourIdType) source;
return String.format("%s_%s", …);
}
#Override
public boolean supports(Class<?> type) {
return YourDomainType.class.equals(type);
}
}

Answer 2

If you can't use #EmbeddedId, you can still use #IdClass. For that, you need the BackendIdConverter as Oliver Gierke answered, but you also need to add a Lookup for your domain type:
#Configuration
public class IdClassAllowingConfig extends RepositoryRestConfigurerAdapter {
#Override
public void configureRepositoryRestConfiguration(RepositoryRestConfiguration config) {
config.withEntityLookup().forRepository(EmployeeDepartmentRepository.class, (EmployeeDepartment ed) -> {
EmployeeDepartmentPK pk = new EmployeeDepartmentPK();
pk.setDepartmentId(ed.getDepartmentId());
pk.setEmployeeId(ed.getEmployeeId());
return pk;
}, EmployeeDepartmentRepository::findOne);
}
}

Answer 3

Use #BasePathAwareController to customize Spring data rest controller.
#BasePathAwareController
public class CustInfoCustAcctController {
#Autowired
CustInfoCustAcctRepository cicaRepo;
#RequestMapping(value = "/custInfoCustAccts/{id}", method = RequestMethod.GET)
public #ResponseBody custInfoCustAccts getOne(#PathVariable("id") String id) {
String[] parts = id.split("_");
CustInfoCustAcctKey key = new CustInfoCustAcctKey(parts[0],parts[1]);
return cicaRepo.getOne(key);
}
}
It's work fine for me with sample uri /api/custInfoCustAccts/89232_70

Answer 4

A more generic approach would be following -
package com.pratham.persistence.config;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.sun.istack.NotNull;
import lombok.RequiredArgsConstructor;
import org.springframework.data.rest.webmvc.spi.BackendIdConverter;
import org.springframework.lang.NonNull;
import org.springframework.stereotype.Component;
import javax.persistence.EmbeddedId;
import java.io.Serializable;
import java.lang.reflect.Field;
import java.util.Arrays;
import java.util.Base64;
import java.util.Optional;
import static java.nio.charset.StandardCharsets.UTF_8;
/**
* Customization of how composite ids are exposed in URIs.
* The implementation will convert the Ids marked with {#link EmbeddedId} to base64 encoded json
* in order to expose them properly within URI.
*
* #author im-pratham
*/
#Component
#RequiredArgsConstructor
public class EmbeddedBackendIdConverter implements BackendIdConverter {
private final ObjectMapper objectMapper;
#Override
public Serializable fromRequestId(String id, Class<?> entityType) {
return getFieldWithEmbeddedAnnotation(entityType)
.map(Field::getType)
.map(ret -> {
try {
String decodedId = new String(Base64.getUrlDecoder().decode(id));
return (Serializable) objectMapper.readValue(decodedId, (Class) ret);
} catch (JsonProcessingException ignored) {
return null;
}
})
.orElse(id);
}
#Override
public String toRequestId(Serializable id, Class<?> entityType) {
try {
String json = objectMapper.writeValueAsString(id);
return Base64.getUrlEncoder().encodeToString(json.getBytes(UTF_8));
} catch (JsonProcessingException ignored) {
return id.toString();
}
}
#Override
public boolean supports(#NonNull Class<?> entity) {
return isEmbeddedIdAnnotationPresent(entity);
}
private boolean isEmbeddedIdAnnotationPresent(Class<?> entity) {
return getFieldWithEmbeddedAnnotation(entity)
.isPresent();
}
#NotNull
private static Optional<Field> getFieldWithEmbeddedAnnotation(Class<?> entity) {
return Arrays.stream(entity.getDeclaredFields())
.filter(method -> method.isAnnotationPresent(EmbeddedId.class))
.findFirst();
}
}