Add mapping for converted objects [DATAREST-533]

[spring-projects-issues]

Vasily Kartashov opened DATAREST-533 and commented

I have an entity with an embedded object that is stored as a serialised JSON in the database:

@Entity
public class Unit {
    ...
    @Column
    @Convert(converter = ConnectionStatusConverter.class)
    private ConnectionStatus connectionStatus;
    ...
}

@Converter
public class ConnectionStatusConverter implements AttributeConverter<ConnectionStatus, String> {
    public String convertToDatabaseColumn(ConnectionStatus attribute) { ... }
    public ConnectionStatus convertToEntityAttribute(String dbData) { ... }
}

Everything is fine with serialisation and deserialisation except when I try to PATCH an object with the following payload

{
    "connectionStatus": {
        ...
    }
}

I get NullPointerException. It is caused by the DomainObjectReader.doMerge expecting embedded object to be an entity, and this one (of type ConnectionStatus) is obviously not.

The solution maybe fairly simple, unless I badly misjudge the code: As long as the entity's property is marked with @Column don't try to find an embedded entity, but stick with current one (in my case Unit) while merging the fields.

---

Affects: 2.3 GA (Fowler)

[spring-projects-issues]

Oliver Drotbohm commented

What's the exact exception you see? What does ConnectionStatus look like? I am not sure I get the connection to the type conversion on the persistence provider level. For Spring Data REST ConnectionStatus is a complex object, not sure what makes you think it's "obviously not". Nothing very obvious here :).

Unfortunately the solution is not that fairly simple, as SD REST does not make any assumptions about the underlying store so that there's no way we can refer to @Column from SD REST code

[spring-projects-issues]

Vasily Kartashov commented

Hi Oliver,

thanks for the reply. ConnectionStatus is a fairly simple value object

public class ConnectionStatus {

    private String status;
    ...

    @JsonCreator
    public ConnectionStatus(@JsonProperty("status") String status, ...) {
        this.status = status;
        ...
    }

    @JsonProperty
    public String getStatus() { return status; }
    ...
}

The exception is

org.springframework.http.converter.HttpMessageNotReadableException: Could not read an object of type class net.observant.beobachter.domain.entities.fieldunit.FieldUnit from the request!; nested exception is org.springframework.http.converter.HttpMessageNotReadableException: Could not read payload!; nested exception is java.lang.NullPointerException
    at org.springframework.data.rest.webmvc.config.PersistentEntityResourceHandlerMethodArgumentResolver.readPatch(PersistentEntityResourceHandlerMethodArgumentResolver.java:183)
    at org.springframework.data.rest.webmvc.config.PersistentEntityResourceHandlerMethodArgumentResolver.read(PersistentEntityResourceHandlerMethodArgumentResolver.java:160)
    at org.springframework.data.rest.webmvc.config.PersistentEntityResourceHandlerMethodArgumentResolver.resolveArgument(PersistentEntityResourceHandlerMethodArgumentResolver.java:125)
    at org.springframework.web.method.support.HandlerMethodArgumentResolverComposite.resolveArgument(HandlerMethodArgumentResolverComposite.java:77)
    at org.springframework.web.method.support.InvocableHandlerMethod.getMethodArgumentValues(InvocableHandlerMethod.java:162)
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:129)
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:110)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:776)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:705)
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:959)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:893)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:966)
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:839)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:725)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:291)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:77)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:85)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:219)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:501)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:142)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:516)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1086)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:659)
    at org.apache.coyote.http11.Http11NioProtocol$Http11ConnectionHandler.process(Http11NioProtocol.java:223)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1558)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1515)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Thread.java:745)
Caused by: org.springframework.http.converter.HttpMessageNotReadableException: Could not read payload!; nested exception is java.lang.NullPointerException
    at org.springframework.data.rest.webmvc.json.DomainObjectReader.read(DomainObjectReader.java:90)
    at org.springframework.data.rest.webmvc.config.JsonPatchHandler.applyMergePatch(JsonPatchHandler.java:129)
    at org.springframework.data.rest.webmvc.config.JsonPatchHandler.apply(JsonPatchHandler.java:99)
    at org.springframework.data.rest.webmvc.config.PersistentEntityResourceHandlerMethodArgumentResolver.readPatch(PersistentEntityResourceHandlerMethodArgumentResolver.java:181)
    ... 43 common frames omitted
Caused by: java.lang.NullPointerException: null
    at org.springframework.data.rest.webmvc.json.DomainObjectReader.getJacksonProperties(DomainObjectReader.java:204)
    at org.springframework.data.rest.webmvc.json.DomainObjectReader.doMerge(DomainObjectReader.java:157)
    at org.springframework.data.rest.webmvc.json.DomainObjectReader.doMerge(DomainObjectReader.java:185)
    at org.springframework.data.rest.webmvc.json.DomainObjectReader.read(DomainObjectReader.java:88)
    ... 46 common frames omitted

I see now that the PersistenceEntity is not really a JPA entity, that might be the core misunderstanding on my part. Would some annotation like @ComplexProperty or something along those lines be an option?

[spring-projects-issues]

Oliver Drotbohm commented

What is FieldUnit? ConnectionStatus is not even mentioned in the stack trace. It seems that our metamodel detects ConnectionStatus as managed entity but fails to lookup a PersistentEntity for it later on. Any chance you create a tiny reproducing sample project to investigate?

Let's start thinking about a solution once we clearly understood what the problem is ;)

[spring-projects-issues]

Vasily Kartashov commented

I've created the sample project here: https://github.com/vasily-kartashov/spring-data-rest-converters

The README contains the steps necessary to reproduce the exception. Interesting enough, that the first PATCH gets through as the connectionStatus is null

[spring-projects-issues]

Oliver Drotbohm commented

It seems like there's a POM missing. Any chance you create a test case that reproduces the error? Ideally mvn clean test shows a failing test

[spring-projects-issues]

Vasily Kartashov commented

Hi Oliver,

Oops, missed the POM. I've updated the code and added a unit test that shows that the second PATCH is failing.

https://github.com/vasily-kartashov/spring-data-rest-converters