[SOLVED] Bi-directional navigation in OData V4

* I will accept the answer with bounty if it just solves my problem (if you don't have a detailed canonical solution) *

When i try to access the metadata from browser (http://......Service.svc/$metadata), I see below error.

500 Cannot find navigation property with name: projectConfigs at type ProjectConfig

I am trying to design a bi-directional association in OData v4 (I am using Partner, any other way available?!). I am not sure what is the mistake I am doing while implementing it.

I have two classes namely “Project” and “ProjectConfig”. I need navigation from Project to ProjectConfig and vice-versa. The idea is that for a defined Project, I should be able to see the ProjectConfig(urations) and from there I want navigation back to the Project it belongs to.

I am using Olingo framework for writing application code. This is the example i followed.

The challenge i see in this example is that navigation name "Products" and EntitySet name "Products" are same.

To my understanding when we define partner on a navigation, we should be able to find a property with the same name in the "Nav Type". This will ideally setup the navigation back to the entitytype.

I have pasted the metadata and java application code that is of interest.

metadata.xml

<EntityType Name="Project">
    <Key>
        <PropertyRef Name="id"/>
    </Key>
    <Property Name="id" Type="Edm.Int32"/>
    <Property Name="name_artifact_id" Type="Edm.String"/>
    <Property Name="groupid" Type="Edm.String"/>
    <Property Name="project_display_name" Type="Edm.String"/>

    <NavigationProperty Name="projectConfigs"
                        Type="Collection(devplatform.config.ProjectConfig)"
                        Partner="project"/>
</EntityType>

<EntityType Name="ProjectConfig">
    <Key>
        <PropertyRef Name="id"/>
    </Key>
    <Property Name="id" Type="Edm.Int32"/>

    <NavigationProperty Name="project"
                        Type="devplatform.config.Project"
                        Partner="projectConfigs"/>
</EntityType>

<EntitySet Name="Projects" EntityType="devplatform.config.Project">
    <NavigationPropertyBinding Path="ProjectConfigs" Target="ProjectConfigs"/>
</EntitySet>

<EntitySet Name="ProjectConfigs" EntityType="devplatform.config.ProjectConfig">
    <NavigationPropertyBinding Path="Projects" Target="Projects"/>
</EntitySet>

DemoEdmProvider.java

public static void main(String[] args) {
public static final String ET_PROJECT_NAME = "Project";
public static final FullQualifiedName ET_PROJECT_FQN = 
        new FullQualifiedName(NAMESPACE, ET_PROJECT_NAME);

public static final String ET_PROJECTCONFIG_NAME = "ProjectConfig";
public static final FullQualifiedName ET_PROJECTCONFIG_FQN = 
        new FullQualifiedName(NAMESPACE, ET_PROJECTCONFIG_NAME);

public static final String ES_PROJECTS_NAME = "Projects";
public static final String ES_PROJECTCONFIGS_NAME = "ProjectConfigs";

public static final String NAV_TO_PROJECT = "Project";
public static final String NAV_TO_PROJECTCONFIG = "ProjectConfig";


if (entityTypeName.equals(ET_PROJECT_FQN)) {
    List<CsdlProperty> propertyList = new ArrayList<CsdlProperty>();
    // create EntityType properties
    CsdlProperty id = 
            new CsdlProperty().setName("id")
                              .setType(EdmPrimitiveTypeKind.Int32.getFullQualifiedName());
    propertyList.add(id);
    CsdlProperty name_artifact_id = 
            new CsdlProperty().setName("name_artifact_id")
                              .setType(EdmPrimitiveTypeKind.String.getFullQualifiedName());
    propertyList.add(name_artifact_id);
    CsdlProperty groupid = 
            new CsdlProperty().setName("groupid")
                              .setType(EdmPrimitiveTypeKind.String.getFullQualifiedName());
    propertyList.add(groupid);
    CsdlProperty project_display_name = 
            new CsdlProperty().setName("project_display_name")
                              .setType(EdmPrimitiveTypeKind.String.getFullQualifiedName());
    propertyList.add(project_display_name);


    // create PropertyRef for Key element
    CsdlPropertyRef propertyRef = new CsdlPropertyRef();
    propertyRef.setName("id");

    // navigation property: many-to-one, null not allowed (product must have a category)
    List<CsdlNavigationProperty> navPropList = new ArrayList<CsdlNavigationProperty>();

    CsdlNavigationProperty projectconfigs = 
            new CsdlNavigationProperty().setName(NAV_TO_PROJECTCONFIGS)
                                        .setType(ET_PROJECTCONFIG_FQN)
                                        .setCollection(true)
                                        .setPartner("projectConfigs");
    navPropList.add(projectconfigs);


    // configure EntityType
    entityType = new CsdlEntityType();
    entityType.setName(ET_PROJECT_NAME);
    entityType.setProperties(propertyList);
    entityType.setKey(Arrays.asList(propertyRef));
    entityType.setNavigationProperties(navPropList);
}

if (entityTypeName.equals(ET_PROJECTCONFIG_FQN)) {
    List<CsdlProperty> propertyList = new ArrayList<CsdlProperty>();
    // create EntityType properties
    CsdlProperty id = 
            new CsdlProperty().setName("id")
                              .setType(EdmPrimitiveTypeKind.Int32.getFullQualifiedName());
    propertyList.add(id);

    // create PropertyRef for Key element
    CsdlPropertyRef propertyRef = new CsdlPropertyRef();
    propertyRef.setName("id");

    // navigation property: many-to-one, null not allowed (product must have a category)
    List<CsdlNavigationProperty> navPropList = new ArrayList<CsdlNavigationProperty>();

    // ERROR CAUSING LINE
    CsdlNavigationProperty project = 
            new CsdlNavigationProperty().setName(NAV_TO_PROJECT)
                                        .setType(ET_PROJECT_FQN)
                                        .setNullable(true)
                                        .setPartner("project");
    navPropList.add(project);

    // configure EntityType
    entityType = new CsdlEntityType();
    entityType.setName(ET_PROJECTCONFIG_NAME);
    entityType.setProperties(propertyList);
    entityType.setKey(Arrays.asList(propertyRef));
    entityType.setNavigationProperties(navPropList);
}

I can provide any missing details if needed! :) Could not get responses! Not sure, if my question is relevant to a small community!!