获取重数为0到1的导航属性的VDM调用，为0响应提供NullPointerException

Question

我使用VDM来获取重数为0..1的导航属性。

每当从S4返回的响应是0(即“204No Content")时，我就会得到一个NullPointerException。

HeaderCDSForPRForGuidedBuying requisitionHeader = isActiveEntity ? readActivatedHeader(purchaseRequisition) : readHeaderInternal(draftUUID);
    GuidedProcurementDeliveryAddressAtHeader requisitionHeaderAddress;

    requisitionHeaderAddress = requisitionHeader.getGuidedProcmtReqnDelivAddrOrFetch();

    return S4ToGBServiceMapper.mapToRequisitionHeader(requisitionHeader, requisitionHeaderAddress);

这里的requisitionHeader.getGuidedProcmtReqnDelivAddrOrFetch();是导航实体，只要没有数据，它就会从S4中产生“204No Content”。

实体的元数据

    <EntityType Name="C_GuidedProcmtReqnHdrTPType" sap:label="Header CDS 
     for PR for guided buying" sap:content-version="1">
<Key> 
<PropertyRef Name="PurchaseRequisition"/>
<PropertyRef Name="DraftUUID"/>
<PropertyRef Name="IsActiveEntity"/>
</Key>
<Property Name="Activation_ac" Type="Edm.Boolean" sap:label="Dyn. Action Control" sap:creatable="false" sap:updatable="false" sap:sortable="false" sap:filterable="false"/>
<Property Name="Edit_ac" Type="Edm.Boolean" sap:label="Dyn. Action Control" sap:creatable="false" sap:updatable="false" sap:sortable="false" sap:filterable="false"/>
<Property Name="Preparation_ac" Type="Edm.Boolean" sap:label="Dyn. Action Control" sap:creatable="false" sap:updatable="false" sap:sortable="false" sap:filterable="false"/>
<Property Name="Validation_ac" Type="Edm.Boolean" sap:label="Dyn. Action Control" sap:creatable="false" sap:updatable="false" sap:sortable="false" sap:filterable="false"/>
<Property Name="PurReqnDescription_fc" Type="Edm.Byte" sap:label="Dyn. Field Control" sap:creatable="false" sap:updatable="false" sap:sortable="false" sap:filterable="false"/>
<Property Name="PurReqnSSPRequestor_fc" Type="Edm.Byte" sap:label="Dyn. Field Control" sap:creatable="false" sap:updatable="false" sap:sortable="false" sap:filterable="false"/>
<Property Name="PurchaseRequisition" Type="Edm.String" Nullable="false" MaxLength="10" sap:display-format="UpperCase" sap:label="Purchase requisition" sap:quickinfo="Purchase requisition number" sap:value-list="standard"/>
<Property Name="PurReqnDescription" Type="Edm.String" MaxLength="40" sap:field-control="PurReqnDescription_fc" sap:label="Purchase Requisition Name" sap:quickinfo="Short Text"/>
<Property Name="PurReqnSSPRequestor" Type="Edm.String" MaxLength="60" sap:field-control="PurReqnSSPRequestor_fc" sap:label="Requestor" sap:value-list="standard"/>
<Property Name="PurReqnSSPAuthor" Type="Edm.String" MaxLength="12" sap:display-format="UpperCase" sap:label="Author" sap:quickinfo="Author of Requisition"/>
<Property Name="PurchaseRequisitionType" Type="Edm.String" MaxLength="4" sap:display-format="UpperCase" sap:label="Document Type" sap:quickinfo="Purchase Requisition Document Type"/>
<Property Name="CreationDate" Type="Edm.DateTime" Precision="0" sap:display-format="Date" sap:label="Created On"/>
<Property Name="EmployeeFullName" Type="Edm.String" MaxLength="80" sap:label="Requested By" sap:quickinfo="Full Name of Person"/>
<Property Name="PurReqnOrigin" Type="Edm.String" MaxLength="1" sap:display-format="UpperCase" sap:label="Creation indicator" sap:quickinfo="Creation indicator (purchase requisition/schedule lines)"/>
<Property Name="PurReqnLifeCycleStatus" Type="Edm.String" MaxLength="2" sap:display-format="UpperCase" sap:label="LifeCycle Status" sap:quickinfo="Purchase requistion status" sap:creatable="false" sap:updatable="false" sap:sortable="false" sap:filterable="false"/>
<Property Name="PurReqnLifeCycleStatusName" Type="Edm.String" MaxLength="60" sap:label="Status" sap:quickinfo="Short Text for Fixed Values" sap:creatable="false" sap:updatable="false" sap:sortable="false" sap:filterable="false"/>
<Property Name="NumberOfItems" Type="Edm.Int32" sap:creatable="false" sap:updatable="false" sap:sortable="false" sap:filterable="false"/>
<Property Name="TotalNetAmount" Type="Edm.Decimal" Precision="16" Scale="3" sap:unit="Currency" sap:label="Total Net Value" sap:creatable="false" sap:updatable="false" sap:sortable="false" sap:filterable="false"/>
<Property Name="Currency" Type="Edm.String" MaxLength="5" sap:creatable="false" sap:updatable="false" sap:sortable="false" sap:filterable="false" sap:semantics="currency-code"/>
<Property Name="IsSrchEnabled" Type="Edm.Boolean" sap:display-format="UpperCase" sap:label="Hide Search Bar" sap:creatable="false" sap:updatable="false"/>
<Property Name="IsExtPurgScenario" Type="Edm.Boolean" sap:display-format="UpperCase" sap:label="Is External Purch." sap:quickinfo="Indicator for external purchasing scenario" sap:creatable="false" sap:updatable="false" sap:sortable="false" sap:filterable="false"/>
<Property Name="IsOnBehalfCart" Type="Edm.String" MaxLength="1" sap:display-format="UpperCase" sap:label="Shop On Behalf Ind." sap:quickinfo="Shop on behalf indicator"/>
<Property Name="PurReqnIsCopyDraft" Type="Edm.Boolean" sap:display-format="UpperCase" sap:label="Draft Is Copied" sap:quickinfo="Draft is copied from active document"/>
<Property Name="BusinessUser" Type="Edm.String" MaxLength="12" sap:display-format="UpperCase" sap:label="User ID"/>
<Property Name="PurReqnIsCreatedInExpertMode" Type="Edm.Boolean" sap:display-format="UpperCase" sap:label="PR in Expert Mode" sap:quickinfo="PR Created in Expert Mode"/>
<Property Name="AccountAssignmentCategory" Type="Edm.String" MaxLength="1" sap:display-format="UpperCase" sap:label="Acct Assignment Cat." sap:quickinfo="Account Assignment Category" sap:creatable="false" sap:updatable="false" sap:sortable="false" sap:filterable="false"/>
<Property Name="AcctAssignmentCategoryName" Type="Edm.String" MaxLength="20" sap:label="AcctAssgntCateg Desc" sap:quickinfo="Account Assignment Category Description" sap:creatable="false" sap:updatable="false" sap:sortable="false" sap:filterable="false"/>
<Property Name="PrimaryCostObject" Type="Edm.String" MaxLength="30" sap:display-format="UpperCase" sap:label="Primary Cost Object" sap:quickinfo="Account Assignment Primary Cost Object" sap:creatable="false" sap:updatable="false" sap:sortable="false" sap:filterable="false"/>
<Property Name="PrimaryCostObjectName" Type="Edm.String" MaxLength="60" sap:display-format="UpperCase" sap:label="Prim. Cost Obj. Name" sap:quickinfo="Account Assignment Primary Cost Object Name" sap:creatable="false" sap:updatable="false" sap:sortable="false" sap:filterable="false"/>
<Property Name="DeliveryDurationInDays" Type="Edm.Decimal" Precision="3" Scale="0" sap:label="Delivery time (days)" sap:quickinfo="Delivery time in days" sap:creatable="false" sap:updatable="false" sap:sortable="false" sap:filterable="false"/>
<Property Name="DeliveryTime" Type="Edm.Decimal" Precision="3" Scale="0" sap:label="Delivery time (days)" sap:quickinfo="Delivery time in days" sap:creatable="false" sap:updatable="false" sap:sortable="false" sap:filterable="false"/>
<Property Name="DeliveryDate" Type="Edm.DateTime" Precision="0" sap:display-format="Date" sap:label="Delivery date" sap:quickinfo="Item delivery date" sap:creatable="false" sap:updatable="false" sap:sortable="false" sap:filterable="false"/>
<Property Name="HasDraftEntity" Type="Edm.Boolean" sap:display-format="UpperCase" sap:label="Has Draft" sap:heading="" sap:quickinfo="" sap:creatable="false" sap:updatable="false"/>
<Property Name="DraftUUID" Type="Edm.Guid" Nullable="false" sap:label="Key" sap:heading="" sap:quickinfo="" sap:creatable="false" sap:updatable="false"/>
<Property Name="DraftEntityCreationDateTime" Type="Edm.DateTimeOffset" Precision="7" sap:label="Draft Created On" sap:heading="" sap:quickinfo="" sap:creatable="false" sap:updatable="false"/>
<Property Name="DraftEntityLastChangeDateTime" Type="Edm.DateTimeOffset" Precision="7" sap:label="Draft Last Changed On" sap:heading="" sap:quickinfo="" sap:creatable="false" sap:updatable="false"/>
<Property Name="HasActiveEntity" Type="Edm.Boolean" sap:display-format="UpperCase" sap:label="Has active" sap:heading="" sap:quickinfo="" sap:creatable="false" sap:updatable="false"/>
<Property Name="IsActiveEntity" Type="Edm.Boolean" Nullable="false" sap:display-format="UpperCase" sap:label="Is active" sap:heading="" sap:quickinfo="" sap:creatable="false" sap:updatable="false"/>
<NavigationProperty Name="DraftAdministrativeData" Relationship="MMPUR_REQ_GPR_MAINTAIN_SRV.assoc_76A4502D0F516EE52DD3CBBBE346E4D9" FromRole="FromRole_assoc_76A4502D0F516EE52DD3CBBBE346E4D9" ToRole="ToRole_assoc_76A4502D0F516EE52DD3CBBBE346E4D9"/>
<NavigationProperty Name="SiblingEntity" Relationship="MMPUR_REQ_GPR_MAINTAIN_SRV.assoc_3CC1A0E5A29B95AA58385E4B4E670133" FromRole="FromRole_assoc_3CC1A0E5A29B95AA58385E4B4E670133" ToRole="ToRole_assoc_3CC1A0E5A29B95AA58385E4B4E670133"/>
<NavigationProperty Name="to_GuidedProcmtReqnDelivAddr" Relationship="MMPUR_REQ_GPR_MAINTAIN_SRV.assoc_ABFFAA8E73382AA60F058244C4ABBB35" FromRole="FromRole_assoc_ABFFAA8E73382AA60F058244C4ABBB35" ToRole="ToRole_assoc_ABFFAA8E73382AA60F058244C4ABBB35"/>
<NavigationProperty Name="to_GuidedProcmtReqnUserDefaults" Relationship="MMPUR_REQ_GPR_MAINTAIN_SRV.assoc_1579C23A5F4ED87BDC6BD58F2005A338" FromRole="FromRole_assoc_1579C23A5F4ED87BDC6BD58F2005A338" ToRole="ToRole_assoc_1579C23A5F4ED87BDC6BD58F2005A338"/>
<NavigationProperty Name="to_Purchaserequisitionitem_Wd" Relationship="MMPUR_REQ_GPR_MAINTAIN_SRV.assoc_3F09BE43BBC7F408BF50540B885968FB" FromRole="FromRole_assoc_3F09BE43BBC7F408BF50540B885968FB" ToRole="ToRole_assoc_3F09BE43BBC7F408BF50540B885968FB"/>
<NavigationProperty Name="to_PurReqnEmplByCoOfAuthorVH" Relationship="MMPUR_REQ_GPR_MAINTAIN_SRV.assoc_F51CC3D827FD02E8485693F0D8E2BECB" FromRole="FromRole_assoc_F51CC3D827FD02E8485693F0D8E2BECB" ToRole="ToRole_assoc_F51CC3D827FD02E8485693F0D8E2BECB"/>
<NavigationProperty Name="to_SSPReqnConfiguration" Relationship="MMPUR_REQ_GPR_MAINTAIN_SRV.assoc_8453857C8C3E316B4D665A8FF57BD512" FromRole="FromRole_assoc_8453857C8C3E316B4D665A8FF57BD512" ToRole="ToRole_assoc_8453857C8C3E316B4D665A8FF57BD512"/>
</EntityType>

这里的问题是导航问题

<NavigationProperty Name="to_GuidedProcmtReqnDelivAddr" Relationship="MMPUR_REQ_GPR_MAINTAIN_SRV.assoc_ABFFAA8E73382AA60F058244C4ABBB35" FromRole="FromRole_assoc_ABFFAA8E73382AA60F058244C4ABBB35" ToRole="ToRole_assoc_ABFFAA8E73382AA60F058244C4ABBB35"/>

<Association Name="assoc_ABFFAA8E73382AA60F058244C4ABBB35" sap:content-version="1">
<End Type="MMPUR_REQ_GPR_MAINTAIN_SRV.C_GuidedProcmtReqnHdrTPType" Multiplicity="1" Role="FromRole_assoc_ABFFAA8E73382AA60F058244C4ABBB35"/>
<End Type="MMPUR_REQ_GPR_MAINTAIN_SRV.C_GuidedProcmtReqnDelivAddrType" Multiplicity="0..1" Role="ToRole_assoc_ABFFAA8E73382AA60F058244C4ABBB35"/>
</Association>

Answer 1

谢谢你的详细问题。

看起来您确实在一个与SAP Cloud SDK相关的间接使用的组件中发现了一个bug。我已经在票务系统中创建了一个事件(#1970496164)。目前还不清楚这个NullPointerException什么时候会被修复，希望在下一个即将到来的版本中。

同时，我建议使用VAVR库的Try API作为变通方法--在运行时处理错误。

import io.vavr.control.Try;

// ...

@Nonnull
HeaderCDSForPRForGuidedBuying requisitionHeader;

@Nullable
GuidedProcurementDeliveryAddressAtHeader requisitionHeaderAddress;

// tolerant error handling
requisitionHeaderAddress = Try.of(requisitionHeader::getGuidedProcmtReqnDelivAddrOrFetch).getOrNull();

return S4ToGBServiceMapper.mapToRequisitionHeader(requisitionHeader, requisitionHeaderAddress);

(假设您的mapToRequisitionHeader方法期望第二个参数为@Nullable)

将依赖添加到您的pom中：

<dependency>
  <groupId>io.vavr</groupId>
  <artifactId>vavr</artifactId>
  <version>0.10.2</version>
</dependency>

当然，作为我的建议的替代方案，您可以只使用笨重的try-catch块。