SAP集成中ODATA $batch请求传递ETag的实现疑问

核心问题说明 #

OData的$batch请求中，同一个**changeset（变更集）**内的请求是原子性执行的——要么全部成功，要么全部回滚。在此过程中，客户端无法获取中间请求的响应头（包括修改实体后生成的新ETag），因此无法在同一个changeset内的请求间动态传递ETag。

可行解决方案 #

将依赖ETag的操作拆分为多轮独立的batch请求序列，每轮完成后从响应中提取最新ETag，用于下一轮的修改请求。具体步骤如下：

1. 第一轮：获取初始ETag并更新出库交付行项目

Content-Type: multipart/mixed; boundary=batch_01

--batch_01
Content-Type: application/http
Content-Transfer-Encoding: binary

GET A_OutbDeliveryHeader(DeliveryDocument='0000000001') HTTP/1.1
sap-context-accept: header
Content-Type: application/json
Accept: application/json
Content-ID: C1

--batch_01
Content-Type: multipart/mixed; boundary=changeset_01

--changeset_01
Content-Type: application/http
Content-Transfer-Encoding: binary

PATCH A_OutbDeliveryItem(DeliveryDocument='0000000001',DeliveryDocumentItem='10') HTTP/1.1
sap-context-accept: header
Content-Type: application/json
Accept: application/json
If-Match: <从C1响应头中提取的初始ETag>

{
  "ActualDeliveryQuantity": "2.000"
}
--changeset_01--
--batch_01--

2. 第二轮：获取更新后的表头ETag，修改表头并执行过账

Content-Type: multipart/mixed; boundary=batch_02

--batch_02
Content-Type: application/http
Content-Transfer-Encoding: binary

GET A_OutbDeliveryHeader(DeliveryDocument='0000000001') HTTP/1.1
sap-context-accept: header
Content-Type: application/json
Accept: application/json
Content-ID: C3

--batch_02
Content-Type: multipart/mixed; boundary=changeset_02

--changeset_02
Content-Type: application/http
Content-Transfer-Encoding: binary

PATCH A_OutbDeliveryHeader(DeliveryDocument='0000000001') HTTP/1.1
sap-context-accept: header
Content-Type: application/json
Accept: application/json
If-Match: <从C3响应头中提取的最新ETag>

{
  "ActualGoodsMovementDate": "2023-03-14T13:33:10",
  "ActualGoodsMovementTime": "PT13H33M10S"
}
--changeset_02--

--batch_02
Content-Type: application/http
Content-Transfer-Encoding: binary

GET A_OutbDeliveryHeader(DeliveryDocument='0000000001') HTTP/1.1
sap-context-accept: header
Content-Type: application/json
Accept: application/json
Content-ID: C4

--batch_02
Content-Type: multipart/mixed; boundary=changeset_03

--changeset_03
Content-Type: application/http
Content-Transfer-Encoding: binary

POST PostGoodsIssue?DeliveryDocument='0000000001' HTTP/1.1
sap-context-accept: header
Content-Type: application/json
Accept: application/json
If-Match: <从C4响应头中提取的最新ETag>
--changeset_03--
--batch_02--

关键注意事项 #

• 每轮batch执行完成后，务必从对应GET请求的响应头中提取ETag字段，替换下一轮请求的If-Match值。
• 禁止将依赖动态ETag的修改请求放在同一个changeset内，否则无法获取中间步骤生成的新ETag。
• 无依赖关系的请求可合并到同一个batch的独立段中，减少请求次数。

内容的提问来源于stack exchange，提问作者Jijo Joseph