Merge branch 'main' into java-aggregating

Author: agoerler

.vitepress/config.js

@@ -106,8 +106,8 @@ config.rewrites = rewrites
 // Add custom capire info to the theme config
 config.themeConfig.capire = {
   versions: {
-    java_services: '4.3.2',
-    java_cds4j: '4.3.2'
+    java_services: '4.4.0',
+    java_cds4j: '4.4.0'
   },
   gotoLinks: []
 }

java/outbox.md

@@ -163,6 +163,73 @@ To be sure that the deployment version has been set correctly, you can find a lo
 
 And finally, if for some reason you don't want to use a version check for a particular outbox collector, you can switch it off via the outbox configuration [<Config java filesOnly>cds.outbox.services.MyCustomOutbox.checkVersion: false</Config>](../java/developing-applications/properties#cds-outbox-services-<key>-checkVersion).
 
+### Outbox for Shared Databases
+
+Currently, CAP Java does not yet support microservices with shared database out of the box, as this can lead to unexpected behavior when different isolated services use the same outboxes.
+Since CAP automatically creates two outboxes with a static name — **DefaultOutboxOrdered** and **DefaultOutboxUnordered** — these would be shared across all services which introduces conflicts.
+
+To avoid this, you can apply a manual workaround as follows:
+
+ 1. Customize the outbox configuration and isolating them via distinct namespaces for each service.
+ 2. Adapt the Audit Log outbox configuration.
+ 3. Adapt the messaging outbox configuration per service.
+ 
+ These steps are described in the following sections.
+
+#### Deactivate Default Outboxes
+
+First, deactivate the two default outboxes and create custom outboxes with configurations tailored to your needs.
+
+```yaml
+cds:
+  outbox:
+    services:
+      # deactivate default outboxes
+      DefaultOutboxUnordered.enabled: false
+      DefaultOutboxOrdered.enabled: false
+      # custom outboxes with unique names
+      Service1CustomOutboxOrdered:
+        maxAttempts: 10
+        storeLastError: true
+        ordered: true
+      Service1CustomOutboxUnordered:
+        maxAttempts: 10
+        storeLastError: true
+        ordered: false
+
+```
+
+#### Adapt Audit Log Configuration
+
+The **DefaultOutboxUnordered** outbox is automatically used for audit logging. Therefore, you must update the audit log configuration to point to the custom one.
+
+```yaml
+cds:
+  ...
+  auditlog:
+    outbox.name: Service1CustomOutboxUnordered
+```
+
+#### Adapt Messaging Configuration
+
+Next, adapt the messaging configuration of **every** messaging service in the application so that they use the custom-defined outboxes.
+
+```yaml
+cds:
+  messaging:
+    services:
+      MessagingService1:
+        outbox.name: Service1CustomOutboxOrdered
+      MessagingService2:
+        outbox.name: Service1CustomOutboxOrdered
+```
+
+
+::: tip Important Note
+It is crucial to **deactivate** the default outboxes, and	ensure **unique outbox namespaces** in order to achieve proper isolation between services in a shared DB scenario.
+:::
+  
+
 ## Outboxing CAP Service Events
 
 Outbox services support outboxing of arbitrary CAP services. A typical use case is to outbox remote OData

java/working-with-cql/query-api.md

@@ -1483,6 +1483,10 @@ Scalar functions are values that are calculated from other values. This calculat
       .where(e -> e.get("name").substring(2).eq("ter"));
     ```
 
+* Concat
+
+  See [`Concat`](#string-expressions) String Expression
+
 #### Case-When-Then Expressions
 
 Use a case expression to compute a value based on the evaluation of conditions. The following query converts the stock of Books into a textual representation as 'stockLevel':
@@ -1494,6 +1498,17 @@ Select.from(BOOKS).columns(
         .when(b.stock().gt(100)).then("high")
         .orElse("medium").as("stockLevel").type(CdsBaseType.STRING));
 ```
+#### String Expressions
+
+* Concat
+
+    Function `concat` creates a string expression to concatenate a specified value to this value.
+
+    ```java
+    // SELECT from Author {name || ' - the Author' as author_name : String}
+    Select.from(AUTHOR)
+      .columns(a -> a.name().concat(" - the Author").as("author_name"));
+    ```
 
 #### Arithmetic Expressions