Fix: how to configure BeforeSend callback with Spring (#4629)

Author: maciejwalkowiak

src/includes/configuration/before-send-fingerprint/java.spring.mdx

@@ -0,0 +1,32 @@
+```java
+import io.sentry.SentryEvent;
+import io.sentry.SentryOptions;
+import org.springframework.stereotype.Component;
+
+@Component
+public class CustomBeforeSendCallback implements SentryOptions.BeforeSendCallback {
+  @Override
+  public SentryEvent execute(SentryEvent event, Object hint) {
+    if (event.getThrowable() instanceof SQLException) {
+      event.setFingerprints(Arrays.asList("database-connection-error"));
+    }
+    return event;
+  }
+}
+```
+
+```kotlin
+import io.sentry.SentryEvent
+import io.sentry.SentryOptions
+import org.springframework.stereotype.Component
+
+@Component
+class CustomBeforeSendCallback : SentryOptions.BeforeSendCallback {
+  override fun execute(event: SentryEvent, hint: Any?): SentryEvent? {
+    if (event.throwable is SQLException) {
+      event.fingerprints = listOf("database-connection-error")
+    }
+    event
+  }
+}
+```

src/includes/configuration/before-send-hint/java.spring.mdx

@@ -0,0 +1,36 @@
+A `BiFunction<SentryEvent, Object, SentryEvent>` can be used to mutate, discard (return null), or return a completely new event.
+
+```java
+import io.sentry.SentryEvent;
+import io.sentry.SentryOptions;
+import org.springframework.stereotype.Component;
+
+@Component
+public class CustomBeforeSendCallback implements SentryOptions.BeforeSendCallback {
+  @Override
+  public SentryEvent execute(SentryEvent event, Object hint) {
+    if (hint instanceof MyHint) {
+      return null;
+    } else {
+      return event;
+    }
+  }
+}
+```
+
+```kotlin
+import io.sentry.SentryEvent
+import io.sentry.SentryOptions
+import org.springframework.stereotype.Component
+
+@Component
+class CustomBeforeSendCallback : SentryOptions.BeforeSendCallback {
+  override fun execute(event: SentryEvent, hint: Any?): SentryEvent? {
+    if (hint is MyHint) {
+      null
+    } else {
+      event
+    }
+  }
+}
+```

src/includes/configuration/before-send/java.spring-boot.mdx

@@ -1,4 +1,4 @@
-`beforeSend` callback can be registered simply by creating a Spring bean implementing the `BeforeSendCallback`.
+`beforeSend` callback can be registered by creating a Spring bean implementing the `BeforeSendCallback`.
 
 ```java
 import io.sentry.SentryEvent;

src/includes/configuration/before-send/java.spring.mdx

@@ -0,0 +1,32 @@
+`beforeSend` callback can be registered by creating a Spring bean implementing the `BeforeSendCallback`.
+
+```java
+import io.sentry.SentryEvent;
+import io.sentry.SentryOptions;
+import org.springframework.stereotype.Component;
+
+@Component
+public class CustomBeforeSendCallback implements SentryOptions.BeforeSendCallback {
+  @Override
+  public SentryEvent execute(SentryEvent event, Object hint) {
+    // Example: Never send server name in events
+    event.setServerName(null);
+    return event;
+  }
+}
+```
+
+```kotlin
+import io.sentry.SentryEvent
+import io.sentry.SentryOptions
+import org.springframework.stereotype.Component
+
+@Component
+class CustomBeforeSendCallback : SentryOptions.BeforeSendCallback {
+  override fun execute(event: SentryEvent, hint: Any?): SentryEvent? {
+    // Example: Never send server name in events
+    event.serverName = null
+    return event
+  }
+}
+```