Document setting user filter on spring for transactions (#3493)

Author: maciejwalkowiak

src/platforms/java/guides/spring/advanced-usage.mdx

@@ -8,7 +8,9 @@ Record user information from an HTTP request or by registering a Spring bean for
 
 ## Recording User Information From HTTP Request
 
-To record the user's IP address and `Principal#name` as the username, set the personal information flag to `true`.
+To record the user's IP address and `Principal#name` as the username so you can then view in [Event Details](/product/performance/event-detail/):
+
+1. Set the personal information flag on `@EnableSentry` to `true`.
 
 ```Java {tabTitle:Java}
 import org.springframework.context.annotation.Configuration;
@@ -29,6 +31,140 @@ import io.sentry.spring.EnableSentry
 class SentryConfiguration
 ```
 
+2. Register the servlet filter bean `SentryUserFilter`:
+
+<Alert level="warning" title="Note">
+
+`SentryUserFilter` is available in 5.0 beta version of the Sentry Java SDK.
+
+</Alert>
+
+```java
+import io.sentry.IHub;
+import io.sentry.spring.SentryUserFilter;
+import io.sentry.spring.SentryUserProvider;
+import java.util.List;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+
+@Configuration
+public class SentryFilterConfig {
+
+  @Bean
+  public SentryUserFilter sentryUserFilter(
+      final IHub hub, final List<SentryUserProvider> sentryUserProviders) {
+    return new SentryUserFilter(hub, sentryUserProviders);
+  }
+}
+```
+
+```kotlin
+import io.sentry.IHub
+import io.sentry.spring.SentryUserProvider
+import io.sentry.spring.SentryUserFilter
+import org.springframework.context.annotation.Bean
+import org.springframework.context.annotation.Configuration
+
+@Configuration
+class SentryFilterConfig {
+    @Bean
+    fun sentryUserFilter(hub: IHub, sentryUserProviders: List<SentryUserProvider>) = SentryUserFilter(hub, sentryUserProviders)
+}
+```
+
+3. Configure `SentryUserFilter` in `web.xml` or `WebApplicationInitializer` using `DelegatingFilterProxy`:
+
+```java
+import javax.servlet.Filter;
+import org.springframework.web.filter.DelegatingFilterProxy;
+import org.springframework.web.filter.RequestContextFilter;
+import org.springframework.web.servlet.support.AbstractAnnotationConfigDispatcherServletInitializer;
+
+public class AppInitializer extends AbstractAnnotationConfigDispatcherServletInitializer {
+
+  // ...
+
+  @Override
+  protected Filter[] getServletFilters() {
+    // filter required by Spring Security
+    DelegatingFilterProxy springSecurityFilterChain = new DelegatingFilterProxy();
+    springSecurityFilterChain.setTargetBeanName("springSecurityFilterChain");
+
+    // sets request on RequestContextHolder
+    // alternatively configure RequestContextListener
+    RequestContextFilter requestContextFilter = new RequestContextFilter();
+
+    // sets Sentry user on the scope
+    DelegatingFilterProxy sentryUserFilterProxy = new DelegatingFilterProxy();
+    sentryUserFilterProxy.setTargetBeanName("sentryUserFilter");
+
+    return new Filter[] {
+      springSecurityFilterChain, requestContextFilter, sentryUserFilterProxy
+    };
+  }
+}
+```
+
+```kotlin
+import org.springframework.web.filter.DelegatingFilterProxy
+import org.springframework.web.filter.RequestContextFilter
+import org.springframework.web.servlet.support.AbstractAnnotationConfigDispatcherServletInitializer
+import javax.servlet.Filter
+
+class AppInitializer : AbstractAnnotationConfigDispatcherServletInitializer() {
+
+    // ...
+
+    override fun getServletFilters(): Array<Filter> {
+        // filter required by Spring Security
+        val springSecurityFilterChain = DelegatingFilterProxy()
+        springSecurityFilterChain.setTargetBeanName("springSecurityFilterChain")
+
+        // sets request on RequestContextHolder
+        // alternatively configure RequestContextListener
+        val requestContextFilter = RequestContextFilter()
+
+        // sets Sentry user on the scope
+        val sentryUserFilterProxy = DelegatingFilterProxy()
+        sentryUserFilterProxy.setTargetBeanName("sentryUserFilter")
+        return arrayOf(
+            springSecurityFilterChain, requestContextFilter, sentryUserFilterProxy
+        )
+    }
+}
+```
+
+By default, the username is retrieved from `HttpServletRequest#userPrincipal`. To retrieve the username from Spring Security context, register the `SpringSecuritySentryUserProvider` bean:
+
+```java
+import io.sentry.SentryOptions;
+import io.sentry.spring.SpringSecuritySentryUserProvider;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+
+@Configuration
+class SecuritySentryConfig {
+  @Bean
+  public SpringSecuritySentryUserProvider springSecuritySentryUserProvider(
+      SentryOptions sentryOptions) {
+    return new SpringSecuritySentryUserProvider(sentryOptions);
+  }
+}
+```
+
+```kotlin
+import io.sentry.SentryOptions
+import io.sentry.spring.SpringSecuritySentryUserProvider
+import org.springframework.context.annotation.Bean
+import org.springframework.context.annotation.Configuration
+
+@Configuration
+class SecuritySentryConfig {
+  @Bean
+  fun springSecuritySentryUserProvider(sentryOptions: SentryOptions) = SpringSecuritySentryUserProvider(sentryOptions)
+}
+```
+
 ## Recording Custom User Information
 
 To record custom user information, you can register a bean that implements `SentryUserProvider` interface.