validate namespace strategies on configuration update

scm-webapp/src/main/java/sonia/scm/repository/NamespaceStrategyValidator.java

@@ -0,0 +1,26 @@
+package sonia.scm.repository;
+
+import javax.inject.Inject;
+import java.util.Set;
+
+import static sonia.scm.ScmConstraintViolationException.Builder.doThrow;
+
+public class NamespaceStrategyValidator {
+
+  private final Set<NamespaceStrategy> strategies;
+
+  @Inject
+  public NamespaceStrategyValidator(Set<NamespaceStrategy> strategies) {
+    this.strategies = strategies;
+  }
+
+  public void check(String name) {
+    doThrow()
+      .violation("unknown NamespaceStrategy " + name, "namespaceStrategy")
+      .when(!isValid(name));
+  }
+
+  private boolean isValid(String name) {
+    return strategies.stream().anyMatch(ns -> ns.getClass().getSimpleName().equals(name));
+  }
+}