fix: allow at most one dot in Spanner table names for named schemas (#4418)

Spanner should allow to specify only one dot and it should have text
before and after in a table name to support named schemas.

Fixes #4384

Author: sakthivelmanii

spring-cloud-gcp-data-spanner/src/main/java/com/google/cloud/spring/data/spanner/core/mapping/SpannerPersistentEntityImpl.java

@@ -62,7 +62,7 @@ public class SpannerPersistentEntityImpl<T>
 
   private static final ExpressionParser PARSER = new SpelExpressionParser();
 
-  private static final Pattern TABLE_NAME_ILLEGAL_CHAR_PATTERN = Pattern.compile("[^a-zA-Z0-9_]");
+  private static final Pattern VALID_TABLE_NAME_PATTERN = Pattern.compile("^[a-zA-Z0-9_]+(\\.[a-zA-Z0-9_]+)?$");
 
   private final Class rawType;
 
@@ -376,9 +376,10 @@ public boolean hasMultiFieldKey() {
   // Because SpEL expressions in table name definitions are allowed, validation is
   // required.
   private String validateTableName(String name) {
-    if (TABLE_NAME_ILLEGAL_CHAR_PATTERN.matcher(name).find()) {
+    if (!VALID_TABLE_NAME_PATTERN.matcher(name).matches()) {
       throw new SpannerDataException(
-          "Only letters, numbers, and underscores are " + "allowed in table names: " + name);
+          "Only letters, numbers, and underscores are allowed in table names, and at most one dot: "
+              + name);
     }
     return name;
   }

spring-cloud-gcp-data-spanner/src/test/java/com/google/cloud/spring/data/spanner/core/mapping/SpannerPersistentEntityImplTests.java

@@ -245,7 +245,63 @@ void testInvalidTableName() {
         .isInstanceOf(SpannerDataException.class)
         .hasMessage("Error getting table name for EntityBadName")
         .hasStackTraceContaining(
-            "Only letters, numbers, and underscores are allowed in table names: ;DROP TABLE your_table;");
+            "Only letters, numbers, and underscores are allowed in table names, and at most one dot: ;DROP TABLE your_table;");
+  }
+
+  @Test
+  void testValidTableNameWithDot() {
+    SpannerPersistentEntityImpl<EntityWithValidDotName> entity =
+        new SpannerPersistentEntityImpl<>(
+            TypeInformation.of(EntityWithValidDotName.class),
+            this.spannerMappingContext,
+            this.spannerEntityProcessor);
+
+    assertThat(entity.tableName()).isEqualTo("schema.table");
+  }
+
+  @Test
+  void testInvalidTableNameWithDotAtStart() {
+    SpannerPersistentEntityImpl<EntityWithDotAtStart> entity =
+        new SpannerPersistentEntityImpl<>(
+            TypeInformation.of(EntityWithDotAtStart.class),
+            this.spannerMappingContext,
+            this.spannerEntityProcessor);
+
+    assertThatThrownBy(entity::tableName)
+        .isInstanceOf(SpannerDataException.class)
+        .hasMessage("Error getting table name for EntityWithDotAtStart")
+        .hasStackTraceContaining(
+            "Only letters, numbers, and underscores are allowed in table names, and at most one dot: .table");
+  }
+
+  @Test
+  void testInvalidTableNameWithDotAtEnd() {
+    SpannerPersistentEntityImpl<EntityWithDotAtEnd> entity =
+        new SpannerPersistentEntityImpl<>(
+            TypeInformation.of(EntityWithDotAtEnd.class),
+            this.spannerMappingContext,
+            this.spannerEntityProcessor);
+
+    assertThatThrownBy(entity::tableName)
+        .isInstanceOf(SpannerDataException.class)
+        .hasMessage("Error getting table name for EntityWithDotAtEnd")
+        .hasStackTraceContaining(
+            "Only letters, numbers, and underscores are allowed in table names, and at most one dot: table.");
+  }
+
+  @Test
+  void testInvalidTableNameWithMultipleDots() {
+    SpannerPersistentEntityImpl<EntityWithMultipleDots> entity =
+        new SpannerPersistentEntityImpl<>(
+            TypeInformation.of(EntityWithMultipleDots.class),
+            this.spannerMappingContext,
+            this.spannerEntityProcessor);
+
+    assertThatThrownBy(entity::tableName)
+        .isInstanceOf(SpannerDataException.class)
+        .hasMessage("Error getting table name for EntityWithMultipleDots")
+        .hasStackTraceContaining(
+            "Only letters, numbers, and underscores are allowed in table names, and at most one dot: schema.table.subtable");
   }
 
   @Test
@@ -267,7 +323,7 @@ void testSpelInvalidName() {
         .isInstanceOf(SpannerDataException.class)
         .hasMessage("Error getting table name for EntityWithExpression")
         .hasStackTraceContaining(
-            "Only letters, numbers, and underscores are allowed in table names: "
+            "Only letters, numbers, and underscores are allowed in table names, and at most one dot: "
                 + "table_; DROP TABLE your_table;");
   }
 
@@ -475,6 +531,30 @@ private static class EntityBadName {
     String something;
   }
 
+  @Table(name = "schema.table")
+  private static class EntityWithValidDotName {
+    @PrimaryKey(keyOrder = 1)
+    String id;
+  }
+
+  @Table(name = ".table")
+  private static class EntityWithDotAtStart {
+    @PrimaryKey(keyOrder = 1)
+    String id;
+  }
+
+  @Table(name = "table.")
+  private static class EntityWithDotAtEnd {
+    @PrimaryKey(keyOrder = 1)
+    String id;
+  }
+
+  @Table(name = "schema.table.subtable")
+  private static class EntityWithMultipleDots {
+    @PrimaryKey(keyOrder = 1)
+    String id;
+  }
+
   @Table(name = "custom_test_table")
   private static class TestEntity {
     @PrimaryKey(keyOrder = 1)