Escaper escapes the escape character itself.

Closes #2182
Original pull request #2189

Signed-off-by: Alexander Tochin <alterant@gmail.com>

spring-data-relational/src/main/java/org/springframework/data/relational/core/dialect/Escaper.java

@@ -27,6 +27,7 @@ import org.jspecify.annotations.Nullable;
  *
  * @author Roman Chigvintsev
  * @author Mark Paluch
+ * @author Alexander Tochin
  * @since 2.0
  */
 public class Escaper {
@@ -84,6 +85,7 @@ public class Escaper {
 
 	/**
 	 * Escapes all special like characters ({@code _}, {@code %}) using the configured escape character.
+	 * Escape character itself is also escaped.
 	 *
 	 * @param value value to be escaped
 	 * @return escaped value
@@ -94,6 +96,11 @@ public class Escaper {
 			return null;
 		}
 
-		return toReplace.stream().reduce(value, (it, character) -> it.replace(character, escapeCharacter + character));
+		String escapeCharString = String.valueOf(escapeCharacter);
+		String escapedValue = value.replace(escapeCharString, escapeCharString.repeat(2));
+		for (String character : toReplace) {
+			escapedValue = escapedValue.replace(character, escapeCharacter + character);
+		}
+		return escapedValue;
 	}
 }

spring-data-relational/src/test/java/org/springframework/data/relational/core/dialect/EscaperUnitTests.java

@@ -24,6 +24,7 @@ import org.junit.jupiter.api.Test;
  *
  * @author Roman Chigvintsev
  * @author Mark Paluch
+ * @author Alexander Tochin
  */
 public class EscaperUnitTests {
 
@@ -71,4 +72,16 @@ public class EscaperUnitTests {
 	public void escapesAdditionalCharacters() {
 		assertThat(Escaper.DEFAULT.withRewriteFor("[", "]").escape("Hello Wo[Rr]ld")).isEqualTo("Hello Wo\\[Rr\\]ld");
 	}
+
+	@Test // GH-2182
+	public void escapesCharactersUsingDefaultEscapeCharacter() {
+		assertThat(Escaper.DEFAULT.escape("%te\\st_")).isEqualTo("\\%te\\\\st\\_");
+		//assertThat(Escaper.of('$').escape("_%")).isEqualTo("$_$%");
+	}
+
+	@Test // GH-2182
+	public void escapesCharactersUsingCustomEscapeCharacter() {
+		assertThat(Escaper.DEFAULT.escape("%te\\st_")).isEqualTo("\\%te\\\\st\\_");
+		assertThat(Escaper.of('$').escape("%te$st_")).isEqualTo("$%te$$st$_");
+	}
 }