Deprecate defunct SimpleCondition.

SimpleCondition was defunct and is now deprecated.
An equivalent convenience function is added to Comparison.

Closes #1034

spring-data-relational/src/main/java/org/springframework/data/relational/core/sql/Comparison.java

@@ -23,6 +23,7 @@ import org.springframework.util.Assert;
  * Results in a rendered condition: {@code <left> <comparator> <right>} (e.g. {@code col = 'predicate'}.
  *
  * @author Mark Paluch
+ * @author Jens Schauder
  * @since 1.1
  */
 public class Comparison extends AbstractSegment implements Condition {
@@ -58,6 +59,24 @@ public class Comparison extends AbstractSegment implements Condition {
 		return new Comparison(leftColumnOrExpression, comparator, rightColumnOrExpression);
 	}
 
+	/**
+	 * Creates a new {@link Comparison} from simple {@literal StringP} arguments
+	 * @param unqualifiedColumnName gets turned in a {@link Expressions#just(String)} and is expected to be an unqualified unique column name but also could be an verbatim expression. Must not be {@literal null}.
+	 * @param comparator must not be {@literal null}.
+	 * @param rightValue is considered a {@link Literal}. Must not be {@literal null}.
+	 * @return a new {@literal Comparison} of the first with the third argument using the second argument as comparison operator. Guaranteed to be not {@literal null}.
+	 *
+	 * @since 2.3
+	 */
+	public static Comparison create(String unqualifiedColumnName, String comparator, Object rightValue) {
+
+		Assert.notNull(unqualifiedColumnName, "UnqualifiedColumnName must not be null.");
+		Assert.notNull(comparator, "Comparator must not be null.");
+		Assert.notNull(rightValue, "RightValue must not be null.");
+
+		return new Comparison(Expressions.just(unqualifiedColumnName), comparator, SQL.literalOf(rightValue));
+	}
+
 	@Override
 	public Condition not() {
 

spring-data-relational/src/main/java/org/springframework/data/relational/core/sql/SimpleCondition.java

@@ -20,7 +20,9 @@ package org.springframework.data.relational.core.sql;
  *
  * @author Mark Paluch
  * @since 1.1
+ * @deprecated since 2.2.5 use {@link Comparison} instead.
  */
+@Deprecated
 public class SimpleCondition extends AbstractSegment implements Condition {
 
 	private final Expression expression;
@@ -40,11 +42,6 @@ public class SimpleCondition extends AbstractSegment implements Condition {
 
 	/**
 	 * Creates a simple {@link Condition} given {@code column}, {@code comparator} and {@code predicate}.
-	 *
-	 * @param column
-	 * @param comparator
-	 * @param predicate
-	 * @return
 	 */
 	public static SimpleCondition create(String column, String comparator, String predicate) {
 		return new SimpleCondition(new Column(column, null), comparator, predicate);

spring-data-relational/src/main/java/org/springframework/data/relational/core/sql/render/ExpressionVisitor.java

@@ -19,7 +19,6 @@ import org.springframework.data.relational.core.sql.BindMarker;
 import org.springframework.data.relational.core.sql.Column;
 import org.springframework.data.relational.core.sql.Condition;
 import org.springframework.data.relational.core.sql.Expression;
-import org.springframework.data.relational.core.sql.Literal;
 import org.springframework.data.relational.core.sql.Named;
 import org.springframework.data.relational.core.sql.SimpleFunction;
 import org.springframework.data.relational.core.sql.SubselectExpression;
@@ -79,7 +78,7 @@ class ExpressionVisitor extends TypedSubtreeVisitor<Expression> implements PartR
 			} else {
 				value = segment.toString();
 			}
-		} else if (segment instanceof Literal) {
+		} else { // works for Literal and SimpleExpression and possibly more
 			value = segment.toString();
 		}
 

spring-data-relational/src/test/java/org/springframework/data/relational/core/sql/DeleteValidatorUnitTests.java

@@ -23,6 +23,7 @@ import org.junit.jupiter.api.Test;
  * Unit tests for {@link DeleteValidator}.
  *
  * @author Mark Paluch
+ * @author Jens Schauder
  */
 public class DeleteValidatorUnitTests {
 
@@ -35,7 +36,7 @@ public class DeleteValidatorUnitTests {
 		assertThatThrownBy(() -> {
 			StatementBuilder.delete() //
 					.from(bar) //
-					.where(new SimpleCondition(column, "=", "foo")) //
+					.where(column.isEqualTo(SQL.literalOf("foo"))) //
 					.build();
 		}).isInstanceOf(IllegalStateException.class)
 				.hasMessageContaining("Required table [table] by a WHERE predicate not imported by FROM [bar]");

spring-data-relational/src/test/java/org/springframework/data/relational/core/sql/SelectValidatorUnitTests.java

@@ -23,6 +23,7 @@ import static org.assertj.core.api.Assertions.*;
  * Unit tests for {@link SelectValidator}.
  *
  * @author Mark Paluch
+ * @author Jens Schauder
  */
 public class SelectValidatorUnitTests {
 
@@ -83,7 +84,7 @@ public class SelectValidatorUnitTests {
 		assertThatThrownBy(() -> {
 			StatementBuilder.select(bar.column("foo")) //
 					.from(bar) //
-					.where(new SimpleCondition(column, "=", "foo")) //
+					.where(column.isEqualTo(SQL.literalOf("foo"))) //
 					.build();
 		}).isInstanceOf(IllegalStateException.class)
 				.hasMessageContaining("Required table [table] by a WHERE predicate not imported by FROM [bar] or JOIN []");

spring-data-relational/src/test/java/org/springframework/data/relational/core/sql/render/SelectRendererUnitTests.java

@@ -21,15 +21,7 @@ import org.junit.jupiter.api.Test;
 
 import org.springframework.data.relational.core.dialect.PostgresDialect;
 import org.springframework.data.relational.core.dialect.RenderContextFactory;
-import org.springframework.data.relational.core.sql.Column;
-import org.springframework.data.relational.core.sql.Conditions;
-import org.springframework.data.relational.core.sql.Expressions;
-import org.springframework.data.relational.core.sql.Functions;
-import org.springframework.data.relational.core.sql.OrderByField;
-import org.springframework.data.relational.core.sql.SQL;
-import org.springframework.data.relational.core.sql.Select;
-import org.springframework.data.relational.core.sql.SqlIdentifier;
-import org.springframework.data.relational.core.sql.Table;
+import org.springframework.data.relational.core.sql.*;
 import org.springframework.util.StringUtils;
 
 /**
@@ -349,4 +341,33 @@ public class SelectRendererUnitTests {
 		assertThat(rendered).isEqualTo(
 				"SELECT COUNT(\"my_table\".*) AS counter, \"my_table\".\"reserved_keyword\" FROM \"my_table\" JOIN \"join_table\" ON \"my_table\".source = \"join_table\".target");
 	}
+
+
+	@Test // GH-1034
+	void simpleComparisonWithStringArguments() {
+
+		Table table_user = SQL.table("User");
+		Select select = StatementBuilder
+				.select(table_user.column("name"),table_user.column("age"))
+				.from(table_user)
+				.where(Comparison.create("age",">",20))
+				.build();
+
+		final String rendered = SqlRenderer.toString(select);
+		assertThat(rendered).isEqualTo("SELECT User.name, User.age FROM User WHERE age > 20");
+	}
+
+	@Test // GH-1034
+	void simpleComparison() {
+
+		Table table_user = SQL.table("User");
+		Select select = StatementBuilder
+				.select(table_user.column("name"),table_user.column("age"))
+				.from(table_user)
+				.where(Comparison.create(table_user.column("age"),">",SQL.literalOf(20)))
+				.build();
+
+		final String rendered = SqlRenderer.toString(select);
+		assertThat(rendered).isEqualTo("SELECT User.name, User.age FROM User WHERE User.age > 20");
+	}
 }