Add @SqlTableAlias for generate columns table alias

(cherry picked from commit 21a428b)

Author: mhyeon-lee

spring-data-jdbc-plus-sql/src/main/java/com/navercorp/spring/data/jdbc/plus/sql/annotation/SqlTableAlias.java

@@ -0,0 +1,35 @@
+/*
+ * Spring JDBC Plus
+ *
+ * Copyright 2020-2021 NAVER Corp.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.navercorp.spring.data.jdbc.plus.sql.annotation;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+/**
+ * The annotation Sql table alias
+ *
+ * @author Myeonghyeon Lee
+ */
+@Retention(RetentionPolicy.RUNTIME)
+@Target({ElementType.TYPE, ElementType.FIELD, ElementType.METHOD})
+public @interface SqlTableAlias {
+	String value();
+}

spring-data-jdbc-plus-sql/src/main/java/com/navercorp/spring/data/jdbc/plus/sql/convert/SqlContext.java

@@ -15,11 +15,18 @@
  */
 package com.navercorp.spring.data.jdbc.plus.sql.convert;
 
+import javax.annotation.Nullable;
+
+import org.springframework.data.mapping.PersistentPropertyPath;
 import org.springframework.data.relational.core.mapping.PersistentPropertyPathExtension;
 import org.springframework.data.relational.core.mapping.RelationalPersistentEntity;
+import org.springframework.data.relational.core.mapping.RelationalPersistentProperty;
 import org.springframework.data.relational.core.sql.Column;
 import org.springframework.data.relational.core.sql.SqlIdentifier;
 import org.springframework.data.relational.core.sql.Table;
+import org.springframework.util.Assert;
+
+import com.navercorp.spring.data.jdbc.plus.sql.annotation.SqlTableAlias;
 
 /**
  * Utility to get from path to SQL DSL elements.
@@ -60,8 +67,7 @@ public Table getTable() {
 
 	@Override
 	public Table getTable(PersistentPropertyPathExtension path) {
-
-		SqlIdentifier tableAlias = path.getTableAlias();
+		SqlIdentifier tableAlias = this.getTableAlias(path);
 		Table table = Table.create(path.getTableName());
 		return tableAlias == null ? table : table.as(tableAlias);
 	}
@@ -75,4 +81,52 @@ public Column getColumn(PersistentPropertyPathExtension path) {
 	public Column getReverseColumn(PersistentPropertyPathExtension path) {
 		return getTable(path).column(path.getReverseColumnName()).as(path.getReverseColumnNameAlias());
 	}
+
+	// Refer from PersistentPropertyPathExtension#getTableAlias
+	@Nullable
+	private SqlIdentifier getTableAlias(PersistentPropertyPathExtension path) {
+		PersistentPropertyPathExtension tableOwner = getTableOwningAncestor(path);
+		if (tableOwner.getLength() > 0) {	// path != null
+			return this.assembleTableAlias(tableOwner);
+		}
+
+		// path == null : root
+		SqlTableAlias sqlTableAlias = tableOwner.getLeafEntity().findAnnotation(SqlTableAlias.class);
+		if (sqlTableAlias != null) {
+			return this.table.as(sqlTableAlias.value()).getReferenceName();
+		}
+
+		return null;
+	}
+
+	private PersistentPropertyPathExtension getTableOwningAncestor(PersistentPropertyPathExtension path) {
+		return path.isEntity() && !path.isEmbedded() ? path : this.getTableOwningAncestor(path.getParentPath());
+	}
+
+	private SqlIdentifier assembleTableAlias(PersistentPropertyPathExtension path) {
+
+		Assert.state(path != null, "Path is null");
+
+		PersistentPropertyPath<? extends RelationalPersistentProperty> propertyPath = path.getRequiredPersistentPropertyPath();
+		RelationalPersistentProperty leafProperty = propertyPath.getRequiredLeafProperty();
+
+		String prefix;
+		if (path.isEmbedded()) {
+			prefix = leafProperty.getEmbeddedPrefix();
+		} else {
+			SqlTableAlias sqlTableAlias = leafProperty.findPropertyOrOwnerAnnotation(SqlTableAlias.class);
+			prefix = sqlTableAlias != null ? sqlTableAlias.value() : leafProperty.getName();
+		}
+
+		if (path.getLength() == 1) {
+			Assert.notNull(prefix, "Prefix mus not be null.");
+			return SqlIdentifier.quoted(prefix);
+		}
+
+		PersistentPropertyPathExtension parentPath = path.getParentPath();
+		SqlIdentifier sqlIdentifier = this.assembleTableAlias(parentPath);
+
+		return parentPath.isEmbedded() ? sqlIdentifier.transform(name -> name.concat(prefix))
+			: sqlIdentifier.transform(name -> name + "_" + prefix);
+	}
 }

spring-data-jdbc-plus-sql/src/main/java/com/navercorp/spring/data/jdbc/plus/sql/convert/SqlGenerator.java

@@ -577,7 +577,7 @@ String selectColumns() {
 				new PersistentPropertyPathExtension(mappingContext, path);
 			Column column = getColumn(extPath);
 			if (column != null) {
-				columnExpressions.add(column);
+				columnExpressions.add(getColumnExpression(extPath, column));
 			}
 		}
 
@@ -610,10 +610,10 @@ String selectFrom() {
 			if (join != null) {
 				joinTables.add(join);
 			}
-
+			
 			Column column = getColumn(extPath);
 			if (column != null) {
-				columnExpressions.add(column);
+				columnExpressions.add(getColumnExpression(extPath, column));
 			}
 		}