#113: added a builder to SqlStatementSelect class (#114)

* #113: added a builder to SqlStatementSelect class

Author: AnastasiiaSergienko

pom.xml

@@ -4,7 +4,7 @@
   <modelVersion>4.0.0</modelVersion>
   <groupId>com.exasol</groupId>
   <artifactId>virtual-schema-common-java</artifactId>
-  <version>7.4.0</version>
+  <version>7.5.0</version>
   <name>Common module of Exasol Virtual Schemas Adapters</name>
   <description>This is one of the modules of Virtual Schemas Adapters. The libraries provided by this project are the foundation of the adapter development, i.e. adapters must be implemented on top of them.</description>
   <url>https://github.com/exasol/virtual-schema-common-java</url>

src/main/java/com/exasol/adapter/request/parser/PushdownSqlParser.java

@@ -125,7 +125,8 @@ private SqlStatementSelect parseSelect(final JsonObject select) {
         if (select.containsKey("limit")) {
             limit = parseLimit(select.getJsonObject("limit"));
         }
-        return new SqlStatementSelect(table, selectList, whereClause, groupByClause, having, orderBy, limit);
+        return SqlStatementSelect.builder().selectList(selectList).fromClause(table).whereClause(whereClause)
+              .groupBy(groupByClause).having(having).orderBy(orderBy).limit(limit).build();
     }
 
     private SqlNode parseTable(final JsonObject exp) {

src/main/java/com/exasol/adapter/sql/SqlStatementSelect.java

@@ -14,17 +14,14 @@ public class SqlStatementSelect extends SqlStatement {
     private final SqlOrderBy orderBy;
     private final SqlLimit limit;
 
-    public SqlStatementSelect(final SqlNode fromClause, final SqlSelectList selectList, final SqlNode whereClause,
-            final SqlExpressionList groupBy, final SqlNode having, final SqlOrderBy orderBy, final SqlLimit limit) {
-        this.fromClause = fromClause;
-        this.selectList = selectList;
-        this.whereClause = whereClause;
-        this.groupBy = groupBy;
-        this.having = having;
-        this.orderBy = orderBy;
-        this.limit = limit;
-        assert this.fromClause != null;
-        assert this.selectList != null;
+    private SqlStatementSelect(final Builder builder) {
+        this.fromClause = builder.fromClause;
+        this.selectList = builder.selectList;
+        this.whereClause = builder.whereClause;
+        this.groupBy = builder.groupBy;
+        this.having = builder.having;
+        this.orderBy = builder.orderBy;
+        this.limit = builder.limit;
         this.fromClause.setParent(this);
         this.selectList.setParent(this);
 
@@ -137,4 +134,112 @@ public SqlNodeType getType() {
     public <R> R accept(final SqlNodeVisitor<R> visitor) throws AdapterException {
         return visitor.visit(this);
     }
-}
+
+    /**
+     * Create a new builder for {@link SqlStatementSelect}.
+     *
+     * @return builder instance
+     */
+    public static Builder builder() {
+        return new Builder();
+    }
+
+    /**
+     * Builder for {@link SqlStatementSelect}.
+     */
+    public static class Builder {
+        private SqlNode fromClause;
+        private SqlSelectList selectList;
+        private SqlNode whereClause;
+        private SqlExpressionList groupBy;
+        private SqlNode having;
+        private SqlOrderBy orderBy;
+        private SqlLimit limit;
+
+        /**
+         * Set the from clause of the SQL Select Statement.
+         *
+         * @param fromClause from clause
+         * @return builder instance for fluent programming
+         */
+        public Builder fromClause(final SqlNode fromClause) {
+            this.fromClause = fromClause;
+            return this;
+        }
+
+        /**
+         * Set the select list of the SQL Select Statement.
+         *
+         * @param selectList select list
+         * @return builder instance for fluent programming
+         */
+        public Builder selectList(final SqlSelectList selectList) {
+            this.selectList = selectList;
+            return this;
+        }
+
+        /**
+         * Set the where clause of the SQL Select Statement.
+         *
+         * @param whereClause where clause
+         * @return builder instance for fluent programming
+         */
+        public Builder whereClause(final SqlNode whereClause) {
+            this.whereClause = whereClause;
+            return this;
+        }
+
+        /**
+         * Set the group by clause of the SQL Select Statement.
+         *
+         * @param groupBy group by clause
+         * @return builder instance for fluent programming
+         */
+        public Builder groupBy(final SqlExpressionList groupBy) {
+            this.groupBy = groupBy;
+            return this;
+        }
+
+        /**
+         * Set the having clause of the SQL Select Statement.
+         *
+         * @param having having clause
+         * @return builder instance for fluent programming
+         */
+        public Builder having(final SqlNode having) {
+            this.having = having;
+            return this;
+        }
+
+        /**
+         * Set the order by clause of the SQL Select Statement.
+         *
+         * @param orderBy order by clause
+         * @return builder instance for fluent programming
+         */
+        public Builder orderBy(final SqlOrderBy orderBy) {
+            this.orderBy = orderBy;
+            return this;
+        }
+
+        /**
+         * Set the limit clause of the SQL Select Statement.
+         *
+         * @param limit limit clause
+         * @return builder instance for fluent programming
+         */
+        public Builder limit(final SqlLimit limit) {
+            this.limit = limit;
+            return this;
+        }
+
+        /**
+         * Build a new instance of {@link SqlStatementSelect}
+         *
+         * @return new instance
+         */
+        public SqlStatementSelect build() {
+            return new SqlStatementSelect(this);
+        }
+    }
+}

src/test/java/com/exasol/adapter/sql/SqlNodeTest.java

@@ -36,7 +36,8 @@ private SqlNode getTestSqlNode() {
         final SqlOrderBy orderBy = new SqlOrderBy(List.of(new SqlColumn(0, clicksMeta.getColumns().get(0))),
                 List.of(true), List.of(true));
         final SqlLimit limit = new SqlLimit(10);
-        return new SqlStatementSelect(fromClause, selectList, whereClause, groupBy, having, orderBy, limit);
+        return SqlStatementSelect.builder().selectList(selectList).fromClause(fromClause).whereClause(whereClause)
+                .groupBy(groupBy).having(having).orderBy(orderBy).limit(limit).build();
     }
 
     private TableMetadata getClicksTableMetadata() {

src/test/java/com/exasol/adapter/sql/SqlStatementSelectTest.java

@@ -0,0 +1,14 @@
+package com.exasol.adapter.sql;
+
+import org.junit.jupiter.api.Test;
+
+import static org.hamcrest.CoreMatchers.instanceOf;
+import static org.hamcrest.MatcherAssert.assertThat;
+
+class SqlStatementSelectTest {
+    @Test
+    void builder() {
+        final SqlStatementSelect.Builder sqlStatementSelectBuilder = SqlStatementSelect.builder();
+        assertThat(sqlStatementSelectBuilder, instanceOf(SqlStatementSelect.Builder.class));
+    }
+}