- Tool expression connector included

src/main/java/net/sf/jsqlparser/util/ConnectExpressionsVisitor.java

@@ -0,0 +1,87 @@
+package net.sf.jsqlparser.util;
+
+import java.util.LinkedList;
+import java.util.List;
+import net.sf.jsqlparser.expression.BinaryExpression;
+import net.sf.jsqlparser.statement.select.AllColumns;
+import net.sf.jsqlparser.statement.select.AllTableColumns;
+import net.sf.jsqlparser.statement.select.PlainSelect;
+import net.sf.jsqlparser.statement.select.SelectExpressionItem;
+import net.sf.jsqlparser.statement.select.SelectItem;
+import net.sf.jsqlparser.statement.select.SelectItemVisitor;
+import net.sf.jsqlparser.statement.select.SelectVisitor;
+import net.sf.jsqlparser.statement.select.SetOperationList;
+
+/**
+ * Connect all selected expressions with a binary expression. Out of select a,b from table 
+ * one gets select a || b as expr from table. The type of binary expression is set by 
+ * overwriting this class abstract method createBinaryExpression.
+ * @author tw
+ */
+public abstract class ConnectExpressionsVisitor implements SelectVisitor, SelectItemVisitor {
+
+	private String alias = "expr";
+	private List<SelectExpressionItem> itemsExpr = new LinkedList<SelectExpressionItem>();
+
+	public ConnectExpressionsVisitor() {
+	}
+
+	public ConnectExpressionsVisitor(String alias) {
+		this.alias = alias;
+	}
+
+	/**
+	 * Create instances of this binary expression that connects all selected columns.
+	 * @return 
+	 */
+	protected abstract BinaryExpression createBinaryExpression();
+
+	@Override
+	public void visit(PlainSelect plainSelect) {
+		for (SelectItem item : plainSelect.getSelectItems()) {
+			item.accept(this);
+		}
+
+		if (itemsExpr.size() > 1) {
+			BinaryExpression binExpr = createBinaryExpression();
+			binExpr.setLeftExpression(itemsExpr.get(0).getExpression());
+			for (int i = 1; i < itemsExpr.size() - 1; i++) {
+				binExpr.setRightExpression(itemsExpr.get(i).getExpression());
+				BinaryExpression binExpr2 = createBinaryExpression();
+				binExpr2.setLeftExpression(binExpr);
+				binExpr = binExpr2;
+			}
+			binExpr.setRightExpression(itemsExpr.get(itemsExpr.size() - 1).getExpression());
+
+			SelectExpressionItem sei = new SelectExpressionItem();
+			sei.setExpression(binExpr);
+
+			plainSelect.getSelectItems().clear();
+			plainSelect.getSelectItems().add(sei);
+		}
+
+		((SelectExpressionItem)plainSelect.getSelectItems().get(0)).setAlias(alias);
+	}
+
+	@Override
+	public void visit(SetOperationList setOpList) {
+		for (PlainSelect select : setOpList.getPlainSelects()) {
+			select.accept(this);
+		}
+	}
+
+	@Override
+	public void visit(AllColumns allColumns) {
+		throw new UnsupportedOperationException("Not supported yet.");
+	}
+
+	@Override
+	public void visit(AllTableColumns allTableColumns) {
+		throw new UnsupportedOperationException("Not supported yet.");
+	}
+
+	@Override
+	public void visit(SelectExpressionItem selectExpressionItem) {
+		itemsExpr.add(selectExpressionItem);
+	}
+}

src/test/java/net/sf/jsqlparser/util/ConnectExpressionsVisitorTest.java

@@ -0,0 +1,75 @@
+package net.sf.jsqlparser.util;
+
+import java.io.StringReader;
+import net.sf.jsqlparser.JSQLParserException;
+import net.sf.jsqlparser.expression.BinaryExpression;
+import net.sf.jsqlparser.expression.operators.arithmetic.Addition;
+import net.sf.jsqlparser.expression.operators.arithmetic.Concat;
+import net.sf.jsqlparser.parser.CCJSqlParserManager;
+import net.sf.jsqlparser.statement.select.Select;
+import org.junit.After;
+import org.junit.AfterClass;
+import org.junit.Before;
+import org.junit.BeforeClass;
+import org.junit.Test;
+import static org.junit.Assert.*;
+
+/**
+ *
+ * @author tw
+ */
+public class ConnectExpressionsVisitorTest {
+
+	public ConnectExpressionsVisitorTest() {
+	}
+
+	@BeforeClass
+	public static void setUpClass() {
+	}
+
+	@AfterClass
+	public static void tearDownClass() {
+	}
+
+	@Before
+	public void setUp() {
+	}
+
+	@After
+	public void tearDown() {
+	}
+
+	CCJSqlParserManager parserManager = new CCJSqlParserManager();
+
+	@Test
+	public void testVisit_PlainSelect_concat() throws JSQLParserException {
+		String sql = "select a,b,c from test";
+		Select select = (Select) parserManager.parse( new StringReader(sql));
+		ConnectExpressionsVisitor instance = new ConnectExpressionsVisitor() {
+
+			@Override
+			protected BinaryExpression createBinaryExpression() {
+				return new Concat();
+			}
+		};
+		select.getSelectBody().accept(instance);
+
+		assertEquals("SELECT a || b || c AS expr FROM test", select.toString());
+	}
+
+	@Test
+	public void testVisit_PlainSelect_addition() throws JSQLParserException {
+		String sql = "select a,b,c from test";
+		Select select = (Select) parserManager.parse( new StringReader(sql));
+		ConnectExpressionsVisitor instance = new ConnectExpressionsVisitor("testexpr") {
+
+			@Override
+			protected BinaryExpression createBinaryExpression() {
+				return new Addition();
+			}
+		};
+		select.getSelectBody().accept(instance);
+
+		assertEquals("SELECT a + b + c AS testexpr FROM test", select.toString());
+	}
+}