DATAJDBC-309 - Reworked visitor structure towards a more modular design.

Also added support for conditions.

Original pull request: #119.

Author: schauder

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

@@ -15,13 +15,33 @@
  */
 package org.springframework.data.relational.core.sql;
 
+import org.springframework.util.Assert;
+
 /**
  * Abstract implementation to support {@link Segment} implementations.
  *
  * @author Mark Paluch
  */
 abstract class AbstractSegment implements Segment {
 
+	private final Segment[] children;
+
+	protected AbstractSegment(Segment ... children) {
+		this.children = children;
+	}
+
+	@Override
+	public void visit(Visitor visitor) {
+
+		Assert.notNull(visitor, "Visitor must not be null!");
+
+		visitor.enter(this);
+		for (Segment child : children) {
+			child.visit(visitor);
+		}
+		visitor.leave(this);
+	}
+
 	/*
 	 * (non-Javadoc)
 	 * @see java.lang.Object#hashCode()

spring-data-relational/src/main/java/org/springframework/data/relational/core/sql/SelectTop.java renamed to spring-data-relational/src/main/java/org/springframework/data/relational/core/sql/AliasedExpression.java

@@ -16,35 +16,30 @@
 package org.springframework.data.relational.core.sql;
 
 /**
- * {@code TOP} clause for {@code SELECT TOP …}.
+ * An expression with an alias.
  *
- * @author Mark Paluch
+ * @author Jens Schauder
  */
-public class SelectTop extends AbstractSegment implements Segment {
+public class AliasedExpression extends AbstractSegment implements Aliased, Expression {
 
-	private final int count;
+	private final Expression expression;
+	private final String alias;
 
-	private SelectTop(int count) {
-		this.count = count;
-	}
+	public AliasedExpression(Expression expression, String alias) {
+
+		super(expression);
 
-	public static SelectTop create(int count) {
-		return new SelectTop(count);
+		this.expression = expression;
+		this.alias = alias;
 	}
 
-	/**
-	 * @return the count.
-	 */
-	public int getCount() {
-		return count;
+	@Override
+	public String getAlias() {
+		return alias;
 	}
 
-	/*
-	 * (non-Javadoc)
-	 * @see java.lang.Object#toString()
-	 */
 	@Override
 	public String toString() {
-		return "TOP " + count;
+		return expression.toString() + " AS " + alias;
 	}
 }

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

@@ -15,59 +15,16 @@
  */
 package org.springframework.data.relational.core.sql;
 
-import org.springframework.util.Assert;
-
 /**
  * {@link Condition} representing an {@code AND} relation between two {@link Condition}s.
  *
  * @author Mark Paluch
  * @see Condition#and(Condition)
  */
-public class AndCondition implements Condition {
-
-	private final Condition left;
-	private final Condition right;
-
-	AndCondition(Condition left, Condition right) {
-		this.left = left;
-		this.right = right;
-	}
-
-	/*
-	 * (non-Javadoc)
-	 * @see org.springframework.data.relational.core.sql.Visitable#visit(org.springframework.data.relational.core.sql.Visitor)
-	 */
-	@Override
-	public void visit(Visitor visitor) {
-
-		Assert.notNull(visitor, "Visitor must not be null!");
+public class AndCondition extends MultipleCondition {
 
-		visitor.enter(this);
-		left.visit(visitor);
-		right.visit(visitor);
-		visitor.leave(this);
+	AndCondition(Condition... conditions) {
+		super(" AND ", conditions);
 	}
 
-	/**
-	 * @return the left {@link Condition}.
-	 */
-	public Condition getLeft() {
-		return left;
-	}
-
-	/**
-	 * @return the right {@link Condition}.
-	 */
-	public Condition getRight() {
-		return right;
-	}
-
-	/*
-	 * (non-Javadoc)
-	 * @see java.lang.Object#toString()
-	 */
-	@Override
-	public String toString() {
-		return left.toString() + " AND " + right.toString();
-	}
 }

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

@@ -30,23 +30,14 @@ public class AsteriskFromTable extends AbstractSegment implements Expression {
 	private final Table table;
 
 	AsteriskFromTable(Table table) {
+		super(table);
 		this.table = table;
 	}
 
 	public static AsteriskFromTable create(Table table) {
 		return new AsteriskFromTable(table);
 	}
 
-	@Override
-	public void visit(Visitor visitor) {
-
-		Assert.notNull(visitor, "Visitor must not be null!");
-
-		visitor.enter(this);
-		table.visit(visitor);
-		visitor.leave(this);
-	}
-
 	/**
 	 * @return the associated {@link Table}.
 	 */

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

@@ -22,7 +22,7 @@
  *
  * @author Mark Paluch
  */
-public class BindMarker implements Segment {
+public class BindMarker extends AbstractSegment implements Expression {
 
 	/*
 	 * (non-Javadoc)

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

@@ -28,44 +28,17 @@
 public class Column extends AbstractSegment implements Expression, Named {
 
 	private final String name;
-	private final @Nullable Table table;
+	private final Table table;
 
-	Column(String name, @Nullable Table table) {
+	Column(String name, Table table) {
 
+		super(table);
 		Assert.notNull(name, "Name must not be null");
 
 		this.name = name;
 		this.table = table;
 	}
 
-	/**
-	 * Creates a new {@link Column}.
-	 *
-	 * @param name column name, must not {@literal null} or empty.
-	 * @return the new {@link Column}.
-	 */
-	public static Column create(String name) {
-
-		Assert.hasText(name, "Name must not be null or empty");
-
-		return new Column(name, null);
-	}
-
-	/**
-	 * Creates a new aliased {@link Column}.
-	 *
-	 * @param name column name, must not {@literal null} or empty.
-	 * @param alias alias name, must not {@literal null} or empty.
-	 * @return the new {@link Column}.
-	 */
-	public static Column aliased(String name, String alias) {
-
-		Assert.hasText(name, "Name must not be null or empty");
-		Assert.hasText(alias, "Alias must not be null or empty");
-
-		return new AliasedColumn(name, null, alias);
-	}
-
 	/**
 	 * Creates a new {@link Column} associated with a {@link Table}.
 	 *
@@ -124,23 +97,6 @@ public Column from(Table table) {
 		return new Column(name, table);
 	}
 
-	/*
-	 * (non-Javadoc)
-	 * @see org.springframework.data.relational.core.sql.Visitable#visit(org.springframework.data.relational.core.sql.Visitor)
-	 */
-	@Override
-	public void visit(Visitor visitor) {
-
-		Assert.notNull(visitor, "Visitor must not be null!");
-
-		visitor.enter(this);
-
-		if (table != null) {
-			table.visit(visitor);
-		}
-		visitor.leave(this);
-	}
-
 	/*
 	 * (non-Javadoc)
 	 * @see org.springframework.data.relational.core.sql.Named#getName()
@@ -192,7 +148,7 @@ static class AliasedColumn extends Column implements Aliased {
 
 		private final String alias;
 
-		private AliasedColumn(String name, @Nullable Table table, String alias) {
+		private AliasedColumn(String name, Table table, String alias) {
 			super(name, table);
 			this.alias = alias;
 		}

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

@@ -43,12 +43,7 @@ default Condition or(Condition other) {
 		return new OrCondition(this, other);
 	}
 
-	/**
-	 * Encapsulate this {@link Condition} in a group of parentheses.
-	 *
-	 * @return the grouped {@link Condition}.
-	 */
-	default Condition group() {
-		return new ConditionGroup(this);
+	default Condition not() {
+		return new Not(this);
 	}
 }

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

@@ -46,6 +46,18 @@ public static Condition just(String sql) {
 	private Conditions() {
 	}
 
+	public static Condition isNull(Expression expression) {
+		return new IsNull(expression);
+	}
+
+	public static Condition isEqual(Column bar, Expression param) {
+		return new Equals(bar, param);
+	}
+
+	public static Condition in(Column bar, Expression subselectExpression) {
+		return new In(bar, subselectExpression);
+	}
+
 	static class ConstantCondition extends AbstractSegment implements Condition {
 
 		private final String condition;