DATAJDBC-309 - Polishing.

Javadoc, static factory methods, typos. Refactor SQL rendering from a shared stack-based implementation to independent delegating visitors. Introduce DelegatingVisitor and TypedSubtreeVisitor base classes. Introduce SelectList container. Extract nested renderes to top-level types.

Move SQL renderer to renderer package.

Extend In to multi-expression argument. Introduce helper methods in Table to create multiple columns. Introduce factory method on StatementBuilder to create a new builder given a collection of expressions.

Add support for comparison conditions and LIKE and equal/not equal/less with equals to/greater with equals to conditions.

 Add condition creation methods to Column so Column objects can now create conditions for a fluent DSL as in (.where(left.isGreater(right)).

StatementBuilder.select(left).from(table).where(left.isGreater(right)).build().

Introduce RenderContext and RenderNamingStrategy.

Add since tags. Improve Javadoc.

Original pull request: #119.

Author: mp911de

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

@@ -21,15 +21,20 @@
  * Abstract implementation to support {@link Segment} implementations.
  *
  * @author Mark Paluch
+ * @since 1.1
  */
 abstract class AbstractSegment implements Segment {
 
 	private final Segment[] children;
 
-	protected AbstractSegment(Segment ... children) {
+	protected AbstractSegment(Segment... children) {
 		this.children = children;
 	}
 
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.data.relational.core.sql.Visitable#visit(org.springframework.data.relational.core.sql.Visitor)
+	 */
 	@Override
 	public void visit(Visitor visitor) {
 

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

@@ -19,6 +19,7 @@
  * Aliased element exposing an {@link #getAlias() alias}.
  *
  * @author Mark Paluch
+ * @since 1.1
  */
 public interface Aliased {
 

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

@@ -19,8 +19,9 @@
  * An expression with an alias.
  *
  * @author Jens Schauder
+ * @since 1.1
  */
-public class AliasedExpression extends AbstractSegment implements Aliased, Expression {
+class AliasedExpression extends AbstractSegment implements Aliased, Expression {
 
 	private final Expression expression;
 	private final String alias;
@@ -33,11 +34,19 @@ public AliasedExpression(Expression expression, String alias) {
 		this.alias = alias;
 	}
 
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.data.relational.core.sql.Aliased#getAlias()
+	 */
 	@Override
 	public String getAlias() {
 		return alias;
 	}
 
+	/*
+	 * (non-Javadoc)
+	 * @see java.lang.Object#toString()
+	 */
 	@Override
 	public String toString() {
 		return expression.toString() + " AS " + alias;

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

@@ -19,12 +19,12 @@
  * {@link Condition} representing an {@code AND} relation between two {@link Condition}s.
  *
  * @author Mark Paluch
+ * @since 1.1
  * @see Condition#and(Condition)
  */
 public class AndCondition extends MultipleCondition {
 
 	AndCondition(Condition... conditions) {
 		super(" AND ", conditions);
 	}
-
 }

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

@@ -15,14 +15,19 @@
  */
 package org.springframework.data.relational.core.sql;
 
-import org.springframework.util.Assert;
-
 /**
  * {@link Segment} to select all columns from a {@link Table}.
  * <p/>
- * * Renders to: {@code <table>.*} as in {@code SELECT <table>.* FROM …}.
+ * * Renders to: {@code
+ *
+<table>
+ * .*} as in {@code SELECT
+ *
+<table>
+ * .* FROM …}.
  *
  * @author Mark Paluch
+ * @since 1.1
  * @see Table#asterisk()
  */
 public class AsteriskFromTable extends AbstractSegment implements Expression {
@@ -45,6 +50,10 @@ public Table getTable() {
 		return table;
 	}
 
+	/*
+	 * (non-Javadoc)
+	 * @see java.lang.Object#toString()
+	 */
 	@Override
 	public String toString() {
 

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

@@ -21,6 +21,7 @@
  * Bind marker/parameter placeholder used to construct prepared statements with parameter substitution.
  *
  * @author Mark Paluch
+ * @since 1.1
  */
 public class BindMarker extends AbstractSegment implements Expression {
 

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

@@ -24,6 +24,7 @@
  * Renders to: {@code <name>} or {@code <table(alias)>.<name>}.
  *
  * @author Mark Paluch
+ * @since 1.1
  */
 public class Column extends AbstractSegment implements Expression, Named {
 
@@ -72,7 +73,7 @@ public static Column aliased(String name, Table table, String alias) {
 	}
 
 	/**
-	 * Create a new aliased {@link Column}.
+	 * Creates a new aliased {@link Column}.
 	 *
 	 * @param alias column alias name, must not {@literal null} or empty.
 	 * @return the aliased {@link Column}.
@@ -85,7 +86,7 @@ public Column as(String alias) {
 	}
 
 	/**
-	 * Create a new {@link Column} associated with a {@link Table}.
+	 * Creates a new {@link Column} associated with a {@link Table}.
 	 *
 	 * @param table the table, must not be {@literal null}.
 	 * @return a new {@link Column} associated with {@link Table}.
@@ -97,6 +98,108 @@ public Column from(Table table) {
 		return new Column(name, table);
 	}
 
+	// -------------------------------------------------------------------------
+	// Methods for Condition creation.
+	// -------------------------------------------------------------------------
+
+	/**
+	 * Creates a {@code =} (equals) {@link Condition}.
+	 *
+	 * @param expression right side of the comparison.
+	 * @return the {@link Comparison} condition.
+	 */
+	public Comparison isEqualTo(Expression expression) {
+		return Conditions.isEqual(this, expression);
+	}
+
+	/**
+	 * Creates a {@code !=} (not equals) {@link Condition}.
+	 *
+	 * @param expression right side of the comparison.
+	 * @return the {@link Comparison} condition.
+	 */
+	public Comparison isNotEqualTo(Expression expression) {
+		return Conditions.isNotEqual(this, expression);
+	}
+
+	/**
+	 * Creates a {@code <} (less) {@link Condition} {@link Condition}.
+	 *
+	 * @param expression right side of the comparison.
+	 * @return the {@link Comparison} condition.
+	 */
+	public Comparison isLess(Expression expression) {
+		return Conditions.isLess(this, expression);
+	}
+
+	/**
+	 * CCreates a {@code <=} (greater ) {@link Condition} {@link Condition}.
+	 *
+	 * @param expression right side of the comparison.
+	 * @return the {@link Comparison} condition.
+	 */
+	public Comparison isLessOrEqualTo(Expression expression) {
+		return Conditions.isLessOrEqualTo(this, expression);
+	}
+
+	/**
+	 * Creates a {@code !=} (not equals) {@link Condition}.
+	 *
+	 * @param expression right side of the comparison.
+	 * @return the {@link Comparison} condition.
+	 */
+	public Comparison isGreater(Expression expression) {
+		return Conditions.isGreater(this, expression);
+	}
+
+	/**
+	 * Creates a {@code <=} (greater or equal to) {@link Condition} {@link Condition}.
+	 *
+	 * @param expression right side of the comparison.
+	 * @return the {@link Comparison} condition.
+	 */
+	public Comparison isGreaterOrEqualTo(Expression expression) {
+		return Conditions.isGreaterOrEqualTo(this, expression);
+	}
+
+	/**
+	 * Creates a {@code LIKE} {@link Condition}.
+	 *
+	 * @param expression right side of the comparison.
+	 * @return the {@link Like} condition.
+	 */
+	public Like like(Expression expression) {
+		return Conditions.like(this, expression);
+	}
+
+	/**
+	 * Creates a new {@link In} {@link Condition} given right {@link Expression}s.
+	 *
+	 * @param expression right side of the comparison.
+	 * @return the {@link In} condition.
+	 */
+	public In in(Expression... expression) {
+		return Conditions.in(this, expression);
+	}
+
+	/**
+	 * Creates a {@code IS NULL} condition.
+	 *
+	 * @return the {@link IsNull} condition.
+	 */
+	public IsNull isNull() {
+		return Conditions.isNull(this);
+	}
+
+	/**
+	 * Creates a {@code IS NOT NULL} condition.
+	 *
+	 * @return the {@link Condition} condition.
+	 */
+	public Condition isNotNull() {
+		return isNull().not();
+	}
+
 	/*
 	 * (non-Javadoc)
 	 * @see org.springframework.data.relational.core.sql.Named#getName()

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

@@ -0,0 +1,100 @@
+/*
+ * Copyright 2019 the original author or authors.
+ *
+ * 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 org.springframework.data.relational.core.sql;
+
+import org.springframework.util.Assert;
+
+/**
+ * Comparing {@link Condition} comparing two {@link Expression}s.
+ * <p/>
+ * Results in a rendered condition: {@code <left> <comparator> <right>} (e.g. {@code col = 'predicate'}.
+ *
+ * @author Mark Paluch
+ * @since 1.1
+ */
+public class Comparison extends AbstractSegment implements Condition {
+
+	private final Expression left;
+	private final String comparator;
+	private final Expression right;
+
+	private Comparison(Expression left, String comparator, Expression right) {
+
+		super(left, right);
+
+		this.left = left;
+		this.comparator = comparator;
+		this.right = right;
+	}
+
+	/**
+	 * Creates a new {@link Comparison} {@link Condition} given two {@link Expression}s.
+	 *
+	 * @param leftColumnOrExpression the left {@link Expression}.
+	 * @param comparator the comparator.
+	 * @param rightColumnOrExpression the right {@link Expression}.
+	 * @return the {@link Comparison} condition.
+	 */
+	public static Comparison create(Expression leftColumnOrExpression, String comparator,
+			Expression rightColumnOrExpression) {
+
+		Assert.notNull(leftColumnOrExpression, "Left expression must not be null!");
+		Assert.notNull(comparator, "Comparator must not be null!");
+		Assert.notNull(rightColumnOrExpression, "Right expression must not be null!");
+
+		return new Comparison(leftColumnOrExpression, comparator, rightColumnOrExpression);
+	}
+
+	@Override
+	public Condition not() {
+
+		if ("=".equals(comparator)) {
+			return new Comparison(left, "!=", right);
+		}
+
+		if ("!=".equals(comparator)) {
+			return new Comparison(left, "=", right);
+		}
+
+		return new Not(this);
+	}
+
+	/**
+	 * @return the left {@link Expression}.
+	 */
+	public Expression getLeft() {
+		return left;
+	}
+
+	/**
+	 * @return the comparator.
+	 */
+	public String getComparator() {
+		return comparator;
+	}
+
+	/**
+	 * @return the right {@link Expression}.
+	 */
+	public Expression getRight() {
+		return right;
+	}
+
+	@Override
+	public String toString() {
+		return left.toString() + " " + comparator + " " + right.toString();
+	}
+}

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

@@ -19,6 +19,8 @@
  * AST {@link Segment} for a condition.
  *
  * @author Mark Paluch
+ * @author Jens Schauder
+ * @since 1.1
  * @see Conditions
  */
 public interface Condition extends Segment {
@@ -43,6 +45,11 @@ default Condition or(Condition other) {
 		return new OrCondition(this, other);
 	}
 
+	/**
+	 * Creates a {@link Condition} that negates this {@link Condition}.
+	 *
+	 * @return the negated  {@link Condition}.
+	 */
 	default Condition not() {
 		return new Not(this);
 	}