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Spring Data Relational support
/*
* Copyright 2019-2023 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
*
* https://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.render;
import org.springframework.data.relational.core.sql.*;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
/**
* {@link PartRenderer} for {@link Expression}s.
*
* @author Mark Paluch
* @author Jens Schauder
* @since 1.1
* @see Column
* @see SubselectExpression
*/
class ExpressionVisitor extends TypedSubtreeVisitor implements PartRenderer {
private final RenderContext context;
private final AliasHandling aliasHandling;
private CharSequence value = "";
private @Nullable PartRenderer partRenderer;
/**
* Creates an {@code ExpressionVisitor} that does not use aliases for column names
*
* @param context must not be {@literal null}.
*/
ExpressionVisitor(RenderContext context) {
this(context, AliasHandling.IGNORE);
}
/**
* Creates an {@code ExpressionVisitor}.
*
* @param context must not be {@literal null}.
* @param aliasHandling controls if columns should be rendered as their alias or using their table names.
* @since 2.3
*/
ExpressionVisitor(RenderContext context, AliasHandling aliasHandling) {
Assert.notNull(context, "The render context must not be null");
Assert.notNull(aliasHandling, "The aliasHandling must not be null");
this.context = context;
this.aliasHandling = aliasHandling;
}
/*
* (non-Javadoc)
* @see org.springframework.data.relational.core.sql.render.TypedSubtreeVisitor#enterMatched(org.springframework.data.relational.core.sql.Visitable)
*/
@Override
Delegation enterMatched(Expression segment) {
if (segment instanceof SubselectExpression) {
SelectStatementVisitor visitor = new SelectStatementVisitor(context);
partRenderer = visitor;
return Delegation.delegateTo(visitor);
}
if (segment instanceof SimpleFunction) {
SimpleFunctionVisitor visitor = new SimpleFunctionVisitor(context);
partRenderer = visitor;
return Delegation.delegateTo(visitor);
}
if (segment instanceof AnalyticFunction) {
AnalyticFunctionVisitor visitor = new AnalyticFunctionVisitor(context);
partRenderer = visitor;
return Delegation.delegateTo(visitor);
}
if (segment instanceof Column) {
Column column = (Column) segment;
value = aliasHandling == AliasHandling.USE ? NameRenderer.fullyQualifiedReference(context, column)
: NameRenderer.fullyQualifiedUnaliasedReference(context, column);
} else if (segment instanceof BindMarker) {
if (segment instanceof Named) {
value = NameRenderer.render(context, (Named) segment);
} else {
value = segment.toString();
}
} else if (segment instanceof AsteriskFromTable) {
value = NameRenderer.render(context, ((AsteriskFromTable) segment).getTable()) + ".*";
} else if (segment instanceof Cast) {
CastVisitor visitor = new CastVisitor(context);
partRenderer = visitor;
return Delegation.delegateTo(visitor);
} else {
// works for literals and just and possibly more
value = segment.toString();
}
return Delegation.retain();
}
/*
* (non-Javadoc)
* @see org.springframework.data.relational.core.sql.render.TypedSubtreeVisitor#enterNested(org.springframework.data.relational.core.sql.Visitable)
*/
@Override
Delegation enterNested(Visitable segment) {
if (segment instanceof Condition) {
ConditionVisitor visitor = new ConditionVisitor(context);
partRenderer = visitor;
return Delegation.delegateTo(visitor);
}
if (segment instanceof InlineQuery) {
NoopVisitor partRenderer = new NoopVisitor(InlineQuery.class);
return Delegation.delegateTo(partRenderer);
}
return super.enterNested(segment);
}
/*
* (non-Javadoc)
* @see org.springframework.data.relational.core.sql.render.TypedSubtreeVisitor#leaveMatched(org.springframework.data.relational.core.sql.Visitable)
*/
@Override
Delegation leaveMatched(Expression segment) {
if (partRenderer != null) {
value = partRenderer.getRenderedPart();
partRenderer = null;
}
return super.leaveMatched(segment);
}
/*
* (non-Javadoc)
* @see org.springframework.data.relational.core.sql.render.PartRenderer#getRenderedPart()
*/
@Override
public CharSequence getRenderedPart() {
return value;
}
/**
* Describes how aliases of columns should be rendered.
*
* @since 2.3
*/
enum AliasHandling {
/**
* The alias does not get used.
*/
IGNORE,
/**
* The alias gets used. This means aliased columns get rendered as {@literal }.
*/
USE
}
}