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Spring Data Relational support
/*
* Copyright 2019-2022 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.From;
import org.springframework.data.relational.core.sql.Join;
import org.springframework.data.relational.core.sql.OrderByField;
import org.springframework.data.relational.core.sql.Select;
import org.springframework.data.relational.core.sql.SelectList;
import org.springframework.data.relational.core.sql.Visitable;
import org.springframework.data.relational.core.sql.Where;
/**
* {@link PartRenderer} for {@link Select} statements.
*
* @author Mark Paluch
* @author Jens Schauder
* @author Myeonghyeon Lee
* @since 1.1
*/
class SelectStatementVisitor extends DelegatingVisitor implements PartRenderer {
private final RenderContext context;
private final SelectRenderContext selectRenderContext;
private StringBuilder builder = new StringBuilder();
private StringBuilder selectList = new StringBuilder();
private StringBuilder from = new StringBuilder();
private StringBuilder join = new StringBuilder();
private StringBuilder where = new StringBuilder();
private SelectListVisitor selectListVisitor;
private OrderByClauseVisitor orderByClauseVisitor;
private FromClauseVisitor fromClauseVisitor;
private WhereClauseVisitor whereClauseVisitor;
SelectStatementVisitor(RenderContext context) {
this.context = context;
this.selectRenderContext = context.getSelect();
this.selectListVisitor = new SelectListVisitor(context, selectList::append);
this.orderByClauseVisitor = new OrderByClauseVisitor(context);
this.fromClauseVisitor = new FromClauseVisitor(context, it -> {
if (from.length() != 0) {
from.append(", ");
}
from.append(it);
});
this.whereClauseVisitor = new WhereClauseVisitor(context, where::append);
}
/*
* (non-Javadoc)
* @see org.springframework.data.relational.core.sql.render.DelegatingVisitor#doEnter(org.springframework.data.relational.core.sql.Visitable)
*/
@Override
public Delegation doEnter(Visitable segment) {
if (segment instanceof SelectList) {
return Delegation.delegateTo(selectListVisitor);
}
if (segment instanceof OrderByField) {
return Delegation.delegateTo(orderByClauseVisitor);
}
if (segment instanceof From) {
return Delegation.delegateTo(fromClauseVisitor);
}
if (segment instanceof Join) {
return Delegation.delegateTo(new JoinVisitor(context, it -> {
if (join.length() != 0) {
join.append(' ');
}
join.append(it);
}));
}
if (segment instanceof Where) {
return Delegation.delegateTo(whereClauseVisitor);
}
return Delegation.retain();
}
/*
* (non-Javadoc)
* @see org.springframework.data.relational.core.sql.render.DelegatingVisitor#doLeave(org.springframework.data.relational.core.sql.Visitable)
*/
@Override
public Delegation doLeave(Visitable segment) {
if (segment instanceof Select) {
Select select = (Select) segment;
builder.append("SELECT ");
if (select.isDistinct()) {
builder.append("DISTINCT ");
}
builder.append(selectList);
builder.append(selectRenderContext.afterSelectList().apply(select));
if (from.length() != 0) {
builder.append(" FROM ").append(from);
}
builder.append(selectRenderContext.afterFromTable().apply(select));
if (join.length() != 0) {
builder.append(' ').append(join);
}
if (where.length() != 0) {
builder.append(" WHERE ").append(where);
}
CharSequence orderBy = orderByClauseVisitor.getRenderedPart();
if (orderBy.length() != 0) {
builder.append(" ORDER BY ").append(orderBy);
}
builder.append(selectRenderContext.afterOrderBy(orderBy.length() != 0).apply(select));
return Delegation.leave();
}
return Delegation.retain();
}
/*
* (non-Javadoc)
* @see org.springframework.data.relational.core.sql.render.PartRenderer#getRenderedPart()
*/
@Override
public CharSequence getRenderedPart() {
return builder;
}
}