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Spring Data Relational support
/*
* Copyright 2020-2023 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;
/**
* An interface describing the processing steps for the conversion of {@link SqlIdentifier} to SQL snippets or column
* names.
*
* @author Jens Schauder
* @since 2.0
*/
public interface IdentifierProcessing {
/**
* An {@link IdentifierProcessing} that can be used for databases adhering to the SQL standard which uses double
* quotes ({@literal "}) for quoting and makes unquoted literals equivalent to upper case.
*/
IdentifierProcessing ANSI = create(Quoting.ANSI, LetterCasing.UPPER_CASE);
/**
* An {@link IdentifierProcessing} without applying transformations.
*/
IdentifierProcessing NONE = create(Quoting.NONE, LetterCasing.AS_IS);
/**
* Create a {@link IdentifierProcessing} rule given {@link Quoting} and {@link LetterCasing} rules.
*
* @param quoting quoting rules.
* @param letterCasing {@link LetterCasing} rules for identifier normalization.
* @return a new {@link IdentifierProcessing} object.
*/
static DefaultIdentifierProcessing create(Quoting quoting, LetterCasing letterCasing) {
return new DefaultIdentifierProcessing(quoting, letterCasing);
}
/**
* Converts a {@link String} representing a bare name of an identifier to a {@link String} with proper quoting
* applied.
*
* @param identifier the name of an identifier. Must not be {@literal null}.
* @return a quoted name of an identifier. Guaranteed to be not {@literal null}.
*/
String quote(String identifier);
/**
* Standardizes the use of upper and lower case letters in an identifier in such a way that semantically the same
* identifier results from the quoted and the unquoted version. If this is not possible use of
* {@link LetterCasing#AS_IS} is recommended.
*
* @param identifier an identifier with arbitrary upper and lower cases. must not be {@literal null}.
* @return an identifier with standardized use of upper and lower case letter. Guaranteed to be not {@literal null}.
*/
String standardizeLetterCase(String identifier);
/**
* A conversion from unquoted identifiers to quoted identifiers.
*
* @author Jens Schauder
* @since 2.0
*/
class Quoting {
public static final Quoting ANSI = new Quoting("\"");
public static final Quoting NONE = new Quoting("");
private final String prefix;
private final String suffix;
/**
* Constructs a {@literal Quoting} with potential different prefix and suffix used for quoting.
*
* @param prefix a {@literal String} prefixed before the name for quoting it.
* @param suffix a {@literal String} suffixed at the end of the name for quoting it.
*/
public Quoting(String prefix, String suffix) {
this.prefix = prefix;
this.suffix = suffix;
}
/**
* Constructs a {@literal Quoting} with the same {@literal String} appended in front and end of an identifier.
*
* @param quoteCharacter the value appended at the beginning and the end of a name in order to quote it.
*/
public Quoting(String quoteCharacter) {
this(quoteCharacter, quoteCharacter);
}
public String apply(String identifier) {
return prefix + identifier + suffix;
}
}
/**
* Encapsulates the three kinds of letter casing supported.
*
* @author Jens Schauder
* @since 2.0
*/
enum LetterCasing {
UPPER_CASE {
@Override
public String apply(String identifier) {
return identifier.toUpperCase();
}
},
LOWER_CASE {
@Override
public String apply(String identifier) {
return identifier.toLowerCase();
}
},
AS_IS {
@Override
public String apply(String identifier) {
return identifier;
}
};
abstract String apply(String identifier);
}
}