org.mybatis.dynamic.sql.select.CountDSLCompleter Maven / Gradle / Ivy
/**
* Copyright 2016-2019 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.mybatis.dynamic.sql.select;
import java.util.function.Function;
import java.util.function.ToLongFunction;
import org.mybatis.dynamic.sql.util.Buildable;
import org.mybatis.dynamic.sql.util.mybatis3.MyBatis3Utils;
/**
* Represents a function that can be used to create a general count method. When using this function,
* you can create a method that does not require a user to call the build() and render() methods - making
* client code look a bit cleaner.
*
* This function is intended to by used in conjunction with a utility method like
* {@link MyBatis3Utils#countFrom(ToLongFunction, CountDSL, CountDSLCompleter)}
*
*
For example, you can create mapper interface methods like this:
*
*
* @SelectProvider(type=SqlProviderAdapter.class, method="select")
* long count(SelectStatementProvider selectStatement);
*
* default long count(CountDSLCompleter completer) {
* return MyBatis3Utils.count(this::count, person, completer);
* }
*
*
* And then call the simplified default method like this:
*
*
* long rows = mapper.count(c ->
* c.where(occupation, isNull()));
*
*
* You can implement a "count all" with the following code:
*
*
* long rows = mapper.count(c -> c);
*
*
* Or
*
*
* long rows = mapper.count(CountDSLCompleter.allRows());
*
*
* @author Jeff Butler
*/
@FunctionalInterface
public interface CountDSLCompleter extends
Function, Buildable> {
/**
* Returns a completer that can be used to count every row in a table.
*
* @return the completer that will count every row in a table
*/
static CountDSLCompleter allRows() {
return c -> c;
}
}