001/* 002 * Copyright 2015-2022 Transmogrify LLC, 2022-2025 Revetware LLC. 003 * 004 * Licensed under the Apache License, Version 2.0 (the "License"); 005 * you may not use this file except in compliance with the License. 006 * You may obtain a copy of the License at 007 * 008 * http://www.apache.org/licenses/LICENSE-2.0 009 * 010 * Unless required by applicable law or agreed to in writing, software 011 * distributed under the License is distributed on an "AS IS" BASIS, 012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 013 * See the License for the specific language governing permissions and 014 * limitations under the License. 015 */ 016 017package com.pyranid; 018 019import javax.annotation.Nonnull; 020import javax.annotation.Nullable; 021import javax.annotation.concurrent.ThreadSafe; 022import java.lang.reflect.Constructor; 023import java.lang.reflect.InvocationTargetException; 024import java.util.Arrays; 025 026import static java.lang.String.format; 027import static java.util.Objects.requireNonNull; 028 029/** 030 * Contract for a factory that creates instances given a type. 031 * <p> 032 * Useful for resultset mapping, where each row in the resultset might require a new instance. 033 * <p> 034 * Implementors are suggested to employ application-specific strategies, such as having a DI container handle instance 035 * creation. 036 * <p> 037 * Implementations should be threadsafe. 038 * 039 * @author <a href="https://www.revetkn.com">Mark Allen</a> 040 * @since 1.0.0 041 */ 042@ThreadSafe 043public interface InstanceProvider { 044 /** 045 * Provides an instance of the given {@code instanceType}. 046 * <p> 047 * Whether the instance is new every time or shared/reused is implementation-dependent. 048 * 049 * @param <T> instance type token 050 * @param instanceType the type of instance to create 051 * @return an instance of the given {@code instanceType} 052 */ 053 @Nonnull 054 default <T> T provide(@Nonnull StatementContext<T> statementContext, 055 @Nonnull Class<T> instanceType) { 056 requireNonNull(statementContext); 057 requireNonNull(instanceType); 058 059 try { 060 return instanceType.getDeclaredConstructor().newInstance(); 061 } catch (Exception e) { 062 throw new DatabaseException(format( 063 "Unable to create an instance of %s. Please verify that %s has a public no-argument constructor", 064 instanceType, instanceType.getSimpleName()), e); 065 } 066 } 067 068 /** 069 * Provides an instance of the given {@code recordType}. 070 * <p> 071 * Whether the instance is new every time or shared/reused is implementation-dependent. 072 * 073 * @param <T> instance type token 074 * @param recordType the type of instance to create (must be a record) 075 * @param initargs values used to construct the record instance 076 * @return an instance of the given {@code recordType} 077 * @since 2.0.0 078 */ 079 @Nonnull 080 default <T extends Record> T provideRecord(@Nonnull StatementContext<T> statementContext, 081 @Nonnull Class<T> recordType, 082 @Nullable Object... initargs) { 083 requireNonNull(statementContext); 084 requireNonNull(recordType); 085 086 try { 087 // Find the canonical constructor for the record. 088 // Hat tip to https://stackoverflow.com/a/67127067 089 Class<?>[] componentTypes = Arrays.stream(recordType.getRecordComponents()) 090 .map(rc -> rc.getType()) 091 .toArray(Class<?>[]::new); 092 093 Constructor<T> constructor = recordType.getDeclaredConstructor(componentTypes); 094 return constructor.newInstance(initargs); 095 } catch (NoSuchMethodException | InstantiationException | IllegalAccessException | 096 IllegalArgumentException | InvocationTargetException e) { 097 throw new DatabaseException(String.format("Unable to instantiate Record type %s with args %s", recordType, 098 initargs == null ? "[none]" : Arrays.asList(initargs)), e); 099 } 100 } 101}