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feature: Implement Serialized Entity Pattern (#2150)
* Add files: - App.java - Country.java - CountryDao.java - CountrySchemaSql.java - CountryTest.java - README.md - serialize-entity.urm.puml - pom.xml (inherit from parent pom.xml) Update files: - pom.xml (parent pom.xml, add 1 module called serialized-entity) * Fix duplicated error in pom.xml * Update: - pom.xml (module servant, changed by error, now fixed) - pom.xml (module serialized-entity) * Update: - pom.xml (changed, artifactId) * Update: - pom.xml Add: AppTest.java * Resolved changes required by the reviewer Co-authored-by: Ilkka Seppälä <iluwatar@users.noreply.github.com>
This commit is contained in:
JurenXu
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/*
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* The MIT License
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* Copyright © 2014-2022 Ilkka Seppälä
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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package com.iluwatar.serializedentity;
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import java.io.IOException;
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import java.sql.SQLException;
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import javax.sql.DataSource;
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import lombok.extern.slf4j.Slf4j;
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import org.h2.jdbcx.JdbcDataSource;
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/**
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* Serialized Entity Pattern.
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*
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* <p> Serialized Entity Pattern allow us to easily persist Java objects to the database. It uses Serializable interface
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* and DAO pattern. Serialized Entity Pattern will first use Serializable to convert a Java object into a set of bytes,
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* then it will using DAO pattern to store this set of bytes as BLOB to database.</p>
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*
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* <p> In this example, we first initialize two Java objects (Country) "China" and "UnitedArabEmirates", then we
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* initialize "serializedChina" with "China" object and "serializedUnitedArabEmirates" with "UnitedArabEmirates",
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* then we use method "serializedChina.insertCountry()" and "serializedUnitedArabEmirates.insertCountry()" to serialize
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* "China" and "UnitedArabEmirates" and persist them to database.
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* Last, with "serializedChina.selectCountry()" and "serializedUnitedArabEmirates.selectCountry()" we could read "China"
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* and "UnitedArabEmirates" from database as sets of bytes, then deserialize them back to Java object (Country). </p>
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*
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*/
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@Slf4j
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public class App {
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private static final String DB_URL = "jdbc:h2:~/test";
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private App() {
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}
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/**
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* Program entry point.
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* @param args command line args.
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* @throws IOException if any
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* @throws ClassNotFoundException if any
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*/
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public static void main(String[] args) throws IOException, ClassNotFoundException {
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final var dataSource = createDataSource();
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deleteSchema(dataSource);
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createSchema(dataSource);
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// Initializing Country Object China
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final var China = new Country(
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86,
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"China",
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"Asia",
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"Chinese"
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);
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// Initializing Country Object UnitedArabEmirates
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final var UnitedArabEmirates = new Country(
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971,
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"United Arab Emirates",
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"Asia",
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"Arabic"
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);
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// Initializing CountrySchemaSql Object with parameter "China" and "dataSource"
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final var serializedChina = new CountrySchemaSql(China, dataSource);
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// Initializing CountrySchemaSql Object with parameter "UnitedArabEmirates" and "dataSource"
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final var serializedUnitedArabEmirates = new CountrySchemaSql(UnitedArabEmirates, dataSource);
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/*
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By using CountrySchemaSql.insertCountry() method, the private (Country) type variable within Object
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CountrySchemaSql will be serialized to a set of bytes and persist to database.
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For more details of CountrySchemaSql.insertCountry() method please refer to CountrySchemaSql.java file
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*/
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serializedChina.insertCountry();
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serializedUnitedArabEmirates.insertCountry();
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/*
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By using CountrySchemaSql.selectCountry() method, CountrySchemaSql object will read the sets of bytes from database
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and deserialize it to Country object.
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For more details of CountrySchemaSql.selectCountry() method please refer to CountrySchemaSql.java file
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*/
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serializedChina.selectCountry();
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serializedUnitedArabEmirates.selectCountry();
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}
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private static void deleteSchema(DataSource dataSource) {
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try (var connection = dataSource.getConnection();
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var statement = connection.createStatement()) {
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statement.execute(CountrySchemaSql.DELETE_SCHEMA_SQL);
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} catch (SQLException e) {
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LOGGER.info("Exception thrown " + e.getMessage());
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}
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}
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private static void createSchema(DataSource dataSource) {
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try (var connection = dataSource.getConnection();
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var statement = connection.createStatement()) {
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statement.execute(CountrySchemaSql.CREATE_SCHEMA_SQL);
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} catch (SQLException e) {
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LOGGER.info("Exception thrown " + e.getMessage());
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}
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}
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private static DataSource createDataSource() {
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var dataSource = new JdbcDataSource();
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dataSource.setURL(DB_URL);
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return dataSource;
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}
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}
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@@ -0,0 +1,47 @@
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/*
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* The MIT License
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* Copyright © 2014-2022 Ilkka Seppälä
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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package com.iluwatar.serializedentity;
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import java.io.Serializable;
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import lombok.AllArgsConstructor;
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import lombok.EqualsAndHashCode;
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import lombok.Getter;
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import lombok.Setter;
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import lombok.ToString;
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/**
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* A Country POJO taht represents the data that will serialize and store in database.
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*/
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@Getter
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@Setter
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@EqualsAndHashCode
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@ToString
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@AllArgsConstructor
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public class Country implements Serializable {
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private int code;
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private String name;
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private String continents;
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private String language;
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public static final long serialVersionUID = 7149851;
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}
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@@ -0,0 +1,45 @@
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/*
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* The MIT License
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* Copyright © 2014-2022 Ilkka Seppälä
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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/**
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* In an application the Data Access Object (DAO) is a part of Data access layer. It is an object
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* that provides an interface to some type of persistence mechanism. By mapping application calls to
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* the persistence layer, DAO provides some specific data operations without exposing details of the
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* database. This isolation supports the Single responsibility principle. It separates what data
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* accesses the application needs, in terms of domain-specific objects and data types (the public
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* interface of the DAO), from how these needs can be satisfied with a specific DBMS, database
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* schema, etc.
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*
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* <p>Any change in the way data is stored and retrieved will not change the client code as the
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* client will be using interface and need not worry about exact source.
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*
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* @see InMemoryCustomerDao
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* @see DbCustomerDao
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*/
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package com.iluwatar.serializedentity;
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import java.io.IOException;
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public interface CountryDao {
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int insertCountry() throws IOException;
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int selectCountry() throws IOException, ClassNotFoundException;
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}
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@@ -0,0 +1,122 @@
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/*
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* The MIT License
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* Copyright © 2014-2022 Ilkka Seppälä
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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package com.iluwatar.serializedentity;
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import java.io.ByteArrayInputStream;
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import java.io.ByteArrayOutputStream;
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import java.io.IOException;
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import java.io.ObjectInputStream;
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import java.io.ObjectOutputStream;
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import java.sql.Blob;
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import java.sql.ResultSet;
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import java.sql.SQLException;
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import javax.sql.DataSource;
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import lombok.extern.slf4j.Slf4j;
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/**
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* Country Schema SQL Class.
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*/
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@Slf4j
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public class CountrySchemaSql implements CountryDao {
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public static final String CREATE_SCHEMA_SQL = "CREATE TABLE IF NOT EXISTS WORLD (ID INT PRIMARY KEY, COUNTRY BLOB)";
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public static final String DELETE_SCHEMA_SQL = "DROP TABLE WORLD IF EXISTS";
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private Country country;
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private DataSource dataSource;
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/**
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* Public constructor.
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*
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* @param dataSource datasource
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* @param country country
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*/
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public CountrySchemaSql(Country country, DataSource dataSource) {
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this.country = new Country(
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country.getCode(),
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country.getName(),
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country.getContinents(),
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country.getLanguage()
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);
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this.dataSource = dataSource;
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}
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/**
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* This method will serialize a Country object and store it to database.
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* @return int type, if successfully insert a serialized object to database then return country code, else return -1.
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* @throws IOException if any.
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*/
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@Override
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public int insertCountry() throws IOException {
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var sql = "INSERT INTO WORLD (ID, COUNTRY) VALUES (?, ?)";
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try (var connection = dataSource.getConnection();
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var preparedStatement = connection.prepareStatement(sql);
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ByteArrayOutputStream baos = new ByteArrayOutputStream();
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ObjectOutputStream oss = new ObjectOutputStream(baos)) {
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oss.writeObject(country);
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oss.flush();
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preparedStatement.setInt(1, country.getCode());
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preparedStatement.setBlob(2, new ByteArrayInputStream(baos.toByteArray()));
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preparedStatement.execute();
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return country.getCode();
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} catch (SQLException e) {
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LOGGER.info("Exception thrown " + e.getMessage());
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}
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return -1;
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}
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/**
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* This method will select a data item from database and deserialize it.
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* @return int type, if successfully select and deserialized object from database then return country code,
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* else return -1.
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* @throws IOException if any.
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* @throws ClassNotFoundException if any.
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*/
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@Override
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public int selectCountry() throws IOException, ClassNotFoundException {
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var sql = "SELECT ID, COUNTRY FROM WORLD WHERE ID = ?";
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try (var connection = dataSource.getConnection();
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var preparedStatement = connection.prepareStatement(sql)) {
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preparedStatement.setInt(1, country.getCode());
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try (ResultSet rs = preparedStatement.executeQuery()) {
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if (rs.next()) {
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Blob countryBlob = rs.getBlob("country");
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ByteArrayInputStream baos = new ByteArrayInputStream(countryBlob.getBytes(1, (int) countryBlob.length()));
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ObjectInputStream ois = new ObjectInputStream(baos);
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country = (Country) ois.readObject();
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LOGGER.info("Country: " + country);
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}
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return rs.getInt("id");
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}
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} catch (SQLException e) {
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LOGGER.info("Exception thrown " + e.getMessage());
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}
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return -1;
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}
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}
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