First Draft - BAEL-4122 - A Quick Guide to Autocommit in JDBC
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gjohnson
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package com.baeldung.jdbcautocommit;
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public class Person {
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private Integer id;
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private String name;
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private String lastName;
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private Integer age;
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public Person() {
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}
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public Person(Integer id, String name, String lastName, Integer age) {
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this.id = id;
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this.name = name;
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this.lastName = lastName;
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this.age = age;
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}
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public Integer getId() {
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return id;
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}
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public void setId(Integer id) {
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this.id = id;
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}
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public String getName() {
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return name;
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}
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public void setName(String name) {
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this.name = name;
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}
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public String getLastName() {
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return lastName;
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}
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public void setLastName(String lastName) {
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this.lastName = lastName;
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}
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public Integer getAge() {
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return age;
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}
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public void setAge(Integer age) {
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this.age = age;
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}
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}
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package com.baeldung.jdbcautocommit;
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import static org.hamcrest.MatcherAssert.assertThat;
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import static org.hamcrest.Matchers.equalTo;
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import static org.hamcrest.Matchers.is;
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import java.sql.Connection;
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import java.sql.DriverManager;
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import java.sql.PreparedStatement;
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import java.sql.ResultSet;
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import java.sql.SQLException;
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import java.sql.Statement;
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import java.util.ArrayList;
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import java.util.List;
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import org.junit.jupiter.api.AfterAll;
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import org.junit.jupiter.api.AfterEach;
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import org.junit.jupiter.api.BeforeAll;
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import org.junit.jupiter.api.Test;
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public class AutoCommitUnitTest {
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private static final String INSERT_PERSON_SQL = "INSERT INTO Person VALUES (?,?,?,?)";
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private static final String SELECT_ALL_PEOPLE_SQL = "SELECT * FROM Person";
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private static final String UPDATE_PERSON_AGE_BY_ID_SQL = "UPDATE Person SET age = ? WHERE id = ?";
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private static final String DELETE_ALL_PEOPLE_SQL = "DELETE FROM Person";
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private static final String UPDATE_PERSON_AGE_BY_NAME_SQL
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= "UPDATE Person SET age = ? WHERE id = (SELECT id FROM Person WHERE name = ?)";
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private static final String CREATE_PERSON_TABLE_SQL
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= "CREATE TABLE Person (id INTEGER not null, name VARCHAR(50), lastName VARCHAR(50), age INTEGER, PRIMARY KEY (id))";
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private static Connection connection1;
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private static Connection connection2;
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@BeforeAll
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static void setup() throws SQLException {
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connection1 = DriverManager.getConnection("jdbc:h2:mem:autocommit", "sa", "");
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createPersonTable(connection1);
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connection2 = DriverManager.getConnection("jdbc:h2:mem:autocommit", "sa", "");
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}
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@Test
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void givenAutoCommitTrue_whenInsertAndUpdateRecord_thenDataPersistedAfterEachWithoutCommit() throws SQLException {
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connection1.setAutoCommit(true);
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Person person = new Person(1, "John", "Doe", 45);
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insertPerson(connection1, person);
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// no explicit commit needed here when auto-commit true
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// viewed from different connection, connection2 : assert person has been persisted into
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// the database
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List<Person> people = selectAllPeople(connection2);
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assertThat("person record inserted OK into empty table", people.size(), is(equalTo(1)));
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Person personInserted = people.iterator().next();
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assertThat("id correct", personInserted.getId(), is(equalTo(1)));
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// update age for person in database
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updatePersonAgeById(connection1, 1, 65);
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// no explicit commit needed here
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// viewed from connection2 : assert person's age has been updated to database
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people = selectAllPeople(connection2);
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Person personUpdated = people.iterator().next();
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assertThat("updated age correct", personUpdated.getAge(), is(equalTo(65)));
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}
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@Test
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void givenAutoCommitFalse_whenInsertCommitAndUpdateCommit_thenDataViewableAfterEachCommit() throws SQLException {
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connection1.setAutoCommit(false);
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Person person = new Person(1, "John", "Doe", 45);
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insertPerson(connection1, person);
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// viewed from different connection, connection2 : assert that person has not yet been
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// persisted to database before issuing commit
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List<Person> people = selectAllPeople(connection2);
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assertThat("No people have been inserted into database yet", people.size(), is(equalTo(0)));
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connection1.commit();
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// viewed from connection2 : assert that person has been persisted to database after
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// issuing commit
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people = selectAllPeople(connection2);
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assertThat("Person has been inserted into empty table after commit", people.size(), is(equalTo(1)));
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Person personInserted = people.iterator().next();
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assertThat("id correct", personInserted.getId(), is(equalTo(1)));
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updatePersonAgeById(connection1, 1, 65);
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// assert that person's age has not been updated before issuing commit
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people = selectAllPeople(connection2);
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Person personUpdated = people.iterator().next();
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assertThat("person's age still 45, not updated", personUpdated.getAge(), is(equalTo(45)));
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connection1.commit();
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// viewed from connection2 : assert that person's age has been updated after issuing commit
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people = selectAllPeople(connection2);
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personUpdated = people.iterator().next();
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assertThat("person's age updated to 65", personUpdated.getAge(), is(equalTo(65)));
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}
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@Test
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void givenAutoCommitFalse_whenInsertAndUpdateWithCommitOnlyAtEnd_thenDataOnlyViewableAfterCommit() throws SQLException {
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connection1.setAutoCommit(false);
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Person person = new Person(1, "John", "Doe", 45);
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insertPerson(connection1, person);
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// viewed from different connection, connection2 : assert that person has not yet been
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// persisted to database before issuing commit
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List<Person> people = selectAllPeople(connection2);
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assertThat("No people have been inserted into database yet", people.size(), is(equalTo(0)));
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updatePersonAgeById(connection1, 1, 65);
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// viewed from connection2 : assert that person has still not yet been
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// persisted to database before issuing commit
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people = selectAllPeople(connection2);
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assertThat("No people have been inserted into database yet", people.size(), is(equalTo(0)));
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connection1.commit();
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// viewed from connection2 : assert that person record has been persisted to
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// database and person's age has been updated after issuing commit
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people = selectAllPeople(connection2);
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Person personUpdated = people.iterator().next();
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assertThat("person's age updated to 65", personUpdated.getAge(), is(equalTo(65)));
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}
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@Test
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void givenAutoCommitTrue_whenUpdateWithNestedSelect_thenUpdatePersistedWithoutCommit() throws SQLException {
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connection1.setAutoCommit(true);
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Person person = new Person(1, "John", "Doe", 45);
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insertPerson(connection1, person);
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updatePersonAgeByName(connection1, "John", 77);
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// viewed from connection2 : assert person's age has been updated correctly to database
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// without issuing commit
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List<Person> people = selectAllPeople(connection2);
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Person personUpdated = people.iterator().next();
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assertThat("updated age correct", personUpdated.getAge(), is(equalTo(77)));
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}
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@Test
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void givenAutoCommitFalse_whenModeChangedToTrueAfterSQLUpdate_thenUpdatePersistedWithoutCommit() throws SQLException {
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connection1.setAutoCommit(false);
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Person person = new Person(1, "John", "Doe", 45);
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insertPerson(connection1, person);
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updatePersonAgeByName(connection1, "John", 77);
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connection1.setAutoCommit(true);
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// viewed from connection2 : assert record inserted and person's age has been updated
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// correctly to database after auto-commit changed false -> true ... without explicit commit needed
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List<Person> people = selectAllPeople(connection2);
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Person personUpdated = people.iterator().next();
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assertThat("updated age correct", personUpdated.getAge(), is(equalTo(77)));
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}
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@AfterEach
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void deleteAllRecords() throws SQLException {
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if (connection1.getAutoCommit() == false) {
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connection1.setAutoCommit(true);
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}
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deleteAllPeople(connection1);
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}
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@AfterAll
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static void closeConnections() throws SQLException {
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connection1.close();
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connection2.close();
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}
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private static void createPersonTable(Connection connection) throws SQLException {
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try(Statement statement = connection.createStatement()) {
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statement.executeUpdate(CREATE_PERSON_TABLE_SQL);
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}
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}
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private static int insertPerson(Connection connection, Person person) throws SQLException {
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try (PreparedStatement preparedStatement = connection.prepareStatement(INSERT_PERSON_SQL)) {
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preparedStatement.setInt(1, person.getId());
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preparedStatement.setString(2, person.getName());
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preparedStatement.setString(3, person.getLastName());
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preparedStatement.setInt(4, person.getAge());
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// execute statement and return the number of rows inserted
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return preparedStatement.executeUpdate();
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}
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}
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private static void deleteAllPeople(Connection connection) throws SQLException {
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try (Statement statement = connection.createStatement()) {
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statement.execute(DELETE_ALL_PEOPLE_SQL);
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}
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}
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private static List<Person> selectAllPeople(Connection connection) throws SQLException {
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List<Person> people = null;
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try (Statement statement = connection.createStatement()) {
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people = new ArrayList<>();
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ResultSet resultSet = statement.executeQuery(SELECT_ALL_PEOPLE_SQL);
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while (resultSet.next()) {
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Person person = new Person();
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person.setId(resultSet.getInt("id"));
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person.setName(resultSet.getString("name"));
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person.setLastName(resultSet.getString("lastName"));
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person.setAge(resultSet.getInt("age"));
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people.add(person);
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}
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}
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return people;
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}
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private static void updatePersonAgeById(Connection connection, int id, int newAge) throws SQLException {
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try (PreparedStatement preparedStatement = connection.prepareStatement(UPDATE_PERSON_AGE_BY_ID_SQL)) {
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preparedStatement.setInt(1, newAge);
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preparedStatement.setInt(2, id);
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preparedStatement.executeUpdate();
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}
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}
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private static void updatePersonAgeByName(Connection connection, String name, int newAge) throws SQLException {
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try (PreparedStatement preparedStatement = connection.prepareStatement(UPDATE_PERSON_AGE_BY_NAME_SQL)) {
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preparedStatement.setInt(1, newAge);
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preparedStatement.setString(2, name);
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preparedStatement.executeUpdate();
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}
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}
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}
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