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BAEL-4350: Difference between Statement and PreparedStatement
Signed-off-by: Ali Ben Messaoud <[email protected]>
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‎persistence-modules/core-java-persistence/README.md

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- [Guide to the JDBC ResultSet Interface](https://www.baeldung.com/jdbc-resultset)
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- [Types of SQL Joins](https://www.baeldung.com/sql-joins)
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- [Returning the Generated Keys in JDBC](https://www.baeldung.com/jdbc-returning-generated-keys)
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- [Difference between Statement and PreparedStatement](https://www.baeldung.com/difference-between-statement-and-preparedstatement)

‎persistence-modules/core-java-persistence/src/main/java/com/baeldung/statmentVsPreparedstatment/DatasourceFactory.java

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package com.baeldung.statmentVsPreparedstatment;
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import java.sql.Connection;
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import java.sql.DriverManager;
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import java.sql.SQLException;
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public class DatasourceFactory {
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private Connection connection;
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public Connection getConnection() throws ClassNotFoundException, SQLException {
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Class.forName("org.h2.Driver");
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connection = DriverManager.getConnection("jdbc:h2:mem:db_basic", "SA", "");
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connection.setAutoCommit(false);
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return connection;
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}
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public boolean createTables() throws SQLException {
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String query = "create table if not exists PERSONS (ID INT, NAME VARCHAR(45))";
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return connection.createStatement().executeUpdate(query) == 0;
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}
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}

‎persistence-modules/core-java-persistence/src/main/java/com/baeldung/statmentVsPreparedstatment/PersonEntity.java

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package com.baeldung.statmentVsPreparedstatment;
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import java.util.Objects;
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public class PersonEntity {
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private int id;
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private String name;
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public PersonEntity(int id, String name) {
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this.id = id;
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this.name = name;
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}
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public int getId() {
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return id;
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}
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public void setId(int 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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@Override public boolean equals(Object o) {
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if (this == o)
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return true;
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if (o == null || getClass() != o.getClass())
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return false;
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PersonEntity that = (PersonEntity) o;
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return id == that.id && Objects.equals(name, that.name);
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}
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@Override public int hashCode() {
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return Objects.hash(id, name);
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}
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}

‎persistence-modules/core-java-persistence/src/main/java/com/baeldung/statmentVsPreparedstatment/PreparedStatementPersonDao.java

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package com.baeldung.statmentVsPreparedstatment;
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import java.sql.Connection;
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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.util.ArrayList;
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import java.util.List;
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import java.util.Optional;
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public class PreparedStatementPersonDao {
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private final Connection connection;
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public PreparedStatementPersonDao(Connection connection) {
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this.connection = connection;
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}
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public Optional<PersonEntity> getById(int id) throws SQLException {
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String query = "SELECT id, name FROM persons WHERE id = ?";
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PreparedStatement preparedStatement = connection.prepareStatement(query);
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preparedStatement.setInt(1, id);
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ResultSet resultSet = preparedStatement.executeQuery();
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if (resultSet.first()) {
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PersonEntity result = new PersonEntity(resultSet.getInt("id"),
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resultSet.getString("name"));
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return Optional.of(result);
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} else {
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return Optional.empty();
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}
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}
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public void insert(PersonEntity personEntity) throws SQLException {
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String query = "INSERT INTO persons(id, name) VALUES( ?, ?)";
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PreparedStatement preparedStatement = connection.prepareStatement(query);
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preparedStatement.setInt(1, personEntity.getId());
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preparedStatement.setString(2, personEntity.getName());
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preparedStatement.executeUpdate();
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}
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public void insert(List<PersonEntity> personEntities) throws SQLException {
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String query = "INSERT INTO persons(id, name) VALUES( ?, ?)";
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PreparedStatement preparedStatement = connection.prepareStatement(query);
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for (PersonEntity personEntity : personEntities) {
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preparedStatement.setInt(1, personEntity.getId());
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preparedStatement.setString(2, personEntity.getName());
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preparedStatement.addBatch();
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}
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preparedStatement.executeBatch();
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}
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public void update(PersonEntity personEntity) throws SQLException {
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String query = "UPDATE persons SET name = ? WHERE id = ?";
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PreparedStatement preparedStatement = connection.prepareStatement(query);
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preparedStatement.setString(1, personEntity.getName());
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preparedStatement.setInt(2, personEntity.getId());
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preparedStatement.executeUpdate();
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}
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public void deleteById(int id) throws SQLException {
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String query = "DELETE FROM persons WHERE id = ?";
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PreparedStatement preparedStatement = connection.prepareStatement(query);
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preparedStatement.setInt(1, id);
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preparedStatement.executeUpdate();
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}
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public List<PersonEntity> getAll() throws SQLException {
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String query = "SELECT id, name FROM persons";
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PreparedStatement preparedStatement = connection.prepareStatement(query);
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ResultSet resultSet = preparedStatement.executeQuery();
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List<PersonEntity> result = new ArrayList<>();
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while (resultSet.next()) {
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result.add(new PersonEntity(resultSet.getInt("id"), resultSet.getString("name")));
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}
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return result;
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}
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}

‎persistence-modules/core-java-persistence/src/main/java/com/baeldung/statmentVsPreparedstatment/StatementPersonDao.java

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package com.baeldung.statmentVsPreparedstatment;
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import java.sql.Connection;
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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 java.util.Optional;
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public class StatementPersonDao {
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private final Connection connection;
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public StatementPersonDao(Connection connection) {
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this.connection = connection;
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}
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public Optional<PersonEntity> getById(int id) throws SQLException {
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String query = "SELECT id, name, FROM persons WHERE id = '" + id + "'";
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Statement statement = connection.createStatement();
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ResultSet resultSet = statement.executeQuery(query);
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if (resultSet.first()) {
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PersonEntity result = new PersonEntity(resultSet.getInt("id"),
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resultSet.getString("name"));
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return Optional.of(result);
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} else {
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return Optional.empty();
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}
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}
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public void insert(PersonEntity personEntity) throws SQLException {
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String query = "INSERT INTO persons(id, name) VALUES(" + personEntity.getId() + ", '"
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+ personEntity.getName() + "')";
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Statement statement = connection.createStatement();
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statement.executeUpdate(query);
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}
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public void insert(List<PersonEntity> personEntities) throws SQLException {
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for (PersonEntity personEntity : personEntities) {
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insert(personEntity);
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}
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}
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public void update(PersonEntity personEntity) throws SQLException {
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String query = "UPDATE persons SET name = '" + personEntity.getName() + "' WHERE id = "
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+ personEntity.getId();
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Statement statement = connection.createStatement();
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statement.executeUpdate(query);
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}
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public void deleteById(int id) throws SQLException {
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String query = "DELETE FROM persons WHERE id = " + id;
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Statement statement = connection.createStatement();
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statement.executeUpdate(query);
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}
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public List<PersonEntity> getAll() throws SQLException {
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String query = "SELECT id, name, FROM persons";
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Statement statement = connection.createStatement();
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ResultSet resultSet = statement.executeQuery(query);
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List<PersonEntity> result = new ArrayList<>();
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while (resultSet.next()) {
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result.add(new PersonEntity(resultSet.getInt("id"), resultSet.getString("name")));
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}
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return result;
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}
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}

‎persistence-modules/core-java-persistence/src/test/java/com/baeldung/statmentVsPreparedstatment/DatasourceFactoryUnitTest.java

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package com.baeldung.statmentVsPreparedstatment;
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import org.junit.jupiter.api.Test;
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import java.sql.Connection;
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import java.sql.SQLException;
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import static org.junit.jupiter.api.Assertions.assertFalse;
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import static org.junit.jupiter.api.Assertions.assertTrue;
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class DatasourceFactoryUnitTest {
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@Test
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void whenCreateConnectionAndTables_thenConnectionIsOpenAndTableIsCreated()
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throws SQLException, ClassNotFoundException {
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DatasourceFactory factory = new DatasourceFactory();
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Connection connection = factory.getConnection();
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assertFalse(connection.isClosed());
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assertTrue(factory.createTables());
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}
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}

‎persistence-modules/core-java-persistence/src/test/java/com/baeldung/statmentVsPreparedstatment/PreparedStatementPersonDaoUnitTest.java

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package com.baeldung.statmentVsPreparedstatment;
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import org.junit.jupiter.api.BeforeEach;
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import org.junit.jupiter.api.Test;
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import java.sql.Connection;
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import java.sql.SQLException;
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import java.util.Arrays;
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import java.util.List;
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import java.util.Optional;
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import static org.junit.jupiter.api.Assertions.*;
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class PreparedStatementPersonDaoUnitTest {
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private PreparedStatementPersonDao dao;
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@BeforeEach
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void setup() throws SQLException, ClassNotFoundException {
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DatasourceFactory datasourceFactory = new DatasourceFactory();
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Connection connection = datasourceFactory.getConnection();
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datasourceFactory.createTables();
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dao = new PreparedStatementPersonDao(connection);
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}
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@Test
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void whenInsertAPerson_thenItNeverThrowsAnException() {
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assertDoesNotThrow(() -> dao.insert(new PersonEntity(1, "john")));
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}
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@Test
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void whenInsertAPersonWithQuoteInText_thenItNeverThrowsAnException() {
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assertDoesNotThrow(() -> dao.insert(new PersonEntity(1, "O'Brien")));
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}
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@Test
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void whenGetAPersonById_thenItReturnThePersonInDatabase() throws SQLException {
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dao.insert(new PersonEntity(1, "john"));
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Optional<PersonEntity> maybeEmployee = dao.getById(1);
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assertTrue(maybeEmployee.isPresent());
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PersonEntity personEntity = maybeEmployee.get();
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assertEquals(1, personEntity.getId());
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assertEquals("john", personEntity.getName());
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}
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@Test
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void whenInsertAndGetMultiplePersons_thenItNeverThrowsAnException() throws SQLException {
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assertDoesNotThrow(() -> dao.insert(
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Arrays.asList(new PersonEntity(1, "john"), new PersonEntity(2, "skit"))));
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List<PersonEntity> result = dao.getAll();
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assertEquals(Arrays.asList(new PersonEntity(1, "john"), new PersonEntity(2, "skit")),
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result);
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}
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@Test
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void whenUpdateAnExistentPerson_thenItReturnsTheUpdatedPerson() throws SQLException {
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dao.insert(new PersonEntity(1, "john"));
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dao.update(new PersonEntity(1, "johnny"));
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Optional<PersonEntity> maybePerson = dao.getById(1);
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assertTrue(maybePerson.isPresent());
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PersonEntity personEntity = maybePerson.get();
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assertEquals(1, personEntity.getId());
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assertEquals("johnny", personEntity.getName());
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}
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@Test
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void whenDeleteAPersonById_thenItWillBeAbsentInDatabase() throws SQLException {
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dao.insert(new PersonEntity(1, "john"));
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dao.deleteById(1);
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Optional<PersonEntity> maybePerson = dao.getById(1);
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assertFalse(maybePerson.isPresent());
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}
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@Test
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void whenAHackerUpdateAPerson_thenItUpdatesTheTargetPerson() throws SQLException {
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dao.insert(Arrays.asList(new PersonEntity(1, "john"), new PersonEntity(2, "skeet")));
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dao.update(new PersonEntity(1, "hacker' --"));
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List<PersonEntity> result = dao.getAll();
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assertEquals(Arrays.asList(new PersonEntity(1, "hacker' --"), new PersonEntity(2, "skeet")),
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result);
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}
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}

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