Initial commit

.gitignore

+#Eclipse
+.settings
+.project
+.classpath
+
+#Maven
+target
+
+#General
+bak
+

README.md

+# Ejemplos de JDBC
+
+Ejemplos de JDBC incluidos en el Tema 4 de la asignatura DAI.
\ No newline at end of file

create_db_and_user.sql

+CREATE DATABASE IF NOT EXISTS dai;
+
+CREATE USER IF NOT EXISTS 'dai'@'localhost' IDENTIFIED BY 'dai';
+CREATE USER IF NOT EXISTS 'dai2'@'localhost' IDENTIFIED BY 'dai';
+GRANT ALL ON dai.* TO 'dai'@'localhost' WITH GRANT OPTION;
+GRANT ALL ON dai.user TO 'dai'@'localhost';
\ No newline at end of file

pom.xml

+<?xml version="1.0" encoding="UTF-8"?>
+
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+	<modelVersion>4.0.0</modelVersion>
+
+	<groupId>es.uvigo.esei.dai</groupId>
+	<artifactId>jdbc</artifactId>
+	<version>1.0.0</version>
+
+	<name>Ejemplos de DAI - JDBC</name>
+	<inceptionYear>2014</inceptionYear>
+	<url>https://sing-group.org/dt/gitlab/dai-2324/jdbc</url>
+
+	<developers>
+		<developer>
+			<name>Miguel Reboiro-Jato</name>
+			<organization>Escola Superior de Enxeñaría Informática -
+				Universidade de Vigo</organization>
+			<organizationUrl>https://esei.uvigo.es/</organizationUrl>
+			<email>mrjato@uvigo.gal</email>
+		</developer>
+	</developers>
+
+	<licenses>
+		<license>
+			<name>GNU GENERAL PUBLIC LICENSE, Version 3</name>
+			<url>http://www.gnu.org/licenses/gpl.html</url>
+			<distribution>repo</distribution>
+		</license>
+	</licenses>
+
+	<properties>
+		<maven.compiler.source>11</maven.compiler.source>
+		<maven.compiler.target>11</maven.compiler.target>
+		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+		<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
+
+		<!-- Dependencies versions -->
+		<mysql-connector-j.version>8.1.0</mysql-connector-j.version>
+		
+		<!-- Plugin versions -->
+		<license-maven-plugin.version>2.2.0</license-maven-plugin.version>
+		<maven-compiler-plugin.version>3.11.0</maven-compiler-plugin.version>
+
+		<!-- license-maven-plugin configuration -->
+		<license.licenseName>gpl_v3</license.licenseName>
+		<license.copyrightOwners>Miguel Reboiro Jato</license.copyrightOwners>
+		<license.organizationName>Universidade de Vigo</license.organizationName>
+		<license.addJavaLicenseAfterPackage>false</license.addJavaLicenseAfterPackage>
+	</properties>
+
+	<contributors>
+		<contributor>
+			<name>Miguel Reboiro Jato</name>
+			<email>mrjato@uvigo.gal</email>
+			<organization>Escola Superior de Enxeñaría Informática -
+				Universidade de Vigo</organization>
+			<organizationUrl>https://esei.uvigo.es/</organizationUrl>
+			<roles>
+				<role>author</role>
+				<role>professor</role>
+			</roles>
+		</contributor>
+	</contributors>
+
+	<dependencies>
+		<dependency>
+			<groupId>com.mysql</groupId>
+			<artifactId>mysql-connector-j</artifactId>
+			<version>${mysql-connector-j.version}</version>
+		</dependency>
+	</dependencies>
+
+	<build>
+		<plugins>
+			<plugin>
+				<groupId>org.apache.maven.plugins</groupId>
+				<artifactId>maven-compiler-plugin</artifactId>
+				<version>${maven-compiler-plugin.version}</version>
+			</plugin>
+			<plugin>
+				<groupId>org.codehaus.mojo</groupId>
+				<artifactId>license-maven-plugin</artifactId>
+				<version>${license-maven-plugin.version}</version>
+				<executions>
+					<execution>
+						<id>first</id>
+						<goals>
+							<goal>update-file-header</goal>
+						</goals>
+						<phase>process-sources</phase>
+					</execution>
+				</executions>
+			</plugin>
+		</plugins>
+	</build>
+</project>

src/main/java/es/uvigo/esei/dai/jdbc/examples/ConnectionExamples.java

+/*-
+ * #%L
+ * Ejemplos de DAI - JDBC
+ * %%
+ * Copyright (C) 2014 - 2023 Miguel Reboiro Jato
+ * %%
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ * 
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public
+ * License along with this program.  If not, see
+ * <http://www.gnu.org/licenses/gpl-3.0.html>.
+ * #L%
+ */
+package es.uvigo.esei.dai.jdbc.examples;
+
+import java.sql.Connection;
+import java.sql.DriverManager;
+import java.sql.PreparedStatement;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+import java.sql.Statement;
+
+public class ConnectionExamples {
+  private static final String DB_URL = "jdbc:mysql://localhost/dai";
+  private static final String DB_USER = "dai";
+  private static final String DB_PASSWORD = "dai";
+
+  public static void main(String[] args) throws Exception {
+    statementCreate();
+    statementGrant();
+    statementInsert();
+    preparedStatementInsert();
+    statementSelect();
+    preparedStatementSelect();
+    transaction();
+  }
+
+  private static void statementCreate() throws SQLException {
+    // 1. Conexión a la base de datos
+    try (Connection connection = DriverManager.getConnection(DB_URL, DB_USER, DB_PASSWORD)) {
+      // 2. Creación de la consulta
+      try (Statement statement = connection.createStatement()) {
+
+        // 3. Creación de la tabla Ejemplo
+        int result = statement.executeUpdate(
+          "CREATE TABLE Ejemplo("
+            + "id INT NOT NULL AUTO_INCREMENT,"
+            + "nombre VARCHAR(255) NOT NULL,"
+            + "PRIMARY KEY (id)"
+            + ")"
+        );
+
+        // 4. Comprobación de resultado
+        if (result != 0)
+          throw new SQLException("Unexpected result value: " + result);
+      }
+    }
+  }
+
+  private static void statementGrant() throws SQLException {
+    // 1. Conexión a la base de datos
+    try (Connection connection = DriverManager.getConnection(DB_URL, DB_USER, DB_PASSWORD)) {
+
+      // 2. Creación de la consulta
+      try (Statement statement = connection.createStatement()) {
+        // 3. Modificación de permisos para dai2
+        int result = statement.executeUpdate("GRANT SELECT ON dai.Ejemplo TO 'dai2'@'localhost' ");
+
+        // 4. Comprobación de resultado
+        if (result != 0)
+          throw new SQLException("Unexpected result value: " + result);
+      }
+    }
+  }
+
+  private static void statementInsert() throws SQLException {
+    // 1. Conexión a la base de datos
+    try (Connection connection = DriverManager.getConnection(DB_URL, DB_USER, DB_PASSWORD)) {
+
+      // 2. Creación de la consulta
+      try (Statement statement = connection.createStatement()) {
+        // 3. Creación de la tabla Ejemplo. Con RETURN_GENERATED_KEYS
+        // hacemos que las claves primarias se puedan recuperar
+        int result = statement.executeUpdate(
+          "INSERT INTO Ejemplo (id, nombre) VALUES (0, 'Ana'), (0, 'Juan')", Statement.RETURN_GENERATED_KEYS
+        );
+
+        // 4. Comprobación de resultado
+        if (result == 2) {
+          try (ResultSet generatedKeys = statement.getGeneratedKeys()) {
+            while (generatedKeys.next()) {
+              System.out.println("Clave " + generatedKeys.getInt(1));
+            }
+          }
+        } else {
+          throw new SQLException("Unexpected result value: " + result);
+        }
+      }
+    }
+  }
+
+  private static void preparedStatementInsert() throws SQLException {
+    // 1. Conexión a la base de datos
+    try (Connection connection = DriverManager.getConnection(DB_URL, DB_USER, DB_PASSWORD)) {
+
+      // 2. Creación de la consulta. Con RETURN_GENERATED_KEYS
+      // hacemos que las claves primarias se puedan recuperar
+      try (
+        PreparedStatement statement = connection.prepareStatement(
+          "INSERT INTO Ejemplo (id, nombre) VALUES (0, ?), (0, ?)", Statement.RETURN_GENERATED_KEYS
+        )
+      ) {
+        // 3. Asignación de los valores
+        statement.setString(1, "Ana");
+        statement.setString(2, "Juan");
+
+        // 4. Creación de la tabla Ejemplo.
+        int result = statement.executeUpdate();
+
+        // 5. Comprobación de resultado
+        if (result == 2) {
+          try (ResultSet generatedKeys = statement.getGeneratedKeys()) {
+            while (generatedKeys.next()) {
+              System.out.println("Clave " + generatedKeys.getInt(1));
+            }
+          }
+        } else {
+          throw new SQLException("Unexpected result value: " + result);
+        }
+      }
+    }
+  }
+
+  private static void statementSelect() throws SQLException {
+    // 1. Conexión a la base de datos local "dai"
+    // con login y password "dai"
+    try (Connection connection = DriverManager.getConnection(DB_URL, DB_USER, DB_PASSWORD)) {
+      // 2. Creación de la consulta
+      try (Statement statement = connection.createStatement()) {
+        // 3. Ejecución de la consulta
+        try (ResultSet result = statement.executeQuery("SELECT * FROM Ejemplo WHERE nombre LIKE 'A%'")) {
+          // 4. Visualización de los resultados
+          while (result.next()) {
+            System.out.printf("Id: %d, Nombre: %s%n", result.getInt(1), result.getString(2));
+          }
+        }
+      }
+    }
+  }
+
+  private static void preparedStatementSelect() throws SQLException {
+    // 1. Conexión a la base de datos
+    try (Connection connection = DriverManager.getConnection(DB_URL, DB_USER, DB_PASSWORD)) {
+
+      // 2. Preparación de la consulta
+      try (
+        PreparedStatement statement = connection
+          .prepareStatement("SELECT * FROM Ejemplo WHERE id > ? AND nombre LIKE ?")
+      ) {
+        // 3. Asignación de los valores
+        statement.setInt(1, 5);
+        statement.setString(2, "A%");
+
+        // 4. Ejecución de la consulta
+        try (ResultSet result = statement.executeQuery()) {
+          // 5. Visualización de resultado
+          while (result.next()) {
+            System.out.printf("Id: %d, Nombre: %s%n", result.getInt("id"), result.getString("nombre"));
+          }
+        }
+      }
+    }
+  }
+
+  private static void transaction() throws Exception {
+    // 1. Conexión a la base de datos
+    try (Connection connection = DriverManager.getConnection(DB_URL, DB_USER, DB_PASSWORD)) {
+
+      // 2. Activación del modo transacción
+      connection.setAutoCommit(false);
+      connection.setTransactionIsolation(Connection.TRANSACTION_SERIALIZABLE);
+
+      // 3. Creación de la consulta
+      try (
+        PreparedStatement statement = connection.prepareStatement("INSERT INTO Ejemplo (id, nombre) VALUES (0, ?)")
+      ) {
+        // 4. Asignación de los valores y ejecución de la consulta
+        for (String nombre : new String[] { "María", "Juan", "Luisa" }) {
+          statement.setString(1, nombre);
+
+          if (statement.executeUpdate() != 1) {
+            throw new SQLException("Error inserting value");
+          }
+
+          // 5. Fuerza que se haga un rollback cuando se intente insertar
+          // segundo nombre, de modo que se cancelará también la primera
+          // inserción
+          if (nombre.equals("Juan"))
+            throw new RuntimeException();
+        }
+
+        // 5a. Commit
+        connection.commit();
+      } catch (Exception e) {
+        // 5b. Rollback
+        connection.rollback();
+      }
+    }
+  }
+}

src/main/java/es/uvigo/esei/dai/jdbc/transactions/TransactionExamples.java

+/*-
+ * #%L
+ * Ejemplos de DAI - JDBC
+ * %%
+ * Copyright (C) 2014 - 2023 Miguel Reboiro Jato
+ * %%
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ * 
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public
+ * License along with this program.  If not, see
+ * <http://www.gnu.org/licenses/gpl-3.0.html>.
+ * #L%
+ */
+package es.uvigo.esei.dai.jdbc.transactions;
+
+import java.sql.Connection;
+import java.sql.DriverManager;
+import java.sql.PreparedStatement;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+
+public class TransactionExamples {
+  private static final String DB_URL = "jdbc:mysql://localhost/dai";
+  private static final String DB_USER = "dai";
+  private static final String DB_PASSWORD = "dai";
+
+  private static final int ISOLATION_LEVEL = Connection.TRANSACTION_READ_UNCOMMITTED;
+
+  public static void main(String[] args) throws Exception {
+    lostUpdate();
+    dirtyRead();
+    nonRepeatableRead();
+    phantomRead();
+  }
+
+  private static Connection createConnection() throws SQLException {
+    return DriverManager.getConnection(DB_URL, DB_USER, DB_PASSWORD);
+  }
+
+  // Java no es capaz de manejar este tipo de problemas.
+  // La ejecución de este método puede bloquear la ejecución.
+  private static void lostUpdate() throws SQLException {
+    try (Connection connectionA = createConnection(); Connection connectionB = createConnection()) {
+      connectionA.setTransactionIsolation(ISOLATION_LEVEL);
+      connectionB.setTransactionIsolation(ISOLATION_LEVEL);
+
+      connectionA.setAutoCommit(false);
+      connectionB.setAutoCommit(false);
+
+      String update = "UPDATE Ejemplo SET nombre=? WHERE id = 1";
+      try (
+        PreparedStatement psA = connectionA.prepareStatement(update);
+        PreparedStatement psB = connectionB.prepareStatement(update)
+      ) {
+        psA.setString(1, "NombreA");
+        psB.setString(1, "NombreB");
+
+        psA.executeUpdate();
+        psB.executeUpdate();
+
+        connectionA.commit();
+        connectionB.rollback();
+
+        System.out.println("Lost Update completed");
+      } catch (Exception e) {
+        System.out.println("Lost Update error");
+        e.printStackTrace();
+      }
+    }
+  }
+
+  private static void dirtyRead() throws SQLException {
+    try (Connection connectionA = createConnection(); Connection connectionB = createConnection()) {
+      connectionA.setTransactionIsolation(ISOLATION_LEVEL);
+      connectionB.setTransactionIsolation(ISOLATION_LEVEL);
+
+      connectionA.setAutoCommit(false);
+      connectionB.setAutoCommit(false);
+
+      String update = "UPDATE Ejemplo SET nombre=? WHERE id = 1";
+      String select = "SELECT * FROM Ejemplo WHERE id = 1";
+      try (
+        PreparedStatement psA = connectionA.prepareStatement(select);
+        PreparedStatement psB = connectionB.prepareStatement(update)
+      ) {
+        psB.setString(1, "NombreB");
+
+        psB.executeUpdate();
+        try (ResultSet rs = psA.executeQuery()) {
+          rs.next();
+          System.out.println(rs.getString("nombre"));
+        }
+
+        connectionB.rollback();
+        connectionA.commit();
+
+        System.out.println("Dirty Read completed");
+      } catch (Exception e) {
+        System.out.println("Dirty Read error");
+        e.printStackTrace();
+      }
+    }
+  }
+
+  private static void nonRepeatableRead() throws SQLException {
+    try (Connection connectionA = createConnection(); Connection connectionB = createConnection()) {
+      connectionA.setTransactionIsolation(ISOLATION_LEVEL);
+      connectionB.setTransactionIsolation(ISOLATION_LEVEL);
+
+      connectionA.setAutoCommit(false);
+      connectionB.setAutoCommit(false);
+
+      String select = "SELECT * FROM Ejemplo WHERE id = 1";
+      String update = "UPDATE Ejemplo SET nombre=? WHERE id = 1";
+      try (
+        PreparedStatement psA = connectionA.prepareStatement(select);
+        PreparedStatement psB = connectionB.prepareStatement(update);
+      ) {
+        try (ResultSet rs = psA.executeQuery()) {
+          rs.next();
+          System.out.println("Read 1: " + rs.getString("nombre"));
+        }
+
+        psB.setString(1, "NombreB");
+        psB.executeUpdate();
+        connectionB.commit();
+
+        try (ResultSet rs = psA.executeQuery()) {
+          rs.next();
+          System.out.println("Read 2: " + rs.getString("nombre"));
+        }
+
+        connectionA.commit();
+        System.out.println("Non-repeabable Read completed");
+
+        // No forma parte de la "Lectura no repetible"
+        // Vuelve a dejar la base de datos como estaba para continuar con los ejemplos
+        psB.setString(1, "Ana");
+        psB.executeUpdate();
+        connectionB.commit();
+      } catch (Exception e) {
+        System.out.println("Non-repeabable Read error");
+        e.printStackTrace();
+      }
+    }
+  }
+
+  private static void phantomRead() throws SQLException {
+    try (Connection connectionA = createConnection(); Connection connectionB = createConnection()) {
+      connectionA.setTransactionIsolation(ISOLATION_LEVEL);
+      connectionB.setTransactionIsolation(ISOLATION_LEVEL);
+
+      connectionA.setAutoCommit(false);
+      connectionB.setAutoCommit(false);
+
+      String select = "SELECT COUNT(*) FROM Ejemplo WHERE nombre=?";
+      String update = "INSERT INTO Ejemplo (nombre) VALUES (?)";
+      try (
+        PreparedStatement psA = connectionA.prepareStatement(select);
+        PreparedStatement psB = connectionB.prepareStatement(update);
+      ) {
+        psA.setString(1, "Ana");
+
+        try (ResultSet rs = psA.executeQuery()) {
+          rs.next();
+          System.out.println("Read 1: " + rs.getInt(1));
+        }
+
+        psB.setString(1, "Ana");
+        psB.executeUpdate();
+        connectionB.commit();
+
+        try (ResultSet rs = psA.executeQuery()) {
+          rs.next();
+          System.out.println("Read 2: " + rs.getInt(1));
+        }
+
+        connectionA.commit();
+
+        System.out.println("Phantom Read completed");
+      } catch (Exception e) {
+        System.out.println("Phantom Read error");
+        e.printStackTrace();
+      }
+    }
+  }
+}