add Dev Part

DEV/DEV3.1/TP01/Exercise1/Database.java

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+import java.sql.Connection;
+import java.sql.DriverManager;
+import java.sql.PreparedStatement;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+
+public class Database {
+
+    //Countries
+    public static String COUNTRY_ID = "id";
+    public static String COUNTRY_NAME = "name";
+
+    //Votes table 
+    public static String VOTES_COMPETITOR_ID = "competitor_id";
+    public static String VOTES_VOTER_ID = "voter_id";
+    public static String VOTES_POINTS = "points";
+    
+    private Connection connection; 
+
+    public Database() {
+        try {
+            Class.forName("org.mariadb.jdbc.Driver");
+
+            this.connection = DriverManager.getConnection(
+                "jdbc:mariadb://dwarves.iut-fbleau.fr/baudrier",
+                "baudrier",
+                "baudrier"
+            );
+        } catch(ClassNotFoundException exception) {
+            System.err.println("Class 'org.mariadb.jdbc.Driver' not found.");
+        } catch(SQLException exception) {
+            System.err.println("Error while trying to connect to the database");
+        }
+    }
+
+    public ResultSet getVotesFromCompetitor(String country) {
+        try {
+            PreparedStatement query = this.connection.prepareStatement(
+                "SELECT Countries.name, Countries.points FROM Votes INNER JOIN Countries ON Votes.competitor_id = Countries.id WHERE Votes.competitor_id = Countries.id"
+            );
+
+            ResultSet result = query.executeQuery();
+
+            try {
+                query.close();
+            } catch(SQLException exception) {
+                System.err.println("Error while trying to close the query.");
+            }
+
+            return result;
+        } catch(SQLException exception) {
+            System.err.println("Error while trying to prepare or execute the query.");
+        }
+
+        return null; 
+    }
+
+    public void close() {
+        try {
+            this.connection.close();
+        } catch(SQLException exception) {
+            System.err.println("Error while trying to close the connection.");
+        }
+    }
+}

DEV/DEV3.1/TP01/Exercise1/Main.java

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+import java.sql.ResultSet;
+import java.sql.SQLException;
+
+public class Main {
+
+    public static void main(String[] args) {
+        Database database = new Database();
+
+        String country = "France";
+        ResultSet result = database.getVotesFromCompetitor(country);
+        
+        try {
+            while(result.next()) {
+                System.out.println(country + " -> " + result.getString("name") + " : " + result.getInt("points"));
+            }
+        } catch(SQLException exception) {
+            System.err.println("Error while read the data from the result.");
+        }
+
+        try {
+            result.close();
+        } catch(SQLException exception) {
+            System.err.println("Error while trying to close the result.");
+        }
+    }
+}

DEV/DEV3.1/TP01/Exercise1/data.sql

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+CREATE TABLE Countries ( 
+    id INT PRIMARY KEY, 
+    name VARCHAR(30)
+);
+
+CREATE TABLE Votes (
+    id INT PRIMARY KEY AUTO_INCREMENT,
+    competitor_id INT REFERENCES Countries(id),
+    voter_id INT REFERENCES Countries(id),
+    points INT NOT NULL,
+    UNIQUE (competitor_id, voter_id)
+)
+
+INSERT INTO Countries VALUES (1, "France");
+INSERT INTO Countries VALUES (2, "Pays-Bas");
+INSERT INTO Countries VALUES (3, "Albanie");
+INSERT INTO Countries VALUES (4, "Italie");
+INSERT INTO Countries VALUES (5, "Russie");
+INSERT INTO Votes VALUES (2, 4, 5);
+INSERT INTO Votes VALUES (2, 5, 5);
+INSERT INTO Votes VALUES (4, 2, 16);
+INSERT INTO Votes VALUES (5, 2, 5);
+INSERT INTO Votes VALUES (5, 4, 8);

DEV/DEV3.1/TP01/Exercise1/start.sh

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+javac Main.java;
+java -cp "/export/documents/mariadb-client.jar" Main;