build.gradle

@@ -81,6 +81,8 @@ dependencies {
 
     testImplementation 'junit:junit:4.13.2'
     testImplementation 'org.hamcrest:hamcrest:2.2'
+
+    implementation 'org.xerial:sqlite-jdbc:3.36.0'
 }
 
 task buildProject {

src/de/steamwar/ImplementationProvider.java

@@ -0,0 +1,34 @@
+/*
+ * This file is a part of the SteamWar software.
+ *
+ * Copyright (C) 2022  SteamWar.de-Serverteam
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero 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 Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package de.steamwar;
+
+import java.lang.reflect.InvocationTargetException;
+
+public class ImplementationProvider {
+    private ImplementationProvider() {}
+
+    public static <T> T getImpl(String className) {
+        try {
+            return (T) Class.forName(className).getDeclaredConstructor().newInstance();
+        } catch (InstantiationException | IllegalAccessException | InvocationTargetException | NoSuchMethodException | ClassNotFoundException e) {
+            throw new SecurityException("Could not load SQLConfigProviderImpl", e);
+        }
+    }
+}

src/de/steamwar/sql/SQLConfig.java

@@ -0,0 +1,34 @@
+/*
+ * This file is a part of the SteamWar software.
+ *
+ * Copyright (C) 2022  SteamWar.de-Serverteam
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero 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 Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package de.steamwar.sql;
+
+import de.steamwar.ImplementationProvider;
+
+import java.util.logging.Logger;
+
+public interface SQLConfig {
+    SQLConfig impl = ImplementationProvider.getImpl("de.steamwar.sql.SQLConfigImpl");
+
+    Logger getLogger();
+
+    int maxConnections();
+
+
+}

src/de/steamwar/sql/Statement.java

@@ -0,0 +1,226 @@
+/*
+    This file is a part of the SteamWar software.
+
+    Copyright (C) 2022  SteamWar.de-Serverteam
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU Affero 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 Affero General Public License for more details.
+
+    You should have received a copy of the GNU Affero General Public License
+    along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package de.steamwar.sql;
+
+import java.io.File;
+import java.io.FileReader;
+import java.io.IOException;
+import java.sql.*;
+import java.util.*;
+import java.util.function.Supplier;
+import java.util.logging.Level;
+import java.util.logging.Logger;
+
+public class Statement implements AutoCloseable {
+
+    private static final Logger logger = SQLConfig.impl.getLogger();
+
+    private static final List<Statement> statements = new ArrayList<>();
+    private static final Deque<Connection> connections = new ArrayDeque<>();
+    private static final int MAX_CONNECTIONS;
+    private static final Supplier<Connection> conProvider;
+    static {
+        File file = new File(new File("plugins", "SpigotCore"), "mysql.properties");
+
+        if(file.exists()) {
+            Properties properties = new Properties();
+            try {
+                properties.load(new FileReader(file));
+            } catch (IOException e) {
+                throw new SecurityException("Could not load SQL connection", e);
+            }
+
+            String url = "jdbc:mysql://" + properties.getProperty("host") + ":" + properties.getProperty("port") + "/" + properties.getProperty("database") + "?autoReconnect=true&useServerPrepStmts=true";
+            String user = properties.getProperty("user");
+            String password = properties.getProperty("password");
+
+            MAX_CONNECTIONS = SQLConfig.impl.maxConnections();
+            conProvider = () -> {
+                try {
+                    return DriverManager.getConnection(url, user, password);
+                } catch (SQLException e) {
+                    throw new SecurityException("Could not create MySQL connection", e);
+                }
+            };
+        } else {
+            MAX_CONNECTIONS = 1;
+            Connection connection;
+
+            try {
+                connection = DriverManager.getConnection("jdbc:sqlite:standalone.db");
+            } catch (SQLException e) {
+                throw new SecurityException("Could not create sqlite connection", e);
+            }
+            //TODO ensure schema
+
+            conProvider = () -> connection;
+        }
+    }
+
+    private static int connectionBudget = MAX_CONNECTIONS;
+
+    public static void closeAll() {
+        synchronized (connections) {
+            while(connectionBudget < MAX_CONNECTIONS) {
+                if(connections.isEmpty())
+                    waitOnConnections();
+                else
+                    closeConnection(aquireConnection());
+            }
+        }
+    }
+
+    private final String sql;
+    private final Map<Connection, PreparedStatement> cachedStatements = new HashMap<>();
+
+    public Statement(String sql) {
+        this.sql = sql;
+        synchronized (statements) {
+            statements.add(this);
+        }
+    }
+
+    public <T> T select(ResultSetUser<T> user, Object... objects) {
+        return withConnection(st -> {
+            ResultSet rs = st.executeQuery();
+            T result = user.use(rs);
+            rs.close();
+            return result;
+        }, objects);
+    }
+
+    public void update(Object... objects) {
+        withConnection(PreparedStatement::executeUpdate, objects);
+    }
+
+    private <T> T withConnection(SQLRunnable<T> runnable, Object... objects) {
+        Connection connection = aquireConnection();
+
+        T result;
+        try {
+            result = tryWithConnection(connection, runnable, objects);
+        } catch (SQLException e) {
+            closeConnection(connection);
+            connection = aquireConnection();
+            try {
+                result = tryWithConnection(connection, runnable, objects);
+            } catch (SQLException ex) {
+                closeConnection(connection);
+                throw new SecurityException("Could not execute statement", ex);
+            }
+        }
+
+        synchronized (connections) {
+            connections.push(connection);
+            connections.notify();
+        }
+
+        return result;
+    }
+
+    private <T> T tryWithConnection(Connection connection, SQLRunnable<T> runnable, Object... objects) throws SQLException {
+        PreparedStatement st = cachedStatements.get(connection);
+        if(st == null) {
+            st = connection.prepareStatement(sql);
+            cachedStatements.put(connection, st);
+        }
+
+        for (int i = 0; i < objects.length; i++) {
+            st.setObject(i + 1, objects[i]);
+        }
+
+        return runnable.run(st);
+    }
+
+    @Override
+    public void close() {
+        cachedStatements.values().forEach(st -> closeStatement(st, false));
+        cachedStatements.clear();
+        synchronized (statements) {
+            statements.remove(this);
+        }
+    }
+
+    private void close(Connection connection) {
+        PreparedStatement st = cachedStatements.remove(connection);
+        if(st != null)
+            closeStatement(st, true);
+    }
+
+    private static Connection aquireConnection() {
+        synchronized (connections) {
+            if(connections.isEmpty() && connectionBudget == 0)
+                waitOnConnections();
+
+            if(!connections.isEmpty()) {
+                return connections.pop();
+            } else {
+                Connection connection = conProvider.get();
+                connectionBudget--;
+                return connection;
+            }
+        }
+    }
+
+    private static void closeConnection(Connection connection) {
+        synchronized (statements) {
+            for (Statement statement : statements) {
+                statement.close(connection);
+            }
+        }
+        try {
+            connection.close();
+        } catch (SQLException e) {
+            logger.log(Level.INFO, "Could not close connection", e);
+        }
+
+        synchronized (connections) {
+            connectionBudget++;
+            connections.notify();
+        }
+    }
+
+    private static void waitOnConnections() {
+        synchronized (connections) {
+            try {
+                connections.wait();
+            } catch (InterruptedException e) {
+                Thread.currentThread().interrupt();
+            }
+        }
+    }
+
+    private static void closeStatement(PreparedStatement st, boolean silent) {
+        try {
+            st.close();
+        } catch (SQLException e) {
+            if(!silent)
+                logger.log(Level.INFO, "Could not close statement", e);
+        }
+    }
+
+    public interface ResultSetUser<T> {
+        T use(ResultSet rs) throws SQLException;
+    }
+
+    private interface SQLRunnable<T> {
+        T run(PreparedStatement st) throws SQLException;
+    }
+}