Add Connection and refactoring EntityCollection

src/main/kotlin/fr/postgresjson/connexion/Connection.kt

@@ -0,0 +1,40 @@
+package fr.postgresjson.connexion
+
+import com.github.jasync.sql.db.pool.ConnectionPool
+import com.github.jasync.sql.db.postgresql.PostgreSQLConnection
+import com.github.jasync.sql.db.postgresql.PostgreSQLConnectionBuilder
+import fr.postgresjson.entity.EntityI
+import fr.postgresjson.serializer.Serializer
+
+
+class Connection(
+    private val host: String = "localhost",
+    private val port: Int = 5432,
+    private val database: String = "dc-project",
+    private val username: String = "dc-project",
+    private val password: String = "dc-project"
+) {
+    private lateinit var connection: ConnectionPool<PostgreSQLConnection>
+    val serializer = Serializer()
+
+    fun connect(): ConnectionPool<PostgreSQLConnection> {
+        if (!::connection.isInitialized || !connection.isConnected()) {
+            connection = PostgreSQLConnectionBuilder.createConnectionPool(
+                "jdbc:postgresql://$host:$port/$database?user=$username&password=$password"
+            )
+        }
+        return connection
+    }
+
+    inline fun <T, reified R :EntityI<T?>> execute(sql: String, values: List<Any?> = emptyList()): R? {
+        val future = connect().sendPreparedStatement(sql, values)
+        val json = future.get().rows[0].getString(0)
+        if (json === null) {
+            return null
+        } else {
+            val obj = serializer.deserialize<T, R>(json)
+
+            return obj
+        }
+    }
+}