Fix JDBC resource leaks

Author: MrSnyder

src/main/java/com/wildcodeschool/wildandwizard/repository/WizardRepository.java

@@ -1,8 +1,16 @@
 package com.wildcodeschool.wildandwizard.repository;
 
+import java.sql.Connection;
+import java.sql.Date;
+import java.sql.DriverManager;
+import java.sql.PreparedStatement;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+import java.sql.Statement;
+
 import com.wildcodeschool.wildandwizard.entity.Wizard;
 
-import java.sql.*;
+import util.JdbcUtils;
 
 public class WizardRepository {
 
@@ -13,11 +21,14 @@ public class WizardRepository {
  public Wizard save(String firstName, String lastName, Date birthday,
  String birthPlace, String biography, boolean muggle) {
 
+ Connection connection = null;
+ PreparedStatement statement = null;
+ ResultSet generatedKeys = null;
  try {
- Connection connection = DriverManager.getConnection(
+ connection = DriverManager.getConnection(
  DB_URL, DB_USER, DB_PASSWORD
  );
- PreparedStatement statement = connection.prepareStatement(
+ statement = connection.prepareStatement(
  "INSERT INTO wizard (first_name, last_name, birthday, birth_place, biography, is_muggle) VALUES (?, ?, ?, ?, ?, ?)",
  Statement.RETURN_GENERATED_KEYS
  );
@@ -32,7 +43,7 @@ public Wizard save(String firstName, String lastName, Date birthday,
  throw new SQLException("failed to insert data");
  }
 
- ResultSet generatedKeys = statement.getGeneratedKeys();
+ generatedKeys = statement.getGeneratedKeys();
 
  if (generatedKeys.next()) {
  Long id = generatedKeys.getLong(1);
@@ -43,6 +54,10 @@ public Wizard save(String firstName, String lastName, Date birthday,
  }
  } catch (SQLException e) {
  e.printStackTrace();
+ } finally {
+ JdbcUtils.closeResultSet(generatedKeys);
+ JdbcUtils.closeStatement(statement);
+ JdbcUtils.closeConnection(connection);
  }
  return null;
  }

src/main/java/util/JdbcUtils.java

@@ -0,0 +1,46 @@
+package util;
+
+import java.sql.Connection;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+import java.sql.Statement;
+
+/**
+ * Utility methods for closing JDBC resources.
+ * 
+ * https://docs.spring.io/spring-framework/docs/current/javadoc-api/org/springframework/jdbc/support/JdbcUtils.html
+ * https://www.selikoff.net/2008/07/30/finally-closing-jdbc-resources/
+ */
+public class JdbcUtils {
+
+public static void closeConnection(Connection con) {
+if (con != null) {
+try {
+con.close();
+} catch (SQLException e) {
+e.printStackTrace();
+}
+}
+}
+
+public static void closeResultSet(ResultSet rs) {
+if (rs != null) {
+try {
+rs.close();
+} catch (SQLException e) {
+e.printStackTrace();
+}
+}
+}
+
+public static void closeStatement(Statement stmt) {
+if (stmt != null) {
+try {
+stmt.close();
+} catch (SQLException e) {
+e.printStackTrace();
+}
+}
+}
+
+}