#21 jdbc: refactoring

my-framework/jdbc-practice/src/main/java/org/example/ConnectionManager.java

@@ -3,15 +3,40 @@ package org.example;
 import com.zaxxer.hikari.HikariDataSource;
 
 import javax.sql.DataSource;
+import java.sql.Connection;
+import java.sql.SQLException;
 
 public class ConnectionManager {
-    public static DataSource getDataSource() {
-        HikariDataSource hikariDataSource = new HikariDataSource();
-        hikariDataSource.setDriverClassName("org.h2.Driver");
-        hikariDataSource.setJdbcUrl("jdbc:h2:mem://localhost/~/jdbc-practice;MODE=MySQL;DB_CLOSE_DELAY=-1");
-        hikariDataSource.setUsername("sa");
-        hikariDataSource.setPassword("");
 
-        return hikariDataSource;
+    public static final String DB_DRIVER = "org.h2.Driver";
+    public static final String DB_URL = "jdbc:h2:mem://localhost/~/jdbc-practice;MODE=MySQL;DB_CLOSE_DELAY=-1";
+    public static final String DB_USERNAME = "sa";
+    public static final String DB_PASSWORD = "";
+    public static final int DB_MAX_POOL_SIZE = 40;
+
+    private static final DataSource ds;
+
+    static {
+        HikariDataSource hikariDataSource = new HikariDataSource();
+        hikariDataSource.setDriverClassName(DB_DRIVER);
+        hikariDataSource.setJdbcUrl(DB_URL);
+        hikariDataSource.setUsername(DB_USERNAME);
+        hikariDataSource.setPassword(DB_PASSWORD);
+        hikariDataSource.setMaximumPoolSize(DB_MAX_POOL_SIZE);
+        hikariDataSource.setMinimumIdle(DB_MAX_POOL_SIZE);
+
+        ds = hikariDataSource;
+    }
+
+    public static Connection getConnection() {
+        try {
+            return ds.getConnection();
+        } catch (SQLException e) {
+            throw new IllegalStateException(e);
+        }
+    }
+
+    public static DataSource getDataSource() {
+        return ds;
     }
 }

my-framework/jdbc-practice/src/main/java/org/example/JdbcTemplate.java

@@ -0,0 +1,62 @@
+package org.example;
+
+import java.sql.Connection;
+import java.sql.PreparedStatement;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+
+public class JdbcTemplate {
+
+    public void executeUpdate(User user, String sql, PreparedStatementSetter pss) throws SQLException {
+        Connection con = null;
+        PreparedStatement pstmt = null;
+
+        try {
+            con = ConnectionManager.getConnection();
+
+            pstmt = con.prepareStatement(sql);
+            pss.setter(pstmt);
+
+            pstmt.executeUpdate();
+        } finally {
+            if (pstmt != null) {
+                pstmt.close();
+            }
+            if (con != null) {
+                con.close();
+            }
+        }
+    }
+
+    public Object executeQuery(String sql, PreparedStatementSetter pss, RowMapper rowMapper) throws SQLException {
+        Connection con = null;
+        PreparedStatement pstmt = null;
+        ResultSet rs = null;
+
+        try {
+            con = ConnectionManager.getConnection();
+            pstmt = con.prepareStatement(sql);
+            pss.setter(pstmt);
+
+            rs = pstmt.executeQuery();
+
+            Object obj = null;
+
+            if (rs.next()) {
+                obj = rowMapper.map(rs);
+            }
+
+            return obj;
+        } finally {
+            if (rs != null) {
+                rs.close();
+            }
+            if (pstmt != null) {
+                pstmt.close();
+            }
+            if (con != null) {
+                con.close();
+            }
+        }
+    }
+}

my-framework/jdbc-practice/src/main/java/org/example/PreparedStatementSetter.java

@@ -0,0 +1,9 @@
+package org.example;
+
+import java.sql.PreparedStatement;
+import java.sql.SQLException;
+
+public interface PreparedStatementSetter {
+
+    void setter(PreparedStatement pstmt) throws SQLException;
+}

my-framework/jdbc-practice/src/main/java/org/example/RowMapper.java

@@ -0,0 +1,9 @@
+package org.example;
+
+import java.sql.ResultSet;
+import java.sql.SQLException;
+
+public interface RowMapper {
+
+    Object map(ResultSet rs) throws SQLException;
+}

my-framework/jdbc-practice/src/main/java/org/example/UserDao.java

@@ -4,80 +4,31 @@ import java.sql.*;
 
 public class UserDao {
 
-    private Connection getConnection() {
-        String url = "jdbc:h2:mem://localhost/~/jdbc-practice;MODE=MySQL;DB_CLOSE_DELAY=-1";
-        String id = "sa";
-        String pw = "";
-
-        try {
-            Class.forName("org.h2.Driver");
-            return DriverManager.getConnection(url, id, pw);
-        } catch (Exception e) {
-            return null;
-        }
-    }
-
     public void create(User user) throws SQLException {
-        Connection con = null;
+        JdbcTemplate jdbcTemplate = new JdbcTemplate();
-        PreparedStatement pstmt = null;
 
-        try {
-            con = getConnection();
         String sql = "INSERT INTO USERS VALUES (?, ?, ?, ?)";
 
-            pstmt = con.prepareStatement(sql);
+        jdbcTemplate.executeUpdate(user, sql, pstmt -> {
             pstmt.setString(1, user.getUserId());
             pstmt.setString(2, user.getPassword());
             pstmt.setString(3, user.getName());
             pstmt.setString(4, user.getEmail());
-
+        });
-            pstmt.executeUpdate();
-        } finally {
-            if (pstmt != null) {
-                pstmt.close();
-            }
-            if (con != null) {
-                con.close();
-            }
-        }
     }
 
     public User findByUserId(String userId) throws SQLException {
-        Connection con = null;
+        JdbcTemplate jdbcTemplate = new JdbcTemplate();
-        PreparedStatement pstmt = null;
-        ResultSet rs = null;
-
-        try {
-            con = getConnection();
         String sql = "SELECT userId, password, name, email FROM USERS WHERE userId = ?";
 
-            pstmt = con.prepareStatement(sql);
+        return (User) jdbcTemplate.executeQuery(
-            pstmt.setString(1, userId);
+                sql,
-
+                (pstmt) -> pstmt.setString(1, userId),
-            rs = pstmt.executeQuery();
+                (rs) -> new User(
-
-            User user = null;
-
-            if (rs.next()) {
-                user = new User(
                         rs.getString("userId"),
                         rs.getString("password"),
                         rs.getString("name"),
                         rs.getString("email")
-                );
+                ));
-            }
-
-            return user;
-        } finally {
-            if (rs != null) {
-                rs.close();
-            }
-            if (pstmt != null) {
-                pstmt.close();
-            }
-            if (con != null) {
-                con.close();
-            }
-        }
     }
 }