Java Community | Help. Code. Learn.•2w ago

Week 103 — How can one connect to a database using JDBC?

Question of the Week #103

How can one connect to a database using JDBC?

3 Replies

JDBC is a database-independent API for access to relational databases. Due to this, applications using JDBC need a database-specific JDBC driver to connect to that database. For example, MySQL Connector/J is used to connect to MySQL databases with JDBC. The JDBC driver is added to the classpath/modulepath to ensure it being registered or it can also be registered using DriverManager.registerDriver. When a JDBC driver is registered, it is possible to connect to a database supported by the driver using a JDBC connection string identifying the database to connect to. JDBC URLs start with jdbc: followed by the identifier of the JDBC driver and a driver-specific way to identify the database to connect to as well as possible parameters to the connection. For example, the URL jdbc:mysql://localhost:3306/SomeDatabase can be used to connect to a MySQL database named SomeDatabase running on localhost with the default MySQL port. The JDBC URL can be passed to the DriverManager.getConnection together with credentials to the database.

String username = "your-database-username";
String password = "load-the-super-secret-password-from-somewhere";
Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/SomeDatabase", username, password);

String username = "your-database-username";
String password = "load-the-super-secret-password-from-somewhere";
Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/SomeDatabase", username, password);

After obtaining a Connection object, SQL statements can be executed using the Connection#executeUpdate/Connection#executeQuery or similar methods:

try(ResultSet rs = con.executeQuery("SELECT some_column FROM my_table")){
  while(rs.next()){
    // an entry in the result
    String value = rs.getString("some_column");
    //do something with the value
    System.out.println(value);
  }
}

try(ResultSet rs = con.executeQuery("SELECT some_column FROM my_table")){
  while(rs.next()){
    // an entry in the result
    String value = rs.getString("some_column");
    //do something with the value
    System.out.println(value);
  }
}

Eric McIntyre•2w ago

When including user input in database accesses, it is important to use prepared statements to prevent SQL injections:

try(PreparedStatement pStmt = con.prepareStatement("SELECT some_column FROM my_table WHERE other_column = ?")){
  pStmt.setString(1, someUserInput);
  try(ResultSet rs = pStmt.executeQuery()){
    String value = rs.getString("some_column");
    System.out.println(value);
  }
}

try(PreparedStatement pStmt = con.prepareStatement("SELECT some_column FROM my_table WHERE other_column = ?")){
  pStmt.setString(1, someUserInput);
  try(ResultSet rs = pStmt.executeQuery()){
    String value = rs.getString("some_column");
    System.out.println(value);
  }
}

📖 Sample answer from dan1st

Eric McIntyre•2w ago

Steps for DataBase Connectivity with JDBC Step 1: Register the Driver Class. Step 2: Create a Connection. Step 3: Create a Statement. Step 4: Execute Queries. Step 5: Close Connection.

Submission from aridorika

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Week 103 — How can one connect to a database using JDBC?