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Java访问数据库:使用JDBC操作数据库的完整教程
2023-06-14 21:55:11 深夜i     --     --
Java JDBC MySQL

Java作为一门面向对象的编程语言,可以轻松地访问和操纵数据库。在本教程中,我们将介绍如何使用Java Database Connectivity(JDBC)API来操作数据库。首先,我们将学习如何使用JDBC连接数据库,并执行完整的CRUD操作。接下来,我们将给出一个代码案例来说明如何连接一个MySQL数据库,以及如何执行插入、查询、删除和更新操作。

连接到数据库

要连接到数据库,我们需要通过使用标准的JDBC API驱动程序来创建一个连接对象。以下代码展示了如何连接到MySQL数据库:


import java.sql.*;

public class MySQLConnection {

  public static void main(String[] args) {

  Connection conn = null;

  try {

   String url = "jdbc:mysql://localhost:3306/mydatabase";

   String username = "user";

   String password = "password";

   Class.forName("com.mysql.jdbc.Driver");

   conn = DriverManager.getConnection(url, username, password);

   System.out.println("Connected to the database");

  } catch (SQLException e) {

   System.out.println("Oops, something went wrong!");

   e.printStackTrace();

  } catch (ClassNotFoundException e) {

   e.printStackTrace();

  } finally {

   try {

     if (conn != null) {

      conn.close();

      System.out.println("Disconnected from database");

     }

   } catch (SQLException ex) {

     ex.printStackTrace();

   }

  }

}

}

这段代码会将我们连接到名为“mydatabase”的MySQL数据库。在连接成功后,我们将输出“Connected to the database”,并在最后关闭连接。

执行CRUD操作

接下来,我们将展示如何执行CRUD操作,即插入、查询、删除和更新。

插入

首先,我们将展示如何将数据插入到数据库表中。以下代码展示了如何将数据插入到名为“customers”的表中:


import java.sql.*;

public class MySQLInsert {

  public static void main(String[] args) {

  Connection conn = null;

  Statement stmt = null;

  try {

   String url = "jdbc:mysql://localhost:3306/mydatabase";

   String username = "user";

   String password = "password";

   Class.forName("com.mysql.jdbc.Driver");

   conn = DriverManager.getConnection(url, username, password);

   String sql = "INSERT INTO customers " +

          "VALUES (100, 'John Smith', '15 Main St', 'New York', 'NY')";

   stmt = conn.createStatement();

   stmt.executeUpdate(sql);

   System.out.println("Inserted record into the table");

  } catch (SQLException e) {

   System.out.println("Oops, something went wrong!");

   e.printStackTrace();

  } catch (ClassNotFoundException e) {

   e.printStackTrace();

  } finally {

   try {

     if (stmt != null) {

      stmt.close();

     }

   } catch (SQLException ex) {

     ex.printStackTrace();

   }

   try {

     if (conn != null) {

      conn.close();

      System.out.println("Disconnected from database");

     }

   } catch (SQLException ex) {

     ex.printStackTrace();

   }

  }

}

}

查询

以下代码展示了如何从名为“customers”的表中查询数据:


import java.sql.*;

public class MySQLSelect {

  public static void main(String[] args) {

  Connection conn = null;

  Statement stmt = null;

  ResultSet rs = null;

  try {

   String url = "jdbc:mysql://localhost:3306/mydatabase";

   String username = "user";

   String password = "password";

   Class.forName("com.mysql.jdbc.Driver");

   conn = DriverManager.getConnection(url, username, password);

   String sql = "SELECT id, name, address, city, state FROM customers";

   stmt = conn.createStatement();

   rs = stmt.executeQuery(sql);

   while(rs.next()){

     int id = rs.getInt("id");

     String name = rs.getString("name");

     String address = rs.getString("address");

     String city = rs.getString("city");

     String state = rs.getString("state");

     //Display values

     System.out.print("ID: " + id);

     System.out.print(", Name: " + name);

     System.out.print(", Address: " + address);

     System.out.print(", City: " + city);

     System.out.println(", State: " + state);

   }

  } catch (SQLException e) {

   System.out.println("Oops, something went wrong!");

   e.printStackTrace();

  } catch (ClassNotFoundException e) {

   e.printStackTrace();

  } finally {

   try {

     if (rs != null) {

      rs.close();}

   } catch (SQLException ex) {

     ex.printStackTrace();

   }

   try {

     if (stmt != null) {

      stmt.close();}

   } catch (SQLException ex) {

     ex.printStackTrace();

   }

   try {

     if (conn != null) {

      conn.close();

      System.out.println("Disconnected from database");

     }

   } catch (SQLException ex) {

     ex.printStackTrace();

   }

  }

}

}

删除

以下代码展示了如何从名为“customers”的表中删除行:


import java.sql.*;

public class MySQLDelete {

  public static void main(String[] args) {

  Connection conn = null;

  Statement stmt = null;

  try {

   String url = "jdbc:mysql://localhost:3306/mydatabase";

   String username = "user";

   String password = "password";

   Class.forName("com.mysql.jdbc.Driver");

   conn = DriverManager.getConnection(url, username, password);

   String sql = "DELETE FROM customers WHERE id = 100";

   stmt = conn.createStatement();

   stmt.executeUpdate(sql);

   System.out.println("Deleted record from the table");

  } catch (SQLException e) {

   System.out.println("Oops, something went wrong!");

   e.printStackTrace();

  } catch (ClassNotFoundException e) {

   e.printStackTrace();

  } finally {

   try {

     if (stmt != null) {

      stmt.close();

     }

   } catch (SQLException ex) {

     ex.printStackTrace();

   }

   try {

     if (conn != null) {

      conn.close();

      System.out.println("Disconnected from database");

     }

   } catch (SQLException ex) {

     ex.printStackTrace();

   }

  }

}

}

更新

最后,以下代码展示了如何更新名为“customers”的表中的数据:


import java.sql.*;

public class MySQLUpdate {

  public static void main(String[] args) {

  Connection conn = null;

  Statement stmt = null;

  try {

   String url = "jdbc:mysql://localhost:3306/mydatabase";

   String username = "user";

   String password = "password";

   Class.forName("com.mysql.jdbc.Driver");

   conn = DriverManager.getConnection(url, username, password);

   String sql = "UPDATE customers SET name = 'John Doe' WHERE id = 1";

   stmt = conn.createStatement();

   stmt.executeUpdate(sql);

   System.out.println("Updated record in the table");

  } catch (SQLException e) {

   System.out.println("Oops, something went wrong!");

   e.printStackTrace();

  } catch (ClassNotFoundException e) {

   e.printStackTrace();

  } finally {

   try {

     if (stmt != null) {

      stmt.close();

     }

   } catch (SQLException ex) {

     ex.printStackTrace();

   }

   try {

     if (conn != null) {

      conn.close();

      System.out.println("Disconnected from database");

     }

   } catch (SQLException ex) {

     ex.printStackTrace();

   }

  }

}

}

  
  

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