JDBC（java database connection）

/**
  * jdbc 四大参数
  *   driverClassName : com.mysql.jdbc.Driver
  *   url : jdbc:mysql://localhost:3306/database
  *   username : root
  *   password : yuxing2012
  * 
  */
  Class.forName("com.mysql.jdbc.Driver");
  String url = "jdbc:mysql://localhost:3306/demo";
  String username= "root";
  String password = "yuxing2012";
  Connection connection = DriverManager.getConnection(url, username, password);
  System.out.println(connection);

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Statement

• executeUpdate(String sql ); // DDL DML
• executeQuery(String sql);

  Statement statement = connection.createStatement();
  String sql = "INSERT INTO user(user_name,user_number) VALUES('dapi_"+new Random().nextInt(200)+"','12101010320')";
  int i = statement.executeUpdate(sql);
  System.out.println("i  "+i);
        
        
  //执行查询
  /**
    * 1 得到connection
    * 2 得到Statement
    * 3 解析查询返回的表格对象
    */
  String querySql = "SELECT * FROM user";
  ResultSet resultSet = statement.executeQuery(querySql);
  System.out.println("resultSet "+resultSet);
  resultSet.beforeFirst();//第一条记录的前面
  while(resultSet.next()){
    int id = resultSet.getInt("user_id");
    String name = resultSet.getString("user_name");
    String number = resultSet.getString("user_number");
    System.out.println("id  "+id+"   name  "+name+"   number "+number);
   }
        
  resultSet.close();
  statement.close();
  connection.close();

---

PreparedStatement

String inSql = "INSERT INTO user(user_name,user_number) VALUES(?,?)";
PreparedStatement prepareStatement = connection.prepareStatement(inSql);
prepareStatement.setString(1,"dapi");
prepareStatement.setString(2,"12101010320");
int update = prepareStatement.executeUpdate();
System.out.println("update  "+update);

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Transation

connection.setAutoCommit(false);
// ..do something
connection.commit();
//or 
connection.rollback();

//事务的隔离级别
connection.setTransactionIsolation(Connection.TRANSACTION_READ_COMMITTED);
connection.setTransactionIsolation(Connection.TRANSACTION_READ_UNCOMMITTED);
connection.setTransactionIsolation(Connection.TRANSACTION_REPEATABLE_READ);
connection.setTransactionIsolation(Connection.TRANSACTION_SERIALIZABLE);

---

DBCP

• 依赖的jar commons-dbcp.jar commons-pool.jar

BasicDataSource source = new BasicDataSource();
source.setDriverClassName("");
source.setUrl("");
source.setUsername("");
source.setPassword("");
source.setMaxWaitMillis(2000);
        
Connection connection2 = source.getConnection();
connection2.close(); // to the pool

---

C3P0

• 依赖的jar c3p0.jar mchange-commons.jar

//c3p0
ComboPooledDataSource source2 = new ComboPooledDataSource();

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