import java.sql.Connection;  
import java.sql.DriverManager;  
import java.sql.PreparedStatement;  
import java.sql.ResultSet;  
import java.sql.SQLException;  

public class JDBCTest {  
    public static void main(String[] args) {  
          
        // 数据库连接  
        Connection connection = null;  
        // 预编译的statement,好处是提高数据库的性能  
        PreparedStatement preparedStatement = null;  
        //创建结果集  
        ResultSet resultset = null;  
          
        try {  
            // 记载数据库驱动  
            Class.forName("com.mysql.jdbc.Driver");  
            // 通过驱动管理类来获取数据库连接  
            connection = DriverManager  
                    .getConnection(  
                            "jdbc:mysql://localhost:3306/mybatis?useUnicode=true&characterEncoding=UTF-8",  
                            "root", "123");  
            // 定义sql语句，？表示占位符  
            String sql = "select * from users where username=?";  
            // 获取预处理statement  
            preparedStatement = connection.prepareStatement(sql);  
            // 为占位符赋值  
            preparedStatement.setString(1, "王五");  
            // 向数据库发出sql执行查询，查询出结果集  
            resultset = preparedStatement.executeQuery();  
            // 遍历查询结果集  
            while (resultset.next()) {  
                System.out.println(resultset.getString("id") + ","  
                        + resultset.getString("username"));  
            }  
        } catch (Exception e) {  
            e.printStackTrace();  
        } finally {  
            // 释放资源  
            if (resultset != null) {  
                try {  
                    resultset.close();  
                } catch (SQLException e) {  
                    e.printStackTrace();  
                }  
            }  
            if (preparedStatement != null) {  
                try {  
                    preparedStatement.close();  
                } catch (SQLException e) {  
                    e.printStackTrace();  
                }  
            }  
            if (connection != null) {  
                try {  
                    connection.close();  
                } catch (SQLException e) {  
                    e.printStackTrace();  
                }  
            }  
        }  
    }  
}