import java.sql.Connection; 
import java.sql.DriverManager; 
 
public class DB_Helper { 
 
  public static Connection connect = null; 
 
  static { 
    try { 
      Class.forName("com.mysql.jdbc.Driver"); // 加載MYSQL JDBC驅(qū)動(dòng)程序 
      // 觀察以下2個(gè)語(yǔ)句的差別， 
      // connect = 
      // DriverManager.getConnection("jdbc:mysql://localhost:3306/students", "root", ""); 
      connect = DriverManager.getConnection( 
          "jdbc:mysql://localhost:3306/students?useUnicode=true&characterEncoding=utf-8", "root", ""); 
 
      System.out.println("Success loading Mysql Driver!"); 
    } catch (Exception e) { 
      System.out.print("Error loading Mysql Driver!"); 
      e.printStackTrace(); 
    } 
  } 
 
  public static Connection getConnection() { 
    return connect; 
  } 
} 

public void add(Info_student student) throws SQLException{ 
  // 與特定數(shù)據(jù)庫(kù)的連接（會(huì)話）。 
  Connection conn = (Connection) DB_Helper.getConnection(); 
   
  String sql = "insert into student(Sno,Sname,Ssex,Saddress,Sphone,Sdept) values(?,?,?,?,?,?)"; 
   
  // 創(chuàng)建一個(gè) PreparedStatement 對(duì)象來(lái)將參數(shù)化的 SQL 語(yǔ)句發(fā)送到數(shù)據(jù)庫(kù)。 
  PreparedStatement ptmt = (PreparedStatement) conn.prepareStatement(sql); 
  /* 
   * void setBigDecimal(int parameterIndex,BigDecimal x)throws SQLException 
   * 將指定參數(shù)設(shè)置為給定 Java String 值。在將此值發(fā)送給數(shù)據(jù)庫(kù)時(shí)，驅(qū)動(dòng)程序?qū)⑺D(zhuǎn)換成一個(gè) SQL VARCHAR 
   * 或 LONGVARCHAR 值（取決于該參數(shù)相對(duì)于驅(qū)動(dòng)程序在 VARCHAR 值上的限制的大小）。 
   */ 
  ptmt.setString(1, student.getId()); 
  ptmt.setString(2, student.getName()); 
  ptmt.setString(3, student.getSex()); 
  ptmt.setString(4, student.getAddress()); 
  ptmt.setString(5, student.getPhone()); 
  ptmt.setString(6, student.getDept()); 
   
  // 在此 PreparedStatement 對(duì)象中執(zhí)行 SQL 語(yǔ)句 
  ptmt.execute(); 
} 

public void delete(String id) throws SQLException{ 
  Connection conn = (Connection) DB_Helper.getConnection(); 
  String sql = "delete from student where Sno=?"; 
  PreparedStatement ptmt = (PreparedStatement) conn.prepareStatement(sql); 
   
  ptmt.setString(1, id); 
   
  ptmt.execute(); 
} 

public void update(Info_student student) throws SQLException{ 
  Connection conn = (Connection) DB_Helper.getConnection(); 
  String sql = "update student set Sname=?,Ssex=?,Saddress=?,Sphone=?,Sdept=? where Sno=?"; 
 
  PreparedStatement ptmt = (PreparedStatement) conn.prepareStatement(sql); 
  ptmt.setString(1, student.getName()); 
  ptmt.setString(2, student.getSex()); 
  ptmt.setString(3, student.getAddress()); 
  ptmt.setString(4, student.getPhone()); 
  ptmt.setString(5, student.getDept()); 
  ptmt.setString(6, student.getId()); 
 
  ptmt.execute(); 
} 

public Info_student search(String id) throws SQLException{ 
  Info_student student = null; 
   
  Connection conn = (Connection) DB_Helper.getConnection(); 
  String sql = "select * from student where Sno=?"; 
  PreparedStatement ptmt = (PreparedStatement) conn.prepareStatement(sql); 
   
  ptmt.setString(1, id); 
   
  /* 
   * ResultSet executeQuery()throws SQLException 
   * 在此 PreparedStatement 對(duì)象中執(zhí)行 SQL 查詢(xún)，并返回該查詢(xún)生成的 ResultSet 對(duì)象。 
   */ 
   
  /* 
   * public interface ResultSet extends Wrapper 
   * 表示數(shù)據(jù)庫(kù)結(jié)果集的數(shù)據(jù)表，通常通過(guò)執(zhí)行查詢(xún)數(shù)據(jù)庫(kù)的語(yǔ)句生成。 ResultSet 對(duì)象具有指向其當(dāng)前數(shù)據(jù)行的光標(biāo)。 
   * 最初，光標(biāo)被置于第一行之前。next 方法將光標(biāo)移動(dòng)到下一行；因?yàn)樵摲椒ㄔ?ResultSet 對(duì)象沒(méi)有下一行時(shí) 
   * 返回 false，所以可以在 while 循環(huán)中使用它來(lái)迭代結(jié)果集。 
   * 
   */ 
  ResultSet rs = ptmt.executeQuery(); 
 
  /* 
   * boolean next()throws SQLException 
   * 將光標(biāo)從當(dāng)前位置向前移一行。 
   * ResultSet 光標(biāo)最初位于第一行之前； 
   * 第一次調(diào)用 next 方法使第一行成為當(dāng)前行； 
   * 第二次調(diào)用使第二行成為當(dāng)前行，依此類(lèi)推。 
   */ 
 
  while(rs.next()){ 
    student = new Info_student(); 
    student.setId(rs.getString("Sno")); 
    student.setName(rs.getString("Sname")); 
    student.setSex(rs.getString("Ssex")); 
    student.setAddress(rs.getString("Saddress")); 
   
    student.setPhone(rs.getString("Sphone")); 
    student.setDept(rs.getString("Sdept")); 
  } 
  return student; 
   
}