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1、（1）在类路径(src)下建立文件 db.properties，在该文件内存放数据库的基本信息：数据库驱 动程序名，数据库连接字符串，数据库用户名称及其密码。其内容如下： driver=com.mysql.jdbc.Driver url=jdbc:mysql:/localhost:3306/test?useUnicode=true import java.sql.*; import java.util.Properties; public final class JdbcUtil private static String driver ; private static String url
2、; private static String user ; private static String password ; private static Properties pr=new Properties(); private JdbcUtils() /设计该工具类的静态初始化器中的代码，该代码在装入类时执行，且只执行一次 static try pr.load(JdbcUtils.class.getClassLoader().getResourceAsStream(“db.properties“); driver=pr.getProperty(“driver“); url=pr.ge
3、tProperty(“url“); user=pr.getProperty(“username“); password=pr.getProperty(“password“); Class.forName(driver); catch (Exception e) throw new ExceptionInInitializerError(e); /设计获得连接对象的方法 getConnection() public static Connection getConnection() throws SQLException return DriverManager.getConnection(ur
4、l, user, password); /设计释放结果集、语句和连接的方法 free() public static void free(ResultSet rs, Statement st, Connection conn) try if (rs != null) rs.close(); catch (SQLException e) e.printStackTrace(); finally try if (st != null) st.close(); catch (SQLException e) e.printStackTrace(); finally if (conn != null)
5、try conn.close(); catch (SQLException e) e.printStackTrace(); (3)建立类 User.java 实现记录信息对象化，基于对象对数据库关系表进行操作。 package vo; public class User private String userid,username,sex; public String getUserid() return userid; public void setUserid(String userid) this.userid = userid; public String getUsername()
6、return username; public void setUsername(String username) this.username = username; public String getSex() return sex; public void setSex(String sex) this.sex = sex; （4）在上面步骤的基础上建立类 UserDao.java 封装基本的数据库操作。 package dao; import java.sql.*; import java.util.ArrayList; import vo.User; import dbc.JdbcUt
7、il; public class UserDao /向数据库中添加用户记录的方法 add() public void add(User user) throws Exception Connection conn = null; PreparedStatement ps = null; try conn = JdbcUtil.getConnection(); String sql = “insert into uservalues (?,?,?) “; ps = conn.prepareStatement(sql); ps.setString(1, user.getUserid(); ps.s
8、etString(2,user.getUsername(); ps.setString(3,user.getSex(); ps.executeUpdate(); finally JdbcUtil.free(null,ps, conn); /修改数据库用户记录的方法 update() public void update(User user) throws Exception Connection conn = null; PreparedStatement ps = null; try conn = JdbcUtil.getConnection(); String sql = “update
9、user set username=?,sex=? where userid=? “; ps = conn.prepareStatement(sql); ps.setString(1,user.getUsername(); ps.setString(2,user.getSex(); ps.setString(3, user.getUserid(); ps.executeUpdate(); finally JdbcUtil.free(null,ps, conn); /删除数据库用户记录的方法 delete() public void delete(String userId) throws Ex
10、ception Connection conn = null; PreparedStatement ps = null; try conn = JdbcUtil.getConnection(); String sql = “delete from user where userid=?“; ps = conn.prepareStatement(sql); ps.setString(1,userId); ps.executeUpdate(); finally JdbcUtil.free( null,ps, conn); /根据 id 查询用户的方法 findUserById() public U
11、ser findUserById(String userId) throws Exception Connection conn = null; PreparedStatement ps = null; ResultSet rs = null; User user=null; try conn = JdbcUtil.getConnection(); String sql = “select * from user where userid=? “; ps = conn.prepareStatement(sql); ps.setString(1, userId); rs=ps.executeQu
12、ery(); if(rs.next() user=new User(); user.setUserid(rs.getString(1); user.setUsername(rs.getString(2); user.setSex(rs.getString(3); finally JdbcUtil.free(rs, ps, conn); return user; /查询全部用户的方法 QueryAll() public List QueryAll() throws Exception Connection conn = null; PreparedStatement ps = null; Res
13、ultSet rs = null; List userList=new ArrayList(); try conn = JdbcUtil.getConnection(); String sql = “select * from user “; ps=conn.prepareStatement(sql); rs=ps.executeQuery(); while(rs.next() User user=new User(); user.setUserid(rs.getString(1); user.setUsername(rs.getString(2); user.setSex(rs.getString(3); userList.add(user); finally JdbcUtil.free(rs, ps, conn); return userList;
