用MVC模式的实现对数据库的增删改查 部分代码： package dao; import java.sql.Connection; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.util.ArrayList; import java.util.List; import common.DBConnection; import bean.Contact; public class ContactDAO { public List getAllContact() throws Exception{ Connection conn=DBConnection.getConntion(); PreparedStatement ps=conn.prepareStatement("select * from Contact"); ResultSet rs=ps.executeQuery(); List list = new ArrayList(); while(rs.next()){ int id = rs.getInt("id"); String name = rs.getString("name"); String phone = rs.getString("phone"); String address = rs.getString("address"); Contact c = new Contact(); c.setId(id); c.setName(name); c.setPhone(phone); c.setAddress(address); list.add(c); } rs.close(); ps.close(); conn.close(); return list; } public void addContact(String name,String phone,String address) throws Exception{ String sql = "insert into contact(id,name,phone,address) values(seq_contact.nextval,?,?,?)"; Connection con = DBConnection.getConntion(); PreparedStatement pstmt = con.prepareStatement(sql); pstmt.setString(1, name); pstmt.setString(2, phone); pstmt.setString(3, address); pstmt.executeUpdate(); } public void delContact(int id) throws Exception{ String sql = "delete from contact where id=?"; Connection con = DBConnection.getConntion(); PreparedStatement pstmt = con.prepareStatement(sql); pstmt.setInt(1, id); pstmt.executeUpdate(); } public Contact getContactById(int id) throws Exception{ String sql = "select * from Contact where id=?"; Connection con = DBConnection.getConntion(); PreparedStatement pstmt = con.prepareStatement(sql); pstmt.setInt(1, id); ResultSet rs = pstmt.executeQuery(); Contact c = null; while(rs.next()){ // int id = rs.getInt("id"); String name=rs.getString("name"); String p