jsp只关注于数据的显示，而不关心数据是从哪里来，所以jsp中不应该使用任何sql包，数据库操作代码最好使用PreparedStatement。
j2ee的组件层次：客户端-->表示层-->业务层-->数据层
DAO属于j2ee数据层的操作，操作数据库，DAO封装了数据库中表的全部操作。
实例：
假设表：
create table person
(
id varchar(32) primary key not null,
name varchar(20) not null,
password varchar(20) not null,
age varchar(20) not null,
email varchar(20) not null
);
那么DAO则规定了操作person表或person对象的接口
针对对象插入，而对象包括值对象（VO），传输对象（TO），最根本的java对象（POJO）
客户通过VO操作DAO
DAO设计模式其实就是把数据库中的表用类描述为对象，然后规定该对象的数据库操作接口，最后实现该接口的类。
1，类描述的对象
package cn.lxh.vo;
public class Person {
public String id;
public String name;
public String password;
public String age;
public String email;
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public String getAge() {
return age;
}
public void setAge(String age) {
this.age = age;
}
public String getEmail() {
return email;
}
public void setEmail(String email) {
this.email = email;
}
}
2,对象操作接口
package cn.lxh.dao;
import java.util.List;
import cn.lxh.vo.Person;
public interface PersonDAO {
//增加操作
public void insert(Person person) throws Exception;
//修改操作
public void update(Person person) throws Exception;
//删除操作
public void delete(String id) throws Exception;
//按id查询操作
public void queryById(String id) throws Exception;
//查询全部
public List<Person> queryAll() throws Exception;
//模糊查询
public List<Person> queryByLike(String cond) throws Exception;
}
3，实现该接口的类（数据库操作代码）
数据库连接/关闭类
package cn.lxh.dbc;
import java.sql.*;
public class DataBaseConnection {
//驱动程序
private String url="oracle.jdbc.driver.OracleDriver";
//数据库连接字符串
private String conStr="jdbc:oracle:thin:@192.168.1.113:1521:orcl";
//连接对象
private Connection con=null;
//对象在实例化的时候自动连接数据库
public DataBaseConnection() throws Exception
{
Class.forName(url);
this.con=DriverManager.getConnection(conStr);
}
//取得连接
public Connection getCon()
{
return this.con;
}
//关闭数据库
public void closeDba() throws SQLException
{
con.close();
}
}
对象操作数据库类
package cn.lxh.dao.impl;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.util.ArrayList;
import java.util.List;
import cn.lxh.dao.PersonDAO;
import cn.lxh.vo.Person;
import cn.lxh.dbc.*;
public class PersonDAOImpl implements PersonDAO {
public void delete(String id) throws Exception {
}
public void insert(Person person) throws Exception {
String sql="insert into person(id,name,password,age,email) values(?,?,?,?,?) ";
Connection con=null;
DataBaseConnection conn =null;
try
{
conn = new DataBaseConnection();
con= conn.getCon();
PreparedStatement prepare = con.prepareStatement(sql);
prepare.setString(0, "1");
prepare.setString(1, "jin");
prepare.setString(2, "123");
prepare.setString(3, "14");
prepare.setString(4, "932654256@qq.com");
prepare.executeUpdate();
prepare.close();
}
catch (Exception e) {
throw new Exception("出现错误！");
}
finally
{
conn.closeDba();
}
}
public List<Person> queryAll() throws Exception {
return null;
}
public void queryById(String id) throws Exception {
String sql="select * from person where id=?";
DataBaseConnection con=null;
try {
con = new DataBaseConnection();
Connection conn = con.getCon();
PreparedStatement preState = conn.prepareStatement(sql);
preState.setString(0, "1");
ResultSet rs = preState.executeQuery();
if(rs.next()) {
Person person = new Person();
person.setId(rs.getString(1));
}
preState.close();
} catch (Exception e) {
throw new Exception("出现错误！");
}finally
{
con.closeDba();
}
}
public List<Person> queryByLike(String cond) throws Exception {
List<Person> list=new ArrayList<Person>();
String sql="select * from person where name like ?";
DataBaseConnection con=null;
try {
con = new DataBaseConnection();
Connection conn = con.getCon();
PreparedStatement preState = conn.prepareStatement(sql);
preState.setString(0, "%"+cond+"%");
ResultSet rs = preState.executeQuery();
while (rs.next()) {
Person person = new Person();
person.setId(rs.getString(1));
list.add(person);
}
preState.close();
} catch (Exception e) {
throw new Exception("出现错误！");
}finally
{
con.closeDba();
}
return list;
}
public void update(Person person) throws Exception {
}
}
jsp页面代码：
<%@ page contentType="text/html;charset=gb2312"%>
<%@ page import="cn.lxh.dao.*"%>
<%@ page import="cn.lxh.dao.impl.*"%>
<%@ page import="cn.lxh.vo.*"%>
<%@ page import="cn.lxh.dbc.*"%>
<%
Person person=new Person();
person.setId("jin");
PersonDAO dao=new PersonDAOImpl();
try
{
dao.insert(person);
}
catch(Exception e)
{
throw new Exception("出现错误！");
}
%>
