java 关于封装jdbc操作接口的一些做法

首先建立如下图所示的包结构：

然后首先件里模型model包下的两个类：

package model;

public abstract class Bean {

   

}

下面是User类的代码：

package model;

import java.util.Date;

public class User extends Bean{

private Integer id;

private String name;

private String password;

private String sex;

private String email;

private String pwdQuestion;

private String pwdAnswer;

private Date regDate;

private String lastLoginDate;

private String lastLoginIp;

public Integer getId() {

return id;

}

public void setId(Integer 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 getSex() {

return sex;

}

public void setSex(String sex) {

this.sex = sex;

}

public String getEmail() {

return email;

}

public void setEmail(String email) {

this.email = email;

}

public String getPwdQuestion() {

return pwdQuestion;

}

public void setPwdQuestion(String pwdQuestion) {

this.pwdQuestion = pwdQuestion;

}

public String getPwdAnswer() {

return pwdAnswer;

}

public void setPwdAnswer(String pwdAnswer) {

this.pwdAnswer = pwdAnswer;

}

public Date getRegDate() {

return regDate;

}

public void setRegDate(Date regDate) {

this.regDate = regDate;

}

public String getLastLoginDate() {

return lastLoginDate;

}

public void setLastLoginDate(String lastLoginDate) {

this.lastLoginDate = lastLoginDate;

}

public String getLastLoginIp() {

return lastLoginIp;

}

public void setLastLoginIp(String lastLoginIp) {

this.lastLoginIp = lastLoginIp;

}

}

然后建立dao包，里面的BaseDao代码如下：

package dao;

import java.sql.Connection;

import java.sql.DriverManager;

import java.sql.ResultSet;

import java.sql.SQLException;

import java.sql.Statement;

import java.util.ArrayList;

import model.Bean;

public abstract class BaseDao {

private static String url = "jdbc://localhost:3306/test";

private static String name = "root";

private static String password = "12345";

private static String driverName = "com.mysql.jdbc.Driver";

private Connection getConnection() {

Connection conn = null;

try {

Class.forName(driverName);

conn = DriverManager.getConnection(url, name, password);

} catch (ClassNotFoundException e) {

// TODO Auto-generated catch block

e.printStackTrace();

} catch (SQLException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

return conn;

}

    /**

     * parse ResultSet to Bean's Child

     * @param rt

     * @return

     * Bean

     */

protected abstract Bean fillBean(ResultSet rt);

/**

 * select

 * @param sql

 * @return

 * the result of select operation

 */

public ArrayList select(String sql) {

ArrayList list = new ArrayList();

Connection conn = getConnection();

Statement st = null;

ResultSet rt = null;

try {

st = conn.createStatement();

rt = st.executeQuery(sql);

while (rt.next()) {

list.add(fillBean(rt));

}

} catch (SQLException e) {

// TODO Auto-generated catch block

e.printStackTrace();

} finally {

try {

rt.close();

st.close();

conn.close();

} catch (SQLException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

}

return list;

}

/**

 * update,insert,delete

 * @param sql

 * @return

 * operation columns

 */

public int update(String sql) {

int flag = -1;

Connection conn = getConnection();

Statement st = null;

try {

st = conn.createStatement();

flag = st.executeUpdate(sql);

} catch (SQLException e) {

// TODO Auto-generated catch block

e.printStackTrace();

try {

conn.rollback();// 如果出现异常，当前操作自动回滚

} catch (SQLException e1) {

// TODO Auto-generated catch block

e1.printStackTrace();

}

} finally {

try {

conn.commit();// 如果操作正常，当前操作提交

st.close();

conn.close();

} catch (SQLException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

}

return flag;

}

}

下面是UserDao的代码：

package dao;

import java.sql.ResultSet;

import java.sql.SQLException;

import java.util.ArrayList;

import model.Bean;

import model.User;

public class UserDao extends BaseDao{

    private static final String TABLE_NAME="user";

@Override

protected Bean fillBean(ResultSet rt) {

User user=new User();

try {

user.setId(rt.getInt("id"));

user.setName(rt.getString("name"));

user.setPassword(rt.getString("password"));

user.setSex(rt.getString("sex"));

user.setEmail(rt.getString("email"));

user.setPwdQuestion(rt.getString("pwdquestion"));

user.setPwdAnswer(rt.getString("pwdanswer"));

user.setRegDate(rt.getDate("regdate"));

user.setLastLoginDate(rt.getString("lastlogindate"));

user.setLastLoginIp(rt.getString("lastloginip"));

} catch (SQLException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

return user;

}

public ArrayList selectById(String id){

String sql="select * from "+TABLE_NAME+" where id='"+id+"'";

ArrayList list=super.select(sql);

return list;

}

}

这样书写这两个dao的好处是，BaseDao只是加载一些配置信息，公共重复的sql操作，子类中只需要提供解析ResultSet到实体Bean的方法，那么只需要对sql和参数进行有效地封装就好了。虽然做的很粗糙，但是道理上的封装就是这样的。