JDBC的泛化设计
在mysql数据库中建立如下数据库及表结构作测试使用:
create database market; use market; create table client( id int primary key AUTO_INCREMENT, num nvarchar(12) unique, password varchar(20) not null)engine=innoDB default charset=utf8; insert into client values(1,'root','root');
在eclipse建立一个工程，工程目录结构如下:
1.ConnectionUtil在进行数据库交互的过程中，只使用数据库对象，而不进行具体对象的操作。
在ConnectionUtil中，放置一些数据库的基本对象:
private Connection conn; private Statement stat; private PreparedStatement ps;
在ConnectionUtil的构造器中，进行数据库对象的初始化和数据库的连接:
public ConnectionUtil(String url){
try {
Class.forName("com.mysql.jdbc.Driver");
conn=DriverManager.getConnection(url);
stat=conn.createStatement();
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
在ConnectionUtil中，另保存一些数据库操作的基本方法:
1）.查找
public ResultSet find(String sql){
try {
return stat.executeQuery(sql);
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return null;
}
2）.删除
public int delete(String sql){
try {
return stat.executeUpdate(sql);
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return 0;
}
3）.SQL防注入通过id进行的查找和删除操作
public int executeById(String sql,int id){
try {
ps=conn.prepareStatement(sql);
ps.setInt(1,id);
return ps.executeUpdate();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return 0;
}
4）.SQL防注入根据字段定制的更新操作
public int executeUpdate(String sql,String num,String password,int id){
try {
ps=conn.prepareStatement(sql);
ps.setString(1, num);
ps.setString(2, password);
ps.setInt(3,id);
return ps.executeUpdate();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return 0;
}
public int executeUpdate(String sql,int id,String num,String password){
try {
ps=conn.prepareStatement(sql);
ps.setInt(1,id);
ps.setString(2, num);
ps.setString(3, password);
return ps.executeUpdate();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return 0;
}
在ConnectionUtil中的收尾工作:
1）.关闭Statement
public void close(Statement stat){
try {
stat.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
2）.关闭Connection
public void close(Connection conn){
try {
conn.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
2.Client类 （JavaBean）在业务处理层保存数据信息
public class Client {
private int id;
private String num;
private String password;
public Client() {
super();
// TODO Auto-generated constructor stub
}
public Client(int id, String name, String password) {
super();
this.id = id;
this.num = name;
this.password = password;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getNum() {
return num;
}
public void setNum(String num) {
this.num = num;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public int hashCode() {
final int prime = 31;
int result = 1;
result = prime * result + id;
result = prime * result + ((num == null) ? 0 : num.hashCode());
result = prime * result
+ ((password == null) ? 0 : password.hashCode());
return result;
}
public String toString() {
return "client id=" + id + ", num=" + num + ", password=" + password;
}
}
3.在ClientDao层将数据库对象转换为具体对象，该处为Client类对象
在ClientDao中保存成员工具对象，类初始化的时候实例化该工具对象
private ConnectionUtil util;
public ClientDao(String url) {
super();
util=new ConnectionUtil(url);
}
获取所有的Client对象：
public List<Client> queryClients(){
List<Client> list=new ArrayList<Client>();
ResultSet set=util.find("select * from client");
try {
while(set.next()){
Client temp=new Client(set.getInt(1),set.getString(2),set.getString(3));
list.add(temp);
}
}catch (SQLException e) {
e.printStackTrace();
}
util.close(set);
return list;
}
根据id查找对象：
public Client queryClient(int id){
Client client=null;
ResultSet set=util.preparedFindById("select * from client where id=?", id);
try {
while(set.next())
client=new Client(set.getInt(1),set.getString(2),set.getString(3));
}catch (SQLException e) {
e.printStackTrace();
}
util.close(set);
return client;
}
插入Client对象：
public int insertClient(Client client){
return util.executeUpdate("insert into client values(?,?,?)", client.getId(), client.getNum() , client.getPassword());
}
根据id更新client对象：
public int updateClient(Client client){
return util.executeUpdate("update client set num=?,password=? where id=?", client.getNum(),client.getPassword(),client.getId());
}
根据id删除client对象：
public int deleteById(int id){
return util.executeById("delete from client where id=?", id);
}
删除所有的client对象：
public int deleteClients(){
return util.delete("delete from client");
}
4.最后再写一个测试驱动Tester:
public class Tester {
private static ClientDao dao = new ClientDao(
"jdbc:mysql://localhost:3306/market?user=root&password=" +
"&useUnicode=true&characterEncoding=UTF8");
public static void main(String[] args) {
// test01();
// test02();
// test03();
// test04();
// test05();
// test06();
}
// test:queryClients();
public static void test01(){
List<Client> list = new ArrayList<Client>();
list = dao.queryClients();
System.out.println(list);
}
// test:queryClient(int id);
public static void test02(){
System.out.println(dao.queryClient(1));
}
// test:insertClient(Client client);
public static void test03(){
Client client=new Client(2,"admin","admin");
if(dao.insertClient(client)==1)
System.out.println("Insert successfully!");
else
System.out.println("Insert incorrectly!");
}
// test:updateClient(Client client);
public static void test04(){
Client client=new Client(1,"login","login");
if(dao.updateClient(client)==1)
System.out.println("Update successfully!");
else
System.out.println("Update incorrectly!");
}
// test:deleteById(int id);
public static void test05(){
if(dao.deleteById(2)==1)
System.out.println("Delete successfully by id!");
else
System.out.println("Delete incorrectly by id!");
}
// test:deleteClients();
public static void test06(){
if(dao.deleteClients()==1)
System.out.println("Delete all successfully!");
else
System.out.println("Delete all incorrectly!");
}
}
下面是测试结果:
在jdbc中可以将数据库对象和具体对象的操作绑定在一起，但是每多一个具体对象就需要多一个dao层的转化类。
本文将数据库操作单独封装在一起，每当多一个具体对象时只需要编写实现对具体对象操作的代码就好了。