JAVA jdbc(数据库连接池)学习笔记（一）

Class.forName("com.mysql.Driver");//这种方式是最好的,不会对具体驱动产生依赖...
DriverManager.registerDriver(com.mysql.jdbc.Driver);//会产生两个相同的驱动,并会对具体驱动产生依赖...
System.setProperty("jdbc.drivers","driver1:driver2");//基本不常用,所以可以不用记,一般就使用第一种就行了...

Connection conn = DriverManager.getConnection(url, user, password);

Statement st = conn.createStatement();
st.executeQuery(sql);
PreparedStatement
String sql = "select * from table_name where col_name=?";
PreparedStatement ps = conn.preparedStatement(sql);
ps.setString(1, "col_value");
ps.executeQuery();

ResultSet rs = statement.executeQuery(sql);
While(rs.next()){
rs.getString(“col_name”);
rs.getInt(“col_name”);
}

import java.sql.*;//1.引包是必须的...

public class JDBC_1_1 {
static final String JDBC_DRIVER="com.mysql.jdbc.Driver";
static final String DB_URL ="jdbc:mysql://localhost:3306/emp";//这个链接是我本机的数据库emp...emp里有个表格叫employees....
/*表格的信息
*create table employees
*(
*    id int not null,
*    first varchar(255) not null,
*    last varchar(255) not null,
*    age int not null
*);
*/
static final String USER="root";//登陆数据库时的用户名...
static final String PAS="49681888";登陆时的密码...
public static void main(String[] args) {
// TODO Auto-generated method stub
Connection conn=null;
Statement stmt=null;//
try {
//2.注册JDBC驱动程序...
Class.forName("com.mysql.jdbc.Driver");
//3.打开一个链接...
System.out.println("Connection database....");
conn=DriverManager.getConnection(DB_URL,USER,PAS);

//4.执行一个操作...
System.out.println("Creating statement");
stmt=conn.createStatement();
//          String sql;
//          sql="select id,first,last,age from employees"; 这个是查询操作...
//          ResultSet rs=stmt.executeQuery(sql);
String sql_1="insert into employees " + "values (7, 'z', 'yh', 20)";//插入操作...
stmt.executeUpdate(sql_1);

5.提取数据...
//          while(rs.next()){  //rs用来保存sql执行后的结果...
//              int id=rs.getInt("id");
//              int age=rs.getInt("age");
//              String first=rs.getString("first");
//              String last=rs.getString("last");
//              System.out.println(id+" "+age+" "+first+" "+last);
//          }
6.清理环境
//          rs.close();
stmt.close();
conn.close();
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
System.out.println("no class");
}finally{
if(stmt!=null){
try {
stmt.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
if(conn!=null){
try {
conn.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
System.out.println("Goodbye");
}

}

package JDBC_3;
import java.util.Date;
class User{            //user类..
private int id;
private String name;
private Date birthday;
private float money;
public User(){
}
public User(int id,String name,Date birthday,float money){
this.id=id;
this.name=name;
this.birthday=birthday;
this.money=money;
}
public int getid(){
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Date getBirthday() {
return birthday;
}
public void setBirthday(Date birthday) {
this.birthday = birthday;
}
public float getMoney() {
return money;
}
public void setMoney(float money) {
this.money = money;
}

@Override
public String toString(){
return "[id="+id+",name="+name+",birthday="+birthday+",money="+money+"]";
}
}

package JDBC_3;

interface UserDao{
public abstract void addUser(User user);
public abstract User getUserById(int userid);
public abstract int update(User user);
public abstract int delete(User user);
}

package JDBC_3;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.SQLException;
import java.sql.Date;
import java.sql.ResultSet;
/*
* JDBC实现crud操作
* crud操作就是对数据进行增删改查...
* */
public class JDBC_3_1_server implements UserDao{
static final String DB_URL="jdbc:mysql://localhost:3306/emp";
static final String user_1="root";
static final String pas="49681888";
static{
try {
Class.forName("com.mysql.jdbc.Driver");
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public void addUser(User user){
Connection cn=null;
PreparedStatement ps=null;
try {
cn=DriverManager.getConnection(DB_URL,user_1,pas);
String sql="insert into userr values(2,'clearlove','1995-01-26',200)";
//String sql="insert into userr values(?,?,?,?)";这句话是传参数是未知的，需要我们进行获取...
ps=cn.prepareStatement(sql);
//这四个函数就是为了获取我们插入的信息...上面采用了直接在sql里写入我们要插入的数据，其实我们也可以在主函数里进行传参...见下面主函数...
//            ps.setInt(1,user.getid());
//            ps.setString(2,user.getName());
//            ps.setDate(3, new Date(user.getBirthday().getTime()));
//            ps.setFloat(4, 20);
int count=ps.executeUpdate();
System.out.println("添加的记录数"+count);
ps.close();
cn.close();

} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();

}finally{
if(ps!=null){
try {
ps.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally{
if(cn!=null){
try {
cn.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
}

}
public User getUserById(int userid){
Connection cn=null;
PreparedStatement ps=null;
ResultSet rs=null;
try {
cn=DriverManager.getConnection(DB_URL,user_1,pas);
String sql="select * from userr where id=1";
//导入sql语句...
ps=cn.prepareStatement(sql);
//保存执行sql语句后的结果对象...
rs=ps.executeQuery();
ps.close();
cn.close();
rs.close();
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally{
if(ps!=null){
try {
ps.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
if(rs!=null){
try {
rs.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
if(cn!=null){
try {
cn.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
return null;
}
public int update(User user){
Connection cn=null;
PreparedStatement ps=null;
try {
cn=DriverManager.getConnection(DB_URL,user_1,pas);
String sql="update userr set name='clearlove',birthday='1994-12-19',money=60 where id=1";
ps=cn.prepareStatement(sql);
int count=ps.executeUpdate();
return count;
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally{
try {
cn.close();
ps.close();
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
return 0;
}
public int delete(User user){
Connection cn=null;
PreparedStatement ps=null;
try {
cn=DriverManager.getConnection(DB_URL,user_1,pas);
String sql="delete from userr where id=1";
ps=cn.prepareStatement(sql);
int count=-1;
count=ps.executeUpdate();
return count;
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally{
try {
cn.close();
ps.close();
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
return 0;
}
}

package JDBC_3;
class userserves {

private UserDao userDao;
public userserves(){
userDao =DaoFactory.getInstance().createUserDao();//通过工厂实例化一个例子。。
System.out.println("userDao "+userDao);
}

public void regist(User user){
if(user==null){
System.out.println("注册表信息无效...");
}else{
userDao.addUser(user);
}
}

public User query(int userId){
User user = userDao.getUserById(userId);
if(user == null){
System.out.println("查询结果为空!!");
}else{
System.out.println(user.getid()+"\t"+user.getName()+"\t"+user.getBirthday()+"\t"+user.getMoney());
}
return userDao.getUserById(userId);
}

public void update(User user){
if(user.getid()<0){
System.out.println("用户id无效,重新输入");
}else{
userDao.update(user);
}
}

public void delete(User user){
if(user.getid()<0){
System.out.println("用户id无效,重新输入");
}else{
userDao.delete(user);
}
}
}

package JDBC_3;
class DaoFactory{
private static UserDao userdao=null;
private static DaoFactory instance= new DaoFactory();
private DaoFactory(){
try {
userdao=(UserDao)Class.forName("JDBC_3.JDBC_3_1_server").newInstance();
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public static DaoFactory getInstance(){
return instance;
}
public UserDao createUserDao(){
return userdao;
}
}

package JDBC_3;
import java.sql.Date;
public class JDBC_3_1_ceshi {

public static void main(String[] args) {
// TODO Auto-generated method stub
userserves userse=new userserves();
System.out.println("添加用户");
userse.regist(new User()); //这句话我们也可以这样
//userse.regist(new User(1,"clearlove","1995-01-26",300));这样写我们可以固定传参...但是上面的一些代码就要进行修改了...
}

}

private DaoFactory(){
/**
* 通过读取属性文件来动态的加载Dao层类
*/
Properties prop = new Properties();
try{
FileInputStream fis = new FileInputStream("src/com/weijia/domain/daoconfig.properties");
prop.load(fis);
String className = prop.getProperty("userDaoClass");
Class<?> clazz = Class.forName(className);
userDao = (UserDao)clazz.newInstance();
fis.close();
}catch(Exception e){
}
}

create table userr
(
id int not null,
name varchar(255) not null,
birthday Date,
money float not null
);