本部分内容,主要实现对数据库的基本操作,并更换数据访问部分,将原来的使用文件存储更换为数据库进行数据的存储

在项目中，要引入mysql的驱动程序

在项目根目录下，创建lib文件夹，将mysql的驱动程序复制到lib目录下，然后在项目中引用

一、创建数据库与数据表

数据库名称：dbbook 书籍信息表：tbook 用户信息表：tuser 数据库操作命令如下：

create database dbbook;
use dbbook;
create table tbook( id int autoincrement, bookname varchar(30), bookauthor varchar(30), count int, primary key(id)
)engine=innodb default charset=utf8;
insert into tbook(bookname,bookauthor,count) values('Java','admin',10);
create table tuser( id int autoincrement,name varchar(20) null,password varchar(20) null,email varchar(20) null, primary key(id)
)engine=innodb default charset=utf8;
insert into t_user(name,password,email) values('admin','admin','admin@126.com');

二、创建DBUtil

1.在src下创建db.properties文件

db.properties文件中保存数据库的连接信息，一行一组数据，格式是key=value内容如下

driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/db_book
user=root
password=hyg760414

2.加载配置文件

对应properties文件处理，使用Properties对象进行处理，采用加载properties文件获得流，然后使用Properties对象进行处理，代码如下：

private static String driver;
private static String url;
private static String user;
private static String password;
//静态代码块
static{try {Properties props=new Properties();//使用PropertiesReader is=new FileReader("db.properties");props.load(is);//使用Load方法加载指定的流//通过getProperty(key)，通过key获得需要的值driver=props.getProperty("driver");url=props.getProperty("url");user=props.getProperty("user");password=props.getProperty("password");} catch (FileNotFoundException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();}
}

3.创建连接数据库的方法和关闭连接的方法

在DBUtil类中添加如下方法

/*** 获得连接* @return*/
public static Connection getConnection(){try {Class.forName(driver);Connection conn=DriverManager.getConnection(url,user,password);return conn;} catch (ClassNotFoundException e) {e.printStackTrace();} catch (SQLException e) {e.printStackTrace();}return null;
}/*** 关闭连接* @param conn* @param pstat* @param rs*/
public static void close(Connection conn, PreparedStatement pstat, ResultSet rs){if(rs!=null){try {rs.close();} catch (SQLException e) {e.printStackTrace();}}if(pstat!=null){try {pstat.close();} catch (SQLException e) {e.printStackTrace();}}if(conn!=null){try {conn.close();} catch (SQLException e) {e.printStackTrace();}}
}

三、编写MyDbExecute抽象类

在dao包中创建MyDbExecute抽象类，代码如下

package sky.book.dao;import sky.book.util.DBUtil;import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.SQLException;
import java.util.List;public abstract class MyDbExecut<T> {/*** 执行Insert、Update、Delete语句* @param sql* @param args* @return*/public int executeUpdate(String sql,Object[] args){int n=0;Connection conn=null;PreparedStatement pstat=null;conn=DBUtil.getConnection();try {pstat=conn.prepareStatement(sql);for(int i=0;i<args.length;i++){pstat.setObject((i+1),args[i]);}n=pstat.executeUpdate();} catch (SQLException e) {e.printStackTrace();}finally {DBUtil.close(conn,pstat,null);}return n;}/*** 执行select语句* @param sql* @param args* @return 对象的List集合*/public abstract List<T> executeQuery(String sql,Object[] args);
}

四、编写BookDbExecute类，继承自MyDbExecute类

package sky.book.dao;import sky.book.bean.Book;
import sky.book.util.DBUtil;import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;public class BookDbExecute extends MyDbExecut<Book> {/*** 执行select语句** @param sql* @param args* @return 对象的List集合*/@Overridepublic List<Book> executeQuery(String sql, Object[] args) {List<Book> books=new ArrayList<>();Connection conn=null;PreparedStatement pstat=null;ResultSet rs=null;conn=DBUtil.getConnection();try {pstat=conn.prepareStatement(sql);for(int i=0;i<args.length;i++){pstat.setObject((i+1),args[i]);}rs=pstat.executeQuery();while(rs.next()){Book book=new Book();book.setId(rs.getInt(1));book.setBookname(rs.getString(2));book.setBookauthor(rs.getString(3));book.setCount(rs.getInt(4));books.add(book);}} catch (SQLException e) {e.printStackTrace();}finally {DBUtil.close(conn,pstat,rs);}return books;}
}

五、编写DbBookRepository类实现IBookRepository类

该类主要实现数据访问层的功能

package sky.book.dao;import sky.book.bean.Book;
import sky.book.util.DBUtil;import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.List;public class DbBookRepository implements IBookRepository {private Connection conn=null;private PreparedStatement pstat=null;private ResultSet rs=null;private BookDbExecute bookDbExecute=new BookDbExecute();/*** 保存数据** @return*/@Overridepublic boolean saveDate() {return false;}/*** 取得所有书籍信息** @return 所有书籍信息的集合*/@Overridepublic List<Book> selectAllBook() {String sql="select * from t_book";Object[] args={};return bookDbExecute.executeQuery(sql,args);}/*** 根据书籍的id取得书籍信息** @param id 用户的id* @return*/@Overridepublic Book selectBookById(int id) {String sql="select * from t_book where id=?";Object[] args={id};List<Book> books=bookDbExecute.executeQuery(sql,args);if(books.size()>0){return books.get(0);}else{return null;}}/*** 添加书籍** @param book 欲添加的书籍* @return 返回受影响的记录数*/@Overridepublic int insertBook(Book book) {String sql="insert into t_book(bookname,bookauthor,count) values(?,?,?)";Object[] args={book.getBookname(),book.getBookauthor(),book.getCount()};return bookDbExecute.executeUpdate(sql,args);}/*** 根据书名查找书籍** @param name 用户名* @return 如果有该书籍返回书籍对象，否则返回null*/@Overridepublic Book selectBookByName(String name) {String sql="select * from t_book where bookname=?";Object[] args={name};List<Book> books=bookDbExecute.executeQuery(sql,args);if(books.size()>0){return books.get(0);}else{return null;}}/*** 更新书籍信息** @param book 欲更新的书籍信息* @return 返回受影响的记录数*/@Overridepublic int updateBook(Book book) {String sql="update t_book set bookname=?,bookauthor=?,count=? where id=?";Object[] args={book.getBookauthor(),book.getBookauthor(),book.getBookauthor(),book.getId()};return bookDbExecute.executeUpdate(sql,args);}/*** 删除书籍** @param id 书籍id* @return 返回受影响的记录数*/@Overridepublic int deleteBookById(int id) {String sql="delete from t_book where id=?";Object[] args={id};return bookDbExecute.executeUpdate(sql,args);}
}

六、编写UserDbExecute类继承自MyDbExecute

package sky.book.dao;import sky.book.bean.User;
import sky.book.util.DBUtil;import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;public class UserDbExecute extends MyDbExecut<User> {/*** 执行select语句** @param sql* @param args* @return 对象的List集合*/@Overridepublic List<User> executeQuery(String sql, Object[] args) {List<User> users=new ArrayList<>();Connection conn=null;PreparedStatement pstat=null;ResultSet rs=null;conn=DBUtil.getConnection();try {pstat=conn.prepareStatement(sql);for(int i=0;i<args.length;i++){pstat.setObject((i+1),args[i]);}rs=pstat.executeQuery();while(rs.next()){User u=new User();u.setId(rs.getInt(1));u.setName(rs.getString(2));u.setPassword(rs.getString(3));u.setEmail(rs.getString(4));users.add(u);}} catch (SQLException e) {e.printStackTrace();}finally {DBUtil.close(conn,pstat,rs);}return users;}
}

七、编写DbUserRepository类实现IUserRepository

package sky.book.dao;import sky.book.bean.User;import java.util.List;public class DbUserRepository implements IUserRepository {private UserDbExecute uExecute=new UserDbExecute();/*** 保存数据** @return*/@Overridepublic boolean saveDate() {return false;}/*** 取得所有用户信息** @return 所有用户信息的集合*/@Overridepublic List<User> selectAllUser() {String sql="select * from t_user";Object[] args={};List<User> users=uExecute.executeQuery(sql,args);if(users.size()>0){return users;}return null;}/*** 根据用户的id取得用户信息** @param id 用户的id* @return*/@Overridepublic User selectUserById(int id) {String sql="select * from t_user where id=?";Object[] args={id};List<User> users=uExecute.executeQuery(sql,args);if(users.size()>0){return users.get(0);}return null;}/*** 添加用户** @param user 欲添加的用户* @return 返回受影响的记录数*/@Overridepublic int insertUser(User user) {String sql="insert into t_user(name,password,email) values(?,?,?)";Object[] args={user.getName(),user.getPassword(),user.getEmail()};return uExecute.executeUpdate(sql,args);}/*** 根据用户名查找用户** @param name 用户名* @return 如果有该用户返回用户对象，否则返回null*/@Overridepublic User selectUserByName(String name) {String sql="select * from t_user where name=?";Object[] args={name};List<User> users=uExecute.executeQuery(sql,args);if(users.size()>0){return users.get(0);}return null;}/*** 更新用户信息** @param user 欲更新的用户信息* @return 返回受影响的记录数*/@Overridepublic int updateUser(User user) {String sql="update t_user(name,password,email) values(?,?,?) where id=?";Object[] args={user.getName(),user.getPassword(),user.getEmail(),user.getId()};return uExecute.executeUpdate(sql,args);}
}

八、创建DaoFactory类

1.在dao下创建DalFactory类

package sky.book.dao;public class DaoFactory {public static IBookRepository getBookRepository(){return new DbBookRepository();}public static IUserRepository getUserRepository(){return new DbUserRepository();}
}

2.修改BookService和UserService类

private IBookRepository bookRepository=new BookRepository();//创建数据访问层对象

更改为

private IBookRepository bookRepository=DaoFactory.getBookRepository();//创建数据访问层对象

private IUserRepository userRepository=new UserRepository();

更改为

private IUserRepository userRepository=DaoFactory.getUserRepository();