第八章DAO模式
1.持久化是将程序中数据在瞬时状态和持久状态间转换的机制。
2.JDBC是一种持久化机制,将程序直接保存成文本也是持久化机制的一种实现。
3.DAO就是Data Access Object(数据存取对象),位于业务逻辑和持久化数据之间,实现对持久化数据的访问。
4.DAO模式提供了访问关系型数据库系统所需的操作接口,将数据访问和业务逻辑分离,对上层提供面向对象的数据访问接口。
5.一个典型的DAO模式主要由DAO接口,DAO实现类,实体类组成,基于代码复用考虑,通常创建一个数据库连接和关闭工具类。
//封装
package Pet;
//宠物实体类
public class Pet {
int id;
String name;
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;
}
}
//PetDAO接口
package Pet;
import java.util.List;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.SQLException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.SQLException;
//DAO模式
public interface PetDAO {
int save(Pet pet);
int delect(Pet pet);
int update(Pet pet);
List <Pet> select();
Pet getByName(String name);
List<Pet> findByName(String name);
List<Pet> findBytype(String type);
public interface PetDAO {
int save(Pet pet);
int delect(Pet pet);
int update(Pet pet);
List <Pet> select();
Pet getByName(String name);
List<Pet> findByName(String name);
List<Pet> findBytype(String type);
// 连接及增删改查方法及读取配置文件方法
package Pet;
import java.io.IOException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Properties;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Properties;
import org.omg.CORBA.portable.InputStream;
public class BaseDAO {
Connection conn = null;
private static String driver;
private static String url;
private static String user;
private static String password;
// 从配置文件中读取连接参数
static{
init();
}
public static void init(){
Properties params =new Properties();
String configfile="database.properties";
//加载配置文件到输入流
InputStream is=(InputStream) BaseDAO.class.getClassLoader().getResourceAsStream(configfile);
//从输入流中读取属性列表
try {
params.load(is);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
//根据指定的键获取对应的值
driver=params.getProperty("driver");
url=params.getProperty("url");
user=params.getProperty("user");
password=params.getProperty("password");
}
private static String driver;
private static String url;
private static String user;
private static String password;
// 从配置文件中读取连接参数
static{
init();
}
public static void init(){
Properties params =new Properties();
String configfile="database.properties";
//加载配置文件到输入流
InputStream is=(InputStream) BaseDAO.class.getClassLoader().getResourceAsStream(configfile);
//从输入流中读取属性列表
try {
params.load(is);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
//根据指定的键获取对应的值
driver=params.getProperty("driver");
url=params.getProperty("url");
user=params.getProperty("user");
password=params.getProperty("password");
}
// 连接
public Connection getConntion() {
public Connection getConntion() {
// 连接
try {
Class.forName(driver);
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
Class.forName(driver);
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
try {
conn = DriverManager.getConnection(url,user,password);
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
conn = DriverManager.getConnection(url,user,password);
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
System.out.println("建立连接成功!");
return conn;
}
return conn;
}
// 返回结果集
public ResultSet getResultSet(String sql) {
PreparedStatement ps=null;
ResultSet rs=null;
conn=getConntion();
//获得连接
try {
ps=conn.prepareStatement(sql);
rs=ps.executeQuery();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return rs;
}
public ResultSet getResultSet(String sql) {
PreparedStatement ps=null;
ResultSet rs=null;
conn=getConntion();
//获得连接
try {
ps=conn.prepareStatement(sql);
rs=ps.executeQuery();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return rs;
}
// 增删改
public int Update(String sql, Object[] objects) {
PreparedStatement ps = null;
int num = 0;
conn = getConntion();
try {
ps = conn.prepareStatement(sql);
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
if (objects != null) {
for (int i = 0; i < objects.length; i++) {
try {
ps.setObject(i + 1, objects[i]);
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
try {
num = ps.executeUpdate();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} finally {
public int Update(String sql, Object[] objects) {
PreparedStatement ps = null;
int num = 0;
conn = getConntion();
try {
ps = conn.prepareStatement(sql);
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
if (objects != null) {
for (int i = 0; i < objects.length; i++) {
try {
ps.setObject(i + 1, objects[i]);
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
try {
num = ps.executeUpdate();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} finally {
closeAll(conn, ps, null);
}
}
}
return num;
}
// 关闭连接
public void closeAll(Connection conn, PreparedStatement ps, ResultSet rs) {
if (rs != null) {
public void closeAll(Connection conn, PreparedStatement ps, ResultSet rs) {
if (rs != null) {
}
if (ps != null) {
try {
ps.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
if (ps != null) {
try {
ps.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();
}
}
}
if (conn != null) {
try {
conn.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
//实现类 DriverManager
package Pet;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
import com.mysql.jdbc.Connection;
import com.mysql.jdbc.PreparedStatement;
import com.mysql.jdbc.PreparedStatement;
public class PetDaoimpl extends BaseDAO implements PetDAO {
@Override
public int save(Pet pet) {
String sql="insert into city values(?,?)";
Object[] objects={pet.getId(),pet.getName()};
int result=this.Update(sql, objects);
System.out.println("添加成功!");
return result;
}
public int save(Pet pet) {
String sql="insert into city values(?,?)";
Object[] objects={pet.getId(),pet.getName()};
int result=this.Update(sql, objects);
System.out.println("添加成功!");
return result;
}
@Override
public int delect(Pet pet) {
String sql="delete from city "+"where id=?";
Object[] objects={pet.getId()};
int result=this.Update(sql, objects);
System.out.println("删除成功!");
return result;
public int delect(Pet pet) {
String sql="delete from city "+"where id=?";
Object[] objects={pet.getId()};
int result=this.Update(sql, objects);
System.out.println("删除成功!");
return result;
}
// @Override
public int update(Pet pet) {
String sql="Update city set name='哈哈'"+"where id=?";
Object[] objects={pet.getId()};
int result=this.Update(sql, objects);
System.out.println("修改成功!");
return result;
// Connection conn=null;
// PreparedStatement ps=null;
// //1.数据库连接
//
// //2.更新数据city表
// try {
// Class.forName("com.mysql.jdbc.Driver");
// } catch (ClassNotFoundException e) {
// // TODO Auto-generated catch block
// e.printStackTrace();
// }
// try {
// conn = (Connection) DriverManager.getConnection("jdbc:mysql://localhost:3306/mysql", "root", "root");
// } catch (SQLException e) {
// // TODO Auto-generated catch block
// e.printStackTrace();
// }
// try {
// ps=(PreparedStatement) conn.prepareStatement("Update city set name='哈哈'"+"where id=?");
// } catch (SQLException e) {
// // TODO Auto-generated catch block
// e.printStackTrace();
// }
// try {
// result=ps.executeUpdate();
// } catch (SQLException e) {
// // TODO Auto-generated catch block
// e.printStackTrace();
// }finally{
// if (null!=ps) {
// try {
// ps.close();
// } catch (SQLException e) {
// // TODO Auto-generated catch block
// e.printStackTrace();
// }
//
// }
// if (null!=conn) {
// try {
// conn.close();
// } catch (SQLException e) {
// // TODO Auto-generated catch block
// e.printStackTrace();
// }
//
//}
// return result;
}
@Override
public List<Pet> select(){
List<Pet> list=null;
String sql="select * from city";
ResultSet rs=this.getResultSet(sql);
list=new ArrayList<Pet>();
try {
while (rs.next()) {
Pet pet=new Pet();
pet.setId(rs.getInt("id"));
pet.setName(rs.getString("name"));
list.add(pet);
}
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return list;
}
@Override
public Pet getByName(String name) {
// TODO Auto-generated method stub
return null;
}
public int update(Pet pet) {
String sql="Update city set name='哈哈'"+"where id=?";
Object[] objects={pet.getId()};
int result=this.Update(sql, objects);
System.out.println("修改成功!");
return result;
// Connection conn=null;
// PreparedStatement ps=null;
// //1.数据库连接
//
// //2.更新数据city表
// try {
// Class.forName("com.mysql.jdbc.Driver");
// } catch (ClassNotFoundException e) {
// // TODO Auto-generated catch block
// e.printStackTrace();
// }
// try {
// conn = (Connection) DriverManager.getConnection("jdbc:mysql://localhost:3306/mysql", "root", "root");
// } catch (SQLException e) {
// // TODO Auto-generated catch block
// e.printStackTrace();
// }
// try {
// ps=(PreparedStatement) conn.prepareStatement("Update city set name='哈哈'"+"where id=?");
// } catch (SQLException e) {
// // TODO Auto-generated catch block
// e.printStackTrace();
// }
// try {
// result=ps.executeUpdate();
// } catch (SQLException e) {
// // TODO Auto-generated catch block
// e.printStackTrace();
// }finally{
// if (null!=ps) {
// try {
// ps.close();
// } catch (SQLException e) {
// // TODO Auto-generated catch block
// e.printStackTrace();
// }
//
// }
// if (null!=conn) {
// try {
// conn.close();
// } catch (SQLException e) {
// // TODO Auto-generated catch block
// e.printStackTrace();
// }
//
//}
// return result;
}
@Override
public List<Pet> select(){
List<Pet> list=null;
String sql="select * from city";
ResultSet rs=this.getResultSet(sql);
list=new ArrayList<Pet>();
try {
while (rs.next()) {
Pet pet=new Pet();
pet.setId(rs.getInt("id"));
pet.setName(rs.getString("name"));
list.add(pet);
}
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return list;
}
@Override
public Pet getByName(String name) {
// TODO Auto-generated method stub
return null;
}
@Override
public List<Pet> findByName(String name) {
// TODO Auto-generated method stub
return null;
}
public List<Pet> findByName(String name) {
// TODO Auto-generated method stub
return null;
}
@Override
public List<Pet> findBytype(String type) {
// TODO Auto-generated method stub
return null;
}
public List<Pet> findBytype(String type) {
// TODO Auto-generated method stub
return null;
}
}
}
6数据访问代码和业务之间通过实体类传输数据,在程序中把实体类作为方法的输入参数或返回结果,实现数据的传递,非常的方便。
7.读取配置文件
Properties类来读取配置文件。位于java.util包中,继承Hashtable类
Properties类的方法
8.读取配置步骤:
1)添加.properties文件
src选中-->new -->file-->新建窗口输入database.properties-->finish
效果图如上
|
2)添加文件内容
driver=com.mysql.jdbc.Driverurl=jdbc:mysql://localhost:3306/mysql
user=root
password=root