JAVA DAO

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DAO的组成
1.实体
    一个java类，这个类与数据库中的表对应。
    比如，table_user表与User类对应:
    对应关系指的是:
    table_user表名与User类名对应
    table_user表的列(column)与User类的属性对应

table_user表中的一条记录与User类的一个实例对应

2.数据库

数据库的创建，链接。

3.dao接口
   声明一系列方法（即对数据库进行哪些操作--crud），
   这些方法应该与具体的技术无关。
3.dao实现

实现dao接口的一个具体类DaoImpl

4.dao的代理

对象访问的管理

5.工厂
提供符合接口定义的对象，调用者不用关心对象的创建细节。

也就是说，通过工厂，可以将调用者与要调用的对象解耦了。

显示层->DAO.HTML:

<html><head><title>DAO</title></head><body><form action="createEmp.jsp" method="post"><table><tr><td>用户名：</td><td><input  type="text" name="user" width="20px"/></td></tr><tr><td>密码：</td><td><input  type="password" name="password"/></td></tr><tr><td>邮箱：</td><td><input  type="text" name="email"/></td></tr><tr><td><input type="submit" value=" 注册"/></td><td><input  type="reset" value="重置"/></td></tr></table></form></body></html>

控制层->createEmp.jsp

<%@page contentType="text/html" pageEncoding="GBK"%><%@page import="DAO.VO.Emp"%><html><head><title>createEmp</title></head><body><center>hello</center><jsp:useBean id="emp" class="DAO.VO.Emp" /><jsp:useBean id="factory" class="DAO.Factory.EmpDAOFactory" /><%String user  = request.getParameter("user");String pass  = request.getParameter("password");String email = request.getParameter("email");emp = new Emp(user,pass,email);/*emp.setUser(user);emp.setPassword(pass);emp.setEmail(email);*/factory.instance().createEmp(emp);%><%="user->"+user%><br /><%="pass->"+pass%><br /><%="email->"+email%><br /></body></html>

实体VO->emp.java:

package DAO.VO;public class Emp{private int id;private String user;private String password;private String email;public Emp(){}public Emp(String user,String password,String email){this.user = user;this.password = password;this.email = email;}public Emp(int id,String user,String password,String email){this.id = id;this.user = user;this.password = password;this.email = email;}public void setID(int id){this.id = id;}public void setUser(String user){this.user = user;}public void setPassword(String password){this.password = password;}public void setEmail(String email){this.email = email;}public int getID(){return this.id;}public String getUser(){return user;}public String getPassword(){return password;}public String getEmail(){return email;}/*public static void main(String[] args){Emp e = new Emp();e.setID(2);e.setUser("hua");e.setPassword("aaaaa.0");e.setEmail("980914629@qq.com");println("ID:"+e.getID());println("User:"+e.getUser());println("Password:"+e.getPassword());println("Email:"+e.getEmail());}public static void println(Object obj){System.out.println(obj);}*/}

数据库->DatabaseConnection.java:

package DAO.DBC;import java.sql.*;public class DatabaseConnection {private static final String DRIVER     = "org.gjt.mm.mysql.Driver";private static final String DBURL      = "jdbc:mysql://localhost:3306/emp";private static final String DBUSER   = "scott";private static final String DBPASSWORD = "tiger";private static Connection conn;public DatabaseConnection()throws Exception{Class.forName(DRIVER);//驱动加载conn = DriverManager.getConnection(DBURL,DBUSER,DBPASSWORD);//连接数据库}public Connection getConnection(){return conn;}public void close()throws Exception{conn.close();}/*public static void main(String[] args)throws Exception {DatabaseConnection dc = new DatabaseConnection();dc.connection();printf(dc.getConnection());Connection conn  = dc.getConnection();Statement state  = conn.createStatement();state.executeUpdate("use study");//首先要使用哪个数据库ResultSet result = state.executeQuery("select * from emp");while(result.next()){printf(result.getObject("id"));printf(result.getObject("user"));printf(result.getObject("password"));printf(result.getObject("email"));}dc.close();}public static void printf(Object obj){System.out.println(obj);}*/}

DAO接口->IEmpDAO.java:

package DAO.IEmpDAO;import  DAO.VO.*;import java.util.*;public interface IEmpDAO{public boolean createEmp(Emp emp)throws Exception;public List<Emp> findAll(String keyWord)throws Exception;public Emp findByID(int id)throws Exception;}

DAO实现类->EmpDAOImpl.java:

package DAO.EmpDAOImpl;import DAO.VO.*;import DAO.IEmpDAO.*;import java.util.*;import java.sql.*;public class  EmpDAOImpl implements IEmpDAO {private Connection conn;PreparedStatement preStatement;ResultSet result;public EmpDAOImpl(Connection conn){preStatement = null;result = null;this.conn = conn;}public boolean createEmp(Emp e)throws Exception{preStatement = conn.prepareStatement("INSERT INTO emp(user,password,email) VALUES(?,?,?)");preStatement.setString(1,e.getUser());preStatement.setString(2,e.getPassword());preStatement.setString(3,e.getEmail());preStatement.execute("use study");//先使用哪个数据库preStatement.execute();preStatement.close();return true;}public List<Emp> findAll(String keyWord)throws Exception{List <Emp> emps = new ArrayList<Emp>();preStatement = conn.prepareStatement("select * from emp where user like ? or password like ?");preStatement.setString(1,"%"+keyWord+"%");preStatement.setString(2,"%"+keyWord+"%");preStatement.execute("use study");//先使用哪个数据库result = preStatement.executeQuery();while(result.next()){Emp emp = new Emp(result.getInt("id"),  result.getString("user"),              result.getString("password"),  result.getString("email")  );emps.add(emp);}preStatement.close();return emps;}public Emp findByID(int id)throws Exception{Emp emp = null;preStatement = conn.prepareStatement("select * from emp where id=?");preStatement.setInt(1,id);result = preStatement.executeQuery();while(result.next()){emp = new Emp(result.getInt("id"),  result.getString("user"),  result.getString("password"),  result.getString("email"));}preStatement.close();return emp;}public boolean findEmp(String user)throws Exception{List <Emp> emps = new ArrayList<Emp>();preStatement = conn.prepareStatement("select * from emp where user=?");preStatement.setString(1,user);preStatement.execute("use study");result = preStatement.executeQuery();while(result.next()){ String userTemp = result.getString("user"); if(user.equals(userTemp)){preStatement.close();return true; }}preStatement.close();return false;}/*public static void main(String[] args)throws Exception{EmpDAOImpl edi = new EmpDAOImpl(new DatabaseConnection().getConnection());edi.createEmp(new Emp("hua1","aaaaa.0","435501646@qq.com"));List <Emp> emps = edi.findAll("hu");for(int i=0;i<emps.size();i++){printf(emps.get(i).getID()+" ");printf(emps.get(i).getUser()+" ");printf(emps.get(i).getPassword()+" ");printfln(emps.get(i).getEmail());}Emp emp;emp = edi.findByID(5);printf(emp.getID()+" ");printf(emp.getUser()+" ");printf(emp.getPassword()+" ");printfln(emp.getEmail());}public static void printf(Object obj){System.out.print(obj);}public static void printfln(Object obj){System.out.println(obj);}*/}

DAO代理->EmpDAOProxy.java:

package DAO.EmpProxy;import DAO.VO.*;import DAO.IEmpDAO.*;import DAO.DBC.*;import DAO.EmpDAOImpl.*;import java.util.*;public class EmpDAOProxy implements IEmpDAO{private DatabaseConnection dc;private EmpDAOImpl edi;public EmpDAOProxy()throws Exception{dc  = new DatabaseConnection();edi = new EmpDAOImpl(dc.getConnection());}public boolean createEmp(Emp emp){try{if(!edi.findEmp(emp.getUser()))edi.createEmp(emp);elsereturn false;}catch (Exception e){}finally{try{dc.close();}catch (Exception e){}}return true;}public List<Emp> findAll(String keyWord){List<Emp> emps = new ArrayList<Emp>();try{emps = edi.findAll(keyWord);}catch (Exception e){}return emps;}public Emp findByID(int id){Emp emp = null;try{emp = edi.findByID(id);}catch (Exception e){}return emp;}/*public static void main(String[] args){System.out.println("Hello World!");}*/public static void printf(Object obj){System.out.print(obj);}public static void printfln(Object obj){System.out.println(obj);}}

DAO工厂->EmpDAOFactory.java:

package DAO.Factory;import DAO.VO.*;import DAO.EmpProxy.*;public class EmpDAOFactory {public static EmpDAOProxy instance()throws Exception{return new EmpDAOProxy();}}

我觉得对于初学者，如果是为了测试一下这种的设计模式，最后一步一步来，免得出麻烦，搞到头都大，像我那些注释的那样，

都是一步一步来的，虽然可能有点慢，但是自己会更加注意那些细节，而且如果一下子写完的话，如果出错了，那时候头就大了，

不要看到那些代码都是一下子出现你面前，你就要一下子写完它，应该理解之后，再一步一步慢慢写，这样才能有好的收获的。

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