爱华网一、DAO的介绍
一个JAVA项目包括表示层、业务层和持久化层（数据访问层）。
表示层用于和用户进行交互，业务层用于表示层和持久化层进行交互，持久化层用于和数据库交互。
这里我们的DAO（Data Access Objects：数据访问对象）就是完成持久化层的一些功能。
二、本文所用到的数据库
--建库
use master
go
if exists(select *from sysdatabases where name ='myDB' )
drop database myDB
go
create database myDB
go
--建表
use myDB
go
if exists(select * from sysobjects wherename='student')
drop table student
go
create table student(
stuId int not null,
stuName varchar(50) not null,
birsday date not null
)
go
insert into student(stuId,stuName,birsday)
values (1,'张三','1988-01-12')
insert into student (stuId,stuName,birsday)
values (2,'李斯','1989-04-10')
三、DAO编写步骤
一般建立四个包：dao包、db包、entity包、test包。
dao包中编写DAO类，如StudentDAO。
db包中编写Config常量接口，DbManager类用于加载驱动程序，创建连接等。
entity包中为实体类，一般一个表对应一个实体类。
test包中编写主函数和测试类。
1、在entity包中创建实体类
实体类的名称一般与表一致，这里为Student
需要包含Student中的所有属性，构造函数（一般为两个：不带参数的和带全部参数的）getset方法，重写toString和equals方法。
2、在db包中添加Config常量接口和DbManager类
Config中的常量一般为DRIVER、URL、DBNAME、UNAME、PWD等，方便以后想更改时直接在这里更改。
DbMagager是一个工具类，里面包含静态属性和静态方法。方法主要有：
public static int update(Stringsql)用来执行insert update delete语句。
public static ResultSet query(Stringsql) 用来执行select语句。
public static voidclose()用来关闭资源。
3、在dao包中添加DAO类（这里为Student）
用来对数据库和数据库数据进行操作。主要方法包括：
public boolean save(Studentstudent)
public boolean delete(int id)
public boolean update(Student student)
public void findAll()
public Student findById(int id)
方法体中主要是编写SQL语句，然后调用工具类DbManager中对应方法。如
public boolean save(Student student) {
DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd");
String birthday = dateFormat.format(student.getBirsday());
String sql = "insert into student" +
"(stuId,stuName,birsday)" +
"values " +
"('"+ student.getStuId() + "','" + student.getStuName() + "','" +birthday + "')";
return DBManager.update(sql) == 1;
}
4、在test包中编写测试类（这里为StudentTest）
publicclass StudentTest {
public static void main(String[] args) {
StudentTest test = new StudentTest();
test.testSave();
}
public void testSave() {
Datedate = new Date();
DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd");
try {
date = dateFormat.parse("1912-12-12");
}catch (ParseException e) {
e.printStackTrace();
}
Student student = new Student(1,"三毛",date);
StudentDAOstudentDAO = new StudentDAO();
if (studentDAO.save(student)) {
System.out.println("添加数据成功");
} else {
System.out.println("添加数据失败");
}
}
}
四、源程序
entity包：
package com.entity;
import java.util.Date;
public class Student {
private int stuId;//学生学号
private StringstuName;//学生姓名
private Datebirsday;//学生出生日期
public Student() {
super();
}
public Student(int stuId, String stuName, Datebirsday) {
super();
this.stuId = stuId;
this.stuName = stuName;
this.birsday = birsday;
}
public int getStuId() {
return stuId;
}
public void setStuId(int stuId) {
this.stuId = stuId;
}
public String getStuName() {
return stuName;
}
public void setStuName(String stuName) {
this.stuName = stuName;
}
public Date getBirsday() {
return birsday;
}
public void setBirsday(Date birsday) {
this.birsday = birsday;
}
@Override
public boolean equals(Object obj) {
if (this == obj)
returntrue;
if (obj == null)
returnfalse;
if (getClass() !=obj.getClass())
returnfalse;
Student other = (Student)obj;
if (birsday == null) {
if(other.birsday != null)
returnfalse;
} else if(!birsday.equals(other.birsday))
returnfalse;
if (stuId != other.stuId)
returnfalse;
if (stuName == null) {
if(other.stuName != null)
returnfalse;
} else if(!stuName.equals(other.stuName))
returnfalse;
return true;
}
@Override
public String toString() {
return "Student [stuId=" +stuId + ", stuName=" + stuName
+", birsday=" + birsday + "]";
}
}
db包：
packagecom.db;
public interface Config{
public static final String DRIVER ="com.microsoft.sqlserver.jdbc.SQLServerDriver";
public static final StringURL ="jdbc:sqlserver://127.0.0.1:1433;databaseName=";
public static final String DBNAME = "myDB";
public static final StringUNAME = "as";
public static final StringPWD ="";
}
package com.db;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public class DbManager {
public static Connection con = null;
public static Statement sta = null;
public static ResultSet rs = null;
public static int update(String sql) {
System.out.println(sql);
int row = 0;
try {
Class.forName(Config.DRIVER);
con =DriverManager.getConnection(Config.URL+Config.DBNAME, Config.UNAME,Config.PWD);
sta =con.createStatement();
row =sta.executeUpdate(sql);
System.out.println(1== row);
} catch (ClassNotFoundExceptione) {
System.out.println("驱动程序没有找到");
e.printStackTrace();
} catch (SQLException e){
e.printStackTrace();
} finally {
close();
}
return row;
}
public static ResultSet query(String sql){
try{
Class.forName(Config.DRIVER);
con =DriverManager.getConnection(Config.URL+Config.DBNAME, Config.UNAME,Config.PWD);
sta =con.createStatement();
rs= sta.executeQuery(sql);
} catch (C lassNotFoundExceptione) {
System.out.println("驱动程序没有找到");
e.printStackTrace();
} catch (SQLException e){
e.printStackTrace();
}
return rs;
}
public static void close() {
try {
if (rs !=null) {
rs.close();
rs=null;
}
if (sta !=null) {
sta.close();
sta= null;
}
if (con !=null) {
con.close();
con= null;
}
} catch (SQLException e){
e.printStackTrace();
}
}
}
dao包：
package com.dao;
import java.sql.SQLException;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import com.fan.db.DBManager;
import com.fan.entity.Student;
public class StudentDAO {
public boolean save(Student student) {
DateFormat dateFormat = newSimpleDateFormat("yyyy-MM-dd");
String birthday =dateFormat.format(student.getBirsday());
String sql = "insert intostudent" +
"(stuId,stuName,birsday)" +
"values " +
"('"+ student.getStuId() + "','" + student.getStuName() + "','" +birthday + "')";
return DBManager.update(sql) ==1;
}
public boolean delete(int id) {
String sql = " delete fromstudent where stuId = " + id + "";
return DBManager.update(sql)==1;
}
public boolean update(int id) {
String sql = " update student "+
"set" +
"stuName= '张大嘴', " +
"birsday= '1990-10-21' " +
"where" +
"stuId= " + id + "";
return DBManager.update(sql) ==1;
}
public Student findbyID(int id) {
String sql = "select * fromstudent where stuId=" + id + "";
DBManager.rs =DBManager.query(sql);
Student student = newStudent();
int i = 1;
try {
while(DBManager.rs.next()) {
student.setStuId(DBManager.rs.getInt(i++));
student.setStuName(DBManager.rs.getString(i++));
student.setBirsday(DBManager.rs.getDate(i++));
}
} catch (SQLException e){
e.printStackTrace();
} finally {
DBManager.close();
}
return student;
}
}
test包:
package com.test;
import java.text.DateFormat;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import com.fan.dao.StudentDAO;
import com.fan.entity.Student;
public class StudentTest {
public static void main(String[] args) {
StudentTest test = newStudentTest();
test.testSave();
test.testFindByID();
}
public void testSave(){
Date date = new Date();
DateFormat dateFormat = newSimpleDateFormat("yyyy-MM-dd");
try {
date =dateFormat.parse("1912-12-12");
} catch (ParseException e){
e.printStackTrace();
}
Student student = newStudent(1,"三毛",date);
StudentDAO studentDAO = newStudentDAO();
if (studentDAO.save(student)){
System.out.println("添加数据成功");
} else {
System.out.println("添加数据失败");
}
}
public voidtestFindByID(){
StudentDAO studentDAO = newStudentDAO();
Student student = newStudent();
student =studentDAO.findbyID(1);
System.out.println(student);
}
}
