JDBC中DAO模式的例子示范

----------------------------------------JDBC中DAO模式的例子示范---------------------------------------

1　JdbcUtils的作用

你也看到了，连接数据库的四大参数是：驱动类、url、用户名，以及密码。这些参数都与特定数据库关联，如果将来想更改数据库，那么就要去修改这四大参数，那么为了不去修改代码，我们写一个JdbcUtils类，让它从配置文件中读取配置参数，然后创建连接对象。

2　DAO模式

DAO（Data Access Object）模式就是写一个类，把访问数据库的代码封装起来。DAO在数据库与业务逻辑（Service）之间。

l  实体域（JavaBean），即操作的对象，例如我们操作的表是user表，那么就需要先写一个User类；

l  DAO模式需要先提供一个DAO接口；

l  然后再提供一个DAO接口的实现类；

l  再编写一个DAO工厂，Service通过工厂来获取DAO实现。

代码示例：

DBAutil类  主要功能，建立数据库连接，返回执行sql语句对象，释放资源

package com.rl.jdbc.utils;   import java.io.InputStream; import java.sql.Connection; import java.sql.DriverManager; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; import java.sql.Statement; import java.util.Properties;   publicclass DBUtils {           /**      * 获得connction方法      * @return      */     publicstatic Connection getConn(){         //获得字节输入流对象         InputStream in = DBUtils.class.getClassLoader().getResourceAsStream("db.propertise");         Properties pps = new Properties();         Connection conn = null;         try {            //将文件加载到properties集合中            pps.load(in);            //取得properties中的配置文件参数            String driverClass = pps.getProperty("driverClass");            String url = pps.getProperty("url");            String username = pps.getProperty("username");            String password = pps.getProperty("password");            //加载Oracle驱动            Class.forName(driverClass);            //获得connection对象            conn = DriverManager.getConnection(url, username, password);         } catch (Exception e) {            e.printStackTrace();         }         returnconn;     }         /**      * 获得执行sql语句返回的预编译PreparedStatement对象      */     publicstatic PreparedStatement getPrepare(String sql){         PreparedStatement ps = null;         try {            Connection conn = getConn();            ps = conn.prepareStatement(sql);         } catch (SQLException e) {            e.printStackTrace();         }         returnps;     }         /**      * 关闭修改数据库所用到的资源      */     publicstaticvoid closeUpdate(PreparedStatement ps){      try {          if(ps != null){            Connection conn = ps.getConnection();            ps.close();            if(conn != null)                conn.close();          }        } catch (SQLException e) {            e.printStackTrace();        }     }         /**      * 关闭查询数据库时所用到的资源      */     publicstaticvoid closeQuery(ResultSet rs){         try {            if(rs != null){                Statement st = rs.getStatement();                rs.close();                if(st != null){                    Connection conn = st.getConnection();                    st.close();                    if(conn != null){                        conn.close();                    }                }            }         } catch (SQLException e) {            e.printStackTrace();         }     } }

Person类，用于插入，数据库中的表单到java中的数据共享。

package com.rl.jdbc.utils;   import java.util.Date;   publicclass Person {       private Integer id;         private String name;         private String address;         private Date birthday;       public Integer getId() {         returnid;     }       publicvoid setId(Integer id) {         this.id = id;     }       public String getName() {         returnname;     }       publicvoid setName(String name) {         this.name = name;     }       public String getAddress() {         returnaddress;     }       publicvoid setAddress(String address) {         this.address = address;     }       public Date getBirthday() {         returnbirthday;     }       publicvoid setBirthday(Date birthday) {         this.birthday = birthday;     }       @Override     public String toString() {         return"Person [id=" + id + ", name=" + name + ", address=" + address + ", birthday=" + birthday + "]\n";     } }

PersonDAO接口，定义person类于数据库中的一些方法

package com.rl.jdbc.dao; import java.util.List; import com.rl.jdbc.utils.Person; public interface PersonDAO {               public void savePerson(Person p);               public void updatePerson(Person p);               public Person getPersonById(Integer id);               public List<Person> listPerson(); }

PersonDaoImpl类主要是实现PersonDAO接口中的方法

package com.rl.jdbc.dao.impl; import java.sql.Date; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; import java.util.ArrayList; import java.util.List; import com.rl.jdbc.dao.PersonDAO; import com.rl.jdbc.utils.DBUtils; import com.rl.jdbc.utils.Person; public class PersonDaoImpl implements PersonDAO {        /**         * 將person的屬性值寫入數據庫中         */        @Override        public void savePerson(Person p) {               //要執行的sql语句               String sql = "insert into person values(personid.nextval,?,?,?)";               //获得预编译对象               PreparedStatement ps = DBUtils.getPrepare(sql);               try {                      ps.setString(1, p.getName());                      ps.setString(2, p.getAddress());                      ps.setDate(3, new Date(p.getBirthday().getTime()));                      int count = ps.executeUpdate();                      System.out.println("数据库插入数据");               } catch (SQLException e) {                      e.printStackTrace();               } finally{                      //关闭资源                      DBUtils.closeUpdate(ps);               }        }               /**         * 对数据库中的person表进行修改         */        @Override        public void updatePerson(Person p) {               String sql = "update person t set t.id = ?,t.name = ?,t.address = ?, t.birthday = ? ";               PreparedStatement ps = DBUtils.getPrepare(sql);               try {                      ps.setInt(1, p.getId());                      ps.setString(2, p.getName());                      ps.setString(3, p.getAddress());                      ps.setDate(4, new Date(p.getBirthday().getTime()));                      int count = ps.executeUpdate();                      System.out.println("数据已经修改成功");               } catch (SQLException e) {                      e.printStackTrace();               } finally{                      DBUtils.closeUpdate(ps);               }                      }        /**         * 按指定的ID获取person表的一行数据，并传入到返回的一个person对象属性中         */        @Override        public Person getPersonById(Integer id) {               String sql = "select * from person t where t.id = ?";               PreparedStatement ps = DBUtils.getPrepare(sql);               ResultSet rs = null;               Person p = new Person();               try {                      ps.setInt(1, id);                      //获得结果集对象                      rs = ps.executeQuery();                      //游标向下移动                      rs.next();                      //获取结果集对象中的值                      Integer personid = rs.getInt("id");                      String name = rs.getString("name");                      String address = rs.getString("address");                      java.util.Date birthday = rs.getDate("birthday");                                           //将结果集中的集写入到Person对象中                      p.setId(personid);                      p.setName(name);                      p.setAddress(address);                      p.setBirthday(birthday);                      System.out.println("数据已写入Person对象中");               } catch (SQLException e) {                      e.printStackTrace();               } finally{                      DBUtils.closeQuery(rs);               }                             return p;        }        /**         * 查询Person表所有的数据放入返回的Person集合中         */        @Override        public List<Person> listPerson() {               String sql = "select * from person";               PreparedStatement ps = DBUtils.getPrepare(sql);               ResultSet rs = null;               //创建Person对象集合               List<Person> listPerson = new ArrayList<Person>();               Person p = new Person();               try {                      //获得结果集对象                      rs = ps.executeQuery();                      //定义计算插入数据数量的变量                      int i = 0;                      //循环游标向下移动                      while(rs.next()){                             //获取结果集对象中的值                             Integer personid = rs.getInt("id");                             String name = rs.getString("name");                             String address = rs.getString("address");                             java.util.Date birthday = rs.getDate("birthday");                                                         //将结果集中的集写入到Person对象中                             p.setId(personid);                             p.setName(name);                             p.setAddress(address);                             p.setBirthday(birthday);                             listPerson.add(p);                             i++;                             System.out.println(i + "条数据已写入Person对象中并且添加到集合中");                      }               } catch (SQLException e) {                      e.printStackTrace();               } finally{                      DBUtils.closeQuery(rs);               }                             return listPerson;        } }

PersonTest类为了测试以上类功能是否能正常运转

package com.rl.jdbc.test;   import java.util.Date; import java.util.List;   import com.rl.jdbc.dao.impl.PersonDaoImpl; import com.rl.jdbc.utils.Person;   publicclass PersonTest {       publicstaticvoid main(String[] args) {         PersonDaoImpl pd = new PersonDaoImpl();         Person p = new Person();         //p.setId(1);         p.setName("李昆鹏");         p.setAddress("地球之上");         p.setBirthday(new Date());         //插入数据         //pd.savePerson(p);         //修改数据         //pd.updatePerson(p);         //给出指定的ID从数据库中获取数据到person对象         //p = pd.getPersonById(1);         //System.out.println(p);           //将数据库Person表中所有的数据写入Person集合中         List<Person> list = pd.listPerson();         System.out.println(list);     } }