10.24

跟着模板敲代码（1）

项目的架构

 Dao为数据持久层，用于实现数据库的增删改查

entity为javabean用于封装数据库中的对象

servlet为前端数据的处理层

jsp为前端页面

现在来一个个实现

BaseDao用于链接mysql数据库

public class BaseDao {
    static {
        try{
            Class.forName("com.mysql.jdbc.Driver");
        }catch (ClassNotFoundException e){
            e.printStackTrace();
        }
    }

    public static Connection getConnection(){
        Connection conn=null;
        try{
            String url="jdbc:mysql://localhost:3306/fruit";

            String username="root";

            String password="1234";
            conn= DriverManager.getConnection(url,username,password);
        }catch (SQLException e) {
            e.printStackTrace();
        }
        return conn;
    }
    public static  void closeConnection(Connection conn, PreparedStatement pstmt, ResultSet rs){
        try {
            if(rs!=null){
                rs.close();
            }
            pstmt.close();
            conn.close();

        }catch (SQLException e){
            e.printStackTrace();
        }
    }

}

Fruit为实体类

public class Fruit {
    public Integer id;

    public String name;
    public Integer price;
    public Integer weight;

    public  String location;

    public Fruit() {
    }

    public Fruit(Integer id, String name, Integer price, Integer weight, String location) {
        this.id = id;
        this.name = name;
        this.price = price;
        this.weight = weight;
        this.location = location;
    }

    public Fruit(String name, Integer price, Integer weight, String location) {
        this.name = name;
        this.price = price;
        this.weight = weight;
        this.location = location;
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Integer getPrice() {
        return price;
    }

    public void setPrice(Integer price) {
        this.price = price;
    }

    public Integer getWeight() {
        return weight;
    }

    public void setWeight(Integer weight) {
        this.weight = weight;
    }

    public String getLocation() {
        return location;
    }

    public void setLocation(String location) {
        this.location = location;
    }
}

接着实现增删改查

public class FruitDao {
    /**
     * 查看全部
     * @return
     */
    public List<Fruit> selectAll(){
        List<Fruit> list=new ArrayList<>();
        Connection conn = BaseDao.getConnection();
        PreparedStatement pstmt=null;
        ResultSet rs=null;
        try {
            pstmt=conn.prepareStatement("select * from fruit");
            rs=pstmt.executeQuery();
            while (rs.next()){
                Fruit f=new Fruit(rs.getInt(1),rs.getString(2),rs.getInt(3),rs.getInt(4),rs.getString(5));
                list.add(f);
            }
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            BaseDao.closeConnection(conn,pstmt,rs);
        }
        return list;
    }

    /**
     * 增加
     * @param f
     * @return
     */
    public int insert(Fruit f ){
        int count=0;
        Connection conn = BaseDao.getConnection();
        PreparedStatement pstmt=null;
        ResultSet rs=null;
        try {
            pstmt=conn.prepareStatement("insert into fruit(name,price,weight,location) values (?,?,?,?)");
//            rs=pstmt.executeQuery();
            pstmt.setString(1,f.getName());
            pstmt.setInt(2,f.getPrice());
            pstmt.setInt(3,f.getWeight());
            pstmt.setString(4,f.getLocation());
            count=pstmt.executeUpdate();
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            BaseDao.closeConnection(conn,pstmt,rs);
        }
        return count;
    }


    /**
     * 根据id进行查询
     * @param id
     * @return
     */
    public Fruit selectById(int id){
        Fruit f=new Fruit();
        Connection conn = BaseDao.getConnection();
        PreparedStatement pstmt=null;
        ResultSet rs=null;
        try {
            pstmt=conn.prepareStatement("select * from fruit where id=?");
            pstmt.setInt(1,id);
            rs=pstmt.executeQuery();
            while (rs.next()){
                f=new Fruit(rs.getInt(1),rs.getString(2),rs.getInt(3),rs.getInt(4),rs.getString(5));
//                pstmt.setInt(1,id);
            }
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            BaseDao.closeConnection(conn,pstmt,rs);
        }
        return f;
    }


    public int update(Fruit f ){
        int count=0;
        Connection conn = BaseDao.getConnection();
        PreparedStatement pstmt=null;
        ResultSet rs=null;
        try {
            pstmt=conn.prepareStatement("update fruit set name=? , price=? , weight=? , location=? where id=?");

            pstmt.setString(1,f.getName());
            pstmt.setInt(2,f.getPrice());
            pstmt.setInt(3,f.getWeight());
            pstmt.setInt(5,f.getId());
            pstmt.setString(4,f.getLocation());
            count=pstmt.executeUpdate();
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            BaseDao.closeConnection(conn,pstmt,rs);
        }
        return count;
    }

    /**
     * 根据id进行删除
     * @param id
     * @return
     */
    public int delete(int id){
        int count=0;
        Connection conn = BaseDao.getConnection();
        PreparedStatement pstmt=null;
        ResultSet rs=null;
        try {
            pstmt=conn.prepareStatement("delete from fruit where id=?");
            pstmt.setInt(1,id);
            count=pstmt.executeUpdate();
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            BaseDao.closeConnection(conn,pstmt,rs);
        }
        return count;
    }


}

剩下的明天继续