servlet-mvc手写（小型）

dao：

package dao.imp;

import java.lang.reflect.Field;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;

public abstract class BaseDAO<T> {
    public final String DRIVER = "com.mysql.cj.jdbc.Driver" ;
    public final String URL = "jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=utf-8&useSSL=false";
    public final String USER = "root";
    public final String PWD = "110120" ;

    protected Connection conn ;
    protected PreparedStatement psmt ;
    protected ResultSet rs ;

    //T的Class对象
    private Class entityClass ;

    public BaseDAO(){
        //getClass() 获取Class对象，当前我们执行的是new FruitDAOImpl() , 创建的是FruitDAOImpl的实例
        //那么子类构造方法内部首先会调用父类（BaseDAO）的无参构造方法
        //因此此处的getClass()会被执行，但是getClass获取的是FruitDAOImpl的Class
        //所以getGenericSuperclass()获取到的是BaseDAO的Class
        Type genericType = getClass().getGenericSuperclass();
        //ParameterizedType 参数化类型
        Type[] actualTypeArguments = ((ParameterizedType) genericType).getActualTypeArguments();
        //获取到的<T>中的T的真实的类型
        Type actualType = actualTypeArguments[0];
        try {
            entityClass = Class.forName(actualType.getTypeName());
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }

    protected Connection getConn(){
        try {
            //1.加载驱动
            Class.forName(DRIVER);
            //2.通过驱动管理器获取连接对象
            return DriverManager.getConnection(URL, USER, PWD);
        } catch (ClassNotFoundException | SQLException e) {
            e.printStackTrace();
        }
        return null ;
    }

    protected void close(ResultSet rs , PreparedStatement psmt , Connection conn){
        try {
            if (rs != null) {
                rs.close();
            }
            if(psmt!=null){
                psmt.close();
            }
            if(conn!=null && !conn.isClosed()){
                conn.close();
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    //给预处理命令对象设置参数
    private void setParams(PreparedStatement psmt , Object... params) throws SQLException {
        if(params!=null && params.length>0){
            for (int i = 0; i < params.length; i++) {
                psmt.setObject(i+1,params[i]);
            }
        }
    }

    //执行更新，返回影响行数
    protected int executeUpdate(String sql , Object... params){
        boolean insertFlag = false ;
        insertFlag = sql.trim().toUpperCase().startsWith("INSERT");
        try {
            conn = getConn();
            if(insertFlag){
                psmt = conn.prepareStatement(sql,Statement.RETURN_GENERATED_KEYS);
            }else {
                psmt = conn.prepareStatement(sql);
            }
            setParams(psmt,params);
            int count = psmt.executeUpdate() ;

            if(insertFlag){
                rs = psmt.getGeneratedKeys();
                if(rs.next()){
                    return ((Long)rs.getLong(1)).intValue();
                }
            }

            return count ;
        } catch (SQLException e) {
            e.printStackTrace();
        }finally {
            close(rs,psmt,conn);
        }
        return 0;
    }

    //通过反射技术给obj对象的property属性赋propertyValue值
    private void setValue(Object obj ,  String property , Object propertyValue){
        Class clazz = obj.getClass();
        try {
            //获取property这个字符串对应的属性名 ， 比如 "fid"  去找 obj对象中的 fid 属性
            Field field = clazz.getDeclaredField(property);
            if(field!=null){
                field.setAccessible(true);
                field.set(obj,propertyValue);
            }
        } catch (NoSuchFieldException | IllegalAccessException e) {
            e.printStackTrace();
        }
    }

    //执行复杂查询，返回例如统计结果
    protected Object[] executeComplexQuery(String sql , Object... params){
        try {
            conn = getConn() ;
            psmt = conn.prepareStatement(sql);
            setParams(psmt,params);
            rs = psmt.executeQuery();

            //通过rs可以获取结果集的元数据
            //元数据：描述结果集数据的数据 , 简单讲，就是这个结果集有哪些列，什么类型等等

            ResultSetMetaData rsmd = rs.getMetaData();
            //获取结果集的列数
            int columnCount = rsmd.getColumnCount();
            Object[] columnValueArr = new Object[columnCount];
            //6.解析rs
            if(rs.next()){
                for(int i = 0 ; i<columnCount;i++){
                    Object columnValue = rs.getObject(i+1);     //33    苹果      5
                    columnValueArr[i]=columnValue;
                }
                return columnValueArr ;
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            close(rs,psmt,conn);
        }
        return null ;
    }

    //执行查询，返回单个实体对象
    protected T load(String sql , Object... params){
        try {
            conn = getConn() ;
            psmt = conn.prepareStatement(sql);
            setParams(psmt,params);
            rs = psmt.executeQuery();

            //通过rs可以获取结果集的元数据
            //元数据：描述结果集数据的数据 , 简单讲，就是这个结果集有哪些列，什么类型等等

            ResultSetMetaData rsmd = rs.getMetaData();
            //获取结果集的列数
            int columnCount = rsmd.getColumnCount();
            //6.解析rs
            if(rs.next()){
                T entity = (T)entityClass.newInstance();

                for(int i = 0 ; i<columnCount;i++){
                    String columnName = rsmd.getColumnName(i+1);            //fid   fname   price
                    Object columnValue = rs.getObject(i+1);     //33    苹果      5
                    setValue(entity,columnName,columnValue);
                }
                return entity ;
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InstantiationException e) {
            e.printStackTrace();
        } finally {
            close(rs,psmt,conn);
        }
        return null ;
    }


    //执行查询，返回List
    protected List<T> executeQuery(String sql , Object... params){
        List<T> list = new ArrayList<>();
        try {
            conn = getConn() ;
            psmt = conn.prepareStatement(sql);
            setParams(psmt,params);
            rs = psmt.executeQuery();

            //通过rs可以获取结果集的元数据
            //元数据：描述结果集数据的数据 , 简单讲，就是这个结果集有哪些列，什么类型等等

            ResultSetMetaData rsmd = rs.getMetaData();
            //获取结果集的列数
            int columnCount = rsmd.getColumnCount();
            //6.解析rs
            while(rs.next()){
                T entity = (T)entityClass.newInstance();

                for(int i = 0 ; i<columnCount;i++){
                    String columnName = rsmd.getColumnName(i+1);            //fid   fname   price
                    Object columnValue = rs.getObject(i+1);     //33    苹果      5
                    setValue(entity,columnName,columnValue);
                }
                list.add(entity);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InstantiationException e) {
            e.printStackTrace();
        } finally {
            close(rs,psmt,conn);
        }
        return list ;
    }
}

package dao.imp;

public class Fruit {
    private Integer fid ;
    private String fname ;
    private Integer price ;
    private Integer fcount ;
    private String remark ;

    public Fruit(){}

    public Fruit(Integer fid, String fname, Integer price, Integer fcount, String remark) {
        this.fid = fid;
        this.fname = fname;
        this.price = price;
        this.fcount = fcount;
        this.remark = remark;
    }

    public Integer getFid() {
        return fid;
    }

    public void setFid(Integer fid) {
        this.fid = fid;
    }

    public String getFname() {
        return fname;
    }

    public void setFname(String fname) {
        this.fname = fname;
    }

    public Integer getPrice() {
        return price;
    }

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

    public Integer getFcount() {
        return fcount;
    }

    public void setFcount(Integer fcount) {
        this.fcount = fcount;
    }

    public String getRemark() {
        return remark;
    }

    public void setRemark(String remark) {
        this.remark = remark;
    }

    @Override
    public String toString() {
        return fid + "\t\t" + fname + "\t\t" + price +"\t\t" + fcount +"\t\t" + remark ;
    }
}

package dao.imp;



import java.util.List;

public interface FruitDAO {
    //获取指定页码的库存列表信息 每页显示五条
    List<Fruit> getFruitList(String keyword ,Integer pageNo);

    //根据fid获取特定的水果库存信息
    Fruit getFruitByFid(Integer fid);

    //修改指定的库存记录
    void updateFruit(Fruit fruit);

    //根据fid删除指定的库存记录
    void delFruit(Integer fid);

    //添加新库存记录
    void addFruit(Fruit fruit);
    //获取总个数
    int getFruitCount(String keyword);
}

package dao.imp;



import java.util.List;

public class FruitDAOImpl extends BaseDAO<Fruit> implements FruitDAO {
    @Override
    public List<Fruit> getFruitList( String keyword,Integer pageNo) {
        return super.executeQuery("select * from t_fruit where fname like ? or remark like ? limit ?,5","%" +keyword+"%","%" +keyword+"%",(pageNo-1)*5);
    }

    @Override
    public Fruit getFruitByFid(Integer fid) {
        return super.load("select * from t_fruit where fid = ? " , fid);
    }

    @Override
    public void updateFruit(Fruit fruit) {
        String sql = "update t_fruit set fname = ? , price = ? , fcount = ? , remark = ? where fid = ? " ;
        super.executeUpdate(sql,fruit.getFname(),fruit.getPrice(),fruit.getFcount(),fruit.getRemark(),fruit.getFid());
    }

    @Override
    public void delFruit(Integer fid) {
        super.executeUpdate("delete from t_fruit where fid = ? " , fid) ;
    }

    @Override
    public void addFruit(Fruit fruit) {
        String sql = "insert into t_fruit values(0,?,?,?,?)";
        super.executeUpdate(sql,fruit.getFname(),fruit.getPrice(),fruit.getFcount(),fruit.getRemark());
    }

    @Override
    public int getFruitCount( String keyword) {
        return ((Long)super.executeComplexQuery("select count(*) from t_fruit where fname like ? or remark like ?","%" +keyword+"%","%" +keyword+"%")[0]).intValue();
    }

}
servlet类：

package Servlet;



import dao.imp.Fruit;
import dao.imp.FruitDAO;
import dao.imp.FruitDAOImpl;
import myssm.ViewBaseServlet;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;


public class AddServlet extends ViewBaseServlet {

    private FruitDAO fruitDAO = new FruitDAOImpl();

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.setCharacterEncoding("UTF-8");

        String fname = request.getParameter("fname");
        Integer price = Integer.parseInt(request.getParameter("price")) ;
        Integer fcount = Integer.parseInt(request.getParameter("fcount"));
        String remark = request.getParameter("remark");

        Fruit fruit = new Fruit(0,fname , price , fcount , remark ) ;

        fruitDAO.addFruit(fruit);

//        super.processTemplate("add",request,response);
        response.sendRedirect("index");
    }
}

package Servlet;



import dao.imp.Fruit;
import dao.imp.FruitDAO;
import dao.imp.FruitDAOImpl;
import myssm.ViewBaseServlet;
import util.StringUtil;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;
import java.util.List;

//Servlet从3.0版本开始支持注解方式的注册

public class IndexServlet extends ViewBaseServlet {
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req,resp);
    }

    @Override
    public void doGet(HttpServletRequest request , HttpServletResponse response)throws IOException, ServletException {
        request.setCharacterEncoding("UTF-8");
        HttpSession session = request.getSession() ;
        Integer pageNo = 1 ;

        String oper = request.getParameter("oper");
        //如果oper!=null 说明 通过表单的查询按钮点击过来的
        //如果oper是空的，说明 不是通过表单的查询按钮点击过来的

        String keyword = null ;
        if(StringUtil.isNotEmpty(oper) && "search".equals(oper)){
            //说明是点击表单查询发送过来的请求
            //此时，pageNo应该还原为1 ， keyword应该从请求参数中获取
            pageNo = 1 ;
            keyword = request.getParameter("keyword");
            if(StringUtil.isEmpty(keyword)){
                keyword = "" ;
            }
            session.setAttribute("keyword",keyword);
        }else{
            //说明此处不是点击表单查询发送过来的请求（比如点击下面的上一页下一页或者直接在地址栏输入网址）
            //此时keyword应该从session作用域获取
            String pageNoStr = request.getParameter("pageNo");
            if(StringUtil.isNotEmpty(pageNoStr)){
                pageNo = Integer.parseInt(pageNoStr);
            }
            Object keywordObj = session.getAttribute("keyword");
            if(keywordObj!=null){
                keyword = (String)keywordObj ;
            }else{
                keyword = "" ;
            }
        }

        session.setAttribute("pageNo",pageNo);

        FruitDAO fruitDAO = new FruitDAOImpl();
        List<Fruit> fruitList = fruitDAO.getFruitList(keyword , pageNo);

        session.setAttribute("fruitList",fruitList);

        //总记录条数
        int fruitCount = fruitDAO.getFruitCount(keyword);
        //总页数
        int pageCount = (fruitCount+5-1)/5 ;
        /*
        总记录条数       总页数
        1               1
        5               1
        6               2
        10              2
        11              3
        fruitCount      (fruitCount+5-1)/5
         */
        session.setAttribute("pageCount",pageCount);

        //此处的视图名称是 index
        //那么thymeleaf会将这个 逻辑视图名称 对应到 物理视图 名称上去
        //逻辑视图名称 ：   index
        //物理视图名称 ：   view-prefix + 逻辑视图名称 + view-suffix
        //所以真实的视图名称是：      /       index       .html
        super.processTemplate("index",request,response);
    }
}