前后端交互案例分析

综合练习：
    1. 简单功能
        1. 列表查询
        2. 登录
        3. 添加
        4. 删除
        5. 修改
        
    2. 复杂功能
        1. 删除选中
        2. 分页查询
        3. 复杂条件查询

添加功能：

删除功能： 

 修改功能：

删除选中功能：

 分页查询功能：

复杂条件查询功能 

一些类的实现

FindUserByPageServlet：

 UserService userService = new UserServiceImpl();
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.setCharacterEncoding("utf-8");
//        System.out.println("已进入1");
        //1.获取参数
        String currentPage = request.getParameter("currentPage");//当前页码
        String rows = request.getParameter("rows");//每页显示的条数
 
        if (currentPage ==null || "".equals(currentPage) ){
            currentPage = "1";
        }
        if (rows ==null || "".equals(rows)){
            rows = "5";
        }
 
        //条件查询参数
        Map<String, String[]> condition = request.getParameterMap();
 
        PageBean<User> pb =userService.findUserBypage(currentPage,rows,condition);
 
        //存储转发
        request.setAttribute("pb",pb);
        request.setAttribute("condition",condition);
 
        request.getRequestDispatcher("/list.jsp").forward(request,response);
 
    }
 
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doPost(request, response);
    }

UserServiceImpl：

public class UserServiceImpl implements UserService {
 
    UserDao userDao = new UserDaoImpl();
    @Override
    public List<User> findAll() {
        
        return userDao.findAll();
    }
 
    @Override
    public int addUser(User user) {
        return userDao.addUder(user);
    }
 
    @Override
    public int updateUser(User user) {
        return userDao.updateUser(user);
 
    }
 
    @Override
    public User queryByid(int id) {
        return userDao.queryByid(id);
    }
 
    @Override
    public void delstlected(String[] uid) {
 
        if (uid != null && uid.length != 0){
            for (String u: uid){
//                System.out.println("u:"+u);
                userDao.deleteUser(Integer.parseInt(u));
            }
        }
 
    }
 
    @Override
    public PageBean<User> findUserBypage(String currentPage1, String rows1, Map<String, String[]> condition) {
 
        int currentPage = Integer.parseInt(currentPage1);
        int rows = Integer.parseInt(rows1);
 
        if (currentPage < 1){
            currentPage =1;
        }
 
        PageBean<User> pb = new PageBean<User>();
 
 
        pb.setRows(rows);//每页显示的个数
 
        //查询数据库中总条数
        int totalCount = userDao.findTetalCount(condition);
        pb.setTotalCount(totalCount);//总条数
 
        //开始索引
        int start = (currentPage-1) * rows;
        //查询list集合
        List<User> list = userDao.findByPage(start,rows,condition);
        pb.setList(list);//list集合
 
 
 
        int totalPage = totalCount%rows == 0 ? totalCount/rows : totalCount/rows +1;
        if (currentPage >= totalPage+1){
            currentPage = totalPage;
        }
 
        pb.setTotalPage(totalPage);//总页码数
 
        pb.setCurrentPage(currentPage);//当前页数
 
 
 
        return pb;
    }
}

UserDaoImpl：

public class UserDaoImpl implements UserDao {
 
    private JdbcTemplate template = new JdbcTemplate(JDBCUtils.getDataSource());
 
    @Override
    public List<User> findAll() {
        List<User> users = null;
        try {
            String sql = "select * from user";
            users = template.query(sql, new BeanPropertyRowMapper<User>(User.class));
            return users;
        }catch (Exception e){
            return users;
        }
    }
 
    @Override
    public User login(User user) {
        try {
            String sql = "select * from user where username=?&&password=?";
            User user1 = template.queryForObject(sql, new BeanPropertyRowMapper<User>(User.class), user.getUsername(), user.getPassword());
            return user1;
        }catch (Exception e){
            return null;
        }
 
    }
 
    @Override
    public int addUder(User user) {
        try{
            String sql = "insert into user values(null,?,?,?,?,?,?,null,null)";
            int update = template.update(sql, user.getName(), user.getGender(), user.getAge(), user.getAddress(), user.getQq(), user.getEmail());
            return update;
        }catch (Exception e){
            return 0;
        }
    }
 
    @Override
    public int deleteUser(int id) {
        try{
            String sql ="delete from user where id=? ";
            int update = template.update(sql, id);
            return update;
        }catch (Exception e){
            return 0;
        }
    }
 
    @Override
    public User queryByid(int id) {
        try{
            String sql ="select * from user where id=?";
            User user = template.queryForObject(sql, new BeanPropertyRowMapper<User>(User.class), id);
            return user;
        }catch (Exception e){
            return null;
        }
    }
 
    @Override
    public int updateUser(User user) {
        try{
            String sql ="update user set gender=?,age=?,address=?,qq=?,email=? where id=?";
            int update = template.update(sql, user.getGender(), user.getAge(), user.getAddress(), user.getQq(), user.getEmail(),user.getId());
            return update;
        }catch (Exception e){
            return 0;
        }
    }
 
    @Override
    public int findTetalCount(Map<String, String[]> condition) {
        try{
            String sql = "select count(*) from user where 1 = 1 ";
            StringBuilder sb = new StringBuilder(sql);
            Set<String> strings = condition.keySet();
            List<Object> parms = new ArrayList<>();
            for (String key: strings){
 
                if ("currentPage".equals(key) || "rows".equals(key)){
                    continue;
                }
 
                String value = condition.get(key)[0];
                System.out.println("value"+value);
 
                if (value != null && !"".equals(value)){
                    sb.append(" and "+key+" like ? ");
                    parms.add("%"+value+"%");//?条件里面的值
                }
            }
            System.out.println(sb.toString());
            System.out.println(parms);
            //parms.toArray() 转为数组
            return template.queryForObject(sb.toString(), Integer.class,parms.toArray());
        }catch (Exception e){
            return 0;
        }
    }
 
    @Override
    public List<User> findByPage(int start, int rows, Map<String, String[]> condition) {
        try{
            String sql ="select * from user where 1 = 1 ";
 
//            String sql = "select count(*) from user where 1 = 1 ";
            StringBuilder sb = new StringBuilder(sql);
            Set<String> strings = condition.keySet();
            List<Object> parms = new ArrayList<>();
            for (String key: strings){
 
                if ("currentPage".equals(key) || "rows".equals(key)){
                    continue;
                }
 
                String value = condition.get(key)[0];
                System.out.println("value"+value);
 
                if (value != null && !"".equals(value)){
                    sb.append(" and "+key+" like ? ");
                    parms.add("%"+value+"%");//?条件里面的值
                }
            }
 
            sb.append(" limit ?,? ");
            parms.add(start);
            parms.add(rows);
 
 
            return template.query(sb.toString(), new BeanPropertyRowMapper<User>(User.class), parms.toArray());
        }catch (Exception e){
            return null;
        }
    }
}