Java第十三周心得体会

1.本周思维导图

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2.个人总结

操作域

• page域

<%
    //往pageContext域中存储了一个msg变量
    pageContext.setAttribute("msg" ,"hello page msg");
%>

<%
    //往pageContext域中存储了一个msg变量
    Object msg = pageContext.getAttribute("msg");
    System.out.println(msg);
%>

• request域

<%
    //定义变量的意义! 提高复用性！ 提高可维护性!
    //String name : 参数名称
    //Object value : 参数值
    //int scope : 操作的域
    pageContext.setAttribute("msg1","hello page1",PageContext.REQUEST_SCOPE);
    //请求转发
    request.getRequestDispatcher("/demo06.jsp").forward(request,response);
%>

<%
    //变量msg1定义到_jspService方法中
    Object msg1 = request.getAttribute("msg1");
    System.out.println("msg1 : "+msg1);

    Object msg11 = pageContext.getAttribute("msg1", PageContext.REQUEST_SCOPE);
    System.out.println(msg11);
%>

 

 

 

• session域

<%
    pageContext.setAttribute("msg2","hello page2",PageContext.SESSION_SCOPE);
%>

• application域

<%
    pageContext.setAttribute("msg3","hello page3",PageContext.APPLICATION_SCOPE);
%>

el获取域数据

• 获取page域数据

<%
　　pageContext.setAttribute("msg1","hello page1");
%>

　　${pageScope.msg1}

• 获取request域数据

<%
    request.setAttribute("msg1","hello page1");
%>

    ${requestScope.msg1}

• 获取session域数据

<%
    session.setAttribute("msg1","hello page1");
%>

    ${sessionScope.msg1}

• 获取application域数据

<%
    application.setAttribute("msg1","hello page1");
%>

    ${applicationScope.msg1}

el获取复杂域数据

• 获取数组

<%
    //数组静态初始化
    String[] msgs = {"获取","复杂","域"};
    pageContext.setAttribute("msgs",msgs);
%>
<%--jsp输出脚本--%>
<%=
    ((String[])pageContext.getAttribute("msgs"))[0]
%>
    ${msgs[1]}

• 获取List集合

<%
    List msgs1 = new ArrayList<>();
    msgs1.add("复杂的");
    msgs1.add("域数据");
    request.setAttribute("msgs1",msgs1);
%>

<%=
    ((List)request.getAttribute("msgs1")).get(0)
%>

    ${msgs1[1]}

• 获取map集合

<%
    HashMap map = new HashMap<>();
    map.put("username","白鸽");
    map.put("age",18);
    session.setAttribute("map",map);
%>

<%=
    ((HashMap)session.getAttribute("map")).get("username")
%>
    ${map.age}

• 获取java对象

<%
    User user = new User();
    user.setId(1);
    user.setUsername("黑鸦");
    user.setPassword("123456");
    application.setAttribute("user",user);
%>
<%=
    ((User)application.getAttribute("user")).getUsername()
%>

    ${user.password}

jstl标签库

• 使用taglib指令导入

<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>

<%
    int num = 1;
    request.setAttribute("num" , num);
%>


    num等于1



    num不等于1

• set标签
  • 向域对象(page域、request域、session域、application域)中存储数据

${msg}

• remove标签
  • 移除域对象中的数据

${msg}

• catch标签
  • 捕获jsp页面的异常，相当于try...catch，var：声明异常对象名称，比如：var="e" ，变量e就可以接收异常对象

    <%
        int num = 1 / 0;
    %>

${e}

• if标签
  • 条件判断

 
    num 等于 1 
 

 
    num 不等于 1

 

• forEach标签
  • 遍历集合或数组　begin：开始、end：结束、step：步数、var：元素名称、items：集合/数组
  • varStatus：元素状态对象    first：是否是第一个元素，last：是否是最后一个元素，current：当前元素，index：当前脚标

 
 ${num} 
 
<% 
    List strs = new ArrayList<>(); 
    strs.add("aaa"); 
    strs.add("bbb"); 
    strs.add("ccc"); 
    request.setAttribute("strs",strs); %> 
 
 
    ${strs[i]} 
 
 
 
    ${str}
 ${status.current} -- ${status.index} -- ${status.first} -- ${status.last}
 

 

• forToken标签
  • 分割字符串：items：要分割的字符串，delims：分割的规则，var：分割产生的元素

<%
    String msg1 = "aaa--bbb--ccc";
    request.setAttribute("msg1",msg1);
%>


    ${sonMsg}

jstl综合案例

• ProductDao

public class ProductDaoImpl implements ProductDao {
    @Override
    public List selectProductList() throws Exception {
        return new QueryRunner(JDBCUtils.getDataSource())
                .query("select * from tb_product",
                        new BeanListHandler(Product.class));
    }
 }

• ProductServlet

@WebServlet(name = "ProductServlet" ,urlPatterns = "/selectProductList")
public class ProductServlet extends HttpServlet {

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        ProductDao productDao = new ProductDaoImpl();
        try {
            List productList = productDao.selectProductList();
            System.out.println(productList);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request, response);
    }
}

• productList.jsp

    <%--循环之前，总价为0--%>
    
        <%--forEach标签，循环一次就是一个小计!--%>
        
    <%--循环之后，计算出总价--%>
    

    

        
ID
        
名称
        
单价
        
数量
        
小计
    
    

            
${product.id}
            
${product.name}
            
${product.price}
            
${product.count}
            
${product.price * product.count}
        
        
    

        

            总价：${total}元
        
    

BeanUtils框架的使用

• 注意

页面上的name属性值要和java对象中的属性名一致

自定义BeanUtils框架

• MyBeanUtils

public class MyBeanUtils {
    /**
     * 将map集合中的请求参数值封装到对象t中
     * @param t
     * @param map : 键：参数名称；值：一组参数值。
     * @param 
     */
    public static void populate(T t , Map map ){
        Class clazz = t.getClass();
        Field[] fields = clazz.getDeclaredFields();
        for (Field field : fields) {
            String fieldName = field.getName();
            String methodName = "set"+fieldName.substring(0,1).toUpperCase()+fieldName.substring(1);
            System.out.println(methodName);
            //获取对应的set方法
            try {
                Class type = field.getType();
                Method method = clazz.getMethod(methodName, type);
                if (null != method) {
                    //第二个参数：请求参数的值
                    //id、username、password、age
                    Object object = map.get(fieldName);
                    if (null != object) {
                        String[] strs = (String[]) object;
                        if (type.getName().equals("java.lang.Integer")) {
                            method.invoke(t,Integer.parseInt(strs[0]));
                        } else {
                            method.invoke(t,strs[0]);
                        }
                    }
                }
            } catch (Exception e) {
              　　throw new MyNoSuchMethodException("field " + fieldName + " there is no setter method!!!");
            }
        }
    }
}

• MyNoSuchMethodException

public class MyNoSuchMethodException extends RuntimeException{

    public MyNoSuchMethodException() {
    }

    public MyNoSuchMethodException(String message) {
        super(message);
    }

    public MyNoSuchMethodException(String message, Throwable cause) {
        super(message, cause);
    }

    public MyNoSuchMethodException(Throwable cause) {
        super(cause);
    }

    public MyNoSuchMethodException(String message, Throwable cause, boolean enableSuppression, boolean writableStackTrace) {
        super(message, cause, enableSuppression, writableStackTrace);
    }
}

三层结构优化登录案例

• UserDao

 @Override
    public User login(User inputUser) throws Exception {
        return new QueryRunner(JDBCUtils.getDataSource())
                .query("select * from tb_user where username = ? and password = ?",
                        new BeanHandler(User.class),
                        inputUser.getUsername(),
                        inputUser.getPassword());
    }

• UserService

 @Override
    public User login(User inputUser) throws Exception {
        UserDao userDao = new UserDaoImpl();
        return userDao.login(inputUser);
    }

• UserServlet类的login方法

 private UserService userService = new UserServiceImpl();

    public String login(HttpServletRequest request,HttpServletResponse response){
        User inputUser = new User();
        //将请求参数封装到inputUser中
        try {
            BeanUtils.populate(inputUser,request.getParameterMap());
            User existUser = userService.login(inputUser);
            //没有异常有返回值
            if (null != existUser) {
                //登录成功 , 修改登录状态，跳转到首页
                request.getSession().setAttribute("existUser",existUser);
                return "redirect:/index.jsp";
            } else {
                //登录失败 ，记录错误信息，跳转到登录页面
                request.setAttribute("errorMsg","账户或密码错误");
                return "/login.jsp";
            }
        } catch (Exception e) {
            e.printStackTrace();
        }

        //有异常，应该有返回值 。意味着登录失败，返回登录页面，重新登录
        return "/login.jsp";
    }

• login.jsp

${errorMsg}


    
    账户:

    密码:

    登录

• index.jsp

  <%--
  在登录状态
    显示用户名
  --%>
    
        欢迎回来~~~  ${existUser.username}  注销
    

  <%--
  不在登录状态
     提示登录
  --%>
    
        您还没有登录，请登录
    

三层结构优化用户列表案例

• UserDao

 @Override
    public List selectUserList() throws Exception {
        return new QueryRunner(JDBCUtils.getDataSource())
                .query("select * from tb_user",
                        new BeanListHandler(User.class));
    }

• UserServlet类的selectUserList方法

public String selectUserList(HttpServletRequest request,HttpServletResponse response) throws Exception {
        List userList = userService.selectUserList();
        request.getSession().setAttribute("userList",userList);
        return "/index.jsp";
}

• index.jsp

  <%--
  在登录状态
    显示用户名
  --%>
    
        欢迎回来~~~  ${existUser.username}  注销
        <%--显示用户列表--%>
        
                

            

                
ID
                
账户
                
密码
            

            

                    
${user.id}
                    
${user.username}
                    
${user.password}
                
            


        
    

  <%--
  不在登录状态
     提示登录
  --%>
    
        您还没有登录，请登录
    

登录校验案例

@WebFilter(filterName = "LoginFilter" ,urlPatterns = "/*")
public class LoginFilter implements Filter {
    public void destroy() {
    }

    public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws ServletException, IOException {
        System.out.println("LoginFilter doFilter");
        HttpServletRequest request = (HttpServletRequest) req;
        HttpServletResponse response = (HttpServletResponse) resp;
        //登录校验
        String requestURI = request.getRequestURI();
        String methodName = request.getParameter("methodName");
        if (requestURI.contains("login") || ( methodName != null && methodName.equals("login"))) {
            //和登录相关的资源，直接放行
            chain.doFilter(req, resp);
        } else {
            //和登录无关的资源
            Object existUser = request.getSession().getAttribute("existUser");
            if (null == existUser) {
                //不在登录状态，跳转到login.jsp
                response.sendRedirect("/day64/login.jsp");
            }  else {
                //在登录状态，直接放行
                chain.doFilter(req, resp);
            }
        }
    }

    public void init(FilterConfig config) throws ServletException {

    }
}

三层结构优化删除用户案例

• UserDao

 @Override
    public int deleteUserById(Integer id) throws Exception {
        return new QueryRunner(JDBCUtils.getDataSource())
                .update("delete from tb_user where id = ?",id);
}

• UserService

 @Override
    public boolean deleteUserById(Integer id) throws Exception {
        return userDao.deleteUserById(id) == 1;
}

• UserServlet的deleteUserById方法

public String deleteUserById(HttpServletRequest request,HttpServletResponse response){
        Integer id = Integer.parseInt(request.getParameter("id"));
        try {
            boolean flag = userService.deleteUserById(id);
        } catch (Exception e) {
            e.printStackTrace();
        }
        //获取用户列表
        return "/user?methodName=selectUserList";
 }

• index.jsp

    
        ${user.id}
        ${user.username}
        ${user.password}
        
            删除
        
    

三层结构优化修改用户案例

• UserDao

 @Override
    public void updateUserById(User inputUser) throws Exception {
        new QueryRunner(JDBCUtils.getDataSource())
                .update("update tb_user set username = ? , password = ? where id = ?",
                        inputUser.getUsername(),
                        inputUser.getPassword(),
                        inputUser.getId());
}

• UserServlet类toUpdateUserById方法

 public String toUpdateUserById(HttpServletRequest request,HttpServletResponse response) {
        Integer id = Integer.parseInt(request.getParameter("id"));
        User user = null;
        try {
            user = userService.selectUserById(id);
        } catch (Exception e) {
            e.printStackTrace();
        }
        request.setAttribute("user",user);
        return "/updateUser.jsp";

 }

• UserServlet类updateUserById方法

    public String updateUserById(HttpServletRequest request,HttpServletResponse response){
        User inputUser = new User();
        try {

            BeanUtils.populate(inputUser,request.getParameterMap());
            userService.updateUserById(inputUser);
            //修改成功
            return "/user?methodName=selectUserList";
        } catch (Exception e) {
            e.printStackTrace();
        }
        request.setAttribute("errorMsg","修改失败");
        //修改失败
        return "/user?methodName=toUpdateUserById&id="+inputUser.getId();
    }

• updateUser.jsp

${errorMsg}


    
    
    账户:

    密码:

    修改

分页查询代码

• UserDao

public class UserDaoImpl implements UserDao {
    @Override
    public Integer selectTotalSize() throws Exception {
        return new QueryRunner(JDBCUtils.getDataSource())
                .query("select * from tb_user",
                        new BeanListHandler(User.class))
                .size();
    }

    @Override
    public List selectUserListByPage(Integer begin, Integer pageSize) throws Exception {
        return new QueryRunner(JDBCUtils.getDataSource())
                .query("select * from tb_user limit ? , ?" ,
                        new BeanListHandler(User.class),
                        begin,
                        pageSize);
    }
}

• UserServlet

 public String selectUserListByPage(HttpServletRequest request, HttpServletResponse response){
        String currentPageStr = request.getParameter("currentPage");
        Integer currentPage = getCurrentPage(currentPageStr);
        //调用UserService，传递currentPage
        try {
            PageBean pageBean = userService.selectUserListByPage(currentPage);
            System.out.println(pageBean);
            request.setAttribute("pageBean",pageBean);
            //转发到用户列表页面
            return "/userList.jsp";
        } catch (Exception e) {
            e.printStackTrace();
        }
        return "/index.jsp";

}

• UserService

 public PageBean selectUserListByPage(Integer currentPage) throws Exception {
        PageBean pageBean = new PageBean<>();
        //    currentPage;当前页数
        pageBean.setCurrentPage(currentPage);
        //    totalSize;总记录数
        UserDao userDao = new UserDaoImpl();
        Integer totalSize = userDao.selectTotalSize();
        pageBean.setTotalSize(totalSize);
        //    pageSize;每页记录数
        Integer pageSize = 3;
        pageBean.setPageSize(pageSize);
        //    totalPage:总页数  = 总记录数 / 每页记录数
        Integer totalPage = ( totalSize % pageSize == 0 ) ? ( totalSize / pageSize ) : (totalSize / pageSize + 1 ) ;
        pageBean.setTotalPage(totalPage);
        //    list;当前页数据
        //select * from tb_user limit ? , ?
        //第一个? : 开始脚标 = (当前页数 - 1) * 每页记录数
        //第二个? : 查询多少个 (每页记录数) pageSize
        Integer begin = (currentPage - 1) * pageSize;
        List list = userDao.selectUserListByPage(begin, pageSize);
        pageBean.setList(list);
        return pageBean;
    }

• userList.jsp

        
    <%--分页工具条--%>
    

    

        
ID
        
账户
        
密码
    
    

            
${user.id}
            
${user.username}
            
${user.password}
        
    

        

            第${pageBean.currentPage}/${pageBean.totalPage}页
            总记录数:${pageBean.totalSize}
            每页显示${pageBean.pageSize}条

            
                 
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