js+jQuery+MVC三层架构实现用户管理模块+随机验证码

蔚落 2023-03-12 07:12 14阅读 0赞

### js+jQuery+MVC三层架构实现用户管理模块+随机验证码 ###

*   *   *  0. 环境准备
         *   *  0.1 依赖包 + jQuery库
             *  0.2 JDBC 配置文件 + 工具类
             *  0.3 bean 数据封装类
             *  0.4 通用 Servlet
         *  1. 登陆登出
         *   *  1.1 登陆
             *  1.2 登出
             *  1.3 输入校验：check.js
             *  1.4 随机验证码：validateCode.jsp
         *  2. 注册 C
         *  3. 查询 R
         *   *  3.1 分页查询
         *  4. 修改 U
         *  5. 删除 D
         *   *  5.1 单个删除
             *  5.2 批量删除
         *  6. 注解标记优化通用 Servlet 支持 json

### 0. 环境准备 ###

#### 0.1 依赖包 + jQuery库 ####

![环境准备：依赖包][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NpbmF0XzM2MTg0MDc1_size_16_color_FFFFFF_t_70]

#### 0.2 JDBC 配置文件 + 工具类 ####

c3p0.properties

c3p0.driverClass=com.mysql.jdbc.Driver
    c3p0.jdbcUrl=jdbc:mysql://localhost:3306/companydb
    c3p0.user=root
    c3p0.password=123456

JDBCUtils.java

public class JDBCUtils { 
        private static ComboPooledDataSource dataSource;
        static { 
            dataSource = new ComboPooledDataSource();
        }
        public static ComboPooledDataSource getDataSource() { 
            return dataSource;
        }
    }

JsonUtils.java

public class JsonUtils { 
        /** * 将 java 对象转换为 json 字符串，并返回 * @param object java对象 * @return json字符串 */
        public static String toJsonStr(Object object) throws JsonProcessingException { 
            return new ObjectMapper().writeValueAsString(object);
        }
        /** * 转换 java 对象为 json字符串，并写入到响应 * @param response HTTP响应 * @param object java对象 */
        public static void writeJsonStr(HttpServletResponse response, Object object) { 
            response.setContentType("application/json;charset=utf-8");
            try { 
                response.getWriter().write(toJsonStr(object));
            } catch (IOException e) { 
                e.printStackTrace();
            }
        }
    }

#### 0.3 bean 数据封装类 ####

User.java

public class User { 
        private Integer id;
        private String username;
        private String password;
    	// 构造、get、set、toString...
    }

PageBean.java - 分页查询封装页数相关信息

public class PageBean<T> { 
        private Integer currentPage; // 当前页数
        private Integer totalPage; // 总页数
        private Integer totalSize; // 总记录数
        private Integer pageSize; // 每页记录数
        private List<T> list; // 当前页数据 <T> 针对哪种数据
    	// 构造、get、set、toString...
    }

#### 0.4 通用 Servlet ####

BaseServlet.java

UserServlet.java

@WebServlet(name = "UserServlet", urlPatterns = "/user")
    public class UserServlet extends BaseServlet { 
        private UserService userService = new UserServiceImpl();
        // 方法：登陆、登出、注册、删除、修改、查询
    }

### 1. 登陆登出 ###

#### 1.1 登陆 ####

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
    <html>
    <head>
        <title>用户登陆</title>
        <script src="${pageContext.request.contextPath}/js/jquery-3.5.1.min.js"></script>
        <script src="${pageContext.request.contextPath}/js/check.js"></script>
    </head>
    <body>
    <a href="${pageContext.request.contextPath}/register.jsp">
        <button>注册用户</button>
    </a><br>
    <br>
    <span id="error" style="color: red">${errorMsg}</span>
    <form action="${pageContext.request.contextPath}/user" method="post" onsubmit="return checkInfo()">
        <input type="hidden" name="methodName" value="login">
        账户：<input type="text" name="username" id="username"> <br><br>
        密码：<input type="text" name="password" id="password"> <br><br>
        验证码:<input type="text" name="validateCode">
        <img id="validateCode" src="${pageContext.request.contextPath}/validateCode.jsp" onclick="refreshCode()">
        <br>
        <button type="submit">登陆</button>
    </form>
    </body>
    </html>

UserServlet.java

public String login(HttpServletRequest request, HttpServletResponse response) { 
            // 获取输入验证码
            String inputCode = request.getParameter("validateCode");
            String existCode = (String) request.getSession().getAttribute("key");
            if (!inputCode.equals(existCode)) { 
                // 验证码错误
                request.setAttribute("errorMsg", "验证码错误！");
                return "login.jsp";
            }
    
            User user = new User();
            try { 
                BeanUtils.populate(user, request.getParameterMap());
                User existUser = userService.login(user);
                if (null == existUser) { 
                    // 登陆失败
                    request.setAttribute("errorMsg", "账户或密码错误");
                    return "login.jsp";
                } else { 
                    // 登陆成功
                    request.getSession().setAttribute("existUser", existUser);
                    return "redirect:index.jsp";
                }
            } catch (Exception e) { 
                e.printStackTrace();
            }
            return "login.jsp";
        }

UserServiceImpl.java

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

UserDaoImpl.java

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

#### 1.2 登出 ####

index.jsp

<%--登陆状态：显示用户名，提供注销--%>
    <c:if test="${existUser != null}">
        欢迎回来，<span style="color: orange">${existUser.username}</span>
        <a href="${pageContext.request.contextPath}/user?methodName=logout">注销</a>
    
        <table id="tbl" border="1px" cellspacing="0px" cellpadding="15px" width="500px">
        </table>
        <button onclick="deleteUsers()">批量删除</button>
    </c:if>
    <%--不在登陆状态：提示登陆--%>
    <c:if test="${existUser == null}">
        您还没有登陆，<a href="${pageContext.request.contextPath}/login.jsp">请登陆</a>
    </c:if>

UserServlet.java

public String logout(HttpServletRequest request, HttpServletResponse response) { 
            request.getSession().invalidate();
            return "redirect:index.jsp";
        }

#### 1.3 输入校验：check.js ####

// 刷新验证码
    function refreshCode() { 
        console.log("refreshCode");
        // 因浏览器的缓存技术，故需欺骗浏览器，每次点击是一次新的图片生成
        $("#validateCode").attr("src", "${pageContext.request.contextPath}/../validateCode.jsp?" + Math.random());
    }
    
    // 表单校验 - 前端校验，不需要请求服务器
    function checkInfo() { 
        return checkNull("username") && checkRule("username") && checkUsernameExist() &&
            checkNull("password") && checkRule("password");
    }
    
    function checkNull(id) { 
        var val = $("#" + id).val();
        var reg = /^\s*$/;
        if (reg.test(val)) { 
            // 为空
            $("#error").html(id + "不能为空");
            return false;
        } else { 
            // 不为空
            return true;
        }
    }
    
    // 校验账户和密码
    function checkRule(id) { 
        var val = $("#" + id).val();
        var reg = /^[a-z0-9]{6,9}$/;
        if (reg.test(val)) { 
            return true;
        } else { 
            $("#error").html(id + "由小写字母+数字组成，长度6-9位");
            return false;
        }
    }
    
    /** * 校验用户是否存在 */
    function checkUsernameExist() { 
        var val = $("input[type='hidden']").val();
        if (val === "register") { 
            var username = $("#username").val();
            $.post("${pageContext.request.contextPath}/user", { 
                "methodName": "checkUsernameExist",
                "username": username
            }, function (data) { 
                if (data.flag) { 
                    $("#error").html("用户名已存在");
                    return false;
                } else { 
                    return true;
                }
            }, "json");
        }
    }

#### 1.4 随机验证码：validateCode.jsp ####

<%@ page language="java" contentType="text/html; charset=UTF-8"
             pageEncoding="UTF-8"%>
    <%@ page import="java.util.Random"%>
    <%@ page import="java.io.OutputStream"%>
    <%@ page import="java.awt.Color"%>
    <%@ page import="java.awt.Font"%>
    <%@ page import="java.awt.Graphics"%>
    <%@ page import="java.awt.image.BufferedImage"%>
    <%@ page import="javax.imageio.ImageIO"%>
    <%
        int width = 60;
        int height = 32;
        //创建图片对象
        BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
        Graphics g = image.getGraphics();
        //设置背景颜色
        g.setColor(new Color(0xDCDCDC));
        g.fillRect(0, 0, width, height);
        //设置边框
        g.setColor(Color.black);
        g.drawRect(0, 0, width - 1, height - 1);
        // create a random instance to generate the codes
        Random rdm = new Random();
        String hash1 = Integer.toHexString(rdm.nextInt());
        //画干扰线
        for (int i = 0; i < 50; i++) { 
            int x = rdm.nextInt(width);
            int y = rdm.nextInt(height);
            g.drawOval(x, y, 0, 0);
        }
        //生成四位随机验证码
        String capstr = hash1.substring(0, 4);
        session.setAttribute("key", capstr);
        System.out.println(capstr);
        g.setColor(new Color(0, 100, 0));
        g.setFont(new Font("Candara", Font.BOLD, 24));
        g.drawString(capstr, 8, 24);
        g.dispose();
        response.setContentType("image/jpeg");
        out.clear();
        out = pageContext.pushBody();
        OutputStream strm = response.getOutputStream();
        ImageIO.write(image, "jpeg", strm);
        strm.close();
    %>

### 2. 注册 C ###

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
    <html>
    <head>
        <title>注册页面</title>
        <script src="${pageContext.request.contextPath}/js/jquery-3.5.1.min.js"></script>
        <script src="${pageContext.request.contextPath}/js/check.js"></script>
    </head>
    <body>
    <span id="error" style="color: red">${errorMsg}</span>
    <form action="${pageContext.request.contextPath}/user" method="post" onsubmit="return checkInfo()">
        <input type="hidden" name="methodName" value="register">
        账户：<input type="text" name="username" id="username"> <br><br>
        密码：<input type="text" name="password" id="password"> <br><br>
        验证码:<input type="text" name="validateCode">
        <img id="validateCode" src="${pageContext.request.contextPath}/validateCode.jsp" onclick="refreshCode()">
        <br>
        <button type="submit">注册</button>
    </form>
    </body>
    </html>

UserServlet.java

public void checkUsernameExist(HttpServletRequest request, HttpServletResponse response) { 
            String username = request.getParameter("username");
            boolean flag = false;
            String msg = null;
            if (null != username) { 
                try { 
                    flag = userService.checkUsernameExist(username);
                    msg = flag ? "用户名已存在" : "用户名可用";
                } catch (Exception e) { 
                    e.printStackTrace();
                }
            }
            Map<String, Object> map = new HashMap<>();
            map.put("flag", flag);
            map.put("msg", msg);
            JsonUtils.writeJsonStr(response, map);
        }
        public String register(HttpServletRequest request, HttpServletResponse response) { 
            User user = new User();
            try { 
                BeanUtils.populate(user, request.getParameterMap());
                return userService.addUser(user) ? "redirect:login.jsp" : "register.jsp";
            } catch (Exception e) { 
                e.printStackTrace();
            }
            return "register.jsp";
        }

UserServiceImpl.java

@Override
        public boolean addUser(User user) throws Exception { 
            return userDao.addUser(user) == 1;
        }

UserDaoImpl.java

@Override
        public int addUser(User user) throws Exception { 
            return new QueryRunner(JDBCUtils.getDataSource()).update(
                    "insert into userinfo(username, password) values(?,?)",
                    user.getUsername(),
                    user.getPassword()
            );
        }

### 3. 查询 R ###

#### 3.1 分页查询 ####

index.jsp - 注意 jstl标签库、jQuer库、异步请求。

<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
    <%@ page contentType="text/html;charset=UTF-8" language="java" %>
    <html>
    <head>
        <title>首页</title>
        <style> a { text-decoration: none; } a:hover { text-decoration: underline; } </style>
        <script src="${pageContext.request.contextPath}/js/jquery-3.5.1.min.js"></script>
        <script> console.log("开始异步请求..."); /** * 分页查询用户列表 * @param currentPage 当前页数 */ function selectUserListByPage(currentPage) { // 异步加载列表数据 $.get("${pageContext.request.contextPath}/user", { "methodName": "selectUserListByPage", "currentPage": currentPage }, function (data) { console.log(data); var pageBean = data; // data就是 pageBean (js对象) var html = ""; html += "<tr>"; html += "<th><input type='checkbox'></th>"; html += "<th>ID</th>"; html += "<th>账户</th>"; html += "<th>密码</th>"; html += "<th>操作</th>"; html += "</tr>"; var list = pageBean.list; $(list).each(function (index) { html += "<tr>"; html += "<td style='text-align: center'><input type='checkbox' class='ids' value='" + this.id + "'></td>"; html += "<td>" + this.id + "</td>"; html += "<td>" + this.username + "</td>"; html += "<td>" + this.password + "</td>"; html += "<td>"; html += "<a href='javascript:void(0)' οnclick='deleteUser(" + this.id + ")'>删除</a> "; html += "<a href='${pageContext.request.contextPath}/user?methodName=toUpdateUser&id=" + this.id + "'>修改</a> "; html += "</td>"; html += "</tr>"; }); // 第1/10页 总记录数:100 每页显示10条 [首页][上一页][下一页][尾页] html += "<tr>"; html += "<td colspan='5' style='text-align: center'>"; html += "第" + pageBean.currentPage + "/" + pageBean.totalPage + "页 总数:" + pageBean.totalSize + " 每页" + pageBean.pageSize + "条"; if (pageBean.currentPage !== 1) { // 显示[首页]和[上一页] html += " [<a href='javascript:void(0)' οnclick='selectUserListByPage(1)'>首页</a>]"; html += " [<a href='javascript:void(0)' οnclick='selectUserListByPage(" + (pageBean.currentPage - 1) + ")'>上一页</a>]"; } if (pageBean.currentPage !== pageBean.totalPage) { // 显示[尾页]和[下一页] html += " [<a href='javascript:void(0)' οnclick='selectUserListByPage(" + (pageBean.currentPage + 1) + ")'>下一页</a>]"; html += " [<a href='javascript:void(0)' οnclick='selectUserListByPage(" + pageBean.totalPage + ")'>尾页</a>]"; } html += "</td>"; html += "</tr>"; $("#tbl").html(html); }, "json"); } /** * 删除用户 * @param id 用户编号 */ function deleteUser(id) { var flag = confirm("是否确认删除该用户？"); if (flag) { $.post("${pageContext.request.contextPath}/user", { "methodName": "deleteUser", "id": id }, function (data) { console.log(data); // 如果删除成功，刷新列表区域(查询1次)；删除失败，不错任何处理 if (data.flag) { selectUserListByPage(1); } }, "json"); } } /** * 批量删除用户 */ function deleteUsers() { var eles = $(".ids:checked"); if (eles.length === 0) { alert("请选中需要删除的选项"); } else { var ids = []; eles.each(function (index) { var id = $(this).val(); ids.push(id); }); var idsStr = ids.join(","); var flag = confirm("是否确认删除？"); if (flag) { $.post("${pageContext.request.contextPath}/user", { "methodName": "deleteUsers", "ids": idsStr }, function (data) { alert(data.msg); selectUserListByPage(1); }, "json"); } } } $(function () { selectUserListByPage(1); }); </script>
    </head>
    <body>
    
    <%--登陆状态：显示用户名，提供注销--%>
    <c:if test="${existUser != null}">
        欢迎回来，<span style="color: orange">${existUser.username}</span>
        <a href="${pageContext.request.contextPath}/user?methodName=logout">注销</a>
    
        <table id="tbl" border="1px" cellspacing="0px" cellpadding="15px" width="500px">
        </table>
        <button onclick="deleteUsers()">批量删除</button>
    </c:if>
    <%--不在登陆状态：提示登陆--%>
    <c:if test="${existUser == null}">
        您还没有登陆，<a href="${pageContext.request.contextPath}/login.jsp">请登陆</a>
    </c:if>
    
    </body>
    </html>

UserServlet.java

private Integer getCurrentPage(String currentPageStr) { 
            return Integer.valueOf(currentPageStr) == null ? 1 : Integer.parseInt(currentPageStr);
        }
    
        public void selectUserListByPage(HttpServletRequest request, HttpServletResponse response) { 
            String currentPageStr = request.getParameter("currentPage");
            Integer currentPage = getCurrentPage(currentPageStr);
            try { 
                PageBean<User> pageBean = userService.selectUserListByPage(currentPage);
                // 将 PageBean 转换成 json 字符串
                JsonUtils.writeJsonStr(response, pageBean);
            } catch (Exception e) { 
                e.printStackTrace();
            }
        }

UserServiceImpl.java

@Override
        public PageBean<User> selectUserListByPage(Integer currentPage) throws Exception { 
            PageBean<User> pageBean = new PageBean<>();
            // 当前页数
            pageBean.setCurrentPage(currentPage);
            // 总记录数
            Integer totalSize = userDao.getTotalSize();
            pageBean.setTotalSize(totalSize);
            // 每页记录数
            Integer pageSize = 4;
            pageBean.setPageSize(pageSize);
            // 总页数(没余数为整页，有余数页数+1)
            Integer totalPages = (totalSize%pageSize==0) ? (totalSize/pageSize) : (totalSize/pageSize+1);
            pageBean.setTotalPage(totalPages);
            // 当前页数据
            List<User> list = userDao.queryAllByLimit(pageSize*(currentPage-1), pageSize);
            pageBean.setList(list);
            return pageBean;
        }

UserDaoImpl.java

@Override
        public Integer getTotalSize() throws Exception { 
            return new QueryRunner(JDBCUtils.getDataSource()).query(
                    "select count(id) from userinfo",
                    new ScalarHandler<Long>()
            ).intValue();
        }
    
        @Override
        public List<User> queryAllByLimit(Integer begin, Integer pageSize) throws Exception { 
            return new QueryRunner(JDBCUtils.getDataSource()).query(
                    "select * from userinfo limit ?,?",
                    new BeanListHandler<>(User.class),
                    begin,
                    pageSize
            );
        }

### 4. 修改 U ###

update.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
    <html>
    <head>
        <title></title>
        <script src="${pageContext.request.contextPath}/js/jquery-3.5.1.min.js"></script>
        <script src="${pageContext.request.contextPath}/js/check.js"></script>
    </head>
    <body>
    <span id="error" style="color: red">${errorMsg}</span>
    <form action="${pageContext.request.contextPath}/user" method="post" onsubmit="return checkInfo()">
        <input type="hidden" name="methodName" value="update">
        新账户：<input type="text" name="username" id="username" value="${user.username}"> <br><br>
        新密码：<input type="text" name="password" id="password" value="${user.password}"> <br><br>
        验证码:<input type="text" name="validateCode">
        <img id="validateCode" src="${pageContext.request.contextPath}/validateCode.jsp" onclick="refreshCode()">
        <br>
        <button type="submit">修改</button>
    </form>
    </body>
    </html>

UserServlet.java

public String toUpdateUser(HttpServletRequest request, HttpServletResponse response) { 
            Integer id = Integer.parseInt(request.getParameter("id"));
            try { 
                User user = userService.selectUserById(id);
                if (null != user) { 
                    request.setAttribute("user", user); // 修改页显示当前信息，便于修改
                    return "update.jsp";
                }
            } catch (Exception e) { 
                e.printStackTrace();
            }
            return "redirect:index.jsp";
        }
    
        public String update(HttpServletRequest request, HttpServletResponse response) { 
            User user = new User();
            try { 
                BeanUtils.populate(user, request.getParameterMap());
                if (userService.updateUser(user)) { 
                    return "redirect:index.jsp";
                } else { 
                    request.setAttribute("errorMsg", "修改失败");
                    return "update.jsp";
                }
            } catch (Exception e) { 
                e.printStackTrace();
            }
            return "redirect:index.jsp";
        }

UserServiceImpl.java

@Override
        public User selectUserById(Integer id) throws Exception { 
            return userDao.selectUserById(id);
        }
    
        @Override
        public boolean updateUser(User user) throws Exception { 
            return userDao.updateUser(user) == 1;
        }

UserDaoImpl.java

@Override
        public User selectUserById(Integer id) throws Exception { 
            return new QueryRunner(JDBCUtils.getDataSource()).query(
                    "select * from userinfo where id=?",
                    new BeanHandler<>(User.class),
                    id
            );
        }
    
        @Override
        public int updateUser(User user) throws Exception { 
            return new QueryRunner(JDBCUtils.getDataSource()).update(
                    "update userinfo set username=?, password=? where id=?",
                    user.getUsername(),
                    user.getPassword(),
                    user.getId()
            );
        }

### 5. 删除 D ###

#### 5.1 单个删除 ####

index.jsp - 参考 分页查询。

UserServlet.java

public void deleteUser(HttpServletRequest request, HttpServletResponse response) { 
            Integer id = Integer.parseInt(request.getParameter("id"));
            boolean flag = false;
            String msg = null;
            try { 
                flag = userService.deleteUserById(id);
                msg = flag ? "删除成功" : "删除失败";
            } catch (Exception e) { 
                e.printStackTrace();
            }
            Map<String, Object> map = new HashMap<>();
            map.put("flag", flag);
            map.put("msg", msg);
            JsonUtils.writeJsonStr(response, map);
        }

UserServiceImpl.java

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

UserDaoImpl.java

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

#### 5.2 批量删除 ####

index.jsp - 参考 分页查询。

UserServlet.java

public void deleteUsers(HttpServletRequest request, HttpServletResponse response) { 
            String idsStr = request.getParameter("ids");
            String[] ids = idsStr.split(",");
            boolean flag = false;
            String msg = null;
            for (String id : ids) { 
                try { 
                    flag = userService.deleteUserById(Integer.parseInt(id));
                    if (!flag) { 
                        msg = "删除失败";
                        break;
                    } else { 
                        msg = "删除成功";
                    }
                } catch (Exception e) { 
                    e.printStackTrace();
                }
            }
            Map<String, Object> map = new HashMap<>();
            map.put("flag", flag);
            map.put("msg", msg);
            JsonUtils.writeJsonStr(response, map);
        }

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NpbmF0XzM2MTg0MDc1_size_16_color_FFFFFF_t_70 1]

### 6. 注解标记优化通用 Servlet 支持 json ###

MyResponseBody自定义注解

@Retention(RetentionPolicy.RUNTIME) // 运行时可被反射捕获该注解
    public @interface MyResponseBody { 
    }

UserServlet.java

@MyResponseBody
        public Object deleteUser(HttpServletRequest request, HttpServletResponse response) throws JsonProcessingException { 
            Integer id = Integer.parseInt(request.getParameter("id"));
            boolean flag = false;
            String msg = null;
            try { 
                flag = userService.deleteUserById(id);
                msg = flag ? "删除成功" : "删除失败";
            } catch (Exception e) { 
                e.printStackTrace();
            }
            Map<String, Object> map = new HashMap<>();
            map.put("flag", flag);
            map.put("msg", msg);
            //JsonUtils.writeJsonStr(response, map);
            //return JsonUtils.toJsonStr(map);
            return map;
        }
    
        @MyResponseBody
        public Object deleteUsers(HttpServletRequest request, HttpServletResponse response) throws JsonProcessingException { 
            String idsStr = request.getParameter("ids");
            String[] ids = idsStr.split(",");
            boolean flag = false;
            String msg = null;
            for (String id : ids) { 
                try { 
                    flag = userService.deleteUserById(Integer.parseInt(id));
                    if (!flag) { 
                        msg = "删除失败";
                        break;
                    } else { 
                        msg = "删除成功";
                    }
                } catch (Exception e) { 
                    e.printStackTrace();
                }
            }
            Map<String, Object> map = new HashMap<>();
            map.put("flag", flag);
            map.put("msg", msg);
            //JsonUtils.writeJsonStr(response, map);
            return JsonUtils.toJsonStr(map);
            //return map;
        }

BaseServlet.java 优化兼容 json 字符串

@WebServlet(name = "BaseServlet", urlPatterns = "/base")
    public class BaseServlet extends HttpServlet { 
        protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { 
            String methodName = request.getParameter("methodName");
            try { 
                Method method = this.getClass().getMethod(methodName, HttpServletRequest.class, HttpServletResponse.class);
                Object returnValue = (String) Objects.requireNonNull(method).invoke(this, request, response);
    
                /* 判断方法上是否有 @MyResponseBody 标记注解 */
                boolean present = method.isAnnotationPresent(MyResponseBody.class);
                if (present) { 
                    // 有该标记注解
                    if (returnValue.getClass() == String.class) { 
                        // 情况一：将返回值内容作为 json 类型的响应正文，响应给浏览器
                        response.setContentType("application/json;charset=utf-8");
                        response.getWriter().write(returnValue + "");
                    } else { 
                        // 情况二：将返回值内容作为 java 对象类型的响应正文，响应给浏览器
                        JsonUtils.writeJsonStr(response, returnValue);
                    }
                } else { 
                    // 没有该标记注解
                    String returnValueStr = (String) returnValue;
                    if (null != returnValue) { 
                        int index = returnValueStr.lastIndexOf(":");
                        if (-1 == index) { 
                            // 没有":"
                            request.getRequestDispatcher(returnValueStr).forward(request, response);
                        } else { 
                            // 有":"
                            String path = returnValueStr.substring(index + 1);
                            if (returnValueStr.startsWith("redirect")) { 
                                response.sendRedirect(request.getContextPath() + File.separator + path);
                            } else if (returnValueStr.startsWith("forward")) { 
                                request.getRequestDispatcher(path).forward(request, response);
                            }
                        }
                    }
                }
            } catch (Exception e) { 
                e.printStackTrace();
            }
        }
    
        protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { 
            doPost(request, response);
        }
    }

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NpbmF0XzM2MTg0MDc1_size_16_color_FFFFFF_t_70]: /images/20230312/16031b8c06bb40f4a771ddf278bbc2a8.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NpbmF0XzM2MTg0MDc1_size_16_color_FFFFFF_t_70 1]: /images/20230312/fa639b7a5ed04e819e6cb29d1ea1696c.png