Java的serverlet查询数据，返回前端json数据

缺乏、安全感 2022-10-16 04:54 238阅读 0赞

# 先上代码 #

serverlet类

@WebServlet("/user/findAll")
    public class UserFindAll extends HttpServlet { 
        @Override
        protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { 
            this.doPost(req,resp);
        }
    
        @Override
        protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { 
            //do something...
            resp.setContentType("text/json; charset=utf-8"); //设置请求头，避免中文乱码
            resp.setHeader("Access-Control-Allow-Origin","*"); //设置跨域
            users users = new usersImpl(); //查询所有的用户
    
            List<User> all = users.findAll("", ""); //参数本来是有账号密码的，这里为测试内容
            Mes mes = new Mes("200", "查询成功", all); //自己新建的一个对象
            //System.out.println(mes);
            //System.out.println(all);
            PrintWriter writer = resp.getWriter();
            writer.print(JSON.toJSONString(mes)); //导入fastjson-1.2.47.jar包(后面有)，才能使用，将Java对象转换成json对象
    
        }

Mes类

public class Mes { 
        private String status;
        private String msg;
        private List<User> list;
    
        public Mes() { 
        }
    
        public Mes(String status, String msg, List<User> users) { 
            this.status = status;
            this.msg = msg;
            this.list = users;
        }
    
        public String getStatus() { 
            return status;
        }
    
        public void setStatus(String status) { 
            this.status = status;
        }
    
        public String getMsg() { 
            return msg;
        }
    
        public void setMsg(String msg) { 
            this.msg = msg;
        }
    
        public List<User> getList() { 
            return list;
        }
    
        public void setList(List<User> list) { 
            this.list = list;
        }
    
        @Override
        public String toString() { 
            return "Mes{" +
                    "status='" + status + '\'' +
                    ", msg='" + msg + '\'' +
                    ", list=" + list +
                    '}';
        }
    }

\*注意：这个Mes对象必须要有`get`、`set`方法，，，，`tostring`方法`可以没有`，不然不行，本人已测试过了。

[fastjson-1.2.47.jar包][fastjson-1.2.47.jar]，进去了可能需要检测一下，通过提示检测通过后，直接搜索即可下载

[fastjson-1.2.47.jar]: https://mvnrepository.com/