axaj异步查询学习（多级联动、校对信息）

你的名字 2022-06-10 11:12 86阅读 0赞

要使用异步查询就要用到axaj，也可以说**ajax**有异步查询的功能，所谓的异步查询可以理解为在不整个页面刷新的情况下（即局部刷新）向服务器或者后台发送请求并拿到服务器的响应。

**1. 导入jar包**  
要使用ajax就要先导入一些jar包，一般有json-lib-2.1-jdk15.jar，ezmorph-1.0.3.jar， commons-logging-1.1.1.jar，commons-lang-2.5.jar，commons-collections-3.1.jar， commons-beanutils-1.7.0.jar，jquery-1.10.2.min.js，jar包的版本不一定要与本文一模一样。  
**2.JSP页面上的操作**  
请求有post请求和get请求两种，本文用post请求，

上面的代码也可以这样写

**3.Servlet的操作**

@WebServlet("/IsValidServlet")
    public class IsValidServlet extends HttpServlet { 
        private static final long serialVersionUID = 1L;
    
    
        PrintWriter printWriter=null;
    
        @Override
        protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            //获取参数
            String username = request.getParameter("username");
    
    
            //指定HTTP响应的字符集编码
            response.setCharacterEncoding("utf-8");
            response.setContentType("text/html;charset=utf-8");
    
            //伪校验(不连接数据库)
            PrintWriter writer = response.getWriter();
            if("tomcat".equals(username))
            {
                String message="用户名合法";
                writer.write(message);
                /*也可以用json，代码如下 String message="{\"message\":\"用户名合法\"}"; response.setContentType("application/json;charset=utf-8"); PrintWriter writer = response.getWriter(); writer.write(message); writer.flush(); writer.close(); */
            }
            else
            {
                String message="用户名不合法";
                writer.write(message);
            }
            writer.flush();
            writer.close();
    }

**多级联动**  
**1.jsp页面操作**

**2.servlet的操作**

@WebServlet("/getSclassifyServlet")
    public class GetSclassifyServlet extends HttpServlet { 
        private static final long serialVersionUID = 1L;
        /** * 响应JSON格式文档 */
        protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            //获取参数
            String bclassifyId = request.getParameter("bclassifyId");
    
    
            //根据大分类ID查询小分类中所有符合条件的数据（应该连接数据库找，这里就写死了不去连接数据库了）
            List<Sclassify> sclassifyList = new ArrayList<Sclassify>();//Sclassify实体类里有id和name
            if("1000".equals(bclassifyId))
            {
                sclassifyList.add(new Sclassify(1001,"洗发水"));
                sclassifyList.add(new Sclassify(1002,"沐浴露"));
                sclassifyList.add(new Sclassify(1003,"牙膏"));
            }
            else if("2000".equals(bclassifyId))
            {
                sclassifyList.add(new Sclassify(2001,"厨房用品"));
                sclassifyList.add(new Sclassify(2002,"床上用品"));
                sclassifyList.add(new Sclassify(2003,"清洁用品"));
            }
            else if("3000".equals(bclassifyId))
            {
                sclassifyList.add(new Sclassify(3001,"水果"));
                sclassifyList.add(new Sclassify(3002,"酒类"));
                sclassifyList.add(new Sclassify(3003,"零食"));
            }
            JSONArray jsonArray = JSONArray.fromObject(sclassifyList);
    
            System.out.println("json格式响应内容：" + jsonArray.toString());
    
            //指定http响应字符集编码
            response.setCharacterEncoding("utf-8");
            response.setContentType("application/json;charset=utf-8");
    
            //响应
            PrintWriter writer = response.getWriter();
            writer.write(jsonArray.toString());
            writer.flush();
            writer.close();
        }

一般情况下，大家都喜欢用json。  
**4.附**  
如果一个jsp页面要做多个异步查询的话，需要改动几点  
**1.jsp页面**

比如有两个需要异步查询的地方

$.ajax({
                   type: "POST",
                   //url: "getSclassifyServlet",
                   url: "getSclassifyServlet/getsclassify " //url地址带上后缀getsclassify
                   data: "bclassify="+bclassify,
                   success: function(sclassifies){ 
                    }
                    });
    
        $.ajax({
                   type: "POST",
                   //url: "getSclassifyServlet",
                   url: "getSclassifyServlet/getname " //url地址带上后缀getname
                   data: "bclassify="+bclassify,
                   success: function(sclassifies){ 
                    }
                    });

**2.servlet页面**  
1.使用service方法（此方法会接收所有POST和GET请求），不用dopost和doget方法

@WebServlet("/getSclassifyServlet/*")//代表接收所有发到getSclassifyServlet的post和get请求
    public class GetSclassifyServlet extends HttpServlet { 
        private static final long serialVersionUID = 1L;
    
    
        PrintWriter printWriter=null;
    
        @Override
        protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String url=request.getRequestURI();//获取URL的值
        if(url.endsWith("getsclassify")){
       //如果URL以getsclassify结尾就调用getSclassify()方法
            getSclassify(request, response);
        }else if(url.endsWith("getname")){
            getName(request, response);
        }
    
    protected void getSclassify(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            //获取参数
            String bclassifyId = request.getParameter("bclassifyId");
    
    
            //根据大分类ID查询小分类中所有符合条件的数据（应该连接数据库找，这里就写死了不去连接数据库了）
            List<Sclassify> sclassifyList = new ArrayList<Sclassify>();//Sclassify实体类里有id和name
            if("1000".equals(bclassifyId))
            {
                sclassifyList.add(new Sclassify(1001,"洗发水"));
                sclassifyList.add(new Sclassify(1002,"沐浴露"));
                sclassifyList.add(new Sclassify(1003,"牙膏"));
            }
            else if("2000".equals(bclassifyId))
            {
                sclassifyList.add(new Sclassify(2001,"厨房用品"));
                sclassifyList.add(new Sclassify(2002,"床上用品"));
                sclassifyList.add(new Sclassify(2003,"清洁用品"));
            }
            else if("3000".equals(bclassifyId))
            {
                sclassifyList.add(new Sclassify(3001,"水果"));
                sclassifyList.add(new Sclassify(3002,"酒类"));
                sclassifyList.add(new Sclassify(3003,"零食"));
            }
            JSONArray jsonArray = JSONArray.fromObject(sclassifyList);
    
            System.out.println("json格式响应内容：" + jsonArray.toString());
    
            //指定http响应字符集编码
            response.setCharacterEncoding("utf-8");
            response.setContentType("application/json;charset=utf-8");
    
            //响应
            PrintWriter writer = response.getWriter();
            writer.write(jsonArray.toString());
            writer.flush();
            writer.close();
        }
        protected void getName(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        /* 这里像getSclassify()一样，写需要做的验证 */
        }
    }

希望本文可以带给你一些帮助。