JSON跟JavaScript之间的通信-【使用反射】【使用工具包】

一、使用反射实现服务端口与JSON之间的数据传递

　　在客户端传入用户对象，后台通过格式转换实现在窗口弹出用户信息：

用户类：

package com.zhixi.entity;

/**
 * 创建学生对象
 */

public class User {
    private int userId;
    private String userName;

    public User(int userId, String userName) {
        this.userId = userId;
        this.userName = userName;
    }

    public User() {
    }

    public int getUserId() {
        return userId;
    }

    public void setUserId(int userId) {
        this.userId = userId;
    }

    public String getUserName() {
        return userName;
    }

    public void setUserName(String userName) {
        this.userName = userName;
    }
}

工具类:实现对象转JSON操作

package com.zhixi.util;

import java.lang.reflect.Field;

public class ObjectToJSON {
    /**
     * 将任何类型的数据对象转换为json格式的字符串
     *
     * @param obj :可以是Student对象，或者其他类型的对象
     * @return
     */
    public static String jsonObject(Object obj) {
        //做json格式字符串的拼接
        StringBuffer buffer = new StringBuffer("{");
        //1.获得当前对象隶属的[class文件]
        Class classFile = obj.getClass();
        //2.获得Class文件所有属性值,保存在一个Field数组中
        Field[] fieldArray = classFile.getDeclaredFields();
        //获得当前对象所有属性的值
        try {
            for (int i = 0; i < fieldArray.length; i++) {
                Field field = fieldArray[i];
                field.setAccessible(true);//开启私有属性的访问权限
                String fieldName = field.getName();//获取属性名
                Object fieldValue = field.get(obj);//获取属性值
                //4.将获得属性及其值拼接为JSON格式字符串
                buffer.append(""");
                buffer.append(fieldName);
                buffer.append("":"");
                buffer.append(fieldValue);
                buffer.append(""");// "u_id":"10","u_name":"张志喜"
                //多个属性之间添加逗号的问题
                if (i < fieldArray.length - 1) {
                    buffer.append(",");
                }
            }
        }catch (Exception e){
            e.printStackTrace();
        }
        buffer.append("}");
        return buffer.toString();
    }
}

servlet：将数据转换成JSON格式字符串，放到域中，进行转发

package com.zhixi.servlet;

import com.zhixi.pojo.User;
import com.zhixi.utils.ObjectToJson;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

/**
 * @author zhangzhixi
 */
public class SomeServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        User user1 = new User(21, "张志喜");

         String jsonObject = ObjectToJson.toJson(user1);
        //2、将学生对象放入到作用域中
        request.setAttribute("key", jsonObject);
        //3、请求转发
        request.getRequestDispatcher("/user.jsp").forward(request, response);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
         version="4.0">
    <servlet>
        <servlet-name>some</servlet-name>
        <servlet-class>com.zhixi.servlet.SomeServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>some</servlet-name>
        <url-pattern>/some</url-pattern>
    </servlet-mapping>
</web-app>

index.jsp:首页

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
  <head>
    <title>$Title$</title>
  </head>
  <body>
  Hello
  <a href="${pageContext.request.contextPath}/some">点击这里</a>
  </body>
</html>

user.jsp:接收域中的JSON数据

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>

    <script type="text/javascript">
        var user = ${requestScope.key};
        window.alert("年龄："+user.userId+"姓名："+user.userName);
    </script>
</head>
<body>
</body>
</html>

二、将对象作为集合进行传递

　　需要用到的JSON工具包：

链接：https://pan.baidu.com/s/1z93s2nBcIuTPuWo5D_N0rQ 
提取码：8023 
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　　用户类：

package com.zhixi.entity;

/**
 * @author zhangzhixi
 */
public class User {
    private String name;
    private int age;
    private String sex;

    public User() {
    }

    public User(String name, int age, String sex) {
        this.name = name;
        this.age = age;
        this.sex = sex;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }
}

　　servlet

package com.zhixi.servlet;

import com.zhixi.entity.User;
import net.sf.json.JSONArray;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

/**
 * @author zhangzhixi
 */
public class SomeServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //1、获得一个集合存放用户
        List<User> list = new ArrayList<>();

        User user1 = new User("张三", 23, "男");
        User user2 = new User("李红", 21, "女");
        User user3 = new User("李四", 24, "男");

        list.add(user1);
        list.add(user2);
        list.add(user3);

        //2.通过json. jar工具类将集合内容转换为[JSON数组格式]字符串
        JSONArray jsonArray = JSONArray.fromObject(list);
        //3、将[JSON数组格式]字符串添加到request域中去
        request.setAttribute("user", jsonArray);
        //4、请求转发
        request.getRequestDispatcher("/index.jsp").forward(request, response);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}

　　显示用户页面

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>用户表</title>
</head>

<%--将页面加载完毕后触发调用--%>
<script type="text/javascript">
    function init() {
        // 接收到前端的集合数据
        let userArray = ${requestScope.user};

        for (let i = 0; i < userArray.length; i++) {
            var user = userArray[i]

            // 创建标签
            let domTr = document.createElement("tr");
            let domTd1 = document.createElement("td");
            let domTd2 = document.createElement("td");
            let domTd3 = document.createElement("td");

            // 给标签赋值
            domTd1.innerHTML = user.name;
            domTd2.innerHTML = user.age;
            domTd3.innerHTML = user.sex;

            // tr添加td（添加子标签）
            domTr.appendChild(domTd1);
            domTr.appendChild(domTd2);
            domTr.appendChild(domTd3);

            // body添加tr(添加字标签)
            document.getElementById("demo").appendChild(domTr);
        }
    }
</script>
<body onload="init()">
<table border="2" align="center" id="demo">
    <tr>
        <td>姓名</td>
        <td>年龄</td>
        <td>性别</td>
    </tr>
</table>
</body>
</html>

输出结果：

 

工具包中的两个类的方法区别：

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原文地址：https://www.cnblogs.com/zhangzhixi/p/14289605.html