Ajax实现步骤和原理解析

目录

• Ajax实现步骤和原理
• 一、什么是Ajax?
• 二、Ajax工作原理
• 三、Ajax的使用及实现步骤
• Ajax前后端数据交互–SSM
• 1.导包
• 2.在配置映射器和适配器时使用
• 案例
• 前端
• 后端

function Param(json) {
    var arr = [];
    for (var i in json) {
        arr,
        arr.push(i + "=" + json[i])
    }
    return arr.join("&");
}
function ajax(a) {
    return new Promise(function(resolve, reject) {
        a = a || {};
        a.type = a.type || "get";
        a.data = a.data || "";
        var xhr = null;
　　　　　// 处理兼容问题
        xhr = (window.XMLHttpRequest) ? new XMLHttpRequest() : new ActiveXObject("Microsoft.XMLHTTP");
        if (a.type === "get") {
            a.url += "?" + Param(a.data) + "&t=" + new Date().getTime();
　　　　　　　//调用open()方法并采用异步方式
            xhr.open("get", a.url, true);
　　　　　　　//使用send()方法将请求发送出去
            xhr.send();
        } else if (a.type === "post") {
            xhr.open("post", a.url, true);
            xhr.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
            xhr.send(Param(a.data))
        }
        xhr.onreadystatechange = function() {
            if (xhr.readyState === 4) {
                if (xhr.status === 200) {
                    resolve(JSON.parse(xhr.responseText));
                } else {
                    reject("Err:" + xhr.status)
                }
            }
        }
    })
}

Ajaxclass Ajax {  constructor() {this.xhr = window.XMLHttpRequest ? new XMLHttpRequest() : new ActiveXObject('Microsoft.XMLHTTP')
    }
    fn() {
        this.xhr.onreadystatechange = () => {
            if (this.xhr.readyState === 4) {
                if (this.xhr.status === 200) {
                    if (responseType === 'json') {
                        resolve(JSON.parse(this.xhr.responseText))
                    } else {
                        resolve(this.xhr.responseText)
                    }
                } else {
                    reject(new Error(this.xhr.status))
                }
            }
        }
    }
    get(opt) {
        return new Promise((resolve, reject) => {
            let {
                url,
                async = true,
                params = {},
                responseType = 'json'
            } = opt;
            if (!url) {
                return;
            }
            url = this.formatData(params) ? url + '?' + this.formatData(params) : url
            this.xhr.open('get', url, async);
            this.fn();
            this.xhr.send();
        })
    }
    post(opt) {
        return new Promise((resolve, reject) => {
            let {
                url,
                async = true,
                params = {},
                responseType = 'json',
                paramsType = 'application/x-www-form-urlencoded'
            } = opt;
            if (!url) {
                return;
            }
            this.xhr.open('post', url, async);
            this.fn();
            this.xhr.setRequestHeader('content-type', paramsType)
            this.xhr.send(this.formatData(params, paramsType));
        })
    }
    formatData(params, paramsType = 'application/x-www-form-urlencoded') {
        if (paramsType === 'application/x-www-form-urlencoded') {
            return Object.entries(params).map(val => val[0] + '=' + val[1]).join('&')
        } else {
            return JSON.stringify(params);
        }
    }
}

<dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>fastjson</artifactId>
            <version>1.2.75</version>
        </dependency>

<mvc:annotation-driven></mvc:annotation-driven>

   // 跳转 到tranferaddSub
                        $.ajax({
                            url : "/tranfermixtrue",
                            type : "POST",
                            dataType:"json",
                            contentType : "application/json;charset=UTF-8",
                            <!-- 向后端传输的数据 -->
                            data : JSON.stringify({
                                id:getdate(),
                                accuracy:parseFloat(eval(right/50)),
                                exercises:cons,
                                degreeOfDifficulty:1
                            }),
                            success:function(result) {
                            },
                            error:function(result){
                            }
                        });

  @RequestMapping(value = "/tranferaddSub")
    public  String tranferaddSub(@RequestBody Exercises exercises) {
//        作为addSUb的中转站
        ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
        ExerciseSerivice serivice = context.getBean("ExerciseSeriviceImpl", ExerciseSerivice.class);
        String jsonString = JSON.toJSONString(exercises);
        Exercises exercisess = JSON.parseObject(jsonString, Exercises.class);
        Map<String,Object> map = new HashMap<String,Object>();
        map.put("date",exercisess.getId());
        map.put("data",jsonString);
        serivice.addExercise(map);
        return "redirect:/addSub";
    }

    @RequestMapping(value = "/tranfermulDivide")
    public  String tranfermulDivide(@RequestBody Exercises exercises) {
//        作为mixtrue的中转站
        ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
        ExerciseSerivice serivice = context.getBean("ExerciseSeriviceImpl", ExerciseSerivice.class);
        String jsonString = JSON.toJSONString(exercises);
        Exercises exercisess = JSON.parseObject(jsonString, Exercises.class);
        Map<String,Object> map = new HashMap<String,Object>();
        map.put("date",exercisess.getId());
        map.put("data",jsonString);
        serivice.addExercise(map);
        return "redirect:/mulDivide";
    }
    @RequestMapping(value = "/tranfermixtrue")
    public  String tranfermixtrue(@RequestBody Exercises exercises) {
//        作为mixtrue的中转站

        ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
        ExerciseSerivice serivice = context.getBean("ExerciseSeriviceImpl", ExerciseSerivice.class);
        String jsonString = JSON.toJSONString(exercises);
        Exercises exercisess = JSON.parseObject(jsonString, Exercises.class);
        Map<String,Object> map = new HashMap<String,Object>();
        map.put("date",exercisess.getId());
        map.put("data",jsonString);
        serivice.addExercise(map);
        return "redirect:/mixtrue";
    }