The Ajax of jquery

The Ajax part of jquery API

(1) JQuery object. Load (url,params,function (data) {}); (understanding)
(2) $.get (url,params,function (data) {},type); Ajax that sends a GET request
URL: The requested path
Params: The requested parameter parameter is in the form of Key\value key=value {"": "", "": ""}
Function: callback function parameter is the data sent back by the server
Type: Returns the content format, XML, HTML, script, JSON, text, _default. Use "JSON" later

(3) $.post (url,params,function (data) {},type); Ajax that sends a POST request
　　
(4) $.ajax ([option]);
Optional values for the options:
URL: Request Path
Type: Request method
Data: Sent to the server
SUCCESS:FN the callback after successful
Callback after the ERROR:FN exception
DataType: Return content format often using JSON
Async: Setting Whether it is an asynchronous request
For example:

$.ajax ({                url:url,                type: "Post",                data:params,                success:function (d) {                    alert (d.msg);                },                error:function () {},                DataType: "JSON"                            }); 

If the result is in JSON format, the return value is printed as an object
For example, if the JSON is {"Result": "Success", "MSG": "Success"}
Get msg only requires parameters. msg

1. Front-end Ajax

Import JS:HTTP://PAN.BAIDU.COM/S/1JHLRVTK

<%@ page language= "java" contenttype= "text/html; Charset=utf-8 "pageencoding= "UTF-8"%><! DOCTYPE HTML PUBLIC "-//w3c//dtd HTML 4.01 transitional//en" "Http://www.w3.org/TR/html4/loose.dtd" ><script type= "Text/javascript" src= "${pagecontext.request.contextpath}/js/jquery-1.11.3.min.js" ></ Script><title>insert title Here</title><script type= "Text/javascript" >$ (function () {$ ("#btn"). Click (function () {var URL= "/day15/jqueryajax"; //var params= "Username= Zhang San";var params={"username": "Zhang Suna"}; //Load Mode            /*$ (this). Load (url,params,function (d) {alert (d); }); */                        //Get mode            /*$.get (url,params,function (d) {alert (d)});*/                        //Post Mode            /*$.post (url,params,function (d) {alert (d.msg); }, "JSON"); */                        //Ajax Way$.ajax ({url:url, type:"POST", Data:params, success:function (d) {alert (d.msg); }, Error:function () {}, DataType:"JSON"                            });            }); })</script>
2. servlet
 PackageCom.itheima.jquery_ajax;Importjava.io.IOException;Importjavax.servlet.ServletException;ImportJavax.servlet.http.HttpServlet;Importjavax.servlet.http.HttpServletRequest;ImportJavax.servlet.http.HttpServletResponse;/*** jquery's Ajax*/ Public classJqueryajaxservletextendsHttpServlet {Private Static Final LongSerialversionuid = 1L; protected voidDoget (HttpServletRequest request, httpservletresponse response)throwsservletexception, IOException {System.out.println ("Request method:" +Request.getmethod ()); //Accept ParametersString username = request.getparameter ("username"); Username=NewString (Username.getbytes ("iso-8859-1"), "Utf-8");                SYSTEM.OUT.PRINTLN (username); //Response DataResponse.getwriter (). Print ("Success"); }    protected voidDoPost (HttpServletRequest request, httpservletresponse response)throwsservletexception, IOException {request.setcharacterencoding ("Utf-8"); System.out.println ("Request method:" +Request.getmethod ()); //Accept ParametersString username = request.getparameter ("username");        SYSTEM.OUT.PRINTLN (username); //response.getwriter (). Print ("Success"); //{"Result": "Success", "MSG": "Success"}String s= "{\" result\ ": \" Success\ ", \" msg\ ": \" success \ "}"; //Response DataResponse.setcontenttype ("Text/html;charset=utf-8");    Response.getwriter (). print (s); }}
3. Configure Web. xml
<servlet>    <description></description>    <display-name>jqueryajaxservlet</ display-name>    <servlet-name>JqueryAjaxServlet</servlet-name>    <servlet-class >com.itheima.jquery_ajax. jqueryajaxservlet</servlet-class>  </servlet>  <servlet-mapping>    < Servlet-name>jqueryajaxservlet</servlet-name>    <url-pattern>/jqueryAjax</url-pattern>  </servlet-mapping>
Problem
<script> is it before or after
jquery Selector
Reference: http://www.w3school.com.cn/jquery/jquery_intro.asp
Hierarchy Selector ★ All B        descendants of a b:a        a > b:a allb children        a+B:a's next brother (Big Brother)        a~b:a all the Younger brothers    Basic Filter Selector: ★        : Frist First        : Last        : Odd  index odd        : Even index even        : EQ (index) specify index         >        <     content filtering:        : Has ("selector"): element with the specified selector    visible filter:        : Hidden   In the page does not show element generally refers to input type= "hidden" and style in Display:none        : Visible     Property Filter: ★        [property name]        [property name] = "value"]    form filter:        : Input  All table list label  input Select TextArea button        //  Input
The Ajax of jquery