- jackson
Jackson is a simple java application library. Jackson can easily convert Java objects into json objects
And xml documents, you can also convert json and xml into Java objects
Core code: ObjectMapper mapper = new ObjectMapper(); mapper.writeValueAsString(obj);
//Number of rows to get source data int count = md.getColumnCount(); map.put(md.getColumnName(i), rs.getObject(i));
- jackson will java – > JSON
2.1 JavaBean/Map
{}
//json object
Student stu1=new Student("s001","Zhang San");
ObjectMapper mapper = new ObjectMapper();
System.out.println(mapper.writeValueAsString(stu1));
//Results: {sid: "s001",sname: "Zhang San"}
2.2 array / List/Set
[]
Student stu2=new Student("s002","Li Si");
List<Student> list=new ArrayList<>();
list.add(stu1);
list.add(stu2);
System.out.println(mapper.writeValueAsString(list));
//Results: [{sid: "s001",sname: "Zhang San"}, {sid:"s002",sname: "Li Si"}]
2.3 embedded class
Mixed mode
Map<String, Object> map=new HashMap<>();
map.put("total",2);
map.put("stus",list);
//Results: {"total":2,"stus":[{sid: "s001",sname: "Zhang San"}, {sid:"s002",sname: "Li Si"}]}
-
Java - > JSON loop
Ignore one direction of bidirectional association@JsonIgnore / program control
-
ajax request of jQuery
$.ajax
url
Add a time stamp after the URL to prevent the browser from slowing down: xxx?ts=new Date().getTime()
success
dataType
error -
Ajax of jQuery
//Custom jQuery ajax plug-in
//Get all provinces
$(function(){
var ctx=$("#ctx").val(); / / get the project name according to the id
$.ajax({
url:ctx+"/regionServlet",//Request path
success:function(data){
for(index in data){ //data[index].ID get provincial id, data [index]. Region [name (specific province)
$("#province").append("<option value='"+data[index].ID+"'>"+data[index].REGION_NAME+"</option>")
}
},
dataType:"json"
});
//Get all the cities
$("#province").change(function(){
$("option:gt(0)","#city").remove(); / / clear the city drop-down box
$("option:gt(0)","#Count "). Remove(); / / clear the county dropdown box
$.ajax({
url:ctx+"/regionServlet?ID="+this.value, //ID refers to the city level of the province
success:function(data){
console.log(data);
for(index in data){ //data[index].ID get the city id, data [index]. Region [name (specific city level)
$("#city").append("<option value='"+data[index].ID+"'>"+data[index].REGION_NAME+"</option>")
}
},
dataType:"json"
});
//Get all the counties
$("#city").change(function(){
$("option:gt(0)","#Count "). Remove(); / / clear the county dropdown box
$.ajax({
url:ctx+"/regionServlet?ID="+this.value, //ID refers to the city level of the province
success:function(data){
for(index in data){
//data[index].ID get County id, data [index]. Region [name (specific county)
$("#county").append("<option value='"+data[index].ID+"'>"+data[index].REGION_NAME+"</option>")
}
},
dataType:"json"
});
});
});
})
Page code of three-level linkage
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%@ include file="/jsp/common/head.jsp"%> //Include address of plug-in
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<div>
<h1>$.ajax Realize linkage between provinces and cities</h1>
<input type="hidden" id="ctx" value="${pageContext.request.contextPath}">
<div>
Receiving address
<select id="province">
<option selected="selected">---Please select a province---</option>
</select>
<select id="city">
<option selected="selected">---Please select a city---</option>
</select>
<select id="county">
<option selected="selected">---Please select a county---</option>
</select>
</div>
</div>
</body>
</html>