1.什么是JSON
（1）JSON（Java Script Object Notation）是一种轻量级的数据交换语言，
以文本字符串为基础，且易于让人阅读
XML就是一个重量级的数据交换语言
（2）JSON采用完全独立于任何程序语言的文本格式，使JSON成为理想的数据交换语言
2.struts中使用JSON
引入jar包
struts配置中将包继承自json-default
result中的type属性设置为json
3.JSON实现的三级联动
jsp：
<select id="provinceID" onchange="getCity(this)">
<option >选择省份</option>
<option >广东</option>
<option >山东</option>
</select>
<select id="cityID" onchange="getArea(this)">
<option value="">选择城市</option>
</select>
<select id="areaID" >
<option value="">选择区域</option>
</select>
js：
function getCity(selEle)
{
var province = selEle[selEle.selectedIndex].innerHTML;
//清空城市下拉框
var cityEle = document.getElementById("cityID");
cityEle.options.length=1;
//清空区域下拉框
var areaEle = document.getElementById("areaID");
areaEle.options.length=1;
if(province == "选择省份")
return ;
var ajax = createAJAX();
var method = "POST";
var url = "${pageContext.request.contextPath}/getCity?time="
+new Date().getTime();
ajax.open(method,url);
var content = "loc.province="+province;
ajax.setRequestHeader("content-type","application/x-www-form-urlencoded");
ajax.send(content);
ajax.onreadystatechange = function(){
if(ajax.readyState == 4)
{
if(ajax.status == 200)
{
//返回java格式的json，不能被js执行
var jsonJAVA = ajax.responseText;
//将java格式的json转成js格式的json
var jsonJS = eval("("+jsonJAVA+")");
var array = jsonJS.cityList;
for(var i =0;i<array.length;i++){
var option = document.createElement("option");
option.innerHTML = array[i];
cityEle.appendChild(option);
}
}
}
}
}
function getArea(selEle) {
var city = selEle[selEle.selectedIndex].innerHTML;
//清空区域下拉框
var areaEle = document.getElementById("areaID");
areaEle.options.length=1;
if(city == "选择城市") {
return;
}
var ajax = createAJAX();
var method = "POST";
var url = "${pageContext.request.contextPath}/getArea?time="
+new Date().getTime();
ajax.open(method,url);
ajax.setRequestHeader("content-type","application/x-www-form-urlencoded");
var content = "loc.city="+city;
ajax.send(content);
ajax.onreadystatechange = function(){
if(ajax.readyState == 4)
{
if(ajax.status == 200)
{
var jsonJAVA = ajax.responseText;
var jsonJS = eval("("+jsonJAVA+")");
var array = jsonJS.areaList;
for(var i=0;i<array.length;i++){
var option = document.createElement("option");
option.innerHTML = array[i];
areaEle.appendChild(option);
}
}
}
}
}
struts.xml
<package name="json" extends="json-default">
<action name="getCity" class="jsonAction" method="getCity">
<result name="success" type="json"/>
</action>
<action name="getArea" class="jsonAction" method="getArea">
<result name="success" type="json"/>
</action>
</package>
action：
public class JsonAction extends ActionSupport implements RequestAware{
private Map<String,Object> request;
@Override
public void setRequest(Map<String, Object> map) {
this.request = map;
}
private Location loc;
public void setLoc(Location loc) {
this.loc = loc;
}
public Location getLoc() {
return loc;
}
private List<String> cityList;
public List<String> getCityList() {
return cityList;
}
// 根据省份获得城市
public String getCity(){
cityList = new ArrayList<String>();
if("广东".equals(loc.getProvince()))
{
cityList.add("广州");
cityList.add("深圳");
cityList.add("珠海");
}
else if("山东".equals(loc.getProvince()))
{
cityList.add("济南");
cityList.add("枣庄");
cityList.add("青岛");
cityList.add("烟台");
}
return SUCCESS;
}
// 根据城市获取区域
private List<String> areaList;
public List<String> getAreaList() {
return areaList;
}
public String getArea(){
areaList = new ArrayList<String>();
if("枣庄".equals(loc.getCity()))
{
areaList.add("市中区");
areaList.add("山亭区");
areaList.add("台儿庄区");
}
return SUCCESS;
}
}
4.使用第三方工具，将Bean对象、List、Set、Map对象转成JSON
@Test
public void test1(){
Location location = new Location();
location.setProvince("山东");
location.setCity("枣庄");
JSONArray jsonArray = JSONArray.fromObject(location);
System.out.println(jsonArray);
//[{"province":"山东","city":"枣庄"}]
}
@Test
public void test2(){
ArrayList<Location> locs = new ArrayList<>();
Location location = new Location();
location.setProvince("山东");
location.setCity("枣庄");
Location location2 = new Location();
location2.setProvince("广东");
location2.setCity("广州");
locs.add(location);
locs.add(location2);
JSONArray jsonArray = JSONArray.fromObject(locs);
System.out.println(jsonArray);
//[{"province":"山东","city":"枣庄"},{"province":"广东","city":"广州"}]
}
@Test
public void test3(){
Set<Location> locs = new LinkedHashSet<>();
Location location = new Location();
location.setProvince("山东");
location.setCity("枣庄");
Location location2 = new Location();
location2.setProvince("广东");
location2.setCity("广州");
locs.add(location);
locs.add(location2);
JSONArray jsonArray = JSONArray.fromObject(locs);
System.out.println(jsonArray);
//[{"province":"山东","city":"枣庄"},{"province":"广东","city":"广州"}]
}
@Test
public void test4(){
Department department = new Department();
department.setId(10);
Employee emp1 = new Employee();
emp1.setEmpName("zhang");
emp1.setSalary(1000);
Employee emp2= new Employee();
emp2.setEmpName("lisi");
emp2.setSalary(2000);
List<Employee> employeeList = new ArrayList<Employee>();
employeeList.add(emp1);
employeeList.add(emp2);
department.setEmps(employeeList);
JSONArray jsonArray = JSONArray.fromObject(department);
System.out.println(jsonArray);
//[{
// "emps":[{"empId":0,"empName":"zhang","dept":null,"salary":1000},
// {"empId":0,"empName":"lisi","dept":null,"salary":2000}],
// "id":10
// }]
}
5.JSON的特点
（1）在客户端，直接使用JavaScript语言解析JSON，无需第三方jar包
（2）本质上，就是一个文本，只是该文本有特定的书写格式
（3）可以使用第三方工具，将JavaBean对象或者List/Set/Map<JavaBean>对象转成JSON
（4）优点：JSON与XML很相似，但是它更加轻巧，服务器只需发送一个html普通字符串，不用发送复杂的xml格式文档了
（5）缺点：语法过于严谨，初学者可能觉得代码不易读，写错一点都不行
（6）JSON本质上，就是用JS语法写的特殊文本记号，用JS可以直接解析
时间： 2024-10-25 21:40:36