Ajax（Asynchronous JavaScript and XML），直译为“异步的JavaScript与XML技术”，是一种创建交互式网页应用的网页开发技术，用于创建快速动态网页，由杰西·詹姆士·贾瑞特所提出。与传统的Web应用相比，Ajax通过浏览器与服务器进行少量的数据交换就可以实现网页的异步更新，在不重新加载整个网页的情况下，即可对网页进行更新。
//②jsonStr转json对象方式二：
var jsonStr2 = '{"name" : "黄小邪", "age" : 23, "sex" : true}';
//注意：使用JSON.parse转换jsonStr必须保证jsonStr是标准格式的字符串
var jsonObj2 = JSON.parse(jsonStr2);
console.debug(jsonObj2);
5.JSON与Ajax实现二级联动实例
这里使用JSON字符串操作并向前台传输JSON格式的数据来展示JSON与Ajax之间的操作实现。
后台：
虚拟了两个省、市Domain并提供加载获取省、市的方法供Servlet向前台传输数据：
City.java：
/**
* 城市对象
*
*/
public class City {
private Long id;
private String name;
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public City() {
}
public City(Long id, String name) {
super();
this.id = id;
this.name = name;
}
/**
* 根据省份id查询省份中的城市!
*
* @return
*/
public static List getCityByProvinceId(Long id) {
List citys = new ArrayList();
if (id == 1) {
citys = Arrays.asList(
new City(1L,"成都"),
new City(2L,"南充"),
new City(3L,"绵阳"),
new City(4L,"遂林"),
new City(5L,"达州"),
new City(6L,"德阳"),
new City(7L,"乐山")
);
} else if (id == 2) {
citys = Arrays.asList(
new City(11L,"广州"),
new City(12L,"佛山"),
new City(13L,"东莞")
);
} else if (id == 3) {
citys = Arrays.asList(
new City(21L,"昆明"),
new City(22L,"玉溪"),
new City(23L,"丽江")
);
}
return citys;
}
}
Province.java：
public class Province {
private Long id;
private String name;
public Province(Long id, String name) {
super();
this.id = id;
this.name = name;
}
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Province() {
super();
}
public static List getAllProvince() {
List provinces = new ArrayList();
provinces.add(new Province(1L, "四川"));
provinces.add(new Province(2L, "广东"));
provinces.add(new Province(3L, "云南"));
return provinces;
}
}
提供一个CityProvinceServlet向Ajax提供请求地址：
@WebServlet("/loadData")
public class CityProvinceServlet extends HttpServlet {
@Override
protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
String cmd = req.getParameter("cmd");
String id = req.getParameter("id");
req.setCharacterEncoding("UTF-8");
resp.setContentType("text/json;charset=UTF-8");
//加载省
if(cmd.equals("province")){
List provinceList = Province.getAllProvince();
resp.getWriter().print(JSONSerializer.toJSON(provinceList));
System.out.println("加载省！");
}
//加载市
else {
if(id != null && id != ""){
List cityList = City.getCityByProvinceId(Long.parseLong(id));
resp.getWriter().print(JSONSerializer.toJSON(cityList));
System.out.println("加载市！");
}
}
}
}
