JSON的运用

一）什么是JSON
（1）JSON（Java Script Object Notation（记号,标记））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
注意：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

二）JSON的作用
（1）简化创建自定义对象的方式
注意：JSON就是用JS语法来书写，所以必须放在

<code class="hljs javascript has-numbering"><span class="hljs-keyword">var</span> p = {
            id:<span class="hljs-number">1</span>,
            name:<span class="hljs-string">"哈哈"</span>,
            tel:[
                    {
                        no:<span class="hljs-string">"135"</span>,
                        type:<span class="hljs-string">"中移动"</span>
                    },
                    {
                        no:<span class="hljs-string">"133"</span>,
                        type:<span class="hljs-string">"中联通"</span>
                    }
                ],
            show:<span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">(username)</span>{</span>
                alert(<span class="hljs-string">"你的姓名是:"</span> + p.name+<span class="hljs-string">":"</span>+username);
            },
            isSingle:<span class="hljs-literal">false</span>          
        };

<span class="hljs-keyword">var</span> p = {<span class="hljs-string">'city'</span>:[<span class="hljs-string">'北京'</span>,<span class="hljs-string">'上海'</span>,<span class="hljs-string">'广州'</span>,<span class="hljs-string">'深圳'</span>]};
<span class="hljs-keyword">for</span>(<span class="hljs-keyword">var</span> i=<span class="hljs-number">0</span>;i<p.city.length;i++){
    document.write(p.city[i]+<span class="hljs-string">"<br/>"</span>);
}</code>

（2）在AJAX中，作为数据载体之一
注意：JS可以直接解析JSON格式的文本，前提是：该JSON必须采用JS格式书写的才行，如果该JSON是采用Java格式写的，必须使用eval()函数转换后，方可被JS解析，该eval(“”)函数接收一个字符串格式的内容。
（3）省份-城市-区域三级联动【Struts2 + JSON版】
切记：将来JSON是不能完完全全替代XML的，只能在定义对象和数据交换语言方面替代
action:
/**
* 根据省份查询城市
*/

<code class="hljs lasso has-numbering"><span class="hljs-keyword">public</span> <span class="hljs-built_in">String</span> findCityByProvinceMethod() throws Exception{
        cityList <span class="hljs-subst">=</span> <span class="hljs-literal">new</span> ArrayList<span class="hljs-subst"><</span><span class="hljs-built_in">String</span><span class="hljs-subst">></span>();
        <span class="hljs-keyword">if</span>(<span class="hljs-string">"湖北"</span><span class="hljs-built_in">.</span><span class="hljs-keyword">equals</span>(province)){
            cityList<span class="hljs-built_in">.</span>add(<span class="hljs-string">"武汉"</span>);
            cityList<span class="hljs-built_in">.</span>add(<span class="hljs-string">"黄岗"</span>);
        }<span class="hljs-keyword">else</span> <span class="hljs-keyword">if</span>(<span class="hljs-string">"湖南"</span><span class="hljs-built_in">.</span><span class="hljs-keyword">equals</span>(province)){
            cityList<span class="hljs-built_in">.</span>add(<span class="hljs-string">"岳阳"</span>);
            cityList<span class="hljs-built_in">.</span>add(<span class="hljs-string">"张家界"</span>);
        }<span class="hljs-keyword">else</span> <span class="hljs-keyword">if</span>(<span class="hljs-string">"广东"</span><span class="hljs-built_in">.</span><span class="hljs-keyword">equals</span>(province)){
            cityList<span class="hljs-built_in">.</span>add(<span class="hljs-string">"韶关"</span>);
            cityList<span class="hljs-built_in">.</span>add(<span class="hljs-string">"东莞"</span>);
        }
        <span class="hljs-keyword">return</span> <span class="hljs-string">"ok"</span>;
    }</code>

/**
 * 根据城市查询区域
 */

<code class="hljs lasso has-numbering"><span class="hljs-keyword">public</span> <span class="hljs-built_in">String</span> findAreaByCityMethod() throws Exception{
        areaList <span class="hljs-subst">=</span> <span class="hljs-literal">new</span> ArrayList<span class="hljs-subst"><</span><span class="hljs-built_in">String</span><span class="hljs-subst">></span>();
        <span class="hljs-keyword">if</span>(<span class="hljs-string">"武汉"</span><span class="hljs-built_in">.</span><span class="hljs-keyword">equals</span>(city)){
            areaList<span class="hljs-built_in">.</span>add(<span class="hljs-string">"AA"</span>);
            areaList<span class="hljs-built_in">.</span>add(<span class="hljs-string">"BB"</span>);
        }<span class="hljs-keyword">else</span> <span class="hljs-keyword">if</span>(<span class="hljs-string">"黄岗"</span><span class="hljs-built_in">.</span><span class="hljs-keyword">equals</span>(city)){
            areaList<span class="hljs-built_in">.</span>add(<span class="hljs-string">"CC"</span>);
            areaList<span class="hljs-built_in">.</span>add(<span class="hljs-string">"DD"</span>);
        }<span class="hljs-keyword">else</span> <span class="hljs-keyword">if</span>(<span class="hljs-string">"岳阳"</span><span class="hljs-built_in">.</span><span class="hljs-keyword">equals</span>(city)){
            areaList<span class="hljs-built_in">.</span>add(<span class="hljs-string">"EE"</span>);
            areaList<span class="hljs-built_in">.</span>add(<span class="hljs-string">"FF"</span>);
        }<span class="hljs-keyword">else</span> <span class="hljs-keyword">if</span>(<span class="hljs-string">"张家界"</span><span class="hljs-built_in">.</span><span class="hljs-keyword">equals</span>(city)){
            areaList<span class="hljs-built_in">.</span>add(<span class="hljs-string">"GG"</span>);
            areaList<span class="hljs-built_in">.</span>add(<span class="hljs-string">"HH"</span>);
        }<span class="hljs-keyword">else</span> <span class="hljs-keyword">if</span>(<span class="hljs-string">"韶关"</span><span class="hljs-built_in">.</span><span class="hljs-keyword">equals</span>(city)){
            areaList<span class="hljs-built_in">.</span>add(<span class="hljs-string">"II"</span>);
            areaList<span class="hljs-built_in">.</span>add(<span class="hljs-string">"JJ"</span>);
        }<span class="hljs-keyword">else</span> <span class="hljs-keyword">if</span>(<span class="hljs-string">"东莞"</span><span class="hljs-built_in">.</span><span class="hljs-keyword">equals</span>(city)){
            areaList<span class="hljs-built_in">.</span>add(<span class="hljs-string">"KK"</span>);
            areaList<span class="hljs-built_in">.</span>add(<span class="hljs-string">"LL"</span>);
        }
        <span class="hljs-keyword">return</span> <span class="hljs-string">"ok"</span>;
    }
<span class="hljs-keyword">private</span> <span class="hljs-built_in">List</span><span class="hljs-subst"><</span><span class="hljs-built_in">String</span><span class="hljs-subst">></span> cityList;
    <span class="hljs-keyword">private</span> <span class="hljs-built_in">List</span><span class="hljs-subst"><</span><span class="hljs-built_in">String</span><span class="hljs-subst">></span> areaList;
    <span class="hljs-keyword">public</span> <span class="hljs-built_in">List</span><span class="hljs-subst"><</span><span class="hljs-built_in">String</span><span class="hljs-subst">></span> getCityList() {
        <span class="hljs-keyword">return</span> cityList;
    }
    <span class="hljs-keyword">public</span> <span class="hljs-built_in">List</span><span class="hljs-subst"><</span><span class="hljs-built_in">String</span><span class="hljs-subst">></span> getAreaList() {
        <span class="hljs-keyword">return</span> areaList;
    }</code>

   struts.xml

<code class="hljs xml has-numbering"><span class="hljs-tag"><<span class="hljs-title">package</span> <span class="hljs-attribute">name</span>=<span class="hljs-value">"provinceCityAreaPackage"</span> <span class="hljs-attribute">extends</span>=<span class="hljs-value">"json-default"</span> <span class="hljs-attribute">namespace</span>=<span class="hljs-value">"/"</span>></span>
        <span class="hljs-tag"><<span class="hljs-title">action</span> 
            <span class="hljs-attribute">name</span>=<span class="hljs-value">"findCityByProvinceRequest"</span> 
            <span class="hljs-attribute">class</span>=<span class="hljs-value">"cn.itcast.javaee.js.provincecityarea.ProvinceCityAreaAction"</span> 
            <span class="hljs-attribute">method</span>=<span class="hljs-value">"findCityByProvinceMethod"</span>></span>
            <span class="hljs-tag"><<span class="hljs-title">result</span> <span class="hljs-attribute">name</span>=<span class="hljs-value">"ok"</span> <span class="hljs-attribute">type</span>=<span class="hljs-value">"json"</span>></span>
            <span class="hljs-tag"></<span class="hljs-title">result</span>></span>
        <span class="hljs-tag"></<span class="hljs-title">action</span>></span>
   <span class="hljs-tag"></<span class="hljs-title">package</span>></span></code>

<code class="hljs xml has-numbering"><span class="hljs-tag"><<span class="hljs-title">script</span> <span class="hljs-attribute">type</span>=<span class="hljs-value">"text/javascript"</span>></span><span class="javascript">
        <span class="hljs-comment">//创建一个Photo对象</span>
        <span class="hljs-keyword">var</span> p = <span class="hljs-keyword">new</span> Photo();
        <span class="hljs-comment">//定位隐藏按钮，同时添加单击事件</span>
        $(<span class="hljs-string">"#hide"</span>).onclick = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">()</span>{</span>
            <span class="hljs-comment">//调用Photo对象的方法</span>
            p.hide();
        }
        <span class="hljs-comment">//定位显示按钮，同时添加单击事件</span>
        $(<span class="hljs-string">"#show"</span>).onclick = <span class="hljs-function"><span class="hljs-keyword">function</span><span class="hljs-params">()</span>{</span>
            <span class="hljs-comment">//调用Photo对象的方法</span>
            p.show();
        }
</span><span class="hljs-tag"></<span class="hljs-title">script</span>></span></code>