Ajax跨域调用后台Restful接口时的JSON转换方法

来源：互联网发布：软件开发质量指标编辑：程序博客网时间：2024/05/20 06:29

类：AjaxExchange
作用：将后台取到的数据以JSON或HTML的形式返回

package org.sun.com;import java.io.OutputStreamWriter;import java.io.PrintWriter;import javax.servlet.http.HttpServletResponse;import net.sf.json.JSONArray;import net.sf.json.JsonConfig;public class AjaxExchange {        // 转换成HTML形式返回，参数为String类型    public static void printData(HttpServletResponse response, String msg) {          try {          // 跨域配置            response.setHeader("Access-Control-Allow-Origin","*");            response.setHeader("Access-Control-Allow-Methods", "POST, PUT, GET, OPTIONS, DELETE");            response.setHeader("Access-Control-Allow-Credentials", "true");            response.setHeader("Access-Control-Max-Age", "3600");// 保持跨域Ajax时的Cookie            response.setHeader("Access-Control-Allow-Headers", "x-auth-token, x-requested-with,Authorization,Origin, Accept, Content-Type,x-xsrf-token");            response.setContentType("text/html;charset=utf-8");              response.setCharacterEncoding("UTF-8");              PrintWriter out = new PrintWriter(new OutputStreamWriter(response.getOutputStream(), "UTF-8"));              out.println(msg);              out.close();          } catch (Exception e) {                e.printStackTrace();          }     }      // 将任意类型的item转换成JSON并返回      public static void printDataJason(HttpServletResponse response, Object item) {          try {          // 跨域配置            response.setHeader("Access-Control-Allow-Origin","*");            response.setHeader("Access-Control-Allow-Methods", "POST, PUT, GET, OPTIONS, DELETE");            response.setHeader("Access-Control-Allow-Credentials", "true");            response.setHeader("Access-Control-Max-Age", "3600");// 保持跨域Ajax时的Cookie            response.setHeader("Access-Control-Allow-Headers", "x-auth-token, x-requested-with,Authorization,Origin, Accept, Content-Type,x-xsrf-token");        response.setContentType("text/json;charset=utf-8");          response.setCharacterEncoding("UTF-8");          PrintWriter out = new PrintWriter(new OutputStreamWriter(response.getOutputStream(), "UTF-8"));              // currentUser里面有循环导致json处理不了    JsonConfig jsonConfig = new JsonConfig();  //建立配置文件    jsonConfig.setIgnoreDefaultExcludes(false);  //设置默认忽略    jsonConfig.setExcludes(new String[]{"currentUser"});            JSONArray jsonArr = JSONArray.fromObject(item, jsonConfig);            out.println(jsonArr);               out.close();          } catch (Exception e) {            e.printStackTrace();            }  }      // 带JsonConfig的JSON转换    public static void printDataJason(HttpServletResponse response, Object item, JsonConfig jsonConfig) {          try {          // 跨域配置            response.setHeader("Access-Control-Allow-Origin","*");            response.setHeader("Access-Control-Allow-Methods", "POST, PUT, GET, OPTIONS, DELETE");            response.setHeader("Access-Control-Allow-Credentials", "true");            response.setHeader("Access-Control-Max-Age", "3600");// 保持跨域Ajax时的Cookie            response.setHeader("Access-Control-Allow-Headers", "x-auth-token, x-requested-with,Authorization,Origin, Accept, Content-Type,x-xsrf-token");        response.setContentType("text/json;charset=utf-8");          response.setCharacterEncoding("UTF-8");          PrintWriter out = new PrintWriter(new OutputStreamWriter(response.getOutputStream(), "UTF-8"));                     JSONArray jsonArr = JSONArray.fromObject(item, jsonConfig);            out.println(jsonArr);               out.close();          } catch (Exception e) {            e.printStackTrace();            }  }}

这里第二个方法和第三个方法很像，区别在于第三个方法多了个JsonConfig的参数，这是用来设置Json转换时的一些参数的。

我在返回数据转Json的时候到这样的问题：
我想返回的参数是类型A，但是类型A继承了类型B，类型B里面有些数据是类型C，类型C里面有些类型是类型D
结果变成了这样A→B→C→D→...
JSONArray转换的时候，会根据这个顺序循环，把类型ABCD...里面的数据都JSON化。
如果A→B→C→D→C时，C和D产生循环的话，JSON就无法转换了。

        // currentUser里面有循环导致json处理不了    JsonConfig jsonConfig = new JsonConfig();  //建立配置文件    jsonConfig.setIgnoreDefaultExcludes(false);  //设置默认忽略    jsonConfig.setExcludes(new String[]{"currentUser"});

我找到了发生类型循环出错的参数并在方法2中写死了。也可以在外面设置出错的参数并传到方法3中。

调用方法如下：

    @RequestMapping(value = "/restful/getQuestion")    public void getQuestion(HttpServletRequest request, HttpServletResponse response) {    RestfulResult restfulResult = new RestfulResult();        try{                // 将数据取出放入restfulResult        ...                restfulResult.setData(...);    }catch(Exception ex){  restfulResult.setResult("Error");    restfulResult.setMessage(ex.getMessage());}    AjaxExchange.printDataJason(response, restfulResult);    }

用到的Jar包可以去这里下载：
jsonArray转换需要用到的Jar包

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