1、方式一

response.setContentType("text/html;charset=utf-8");  
response.setHeader("Cache-Control", "no-cache");
String str = "{'msg':'成功','success':'true'}";
out.print(str);
out.flush();
out.close();

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ajax请求获取返回数据后， var objs=eval("("+data+")"); //转化为json对象

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2、方式二

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response.setContentType("text/x-javascript;charset=utf-8");
//或者使用		response.setContentType("application/json; charset=utf-8");

response.setHeader("Cache-Control", "no-cache");

Message msg = new Message();
msg.setSuccess("true");
msg.setMsg("成功");

JSONObject jsonObject = JSONObject.fromObject(msg);
System.out.println(jsonObject.toString());
PrintWriter out = response.getWriter();
// out.print(jsonObject.toString());
// System.out.println("ddd");
// String str = "{\"msg\":\"成功\",\"success\":\"true\"}";
out.print(jsonObject.toString());
out.flush();
out.close();

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如果使用ajax就不用再将文本转化为json对象，?因为已经在返回时指定其类型为json格式

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