net.sf.json.JSONException: A JSONArray text must start with '[' at character

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错误背景

在用ssh框架做第三方接口的时候，可以正常接收前端发送的数据，但是返回json数据给前端页面报错

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错误代码

package cn.com.service;
import java.io.*;
import javax.servlet.http.HttpServletResponse;
import net.*;
import org.*;
import cn.com.bean.User;
@Repository(value="regedit")
@Scope("prototype")
public class Regedit implements ModelDriven<User>{
@Autowired
private SessionFactory sf;
@Autowired
private User user;
@Transactional
public String regedit_user(){
	//获取session对象
	String toast="用户名已存在，请重新输入";	
	 HttpServletResponse response = ServletActionContext.getResponse();
	//设置response输出json便于调试
	 response.setCharacterEncoding("utf-8");
	 PrintWriter out;
	try {
		out = response.getWriter();
		 JSONArray json=JSONArray.fromObject(toast);
	     out.write(json.toString());
	     out.flush();
	     out.close();
	} catch (IOException e) {
		// TODO Auto-generated catch block
		e.printStackTrace();
	}
	
	return "success";
}
public User getModel() {

	return user;
}
}

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解决方案

JSONArray json=JSONArray.fromObject(toast);
         out.write(json.toString());

把改成

        JSONObject json=new JSONObject();
         json.put("tom", toast);     

JSONArray是把集合或者数组变成json

JSONObject是把基础类型的数据变成jon

在这里这个情况只能用JSONObject