json数据转换异常：net.sf.json.JSONException：java.lan。。。

json数据转换异常：net.sf.json.JSONException：n。

1 //存储Product对象的集合是从，Product是从mysql数据库中查询并添加的
2 ArrayList<Product> list = new ArrayList<Product>();
3
4 //设置响应对象编码
5 response.setCharacterEncoding("utf-8");
6 response.setContentType("text/html;charset=utf-8");
7
8 //将list集合转换成json格式
9 JSONArray json = JSONArray.fromObject(list);
10
11 //将json写出浏览器
12 response.getWriter().print(json);
Product类
public class Product implements Serializable{
private static final long serialVersionUID = -992811686857962266L;
private String pid; //商品编号
private String pname; //商品名称
private Double market_price; //市场价格
private Double shop_price; //商城价格
private String pimage; //商品图⽚
private Date pdate; //上架⽇期
private Integer is_hot = 0; //是否热门商品, 1表⽰热门， 0表⽰不热门
private String pdesc; //商品描述
private Integer pflag; //表⽰是否下架， 1表⽰下架， 0表⽰不下架
private Category category; //商品所属的分类对象
public Product() {}
public Product(String pid, String pname, Double market_price, Double shop_price, String pimage, Date pdate,
Integer is_hot, String pdesc, Integer pflag, Category category) {
this.pid = pid;
this.pname = pname;
this.market_price = market_price;
this.shop_price = shop_price;
this.pimage = pimage;
this.pdate = pdate;
this.is_hot = is_hot;
this.pdesc = pdesc;
this.pflag = pflag;
this.category = category;
}
public String getPid() {
return pid;
}
public void setPid(String pid) {
this.pid = pid;
}
public String getPname() {
return pname;
}
public void setPname(String pname) {
this.pname = pname;
}
public Double getMarket_price() {
return market_price;
}
public void setMarket_price(Double market_price) {
this.market_price = market_price;
}
public Double getShop_price() {
return shop_price;
}
public void setShop_price(Double shop_price) {
this.shop_price = shop_price;
}
public String getPimage() {
return pimage;
}
public void setPimage(String pimage) {
this.pimage = pimage;
}
public Date getPdate() {
return pdate;
}
public void setPdate(Date pdate) {
this.pdate = pdate;
}
public Integer getIs_hot() {
return is_hot;
}
public void setIs_hot(Integer is_hot) {
this.is_hot = is_hot;
}
public String getPdesc() {
return pdesc;
}
public void setPdesc(String pdesc) {
this.pdesc = pdesc;
}
public Integer getPflag() {
return pflag;
}
public void setPflag(Integer pflag) {
this.pflag = pflag;
}
public Category getCategory() {
return category;
}
public void setCategory(Category category) {
this.category = category;
}
}　
在将list转换成JSON格式的时候，从数据库⾥读出来的是java.sql.Date赋值给了java.util.Date,转化成JSONArray时出错就会出现 et.sf.json.JSONException: ng.reflect.InvocationTargetException 异常。