hashtable的问题！高手指点
我做了一个购物车bean 是用的hashtable，bean里也写了
public void processRequest(HttpServletRequest clientRequest)
我在jsp页面用
cart.processRequest(request)想从购物车的hashtable中得到一个包含所有商品的迭代器。调试时为何这句报错，以前看过一个例子也是这么做的，只不过它购物车用的是hashmap,难道和这有关么？请高手指点。
问题点数：0、回复次数：10Top
1 楼Jacky1206（胖胖，其实我不胖）回复于 2004-09-03 14:42:29 得分 0
报什么错，贴出来Top
2 楼SJLPY（崩溃）回复于 2004-09-03 14:44:50 得分 0
message
description The server encountered an internal error () that prevented it from fulfilling this request.
exception
org.apache.jasper.JasperException
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:372)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:292)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:236)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
root cause
java.lang.NullPointerException
java.lang.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:980)
java.lang.Float.valueOf(Float.java:205)
com.cart.processRequest(cart.java:32)
org.apache.jsp.cart_jsp._jspService(cart_jsp.java:82)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:94)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:324)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:292)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:236)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
note The full stack trace of the root cause is available in the Apache Tomcat/5.0.27 logs.
--------------------------------------------------------------------------------
Apache Tomcat/5.0.27Top
3 楼miaoliujun（傲龙）回复于 2004-09-03 14:49:46 得分 0
那你用hashmap试试，他们之间的区别只有，key值hashtable不能为空，hashmap可以为空Top
4 楼cao8208（咖啡泡面）回复于 2004-09-03 14:50:39 得分 0
NullPointerException
空指针，看看有什么对象可能为空却没有判断Top
5 楼cocohui（断了线的风）回复于 2004-09-03 16:10:52 得分 0
bangni ding
Top
6 楼oliveyuganfei（龙欣）回复于 2004-09-03 16:22:00 得分 0
upTop
7 楼SJLPY（崩溃）回复于 2004-09-03 17:09:15 得分 0
购物车bean源码如下
（cart.java）
package com;
import java.util.*;
import com.msgCart;
import javax.servlet.http.*;
public class cart{
public Hashtable items;
public void processRequest(HttpServletRequest clientRequest)
{
String id,name,pri,pri1,submit,strNumber;
int number;
float price,price1;
//取得客户端数据
submit=clientRequest.getParameter("submit");
id=clientRequest.getParameter("id");
strNumber=clientRequest.getParameter("strNumber");
pri=clientRequest.getParameter("price");
pri1=clientRequest.getParameter("price1");
name=clientRequest.getParameter("name");
price=(Float.valueOf(pri)).floatValue();
price1=(Float.valueOf(pri1)).floatValue();
number=(Integer.valueOf(strNumber)).intValue();
//点击"clear"按钮的情况
if(submit!=null)
{
if(submit.equals("clear"))
{
clear();
return;
}
//点击"add"按钮的情况
if(submit.equals("add"))
{
add(id,number,price,price1,name);
//return;
}
//点击"remove"按钮的情况
if(submit.equals("remove"))
{
remove(id);
}
//点击"update"按钮的情况
if(submit.equals("update"))
{
update(id,number);
}
}
}
(msgCart.java)
package com;
import java.util.*;
public class msgCart
{
public int pro_count=0;
public float price=0;
public float price1=0;
public String id;
public String pro_name;
public msgCart()
{
}
public void setCart(String id,int number,float price,float price1,String name)
{
this.pro_count=number;
this.price=price;
this.price1=price1;
this.id=id;
this.pro_name=name;
}
public void addPro(int pc) //添加商品
{
pro_count+=pc;
}
public void modPro(int mc) //修改商品数量
{
pro_count=mc;
}
public String getId() //返回产品的ID号
{
return id;
}
public int getProcount() //返回产品的定购数量
{
return pro_count;
}
public float getPrice() //返回产品原价
{
return price;
}
public float getPrice1() //返回产品现价
{
return price1;
}
public float getPricecount() //返回每个产品的订购总价(以现价为准)。
{
return price1*pro_count;
}
public String getProname() //返回每个产品的名字。
{
return pro_name;
}
}
Top
8 楼SJLPY（崩溃）回复于 2004-09-03 17:15:34 得分 0
上边的(cart.java)没贴全重贴如下
package com;
import java.util.*;
import com.msgCart;
import javax.servlet.http.*;
public class cart{
public Hashtable items;
public void processRequest(HttpServletRequest clientRequest)
{
String id,name,pri,pri1,submit,strNumber;
int number;
float price,price1;
//取得客户端数据
submit=clientRequest.getParameter("submit");
id=clientRequest.getParameter("id");
strNumber=clientRequest.getParameter("strNumber");
pri=clientRequest.getParameter("price");
pri1=clientRequest.getParameter("price1");
name=clientRequest.getParameter("name");
price=(Float.valueOf(pri)).floatValue();
price1=(Float.valueOf(pri1)).floatValue();
number=(Integer.valueOf(strNumber)).intValue();
//点击"clear"按钮的情况
if(submit!=null)
{
if(submit.equals("clear"))
{
clear();
return;
}
//点击"add"按钮的情况
if(submit.equals("add"))
{
add(id,number,price,price1,name);
//return;
}
//点击"remove"按钮的情况
if(submit.equals("remove"))
{
remove(id);
}
//点击"update"按钮的情况
if(submit.equals("update"))
{
update(id,number);
}
}
}
public cart()
{
items = new Hashtable();
}
public void add(String id,int number,float price,float price1,String name)
{
String ID=new String(id);
msgCart m_cart=new msgCart();
if(items.containsKey(ID))
{
m_cart=(msgCart)items.get(ID);
m_cart.addPro(number);
}
else
{
number=1;
items.put(ID,m_cart);
m_cart.setCart(id,number,price,price1,name);
}
}
public void update(String id,int num)
{
String ID=new String(id);
if(items.containsKey(ID))
{
msgCart m_cart=new msgCart();
m_cart=(msgCart)items.get(ID);
m_cart.modPro(num);
}
else
{
System.out.print("no modify pc_count");
}
}
public void remove(String id) //删除商品
{
String ID=new String(id);
items.remove(ID);
}
public void clear() //清空购物车
{
items.clear();
}
public Hashtable getCart()
{
return items;
}
public float getCartprice() //购物车总金额
{
Enumeration enum=items.elements();
msgCart m_cart=new msgCart();
float count=0.0f;
while(enum.hasMoreElements())
{
m_cart=(msgCart)enum.nextElement();
count+=m_cart.getPricecount();
}
return count;
}
}
Top
9 楼SJLPY（崩溃）回复于 2004-09-03 17:17:50 得分 0
jsp页面如下，从其它页面通过url传递参数到这个页面
<jsp:useBean id="mycart" class="com.cart" scope="session"/>
<link href="css.css" rel="stylesheet" type="text/css">
<table width="490" border="1" align="center" cellpadding="0" cellspacing="0" bordercolor="#996600" style="border-collapse: collapse">
<tr>
<td colspan="8">欢迎！</td>
</tr>
<tr>
<td width="11%" align="center">商品编码</td>
<td width="23%" align="center">商品名称</td>
<td width="11%" align="center">商品单价</td>
<td width="11%" align="center">订购数量</td>
<td width="12%" align="center">修改数量</td>
<td width="11%" align="center">取消订购</td>
<td colspan="2" align="center">合计</td>
</tr>
<%
mycart.processRequest(request); //从购物车Hashtable中得到一个包含所有商品名称的迭代器
Hashtable cart=new Hashtable();
cart=mycart.getCart();
Iterator ci = cart.keySet().iterator();
while(ci.hasNext())
{
String ID =(String)ci.next();
if(ID!=null){
com.msgCart mcart=new com.msgCart();
mcart=(com.msgCart)cart.get("ID");
String name =mcart.getProname();
String id=mcart.getId();
String price=(String)mcart.getPrice();
//String price1=(String)mcart.getPrice1();
//String cartPrice=(String)
//String proPrice
}
%>
<tr>
<td width="11%" align="center"><%=name%></td>
<td width="23%" align="center"><%=id%></td>
<td width="11%" align="center"><%=price%></td>
<td width="11%" align="center"><input name="Number" type="text" value="strNumber" size="6" align="middle"></td>
<td width="12%" align="center"><input type="button" name="Submit" value="update" ></td>
<td width="11%" align="center"><input type="button" name="Submit" value="delect"></td>
<td width="18%" align="right"><%%></td>
<td width="3%" align="right">元</td>
</tr>
<tr>
<td colspan="8"><table width="100%" cellpadding="0" cellspacing="0" align="center">
<tr>
<td width="75%" align="right">总计:</td>
<td width="23%" align="right"><%%></td>
<td width="2%" align="right">元</td>
</tr>
</table></td>
</tr>
<%//}%>
<tr>
<td colspan="8"><table width="100%" cellpadding="0" cellspacing="0" align="center">
<tr>
<td width="33%" align="center"><a href="">继续购物</a></td>
<td width="34%" align="center">清空购物车</td>
<td width="33%" align="center"><a href="">前往收银台</a></td>
</tr>
</table></td>
</tr>
<tr>
<td colspan="8" align="center"><a href=# onclick="javasrcript:window.close();">关 闭 窗 口</a></td>
</tr>
</table>
<%
Enumeration a= request.getParameterNames();
while(a.hasMoreElements())
{
System.out.println(a.nextElement());
}
%>Top
10 楼hpretty（阿飞）回复于 2004-09-03 17:44:52 得分 0
Hashtable不是线程安全的
Hashmap是线程安全的
考虑改成那种吧
其实操作都差不多吧Top
