新增商品后总是出现goodsList cannot be resolved to a variable

100

101

102

103

104

105

106

107

108

109

110

111

112

113

114

115

116

117

118

119

120

121

122

123

124

125

126

127

128

129

130

131

132

133

134

135

136

137

138

139

140

141

142

143

144

145

146

147

148

149

150

151

152

153

154

155

156

157

158

159

160

161

162

163

164

165

166

167

168

169

170

171

172

173

174

175

176

177

178

179

180

181

182

183

184

185

186

187

188

189

190

191

192

193

194

195

196

197

198

199

200

201

202

203

204

205

206

207

208

209

210

211

212

213

214

215

216

217

218

219

220

221

222

223

224

225

226

227

228

229

230

231

232

233

234

235

236

237

238

239

240

241

242

243

244

245

246

247

248

249

250

251

252

253

254

255

256

257

258

259

260

261

262

263

264

265

266

267

268

269

270

271

272

273

274

275

276

277

278

279

280

281

282

283

284

285

286

287

288

289

290

291

292

293

294

295

296

297

298

299

300

301

package com.imooc.gim;
import java.io.IOException;
import java.util.List;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
 * Servlet implementation class GoodsAddServlet
 */
@WebServlet("/create")
public class GoodsAddServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
        
    /**
     * @see HttpServlet#HttpServlet()
     */
    public GoodsAddServlet() {
        super();
        // TODO Auto-generated constructor stub
    }
/**
 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
 */
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doPost(request, response);
}
/**
 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
 */
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
request.setCharacterEncoding("utf-8");
String goodsId=request.getParameter("goodsId");
    String goodsName=request.getParameter("goodsName");
    String goodsType=request.getParameter("goodsType");
    String price=request.getParameter("goodsPrice");
    String goodsRemark=request.getParameter("description");
    System.out.println(goodsId);
    Goods goods = new Goods(Integer.parseInt(goodsId),goodsName,goodsType,Float.parseFloat(price),goodsRemark);
    ServletContext context=request.getServletContext();
    List goodsList=(List)context.getAttribute("goods");
goodsList.add(goods);
    context.setAttribute("goods", goodsList);
    request.getRequestDispatcher("/goods.jsp").forward(request, response);
}
}
package com.imooc.gim;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
 * Servlet implementation class GoodsAddServlet
 */
@WebServlet("/gl")
public class GoodsListServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
    /**
     * Default constructor. 
     */
    public GoodsListServlet() {
        // TODO Auto-generated constructor stgaub
    }
/**
 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
 */
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
       doPost(request, response);
}
/**
 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
 */
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    request.setCharacterEncoding("utf-8");
    ServletContext context=request.getServletContext();
    if(context.getAttribute("goods")==null) {   
         
    List<Goods> goodsList=new ArrayList<>();
    goodsList.add(new Goods(1001,"格力空调","家用电器",3000.00f,"铂金品质"));
    goodsList.add(new Goods(1002,"LV","服装",18888.00f,"生活一场旅行"));
    context.setAttribute("goods", goodsList);
     
    }    
     
     
    request.getRequestDispatcher("/goods.jsp").forward(request, response);
     
   }
     
}
 
package com.imooc.gim;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
 
/**
 * Servlet implementation class GoodsAddServlet
 */
@WebServlet("/gl")
public class GoodsListServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
 
    /**
     * Default constructor. 
     */
    public GoodsListServlet() {
        // TODO Auto-generated constructor stgaub
    }
 
    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
               doPost(request, response);
    }
 
    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            request.setCharacterEncoding("utf-8");
            ServletContext context=request.getServletContext();
            if(context.getAttribute("goods")==null) {     
                 
                List<Goods> goodsList=new ArrayList<>();
                goodsList.add(new Goods(1001,"格力空调","家用电器",3000.00f,"铂金品质"));
                goodsList.add(new Goods(1002,"LV","服装",18888.00f,"生活一场旅行"));
                context.setAttribute("goods", goodsList);
                 
            }       
             
             
            request.getRequestDispatcher("/goods.jsp").forward(request, response);
             
             }
 
 
             
         
    }
     
    //goods.jsp
     
    <%@ page contentType="text/html; charset=UTF-8" %>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %> 
<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width,initial-scale=1">
    <title>商品列表</title>
    <link href="css/bootstrap.css" type="text/css" rel="stylesheet">
    </link>
    <script type="text/javascript" src="js/jquery-1.11.1.min.js"></script>
    <script type="text/javascript" src="js/bootstrap.js"></script>
    <style type="text/css">
    .pagination {
        margin: 0px
    }
 
    .pagination>li>a,
    .pagination>li>span {
        margin: 0 5px;
        border: 1px solid #dddddd;
    }
 
    .glyphicon {
        margin-right: 3px;
    }
 
    .form-control[readonly] {
        cursor: pointer;
        background-color: white;
    }
 
    #dlgPhoto .modal-body {
        text-align: center;
    }
 
    .preview {
 
        max-width: 500px;
    }
    </style>
    <script>
        $(function () {
             
            $("#btnAdd").click(function () {
                $('#dlgForm').modal()
            });
        })
    </script>
</head>
 
<body>
    <div class="container">
        <div class="row">
            <h1 style="text-align: center">IMOOC商品信息表</h1>
            <div class="panel panel-default">
                <div class="clearfix panel-heading ">
                    <div>
                        <label class="form-inline">
                            <div class="form-group" style="width: 850px;">
                                <button class="btn btn-primary" id="btnAdd">新增
                                </button>
                            </div>
                            <div class="form-group pull-right">
                                <form action="#" method="post">
                                    <input type="text" class="form-control" id="searchById" name="id" placeholder="根据商品id进行查询">
                                    <button type="submit" class="btn btn-primary">查询</button>
                                </form>
                            </div>
                        </label>
                    </div>
                    <table class="table table-bordered table-hover">
                        <thead>
                            <tr>
                                <th>序号</th>
                                <th>商品编号</th>
                                <th>商品名称</th>
                                <th>商品类别</th>
                                <th>价格</th>
                                <th>备注</th>
                                <th>&nbsp;</th>
                            </tr>
                            <c:forEach items="${applicationScope.goods}" var ="good" varStatus="idx">
                            <tr>
                                <th>${idx.index+1}</th>
                                <th>${good.goodsId}</th>
                                <th>${good.goodsName}</th>
                                <th>${good.goodsType}</th>
                                <th>价格</th>
                                <th>${good.goodsRemark}</th>
                                <th>&nbsp;</th>
                            </tr>
                            </c:forEach>
                        </thead>
                    </table>
                </div>
            </div>
        </div>
        <!-- 表单 -->
        <div class="modal fade" tabindex="-1" role="dialog" id="dlgForm">
            <div class="modal-dialog" role="document">
                <div class="modal-content">
                    <div class="modal-header">
                        <button type="button" class="close" data-dismiss="modal" aria-label="Close"><span aria-hidden="true">&times;</span>
                        </button>
                        <h4 class="modal-title">新增商品</h4>
                    </div>
                    <div class="modal-body">
                        <form action="/Gim/create" method="post">
                            <div class="form-group">
                                <label>商品编号</label>
                                <input type="text" name="goodsId" class="form-control" id="empno" placeholder="请输入商品编号">
                            </div>
                            <div class="form-group">
                                <label>商品名称</label>
                                <input type="text" name="goodsName" class="form-control" id="ename" placeholder="请输入商品名称">
                            </div>
                            <div class="form-group">
                                <label>商品类别</label>
                                <select id="gname" name="goodsType" class="form-control">
                                    <option selected="selected">服装</option>
                                    <option value="家用">家用电器</option>
                                    <option value="生活">生活用品</option>
                                </select>
                            </div>
                            <div class="form-group">
                                <label>价格</label>
                                <input type="text" name="price" class="form-control" id="sal" placeholder="请输入价格">
                            </div>
                            <div class="form-group">
                                <label>备注</label>
                                <input type="text" name="description" class="form-control" id="sal" placeholder="请输入备注">
                            </div>
                            <div class="form-group" style="text-align: center;">
                                <button type="submit" class="btn btn-primary">保存</button>
                            </div>
                        </form>
                    </div>
                </div><!-- /.modal-content -->
            </div><!-- /.modal-dialog -->
        </div><!-- /.modal -->
</body>
 
</html>

Description Resource Path Location Type

goodsList cannot be resolved to a variable GoodsAddServlet.java /Gim/src/main/java/com/imooc/gim line 51 Java Problem

晓舟 2021-12-03

源自：JSTL与EL表达式 3-4 项目作业

收起

1回答

好帮手慕小蓝回答被采纳获得+3积分 2021-12-04 09:43:45

同学你好，需要同学提供一下Goods类代码。

祝学习愉快~

收起回答

晓舟提问者 #1

package com.imooc.gim;
public class Goods {
 private Integer goodsId;
 private String goodsName;
 private String goodsType;
 private float price;
 private String goodsRemark;
public Goods(Integer goodsId, String goodsName, String goodsType, float price, String goodsRemark) {
super();
this.goodsId = goodsId;
this.goodsName = goodsName;
this.goodsType = goodsType;
this.price = price;
this.goodsRemark = goodsRemark;
}
public Integer getGoodsId() {
return goodsId;
}
public void setGoodsId(Integer goodsId) {
this.goodsId = goodsId;
}
public String getGoodsName() {
return goodsName;
}
public void setGoodsName(String goodsName) {
this.goodsName = goodsName;
}
public String getgoodsType() {
return goodsType;
}
public void setgoodsType(String goodsType) {
this.goodsType = goodsType;
}
public float getPrice() {
return price;
}
public void setPrice(float price) {
this.price = price;
}
public String getGoodsRemark() {
return goodsRemark;
}
public void setGoodsRemark(String goodsRemark) {
this.goodsRemark = goodsRemark;
}
@Override
public String toString() {
return "Goods [goodsId=" + goodsId + ", goodsName=" + goodsName + ", goodsType=" + goodsType
+ ", price=" + price + ", goodsRemark=" + goodsRemark + "]";
}
  
}

2021-12-04 09:48:26

好帮手慕小蓝回复提问者晓舟 #2

同学你好，同学代码中存在两个错误：
1.同学的GoodsAddServlet中，获取价格时使用的请求参数名为goodsPrice，而JSP中那么属性值为price，会导致参数无法传递，出现空指针异常。
2.如果在直接访问goods.jsp时，使用添加功能，会出现空指针异常。原因是同学的GoodsAddServlet中，List goodsList = (List) context.getAttribute("goods");语句中的goodsList为null，goodsList的setAttribute是在GoodsListServlet中的，而直接访问JSP时没有执行GoodsListServlet导致的。
综上，老师多次测试几种访问方式，都没有复现同学所指的“goodsList cannot be resolved to a variable”错误。
如果该错误依然存在，建议同学详细描述一下操作过程以及提供一下错误的截图。
祝学习愉快~

2021-12-04 10:11:14