Erro HTTP Status 500 - An exception occurred processing JSP page - Aula 13

Sem o método Collection na classe CarrinhoCompras, a tela carrinho retorna erro. Nisso com o método presente, a tela carinho funciona normalmente.

package br.com.casadocodigo.loja.models;

import java.io.Serializable;
import java.math.BigDecimal;
import java.util.Collection;
import java.util.LinkedHashMap;
import java.util.Map;

import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Scope;
import org.springframework.stereotype.Component;
import org.springframework.web.context.WebApplicationContext;

@Component 
@Scope(value = WebApplicationContext.SCOPE_SESSION)
public class CarrinhoCompras implements Serializable{

    private static final long serialVersionUID = 1L;

    private Map<CarrinhoItem, Integer> itens = new LinkedHashMap<CarrinhoItem, Integer>();

    public void add(CarrinhoItem item) {
        itens.put(item, getQuantidade(item) + 1);
    }

    public Integer getQuantidade(CarrinhoItem item) {
        if (!itens.containsKey(item)) {
            itens.put(item, 0);
        }
        return itens.get(item);
    }

    public int getQuantidade() {
        return itens.values().stream().reduce(0, (proximo, acumulador) -> (proximo + acumulador));
    }

    public Collection<CarrinhoItem> getItens() {
        return itens.keySet();
    }

    public BigDecimal getTotal(CarrinhoItem item) {
        return item.getTotal(getQuantidade(item));
    }

    public BigDecimal getTotal() {
        BigDecimal total = BigDecimal.ZERO;
        for (CarrinhoItem item : itens.keySet()) {
            total = total.add(getTotal(item));
        }
        return total;
    }
}

Erro:

HTTP Status 500 - An exception occurred processing JSP page /WEB-INF/views/carrinho/itens.jsp at line 106

type Exception report

message An exception occurred processing JSP page /WEB-INF/views/carrinho/itens.jsp at line 106

description The server encountered an internal error that prevented it from fulfilling this request.

exception

org.apache.jasper.JasperException: An exception occurred processing JSP page /WEB-INF/views/carrinho/itens.jsp at line 106

103:                 </tr>
104:               </thead>
105:               <tbody>
106:                   <c:forEach items="${carrinhoCompras.itens }" var="item">
107:                       <tr>
108: 
109:                       <td class="cart-img-col"><img src="http://cdn.shopify.com/s/files/1/0155/7645/products/css-eficiente-featured_large.png?v=1435245145" width="71px" height="100px"/></td>


Stacktrace:
    org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:580)
    org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:477)
    org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:395)
    org.apache.jasper.servlet.JspServlet.service(JspServlet.java:339)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
    org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    org.springframework.web.servlet.view.InternalResourceView.renderMergedOutputModel(InternalResourceView.java:172)
    org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:303)
    org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1228)
    org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1011)
    org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:955)
    org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:877)
    org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:961)
    org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:852)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:624)
    org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:837)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
    org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88)
    org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
    org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)

root cause

org.apache.jasper.el.JspPropertyNotFoundException: /WEB-INF/views/carrinho/itens.jsp(106,18) '${carrinhoCompras.itens }' Property 'itens' not found on type br.com.casadocodigo.loja.models.CarrinhoCompras
    org.apache.jasper.el.JspValueExpression.getValue(JspValueExpression.java:109)
    org.apache.jsp.WEB_002dINF.views.carrinho.itens_jsp._jspx_meth_c_005fforEach_005f0(itens_jsp.java:391)
    org.apache.jsp.WEB_002dINF.views.carrinho.itens_jsp._jspService(itens_jsp.java:227)
    org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
    org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:439)
    org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:395)
    org.apache.jasper.servlet.JspServlet.service(JspServlet.java:339)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
    org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    org.springframework.web.servlet.view.InternalResourceView.renderMergedOutputModel(InternalResourceView.java:172)
    org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:303)
    org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1228)
    org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1011)
    org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:955)
    org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:877)
    org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:961)
    org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:852)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:624)
    org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:837)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
    org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88)
    org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
    org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)