将产品或类别的链接从Controller Servlet显示到jsp页面

时间：2015-03-19 06:57:05

标签： java jsp jstl el

我正在尝试在用户选择给定产品后将产品链接到他们自己的jsp页面。我做错了，因为数据在product.jsp上没有显示一次。

我尝试使用变量selectedProduct检索数据，但似乎应用程序无法识别它或者不知道在哪里检索变量selectedProduct的数据。

我不知道为什么，因为在我看来，selectedProduct会与selectedCategory相同......显然不是......为什么？我错过了什么吗？

过去一周我一直在寻找解决方案。任何帮助都不仅仅是欢迎！

Controller Servlet：

package controller;


import cart.ShoppingCart;
import wishlist.Wishlist;
import entity.Category;
import entity.Product;
import java.io.IOException;
import java.util.Collection;
import javax.ejb.EJB;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import session.CategoryFacade;
import session.ProductFacade;

public class ControllerServlet extends HttpServlet {


    @EJB
    private CategoryFacade categoryFacade;
    @EJB
    private ProductFacade productFacade;

 @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {

        String userPath = request.getServletPath();
        HttpSession session = request.getSession();
        Category selectedCategory;
        Product selectedProduct;
        Collection<Product> categoryProducts;



      // if category page is requested
            if (userPath.equals("/category")) {

                // get categoryId from request
                String categoryId = request.getQueryString();

                if (categoryId != null) {

                    // get selected category
                    selectedCategory = categoryFacade.find(Short.parseShort(categoryId));

                    // place selected category in session scope
                    session.setAttribute("selectedCategory", selectedCategory);

                    // get all products for selected category
                    categoryProducts = selectedCategory.getProductCollection();

                    // place category products in session scope
                    session.setAttribute("categoryProducts", categoryProducts);
                }


            // if product page is requested
            if (userPath.equals("/product")) {

                // get productId from request
                String productId = request.getQueryString();

                 if (productId != null) {

                // get selected product
                selectedProduct = productFacade.find(Short.parseShort(productId));

// place selected product in session scope
                session.setAttribute("selectedProduct", selectedProduct);
            }}

基于请求的编辑

Product.java： 

package entity;

import java.io.Serializable;
import java.math.BigDecimal;
import java.util.Collection;
import java.util.Date;
import javax.persistence.Basic;
import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.Lob;
import javax.persistence.ManyToMany;
import javax.persistence.NamedQueries;
import javax.persistence.NamedQuery;
import javax.persistence.OneToMany;
import javax.persistence.Table;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;
import javax.validation.constraints.NotNull;
import javax.validation.constraints.Size;
import javax.xml.bind.annotation.XmlRootElement;
import javax.xml.bind.annotation.XmlTransient;

/**
 *
 * @author PC
 */
@Entity
@Table(name = "product")
@XmlRootElement
@NamedQueries({
    @NamedQuery(name = "Product.findAll", query = "SELECT p FROM Product p"),
    @NamedQuery(name = "Product.findById", query = "SELECT p FROM Product p WHERE p.id = :id"),
    @NamedQuery(name = "Product.findByName", query = "SELECT p FROM Product p WHERE p.name = :name"),
    @NamedQuery(name = "Product.findByPrice", query = "SELECT p FROM Product p WHERE p.price = :price"),
    @NamedQuery(name = "Product.findByDescription", query = "SELECT p FROM Product p WHERE p.description = :description"),
    @NamedQuery(name = "Product.findByLastUpdate", query = "SELECT p FROM Product p WHERE p.lastUpdate = :lastUpdate")})
public class Product implements Serializable {
    @Basic(optional = false)
    @NotNull
    @Size(min = 1, max = 45)
    @Column(name = "price")
    private BigDecimal price;
    private static final long serialVersionUID = 1L;
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Basic(optional = false)
    @Column(name = "id")
    private Integer id;
    @Basic(optional = false)
    @NotNull
    @Lob
    @Size(min = 1, max = 16777215)
    @Column(name = "name")
    private String name;
    @Lob
    @Size(max = 2147483647)
    @Column(name = "description")
    private String description;
    @Basic(optional = false)
    @NotNull
    @Column(name = "last_update")
    @Temporal(TemporalType.TIMESTAMP)
    private Date lastUpdate;
    @JoinColumn(name = "category_id", referencedColumnName = "id")
    @ManyToMany(mappedBy = "productCollection")
    private Collection<Category> categoryCollection;
    @OneToMany(cascade = CascadeType.ALL, mappedBy = "product")
    private Collection<OrderedProduct> orderedProductCollection;


    /**
     *
     */
    public Product() {
    }

    /**
     *
     * @param id
     */
    public Product(Integer id) {
        this.id = id;
    }

    /**
     *
     * @param id
     * @param name
     * @param price
     * @param lastUpdate
     */
    public Product(Integer id, String name, BigDecimal price, Date lastUpdate) {
        this.id = id;
        this.name = name;
        this.price = price;
        this.lastUpdate = lastUpdate;
    }

    /**
     *
     * @return
     */
    public Integer getId() {
        return id;
    }

    /**
     *
     * @param id
     */
    public void setId(Integer id) {
        this.id = id;
    }

    /**
     *
     * @return
     */
    public String getName() {
        return name;
    }


    /**
     *
     * @param name
     */
    public void setName(String name) {
        this.name = name;
    }


    /**
     *
     * @return
     */
    public String getDescription() {
        return description;
    }

    /**
     *
     * @param description
     */
    public void setDescription(String description) {
        this.description = description;
    }

    /**
     *
     * @return
     */
    public Date getLastUpdate() {
        return lastUpdate;
    }

    /**
     *
     * @param lastUpdate
     */
    public void setLastUpdate(Date lastUpdate) {
        this.lastUpdate = lastUpdate;
    }

    /**
     *
     * @return
     */
    @XmlTransient
    public Collection<Category> getCategoryCollection() {
        return categoryCollection;
    }

    /**
     *
     * @param categoryCollection
     */
    public void setCategoryCollection(Collection<Category> categoryCollection) {
        this.categoryCollection = categoryCollection;
    }

    /**
     *
     * @return
     */
    @XmlTransient
    public Collection<OrderedProduct> getOrderedProductCollection() {
        return orderedProductCollection;
    }

    /**
     *
     * @param orderedProductCollection
     */
    public void setOrderedProductCollection(Collection<OrderedProduct> orderedProductCollection) {
        this.orderedProductCollection = orderedProductCollection;
    }

    @Override
    public int hashCode() {
        int hash = 0;
        hash += (id != null ? id.hashCode() : 0);
        return hash;
    }

    @Override
    public boolean equals(Object object) {
        // TODO: Warning - this method won't work in the case the id fields are not set
        if (!(object instanceof Product)) {
            return false;
        }
        Product other = (Product) object;
        return !((this.id == null && other.id != null) || (this.id != null && !this.id.equals(other.id)));
    }

    @Override
    public String toString() {
        return "entity.Product[ id=" + id + " ]";
    }

    public BigDecimal getPrice() {
        return price;
    }

    public void setPrice(BigDecimal price) {
        this.price = price;
    }
}

Product.jsp 

<table style="text-align: left; width: 100%; height: 172px;" border="0" cellpadding="0" cellspacing="0">

    <tbody>
        <tr>
            <td colspan="1" rowspan="6" style="vertical-align: top;">product_gallery<br></td>
            <td colspan="1" rowspan="6" style="vertical-align: top;"><img class="img" src="${initParam.productBigImagePath}${product.name}.jpg"><br></td>
            <td style="vertical-align: top;">${selectedProduct.name}<br></td>
            <td style="vertical-align: top;"><br></td>
        </tr>
        <tr>
            <td style="vertical-align: top;">$ ${selectedProduct.price}</td>
            <td style="vertical-align: top;"><br></td>
        </tr>
        <tr>
            <td style="vertical-align: top;"><br></td>
            <td style="vertical-align: top;"><br></td>
        </tr>
        <tr>
            <td style="vertical-align: top;"><br></td>
            <td style="vertical-align: top;"><br></td>
        </tr>
        <tr>
            <td colspan="2" rowspan="1" style="vertical-align: top;">${selectedProduct.description}</td>
        </tr>
        <tr>
            <td style="vertical-align: top;">
                <form action="addToWishlist" method="post"><br><br> 
                    <input name="productId" value="${product.id}" type="hidden"> 
                    <input class="submit" onclick="addedWishlist()" value="<fmt:message key='AddToWishlist'/>" type="submit"> 
                </form><br>
            </td>
            <td style="vertical-align: top;">
                <form action="addToCart" method="post"><br><br> 
                    <input name="productId" value="${product.id}" type="hidden">
                    <input class="submit" onclick="addedCart()" value="<fmt:message key='AddToCart'/>" type="submit"> 
                </form>
            </td>
        </tr>
        <tr>
            <td style="vertical-align: top;"><br></td>
            <td style="vertical-align: top;"><br></td>
            <td colspan="2" rowspan="1" style="vertical-align: top;">
                <ul>
                    <li style="background-color: rgb(198, 255, 201); width:100%; text-align:center; border-radius:2em;">
                        <a href="${value}"><fmt:message key='ContinueShopping'/></a>
                    </li>
                </ul>
                <br>
            </td>
        </tr>
    </tbody>
</table>

Category.jsp 

<table style="text-align: left; width: 100%;" border="0" cellpadding="0" cellspacing="40px">

  <c:forEach var="product" items="${categoryProducts}" varStatus="iter">

    <td>
      <tbody>
        <tr>
          <td style="vertical-align: middle; text-align: center;" class="cell">
            <a href="product?${product.id}">



              <img class="img" alt="" src="${initParam.productImagePath}${product.name}.jpg" />

              <div class="caption">
                <br>view details</div>

            </a>
            <br>


          </td>
          <td style="vertical-align: middle; width: 140px; text-align: center; ">${product.name}
            <br>
          </td>
          <td style="vertical-align: middle; width: 120px; text-align: center; line-height:100%;">$${product.price}
            <br>
          </td>
          <td style="vertical-align: middle; width: 136px; text-align: center; line-height:20%;">

            <form id="wishlistForm" action="addToWishlist" method="post">
              <br>
              <br>
              <input name="productId" value="${product.id}" type="hidden">

              <input class="submit" onclick="addedWishlist()" value="<fmt:message key='AddToWishlist'/>" type="submit">
            </form>
            <br>
          </td>
          <td style="vertical-align: middle; width: 136px; text-align: center; line-height:20%;">


            <form id="cartForm" action="addToCart" method="post">
              <br>
              <br>

              <input name="productId" value="${product.id}" type="hidden">
              <input class="submit" onclick="addedCart()" value="<fmt:message key='AddToCart'/>" type="submit">


            </form>
            <br>
          </td>
        </tr>
      </tbody>
  </c:forEach>
</table>

2 个答案:

答案 0 :(得分：2)

您将会话属性设置为selectProduct，这是一个单独的产品：

Product selectedProduct;
...
session.setAttribute("selectedProduct", selectedProduct);
JSTL标记中的

<c:forEach>用于Collections, Lists or Arrays，不适用于单个对象。

由于这是正常的，你的第一个场景是：<c:forEach var="product" items="${selectedProduct}" varStatus="iter"></c:forEach>它是空白的，因为你不能迭代一个简单的bean。

在您的第二个场景中，您正在迭代${categoryProducts}。我想你将这个对象设置为会话属性（它没有显示在你的代码片段中，但肯定在它上面），至少这个对象是一个集合，所以在你的服务器中我想你已经：

Collection<Product> categoryProducts;
...
session.setAttribute("categoryProducts", categoryProducts);

在这种情况下，如果您使用<c:forEach var="product" items="${categoryProducts}" varStatus="iter"></c:forEach>，则会迭代此类别中的所有产品，这就是所有产品都会显示在您的页面中的原因。

在你的第三种情况下，例如你使用<c:forEach var="product" items="${categoryProducts}" varStatus="iter"></c:forEach>的第二种情况，所以你要为循环的每一步分配一个从categoryProducts集合到product对象的元素，但是在里面这个循环你正在使用${selectedProduct}而不是${product}所以对于每次迭代，你使用相同的对象而不是对象从集合中提供它。

我认为，如果您只想在product中显示一个product.jsp，并且此product存储在selectedProduct会话attributte上，那么就要解决您的问题使用<c:forEach>，将其从product.jsp中删除（因为您只想显示一个产品），并在jsp代码中使用${selectedProduct.yourProperty}而不是${product.yourProperty}。

基于评论的编辑

尝试使用关注product.jsp，如果它继续显示空白页面，请检查您是否真的为您的产品设置了名为selectedProduct的会话属性，并且它的成员有一个值（selectProduct.getName()，selectProduct.getDescription()，selectProduct.getPrice()不是空白的。检查if中的代码，也许它永远不会被执行，或者如果执行了selectProduct有一些空字段

       if (productId != null) {

            // get selected product
            selectedProduct = productFacade.find(Short.parseShort(productId));

            // place selected product in session scope
            session.setAttribute("selectedProduct", selectedProduct);
        }

<强> Product.jsp： 

<table style="text-align: left; width: 100%; height: 172px;" border="0" cellpadding="0" cellspacing="0">
    <tbody>
        <tr>
            <td colspan="1" rowspan="6" style="vertical-align: top;">product_gallery<br></td>
            <td colspan="1" rowspan="6" style="vertical-align: top;"><img class="img" src="${initParam.productBigImagePath}${selectedProduct.name}.jpg"><br></td>
            <td style="vertical-align: top;">${selectedProduct.name}<br></td>
            <td style="vertical-align: top;"><br></td>
        </tr>
        <tr>
            <td style="vertical-align: top;">$ ${selectedProduct.price}</td>
            <td style="vertical-align: top;"><br></td>
        </tr>
        <tr>
            <td style="vertical-align: top;"><br></td>
            <td style="vertical-align: top;"><br></td>
        </tr>
        <tr>
            <td style="vertical-align: top;"><br></td>
            <td style="vertical-align: top;"><br></td>
        </tr>
        <tr>
            <td colspan="2" rowspan="1" style="vertical-align: top;">${selectedProduct.description}</td>
        </tr>
        <tr>
            <td style="vertical-align: top;">
                <form action="addToWishlist" method="post"><br><br> 
                    <input name="productId" value="${selectedProduct.id}" type="hidden"> 
                    <input class="submit" value="<fmt:message key='AddToWishlist'/>" type="submit"> 
                </form><br>
            </td>
            <td style="vertical-align: top;">
                <form action="addToCart" method="post"><br><br> 
                    <input name="productId" value="${selectedProduct.id}" type="hidden">
                    <input class="submit" value="<fmt:message key='AddToCart'/>"type="submit"> 
                </form>
            </td>
        </tr>
        <tr>
            <td style="vertical-align: top;"><br></td>
            <td style="vertical-align: top;"><br></td>
            <td colspan="2" rowspan="1" style="vertical-align: top;">
                <ul>
                    <li style="background-color: rgb(198, 255, 201); width:100%; text-align:center; border-radius:2em;">
                        <a href="${value}"><fmt:message key='ContinueShopping'/></a>
                    </li>
                </ul>
                <br>
            </td>
        </tr>
    </tbody>
</table>

希望这有帮助，

答案 1 :(得分：0)

使用工作回答进行编辑

// if product page is requested
        } else if (userPath.equals("/viewProduct")) {

            String productId = request.getQueryString();

            if (productId != null) {

                // get selected product
                selectedProduct = productFacade.find(Integer.parseInt(productId));

                // place selected product in session scope
                session.setAttribute("selectedProduct", selectedProduct);

            }

            userPath = "/product";
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