Question

因此，此代码正在读取.txt文件，然后将值存储在arraylist中。我试图通过一个名为Product的简单构造函数输出结果。但是，当我尝试在page2.jsp中执行JSP for循环时，不会显示任何内容。当我尝试显示arrayList产品时，它也给了我一个nullpointerexception，但我没有看到读取该文件的类有任何问题。任何建议和帮助表示赞赏。

page2.jsp

<%@page import="java.util.ArrayList"%>
<%@page import="java.util.Iterator"%>
<%@page import="constructor.Product"%>
<%@page import="java.util.List"%>
<%@page import="data.ProductIO"%>

<body>

    <%

    ProductIO pro = new ProductIO();
    ArrayList<Product> userList = pro.selectProducts();
    //Iterator<Product> itr = userList.iterator();
    //Product user = new Product();
    %>
        <table style="width:100%">
            <%
                for(Product product : userList) {
            %>

            <tr>
              <td><%=product.getCode()%></td>
              <td><%=product.getDescription()%></td>
              <td><%=product.getPrice()%></td>
            </tr>
            <% 
                }

            %>

        </table>
</body>

ProductIO.java

public class ProductIO {

private static ArrayList<Product> products = null;

private static String filePath = "product.txt";

public static void main(String [] args) {
    //System.out.println(products);
}

public static void init(String filePath) {

    ProductIO.filePath = filePath;

}

public static ArrayList<Product> selectProducts() {

    products = new ArrayList();

    File file = new File("product.txt");

    try {

        BufferedReader in = new BufferedReader(new FileReader(file));

        String line = in.readLine();

        while (line != null) {

            StringTokenizer t = new StringTokenizer(line, "|");

            if (t.countTokens() >= 3) {

                String code = t.nextToken();

                String description = t.nextToken();

                String priceAsString = t.nextToken();

                double price = Double.parseDouble(priceAsString);

                Product p = new Product();

                p.setCode(code);

                p.setDescription(description);

                p.setPrice(price);

                products.add(p);

            }

            line = in.readLine();

        }

        in.close();

        return products;

    } catch (IOException e) {

        System.out.println(e);

        return products;

    }

}

JSP FOR循环不显示结果

0 个答案: