生成动态内容的JSP文件中自定义标记的奇怪错误

Question

所以我正在使用MVC架构在JSP和Java servlet中编写Web程序，我必须使用自定义的forEach标记列出我从JSP页面上的数据库中检索的一堆项目。我写了标签类：

package ps6;

import java.io.*;
import javax.servlet.jsp.*;
import javax.servlet.jsp.tagext.SimpleTagSupport;

public class ForEachTag extends SimpleTagSupport {

    private Object[] items;
    private String attributeName;

    public void setItems(Object[] items) {
        this.items = items;
    }

    public void setVar(String attributeName) {
        this.attributeName = attributeName;
    }

    public void doTag() throws JspException, IOException {

        for (int i=0; i < items.length; i++) {
            getJspContext().setAttribute(attributeName, items[i]);
            getJspBody().invoke(null);
        }
    }
}

.tld文件：

<?xml version="1.0" encoding="UTF-8"?>
<taglib xmlns="http://java.sun.com/xml/ns/j2ee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
    xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee
    http://java.sun.com/xml/ns/j2ee/web-jsptaglibrary_2_0.xsd"
    version="2.0">
    <tlib-version>1.0</tlib-version>
    <short-name>auction</short-name>

    <tag>
        <description>Outputs a list or something</description>
        <name>forEach</name>
        <tag-class>ps6.ForEachTag</tag-class>
        <body-content>scriptless</body-content>

        <attribute>
            <description>The array of elements</description>
            <name>items</name>
            <required>true</required>
            <rtexprvalue>true</rtexprvalue>
        </attribute>
        <attribute>
            <description>The name of the variable to which each entry is assigned</description>
            <name>var</name>
            <required>true</required>   
        </attribute>
    </tag>
</taglib>

要完成工作的servlet：

package ps6;

import java.io.*;
import java.sql.Connection;
import java.sql.*;
import javax.servlet.*;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class ViewAuctions
 */
@WebServlet("/ViewAuctions")
public class ViewAuctions extends HttpServlet {
    private static final long serialVersionUID = 1L;

    /**
     * @see HttpServlet#HttpServlet()
     */
    public ViewAuctions() {
        super();
        // TODO Auto-generated constructor stub
    }

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        String[][] items = getItems();
        request.setAttribute("items", items);

        RequestDispatcher dispatcher = request.getRequestDispatcher("/WEB-INF/viewAuctions.jsp");
        dispatcher.forward(request, response);
    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
    }

    private String[][] getItems() {

        try {
            Connection connection = DB.openConnection();
            Statement statement = connection.createStatement();

            String query = "SELECT * FROM items WHERE open='1';";
            ResultSet results = statement.executeQuery(query);

            results.last();
            int numItems = results.getRow();
            results.first();
            int numCols = 5;
            String[][] items = new String[numItems][numCols];

            for (int r=0; r < numItems; r++) {

                items[r][0] = results.getString("itemNum");
                items[r][1] = results.getString("username");
                items[r][2] = results.getString("title");
                items[r][3] = results.getString("description");
                items[r][4] = results.getString("highBid");

                results.next();
            }

            return items;

        }
        catch (SQLException sqle) {
            throw new RuntimeException("Error accessing database: " + sqle);
        }

    }

}

最后是.jsp文件本身：

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>See what's for sale</title>
</head>
<body>
<%@ taglib uri="/WEB-INF/auction.tld" prefix="auction" %>

<h1>Open Auctions:</h1>

<table border="1">
<tr><th>Item No.</th><th>Auction Owner</th><th>Title</th><th>Description</th><th>Highest Bid</th></tr>
<auction:forEach items="${items}" var="row">
<tr><auction:forEach items="${row}" var="data">
    <td>${data}</td>
</auction:forEach>
</tr>
</auction:forEach>
</table>

但我一直得到这些错误，我真的不明白：

org.apache.jasper.JasperException: Unable to compile class for JSP: 

An error occurred at line: 16 in the jsp file: /WEB-INF/viewAuctions.jsp
Syntax error on token "[", delete this token
13: 
14: <table border="1">
15: <tr><th>Item No.</th><th>Auction Owner</th><th>Title</th><th>Description</th><th>Highest Bid</th></tr>
16: <auction:forEach items="${items}" var="row">
17: <tr><auction:forEach items="${row}" var="data">
18:     <td>${data}</td>
19: </auction:forEach>


An error occurred at line: 16 in the jsp file: /WEB-INF/viewAuctions.jsp
Ljava.lang.Object cannot be resolved to a type
13: 
14: <table border="1">
15: <tr><th>Item No.</th><th>Auction Owner</th><th>Title</th><th>Description</th><th>Highest Bid</th></tr>
16: <auction:forEach items="${items}" var="row">
17: <tr><auction:forEach items="${row}" var="data">
18:     <td>${data}</td>
19: </auction:forEach>


An error occurred at line: 16 in the jsp file: /WEB-INF/viewAuctions.jsp
Syntax error on token ";", delete this token
13: 
14: <table border="1">
15: <tr><th>Item No.</th><th>Auction Owner</th><th>Title</th><th>Description</th><th>Highest Bid</th></tr>
16: <auction:forEach items="${items}" var="row">
17: <tr><auction:forEach items="${row}" var="data">
18:     <td>${data}</td>
19: </auction:forEach>


An error occurred at line: 16 in the jsp file: /WEB-INF/viewAuctions.jsp
The method getValueFromPropertyEditorManager(Class<?>, String, String) in the type JspRuntimeLibrary is not applicable for the arguments ()
13: 
14: <table border="1">
15: <tr><th>Item No.</th><th>Auction Owner</th><th>Title</th><th>Description</th><th>Highest Bid</th></tr>
16: <auction:forEach items="${items}" var="row">
17: <tr><auction:forEach items="${row}" var="data">
18:     <td>${data}</td>
19: </auction:forEach>


An error occurred at line: 16 in the jsp file: /WEB-INF/viewAuctions.jsp
Syntax error, insert ")" to complete Expression
13: 
14: <table border="1">
15: <tr><th>Item No.</th><th>Auction Owner</th><th>Title</th><th>Description</th><th>Highest Bid</th></tr>
16: <auction:forEach items="${items}" var="row">
17: <tr><auction:forEach items="${row}" var="data">
18:     <td>${data}</td>
19: </auction:forEach>

我真的可以使用一些帮助来破译这些错误的含义，或者他们甚至指的是什么。它提到的那一行没有它抱怨的字符，我也看不出错误的来源，我也无法通过谷歌搜索错误找到任何帮助。任何见解将不胜感激。

Answer 1

由于您的web.xml描述符声明错误，可能会发生这种情况。尝试为Servlet API设置正确的版本（可能是2.4）和正确的架构，如果没有正确设置的话。

Answer 2

我不确定到底出了什么问题，但看起来JSP引擎错误地将类型Object[]（[Ljava.lang.Object;）的二进制表示插入到源代码中。尝试将setItems()的参数声明为Object。