Question

我想在JSP文件中使用表达式语言打印servlet请求属性。我已经完成了以下操作，在我的Servlet中，我用

设置了所有必要的请求属性

setRequestAttributes(String, Object);

在我的JSP页面中，我使用以下行来打印属性：

<c:out value="${string}"/>

在阅读其他帖子后，我检查了在Web XML中是否使用了2.4版本，它是。

When using getAttribute(String)

在Servlet本身中，它打印的值很好。有没有人知道我需要做什么，所以我可以做到这一点。

修改

Servlet代码：

package servlets;

import java.io.IOException;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import classes.DBConnection;

public class MessageDetail extends HttpServlet {

    private static final long serialVersionUID = 1L;
    private String messageid;
    private Connection connect;

    public MessageDetail() {

        super();
    }
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

    }
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        connect = new DBConnection().returnConnection();
        messageid = request.getParameter("xxxxx");

        try {
            handleRequest(request);
        } catch (SQLException e) {
            e.printStackTrace();
        }

        RequestDispatcher dispatcher = request.getRequestDispatcher("messageDetail.jsp");
        dispatcher.forward(request, response);
    }

    private void handleRequest(HttpServletRequest request) throws SQLException{

        ResultSet messageData = getMessageData("xxxxxx");
        ResultSet attachmentData = getMessageData("xxxxxx");
        Map<Integer, List<List<Object>>> messageMap = convertResultSetToMap(messageData);
        Map<Integer, List<List<Object>>> attachmentMap = convertResultSetToMap(attachmentData);
        Map<Integer, List<List<Object>>> totalMap = combineMaps(messageMap, attachmentMap);
        setRequestAttributes(request, totalMap);

    }

    private ResultSet getMessageData(String tableName) throws SQLException{

        String sql = "SELECT * FROM " + tableName + " WHERE xxxxxxxx= "+ xxxxxxx;
        PreparedStatement prestm = connect.prepareStatement(sql, ResultSet.CONCUR_READ_ONLY, ResultSet.TYPE_SCROLL_SENSITIVE);
        ResultSet rs = prestm.executeQuery();
        return rs;
    }

    private Map<Integer, List<List<Object>>> convertResultSetToMap(ResultSet rs) throws SQLException{

        Map <Integer, List<List<Object>>> resultSetMap = new HashMap<Integer, List<List<Object>>>(); 
        ResultSetMetaData rsmd = rs.getMetaData();
        int colTotal = rsmd.getColumnCount();
        int rowNumber = 1;

        rs.beforeFirst();
        while(rs.next()){

            List<List<Object>> row = new ArrayList<List<Object>>();
            for(int colCounter = 1; colCounter<=colTotal; colCounter++){

                List<Object> cellData = new ArrayList<Object>();

                cellData.add(rsmd.getColumnName(colCounter));
                cellData.add(rs.getObject(colCounter));

                row.add(cellData);
            }

            resultSetMap.put(rowNumber, row);
        }
        return resultSetMap;
    }

    private void setRequestAttributes(HttpServletRequest request, Map<Integer, List<List<Object>>> resultSetMap){

        for(Map.Entry<Integer, List<List<Object>>> entry : resultSetMap.entrySet()){
            List<List<Object>> rowData = entry.getValue();
            for(List<Object> listItem : rowData){

                request.setAttribute((String) listItem.get(0), listItem.get(1));
            }
        }
    }

    private Map <Integer, List<List<Object>>> combineMaps(Map <Integer, List<List<Object>>> messageData, Map <Integer, List<List<Object>>> attachmentData){
        Map <Integer, List<List<Object>>> totalMap = new HashMap<Integer, List<List<Object>>>();
        totalMap.putAll(messageData);
        totalMap.putAll(attachmentData);
        return totalMap;
    }
}

JSP代码：

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"%>
    <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<link href="/ArchiveSearch/resources/css/messageDetail.css" rel="stylesheet" type="text/css">

<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Message detail</title>
</head>
<body>
    <div class="wrapper">
            <h1>Message Details</h1>
            <div class="messageMeta1">
                    <div><span class="label">Sender:</span><c:out value="${messageid}"/></div>
                    <div><span class="label">Receiver:</span></div>
                    <div><span class="label">Subject:</span></div><c:out value="${messagesender}"/>
                    <div><span class="label">Attachments:</span></div>
            </div>
            <div class="messageMeta2">
                    <div><span class="label">Case ID:</span></div>
                    <div><span class="label">Date:</span></div>
            </div>
            <div class="messageContent">
            </div>
    </div>
</body>
</html>

Answer 1

这段代码中有太多错误可以给出一个合适的答案。基本上一切都需要重写。您可能会发现以下答案中的启动示例很有用：Show JDBC ResultSet in HTML in JSP page using MVC and DAO pattern。

使用表达式语言打印servlet请求属性

1 个答案: