类型 异常报告
消息 在 [54] 行处理 [/index.
jsp] 时发生异常
描述 服务器遇到一个意外的情况，
阻止它完成请求。
例外情况
org.apache.jasper.JasperException: 在 [54] 行处理 [/index.
jsp] 时发生异常
51: <%
52: List<Article> articles = articleDao.getRecentArticles(5);
53: for (Article article : articles) {
54: User author = userDao.getUserById(article.getAuthorId());
55: %>
56: <div class="article-card">
57: <h4><a
href="article/detail.
jsp?aid=<%= article.getAid() %>"><%= article.getTitle() %></a></h4>
Stacktrace:
org.apache.jasper.servlet.
JspServletWrapper.h
andle
JspException(
JspServletWrapper.java:610)
org.apache.jasper.servlet.
JspServletWrapper.service(
JspServletWrapper.java:489)
org.apache.jasper.servlet.
JspServlet.service
JspFile(
JspServlet.java:376)
org.apache.jasper.servlet.
JspServlet.service(
JspServlet.java:324)
javax.servlet.http.HttpServlet.service(HttpServlet.java:623)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:51)
根本原因。
javax.servlet.ServletException: java.sql.SQLSyntaxErrorException: Unknown column 'id' in 'field list'
org.apache.jasper.runtime.PageContextImpl.h
andlePageException(PageContextImpl.java:654)
org.apache.
jsp.index_
jsp._
jspService(index_
jsp.java:305)
org.apache.jasper.runtime.Http
JspBase.service(Http
JspBase.java:67)
javax.servlet.http.HttpServlet.service(HttpServlet.java:623)
org.apache.jasper.servlet.
JspServletWrapper.service(
JspServletWrapper.java:466)
org.apache.jasper.servlet.
JspServlet.service
JspFile(
JspServlet.java:376)
org.apache.jasper.servlet.
JspServlet.service(
JspServlet.java:324)
javax.servlet.http.HttpServlet.service(HttpServlet.java:623)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:51)
根本原因。
java.sql.SQLSyntaxErrorException: Unknown column 'id' in 'field list'
com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:120)
com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:122)
com.mysql.cj.jdbc.ClientPreparedStatement.executeInternal(ClientPreparedStatement.java:953)
com.mysql.cj.jdbc.ClientPreparedStatement.executeQuery(ClientPreparedStatement.java:1009)
com.myblog.dao.UserDAO.getUserById(UserDAO.java:74)
org.apache.
jsp.index_
jsp._
jspService(index_
jsp.java:261)
org.apache.jasper.runtime.Http
JspBase.service(Http
JspBase.java:67)
javax.servlet.http.HttpServlet.service(HttpServlet.java:623)
org.apache.jasper.servlet.
JspServletWrapper.service(
JspServletWrapper.java:466)
org.apache.jasper.servlet.
JspServlet.service
JspFile(
JspServlet.java:376)
org.apache.jasper.servlet.
JspServlet.service(
JspServlet.java:324)
javax.servlet.http.HttpServlet.service(HttpServlet.java:623)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:51)
):注意 主要问题的全部 stack 信息可以在 server logs 里查看
index.
jsp
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@ page import="com.myblog.model.User, com.myblog.dao.ArticleDAO" %>
<%@ page import="com.myblog.model.Article" %>
<%@ page import="java.util.List" %>
<!DOCTYPE html>
<html>
<head>
<title>MyBlog 首页</title>
<link rel="stylesheet"
href="css/style.css">
<style>
@font-face {
font-family: 'MyFont';
src: url('fonts/MYFont/瀞之故障黑体H4.ttf') format('truetype');
}
</style>
</head>
<body>
<div class="container">
<%@ include file="left.txt" %>
<div class="main-content">
<div class="welcome-section">
<h2>欢迎访问 MyBlog</h2>
<p>分享知识，记录生活</p>
<%
User currentUser = (User) session.
getAttribute("user");
if (currentUser != null) {
%>
<div class="user-info">
<img src="<%= currentUser.getAvatar() %>" class="avatar">
<p>您好, <%= currentUser.getUsername() %>!</p>
<% if (currentUser.getIsAdmin() == 1) { %>
<p>您是管理员，可以发布和管理文章</p>
<% } else { %>
<p>您是普通用户，可以浏览和评论文章</p>
<% } %>
</div>
<% } else { %>
<p>请<a
href="login.
jsp">登录</a>或<a
href="register.
jsp">注册</a>后使用更多功能</p>
<% } %>
</div>
<div class="recent-articles">
<h3>最新文章</h3>
<div class="article-list">
<!-- 从数据库获取最新文章并展示 -->
<
jsp:useBean id="articleDao" class="com.myblog.dao.ArticleDAO" />
<
jsp:useBean id="userDao" class="com.myblog.dao.UserDAO" />
<%
List<Article> articles = articleDao.getRecentArticles(5);
for (Article article : articles) {
User author = userDao.getUserById(article.getAuthorId());
%>
<div class="article-card">
<h4><a
href="article/detail.
jsp?aid=<%= article.getAid() %>"><%= article.getTitle() %></a></h4>
<div class="article-meta">
<span>作者: <%= author.getUsername() %></span>
<span>发布时间: <%= article.getCreatedAt() %></span>
</div>
<div class="article-excerpt">
<%= article.getContent().substring(0, Math.min(100, article.getContent().length())) %>...
</div>
</div>
<% } %>
</div>
</div>
</div>
</div>
</body>
</html>
UserDAO.java
package com.myblog.dao;
import com.myblog.model.User;
import com.myblog.util.DBUtil;
import java.sql.*;
public class UserDAO {
public User getUserByUsername(String username) {
String sql = "SELECT * FROM users WHERE username = ?";
try (Connection conn = DBUtil.getConnection();
PreparedStatement stmt = conn.prepareStatement(sql)) {
stmt.setString(1, username);
try (ResultSet rs = stmt.executeQuery()) {
if (rs.next()) {
User user = new User();
user.setUid(rs.getInt("uid"));
user.setUsername(rs.getString("username"));
user.setPassword(rs.getString("password"));
user.setEmail(rs.getString("email"));
user.setAvatar(rs.getString("avatar"));
user.setIsAdmin(rs.getInt("is_admin"));
user.setCreatedAt(rs.getTimestamp("created_at"));
return user;
}
}
} catch (SQLException e) {
e.printStackTrace();
}
return null;
}
public boolean registerUser(User user) {
String sql = "INSERT INTO users (username, password, email, avatar, is_admin) VALUES (?, ?, ?, ?, ?)";
try (Connection conn = DBUtil.getConnection();
PreparedStatement stmt = conn.prepareStatement(sql)) {
stmt.setString(1, user.getUsername());
stmt.setString(2, user.getPassword());
stmt.setString(3, user.getEmail());
stmt.setString(4, user.getAvatar());
stmt.setInt(5, user.getIsAdmin());
int rows = stmt.executeUpdate();
return rows > 0;
} catch (SQLException e) {
e.printStackTrace();
return false;
}
}
public boolean updateUser(User user) {
String sql = "UPDATE users SET email = ?, avatar = ? WHERE uid = ?";
try (Connection conn = DBUtil.getConnection();
PreparedStatement stmt = conn.prepareStatement(sql)) {
stmt.setString(1, user.getEmail());
stmt.setString(2, user.getAvatar());
stmt.setInt(3, user.getUid());
int rows = stmt.executeUpdate();
return rows > 0;
} catch (SQLException e) {
e.printStackTrace();
return false;
}
}
public User getUserById(int authorId) throws SQLException {
String sql = "SELECT id, username, email, avatar FROM users WHERE id = ?";
try (Connection conn = DBUtil.getConnection();
PreparedStatement stmt = conn.prepareStatement(sql)) {
stmt.setInt(1, authorId);
try (ResultSet rs = stmt.executeQuery()) {
if (rs.next()) {
User user = new User();
user.setUid(rs.getInt("id"));
user.setUsername(rs.getString("username"));
user.setEmail(rs.getString("email"));
user.setAvatar(rs.getString("avatar"));
return user;
}
}
}
return null;
}
}
ArticleDAO.java
package com.myblog.dao;
import com.myblog.model.Article;
import com.myblog.util.DBUtil;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;
public class ArticleDAO {
public boolean saveArticle(Article article) {
String sql = "INSERT INTO articles (title, content, author_id) VALUES (?, ?, ?)";
try (Connection conn = DBUtil.getConnection();
PreparedStatement stmt = conn.prepareStatement(sql, Statement.RETURN_GENERATED_KEYS)) {
stmt.setString(1, article.getTitle());
stmt.setString(2, article.getContent());
stmt.setInt(3, article.getAuthorId());
int rows = stmt.executeUpdate();
if (rows > 0) {
try (ResultSet rs = stmt.getGeneratedKeys()) {
if (rs.next()) {
article.setAid(rs.getInt(1));
}
}
return true;
}
} catch (SQLException e) {
e.printStackTrace();
System.err.println("保存文章失败: " + e.getMessage());
}
return false;
}
public Article getArticleById(int aid) {
String sql = "SELECT * FROM articles WHERE aid = ?";
try (Connection conn = DBUtil.getConnection();
PreparedStatement stmt = conn.prepareStatement(sql)) {
stmt.setInt(1, aid);
try (ResultSet rs = stmt.executeQuery()) {
if (rs.next()) {
Article article = new Article();
article.setAid(rs.getInt("aid"));
article.setTitle(rs.getString("title"));
article.setContent(rs.getString("content"));
article.setAuthorId(rs.getInt("author_id"));
article.setCreatedAt(rs.getTimestamp("created_at"));
article.setUpdatedAt(rs.getTimestamp("updated_at"));
return article;
}
}
} catch (SQLException e) {
e.printStackTrace();
}
return null;
}
public List<Article> getRecentArticles(int limit) {
List<Article> articles = new ArrayList<>();
String sql = "SELECT * FROM articles ORDER BY created_at DESC LIMIT ?";
try (Connection conn = DBUtil.getConnection();
PreparedStatement stmt = conn.prepareStatement(sql)) {
stmt.setInt(1, limit);
try (ResultSet rs = stmt.executeQuery()) {
while (rs.next()) {
Article article = new Article();
article.setAid(rs.getInt("aid"));
article.setTitle(rs.getString("title"));
article.setContent(rs.getString("content"));
article.setAuthorId(rs.getInt("author_id"));
article.setCreatedAt(rs.getTimestamp("created_at"));
articles.add(article);
}
}
} catch (SQLException e) {
e.printStackTrace();
}
return articles;
}
public int getTotalArticles() throws SQLException {
String sql = "SELECT COUNT(*) AS total FROM articles";
try (Connection conn = DBUtil.getConnection();
PreparedStatement stmt = conn.prepareStatement(sql);
ResultSet rs = stmt.executeQuery()) {
if (rs.next()) {
return rs.getInt("total");
}
}
return 0;
}
public List<Article> getArticles(int offset, int pageSize) throws SQLException {
List<Article> articles = new ArrayList<>();
String sql = "SELECT id, title, content, author_id, create_at FROM articles ORDER BY create_at DESC LIMIT ?, ?";
try (Connection conn = DBUtil.getConnection();
PreparedStatement stmt = conn.prepareStatement(sql);) {
stmt.setInt(1, offset);
stmt.setInt(2, pageSize);
try (ResultSet rs = stmt.executeQuery()) {
while (rs.next()) {
Article article = new Article();
article.setAid(rs.getInt("id"));
article.setTitle(rs.getString("title"));
article.setContent(rs.getString("content"));
article.setAuthorId(rs.getInt("author_id"));
article.setCreatedAt(rs.getTimestamp("create_time"));
articles.add(article);
}
}
}
return articles;
}
}
本文探讨了如何通过JavaScript操作DOM元素，特别是getAttribute与setAttribute方法的使用限制，并讲解了如何阻止a标签的默认行为，以及JavaScript事件执行顺序。
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