我正在尝试在我的jsp页面中进行分页。但我没有从数据库中获取数据。我收到错误“您的SQL语法出错;请查看与您的MySQL服务器版本对应的手册，以便在第1行附近的'-10,5'附近使用正确的语法。” / p>
我不明白什么是错的。你能检查我的代码并帮我解决问题吗？
BooksInfo.java
package com.sreejonee.books;
import java.sql.Date;
import java.sql.Timestamp;
public class BooksInfo {
private int book_id;
private String bookName;
private String filename;
private String writerName;
private String book_details;
private Timestamp date_time;
private int rating;
private int parentscat_id;
private String parentscat_name;
private String thumCoverImag;
private String filePath;
public int getBook_id() {
return book_id;
}
public void setBook_id(int book_id) {
this.book_id = book_id;
}
public String getBookName() {
return bookName;
}
public void setBookName(String bookName) {
this.bookName = bookName;
}
public String getFilename() {
return filename;
}
public void setFilename(String filename) {
this.filename = filename;
}
public String getWriterName() {
return writerName;
}
public void setWriterName(String writerName) {
this.writerName = writerName;
}
public String getBook_details() {
return book_details;
}
public void setBook_details(String book_details) {
this.book_details = book_details;
}
public Timestamp getDate_time() {
return date_time;
}
public void setDate_time(Timestamp date_time) {
this.date_time = date_time;
}
public int getRating() {
return rating;
}
public void setRating(int rating) {
this.rating = rating;
}
public int getParentscat_id() {
return parentscat_id;
}
public void setParentscat_id(int parentscat_id) {
this.parentscat_id = parentscat_id;
}
public String getParentscat_name() {
return parentscat_name;
}
public void setParentscat_name(String parentscat_name) {
this.parentscat_name = parentscat_name;
}
public String getThumCoverImag() {
return thumCoverImag;
}
public void setThumCoverImag(String thumCoverImag) {
this.thumCoverImag = thumCoverImag;
}
public String getFilePath() {
return filePath;
}
public void setFilePath(String filePath) {
this.filePath = filePath;
}
}
BooksInfoDAO.java
package com.sreejonee.books;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;
import com.sreejonee.db.ConnectionFactory;
import com.sreejonee.db.DBConnector;
public class BooksInfoDAO {
Connection connection;
Statement stmt;
private int noOfRecords;
private static Connection getConnection()
throws SQLException,
ClassNotFoundException
{
Connection con = ConnectionFactory.
getInstance().getConnection();
System.out.println("connected!");
return con;
}
public List<BooksInfo> viewAllBooksInfo(int offset, int noOfRecords) {
String query = "select SQL_CALC_FOUND_ROWS * from library ORDER by date_time DESC limit"+ offset + ", " + noOfRecords;
List<BooksInfo> bookslist = new ArrayList<BooksInfo>();
BooksInfo books = null;
try {
connection = getConnection();
stmt = connection.createStatement();
ResultSet rs = stmt.executeQuery(query);
while (rs.next()) {
books = new BooksInfo();
books.setBook_id(rs.getInt("book_id"));
books.setBook_details(rs.getString("book_details"));
books.setBookName(rs.getString("bookName"));
books.setWriterName(rs.getString("writerName"));
books.setDate_time(rs.getTimestamp("date_time"));
books.setParentscat_id(rs.getInt("parentscat_id"));
books.setParentscat_name(rs.getString("parentscat_name"));
books.setFilename(rs.getString("filename"));
books.setFilePath(rs.getString("filePath"));
books.setRating(rs.getInt("rating"));
books.setThumCoverImag(rs.getString("thumCoverImag"));
bookslist.add(books);
}
rs.close();
rs = stmt.executeQuery("SELECT FOUND_ROWS()");
if (rs.next())
this.noOfRecords = rs.getInt(1);
} catch (SQLException e) {
e.printStackTrace();
} catch (ClassNotFoundException e) {
e.printStackTrace();
} finally {
try {
if (stmt != null) {
stmt.close();
}
if (connection != null) {
connection.close();
}
} catch (SQLException e2) {
e2.printStackTrace();
}
}
return bookslist;
}
public int getNoOfRecords() {
return noOfRecords;
}
}
的Servlet： BooksInfoServlet.java
package com.sreejonee.servlet;
import java.io.IOException;
import java.util.List;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.sreejonee.books.BooksInfo;
import com.sreejonee.books.BooksInfoDAO;
@WebServlet("/BooksInfoServlet")
public class BooksInfoServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public BooksInfoServlet() {
super();
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
int page = 1;
int recordsPerPage = 5;
if(request.getParameter("page") != null)
page = Integer.parseInt(request.getParameter("page"));
BooksInfoDAO booksInfoDAO = new BooksInfoDAO();
List<BooksInfo> bookslist = booksInfoDAO.viewAllBooksInfo((page-1)*recordsPerPage, recordsPerPage);
int noOfRecords = booksInfoDAO.getNoOfRecords();
int noOfPages = (int) Math.ceil(noOfRecords * 1.0 / recordsPerPage);
request.setAttribute("booksList", bookslist);
request.setAttribute("noOfPages", noOfPages);
request.setAttribute("currentPage", page);
RequestDispatcher view = request.getRequestDispatcher("user.jsp");
view.forward(request, response);
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
}
}
JSP页面：
<c:forEach var="books" items="${bookslist}">
<div id="${books.filename}" class="single_midlecontent_component">
<div class="socialicon_on_post">
<h4>
<i class="fa fa-facebook-square"></i>
</h4>
</div>
<div class="title_of_post ">
<a href="#" class="media-left">
<img class="media-object" src="${books.getFilePath()+File.separator+books.getThumCoverImag()}" alt="...">
</a>
<h5 class="media-body ">
<span><a href="">${books.getBookName()}</a></span>
</h5>
<h5 class="media-body ">
<span>by <a href="">${books.getWriterName()}</a></span>
</h5>
<p class="date_time media-body">${books.getDate_time()}</p>
</div>
<div class="body_of_post">
<p>${books.getBook_details()}</p>
<img src="" class="img-responsive" alt="Responsive image">
</div>
<div class="fb-like" data-href="https://developers.facebook.com/docs/plugins/" data-layout="standard" data-action="like" data-show-faces="true" data-share="true"></div>
<div class="download_book">
<form action="DownloadFileServlet" method="post">
<input type="hidden" name="filename" value="${books.getFilename()}">
<div>
<input type="hidden" name="parentscat_name" value="${books.getParentscat_name()}">
</div>
<div class="download_button">
<input class="btn btn-default " type="submit" value="Download">
</div>
</form>
</div>
<div class="bottom_of_post"></div>
</div>
答案 0 :(得分：1)
我可以在这里看到两个错误。
第一个：
String query = "select SQL_CALC_FOUND_ROWS * from library ORDER by date_time DESC limit"+ offset + ", " + noOfRecords;
limit之后有一个空格 - 您编写它的方式，它将生成... limit10, 5。
第二个：
我认为viewAllBooksInfo()的调用者给出了错误的offset参数。根据错误，我假设offset是-10这是非法的，因为MySQL中limit子句的参数必须是non-negative。
在您更新的问题中，您会显示以下代码：
if(request.getParameter("page") != null)
page = Integer.parseInt(request.getParameter("page"));
BooksInfoDAO booksInfoDAO = new BooksInfoDAO();
List<BooksInfo> bookslist = booksInfoDAO.viewAllBooksInfo((page-1)*recordsPerPage, recordsPerPage);
显然，因为recordsPerPage是5，而offset是-10，page似乎是-1。您没有为调用BooksInfoServlet的页面显示代码，但我猜您已在此处输入-1作为请求的页码。
答案 1 :(得分：0)
在问这个问题之前你应该看看自己。您应该首先尝试自己删除这些错误。
如果您查看错误堆栈，它会说：
“您的SQL语法出错;请查看与您的MySQL服务器版本对应的手册，以便在第1行的'-10,5'附近使用正确的语法
如果你仔细看，限制选项是“ - 10,5”。 MySQL中的限制参数应该是非负的。
在 BooksInfoDAO.java 代码：
public List<BooksInfo> viewAllBooksInfo(int offset, int noOfRecords) {
String query = "select SQL_CALC_FOUND_ROWS * from library ORDER by date_time DESC limit"+ offset + ", " + noOfRecords;
...
你在limit子句和offset参数之间缺少一个空格。