前面写了rs=stmt.executeQuery("select *from bookinfo;");到这里
while(rs.next())//为什么这条while只循环了一次？ 只显示第一条数据
{
out.println("<tr>");
out.println("<td>"+rs.getString("title")+"</td>");
out.println("<td>"+rs.getString("author")+"</td>");
out.println("<td>"+rs.getString("bookconcern")+"</td>");
out.println("<td>"+rs.getFloat("price")+"</td>");
out.println("<td>"+rs.getDate("publish_date")+"</td>");
out.println("</tr>");
}
out.println("</table></body></html>");要是我在循环里面再加一句rs.next() 则它会显示第二条数据，也不会再循环 求解？
while(rs.next())//为什么这条while只循环了一次？ 只显示第一条数据
{
out.println("<tr>");
out.println("<td>"+rs.getString("title")+"</td>");
out.println("<td>"+rs.getString("author")+"</td>");
out.println("<td>"+rs.getString("bookconcern")+"</td>");
out.println("<td>"+rs.getFloat("price")+"</td>");
out.println("<td>"+rs.getDate("publish_date")+"</td>");
out.println("</tr>");
}
out.println("</table></body></html>");要是我在循环里面再加一句rs.next() 则它会显示第二条数据，也不会再循环 求解？
List<Bookinfo> books=new ArrayList<Bookinfo>();
while(rs.next()){
String title = rs.getString("title");
String author= rs.getString("author");
String bookconcern= rs.getString("bookconcern");
String price= rs.getString("price");
String publish_date= rs.getString("publish_date");
Bookinfo book = new Bookinfo();
book.setTitle(title);
book.setAuthor(author);
//下面一样
books.add(book);
}
for(Bookinfo book : books){
out.println("<tr>");
out.println("<td>"+book.getTitle+"</td>");
out.println("<td>"+book.getAuthor+"</td>");
//下面一样
}这样试试 看行不行，不行就Debug 调试调试咯~~~
throws SQLException
{
out.println("<html><head>");
out.println("<title>图书信息</title>");
out.println("</head><body>");
out.println("<table border=1><caption>图书信息</caption>");
out.println("<tr><th>书名</th><th>作者</th><th>出版社</th><th>价格</th><th>发行日期</th></tr>");
while(rs.next())//为什么这条while只循环了一次？
{
out.println("<tr>");
out.println("<td>"+rs.getString("title")+"</td>");
out.println("<td>"+rs.getString("author")+"</td>");
out.println("<td>"+rs.getString("bookconcern")+"</td>");
out.println("<td>"+rs.getFloat("price")+"</td>");
out.println("<td>"+rs.getDate("publish_date")+"</td>");
out.println("</tr>");
}
out.println("</table></body></html>");
}
这是这个类的代码
？？？？？
我没有Bookinfo这个类，这个是数据表
throws SQLException
{
out.println("<html><head>");
out.println("<title>图书信息</title>");
out.println("</head><body>");
out.println("<table border=1><caption>图书信息</caption>");
out.println("<tr><th>书名</th><th>作者</th><th>出版社</th><th>价格</th><th>发行日期</th></tr>");
rs.beforeFirst() ;
while(rs.next())//为什么这条while只循环了一次？
{
out.println("<tr>");
out.println("<td>"+rs.getString("title")+"</td>");
out.println("<td>"+rs.getString("author")+"</td>");
out.println("<td>"+rs.getString("bookconcern")+"</td>");
out.println("<td>"+rs.getFloat("price")+"</td>");
out.println("<td>"+rs.getDate("publish_date")+"</td>");
out.println("</tr>");
}
out.println("</table></body></html>");
} rs.beforeFirst() ; //加这一句看看 ，是不是你在别的地方用了 rs了，没有复位到第一条啊 ？
while(rs.next())//为什么这条while只循环了一次？
while(rs.next())//为什么这条while只循环了一次？
* 和 from之间不用加空格吗？
bookinfo表里有几条记录？
printBookInfo(PrintWriter out,ResultSet rs)传了两个参数，我看看你是怎么调用的！
package org.ch04.servlet;import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;public class ListServlet extends HttpServlet
{
private String url;
private String user;
private String password;
public void init() throws ServletException
{
ServletContext sc=getServletContext();
String driverClass=sc.getInitParameter("driverClass");
url=sc.getInitParameter("url");
user=sc.getInitParameter("user");
password=sc.getInitParameter("password");
try
{
Class.forName(driverClass);
}
catch(ClassNotFoundException ce)
{
throw new ServletException("加载数据库驱动失败！");
}
}
public void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException,IOException
{
Connection conn=null;
Statement stmt=null;
ResultSet rs=null;
req.setCharacterEncoding("gb2312");
String condition=req.getParameter("cond");
if(null==condition || condition.equals(""))
{
resp.sendRedirect("search.html");
return;
}
resp.setContentType("text/html;charset=gb2312");
PrintWriter out=resp.getWriter();
try
{
conn=DriverManager.getConnection(url,user,password);
stmt=conn.createStatement();
if(condition.equals("all"))
{
rs=stmt.executeQuery("select *from bookinfo;");
printBookInfo(out,rs);
out.close();
}
else if(condition.equals("precision"))
{
String title=req.getParameter("title");
String author=req.getParameter("author");
String bookconcern=req.getParameter("bookconcern");
if((null==title || title.equals("")) &&
(null==author || author.equals("")) &&
(null==bookconcern || bookconcern.equals("")))
{
resp.sendRedirect("search.html");
return;
}
StringBuffer sb=new StringBuffer("select * from bookinfo where ");
boolean bFlag=false;
if(!title.equals(""))
{
sb.append("title = "+"'"+title+"'");
bFlag=true;
}
if(!author.equals(""))
{
if(bFlag)
sb.append("and author = "+"'"+author+"'");
else
{
sb.append("author = "+"'"+author+"'");
bFlag=true;
}
}
if(!bookconcern.equals(""))
{
if(bFlag)
sb.append("and bookconcern = "+"'"+bookconcern+"'");
else
sb.append("bookconcern = "+"'"+bookconcern+"'");
}
rs=stmt.executeQuery(sb.toString());
printBookInfo(out,rs);
out.close();
}
else if(condition.equals("keyword"))
{
String keyword=req.getParameter("keyword");
if(null==keyword || keyword.equals(""))
{
resp.sendRedirect("search.html");
return;
}
String strSQL="select * from bookinfo where title like '%"+keyword+"%'";
rs=stmt.executeQuery(strSQL);
printBookInfo(out,rs);
out.close();
}
else
{
resp.sendRedirect("search.html");
return;
}
}
catch(SQLException se)
{
se.printStackTrace();
}
finally
{
closeResultSet(rs);
closeStatement(stmt);
closeConnection(conn);
}
}
public void doPost(HttpServletRequest req, HttpServletResponse resp)
throws ServletException,IOException
{
doGet(req,resp);
}
private void printBookInfo(PrintWriter out,ResultSet rs)
throws SQLException
{
out.println("<html><head>");
out.println("<title>图书信息</title>");
out.println("</head><body>");
out.println("<table border=1><caption>图书信息</caption>");
out.println("<tr><th>书名</th><th>作者</th><th>出版社</th><th>价格</th><th>发行日期</th></tr>");
while(rs.next())//为什么这条while只循环了一次？
{
out.println("<tr>");
out.println("<td>"+rs.getString("title")+"</td>");
out.println("<td>"+rs.getString("author")+"</td>");
out.println("<td>"+rs.getString("bookconcern")+"</td>");
out.println("<td>"+rs.getFloat("price")+"</td>");
out.println("<td>"+rs.getDate("publish_date")+"</td>");
out.println("</tr>");
}
out.println("</table></body></html>");
}
private void closeResultSet(ResultSet rs)
{
if(rs!=null)
{
try
{
rs.close();
}
catch(SQLException se)
{
se.printStackTrace();
}
rs=null;
}
}
private void closeStatement(Statement stmt)
{
if(stmt!=null)
{
try
{
stmt.close();
}
catch(SQLException se)
{
se.printStackTrace();
}
stmt=null;
}
}
private void closeConnection(Connection conn)
{
if(conn!=null)
{
try
{
conn.close();
}
catch(SQLException se)
{
se.printStackTrace();
}
conn=null;
}
}
}这是源代码
要是在While里面再加一句 “rs.next();” 就能显示出第二条数据 但是也只能显示一条数据
不会把三条数据都显示出来。（总共三条数据） 啊啊啊。。纠结
我知道你要实现什么功能，你把SQL语句打印出来看看！
rs=stmt.executeQuery(strSQL);
貌似这里有个rs了嘛
if(condition.equals("all"))
{ rs=stmt.executeQuery("select *from bookinfo;");
printBookInfo(out,rs);
out.close();
}rs这么多次的使用？
如果是执行了all条件里面的，调试看下传参之前的rs变量
if(null != condition && !"".equals(condition)){
if("precision".equals(condition)){
if(null != title && !"".equals(title))
sql.append(" and title='"+title+"'");
if(null != author && !"".equals(author))
sql.append(" and author='"+author+"'");
if(null != bookconcern && !"".equals(bookconcern))
sql.append(" and bookconcern='"+bookconcern+"'");
} else if("keyword".equals(condition)){
if(null != keyword && !"".equals(keyword))
sql.append(" and title like '%"+keyword+"%'");
}
}
上面的SQL就实现了你想要的功能，建议你把它改成我上面写的试下！
希望同学们注意一下:)))