这个错误什么意思？

Question

是不是在用dispatcher重定向时用了out方法?
或者,在buffer内没有东西就输出了?

Answer 1

不能重新设置buffer的大小，没有字节被写入。是不是你buffer定义的大小和实际赋值的大小不一致？

Answer 2

用servlet实现的一个关于单位目录的树型菜单。在同时有多个用户使用的时候。就
会出现这个信息。servlet如下：
package cn.com.pingtech.servlet;import javax.servlet.*;
import javax.servlet.http.*;
import java.io.IOException;
import java.io.PrintWriter;
import java.sql.*;
import cn.com.pingtech.equip.*;
import cn.com.pingtech.database.*;public class equipDeptTree extends HttpServlet {    private PrintWriter out = null;
    private String treeType = null;    private void doRequest(HttpServletRequest request) {
    }    public void doPost(HttpServletRequest request,HttpServletResponse response) {
        Connection con = null;
        try{
            con = GetDbConnect();
            treePrint(con, 0, "top");
        }
        catch(Exception e) {
            System.out.println("equipDeptTree.java doPost() Error1 is :: "+e);
        }
        finally {
            try {
                con.close();
            }
            catch(SQLException e) {
                System.out.println("equipDeptTree.java doPost() Error2 is :: "+e);
            }
        }
    }    public void doGet(HttpServletRequest request,HttpServletResponse response) {
        try {       
            out = response.getWriter();
            request.setCharacterEncoding("gb2312");
            treeType = (String)request.getAttribute("treeType");
            doPost(request,response);
        }
        catch(IOException e)
        {
            System.out.println(" equipDeptTree.java doGet() Error is :: "+e);
        }
    }    private Connection GetDbConnect() {
        
        String strDRV = "oracle.jdbc.driver.OracleDriver";
        String strURL = "jdbc:oracle:thin:ping:[email protected]:1521:ORCL";
        
        
        Connection con = null;//DbConnectionManager.getConnection();        
        
        try {
            Class.forName(strDRV);
            con = DriverManager.getConnection(strURL,"ping","ping");
         }catch(Exception e) {
            System.out.println(" equipDeptTree.java GetDbConnect() Error is :: "+e);
            out.println(" * 连接服务器失败 ！");
             return null;
        }
        
        return con;
    }    private void treePrint(Connection con, int intUpperDeptId, String strLayer) {
        Statement stmt = null;          // 连接陈述
        ResultSet rs = null;            // 查询结果集
        String strSql = null;           // 查询语句        int intDeptId = 0;              // 单位ID （数据库字段）
        String strDeptName = null;      // 单位名称 （数据库字段）
        int intHasSubDept = 0;          // 是否有下一级 （数据库字段）        try {
            stmt = con.createStatement();
            if( intUpperDeptId == 0) {
                //System.out.println("strUpperDeptId :: " + intUpperDeptId);
                strSql = "select * from EquipDept where UpperDeptId=-1";
            }
            else {
                //System.out.println("strUpperDeptId :: " + intUpperDeptId);
                strSql = new String("select * from EquipDept where UpperDeptId = " + intUpperDeptId );
            }
            //System.out.println("sql string is ::::::: "+strSql);
            rs = stmt.executeQuery(strSql);
            
            out.println(" ");
            out.println("<table border=0 cellspacing=0 cellpadding=2 >");            while(rs != null && rs.next()) {
                intDeptId = rs.getInt("DeptId");
                intUpperDeptId = rs.getInt("UpperDeptId");
                strDeptName = rs.getString("DeptName");
                intHasSubDept = rs.getInt("HasSubDept");                //System.out.print(strDeptName);
                if(intHasSubDept == 0){                                 // 如果没有下一级单位
                    out.println("   <tr>");
                    out.println("       <td><img src=\"../images/dot.gif\" width=\"12\" height=\"12\"></td>");
                    out.println("       <td align=left>");
                    out.println("       <div onClick=\"maingo('"+intDeptId+"',\'equipDept\','"+treeType+"','"+strDeptName+"')\" style=\"cursor:'hand'\"><img src=\"../images/close.gif\">");
                    out.println("       "+strDeptName +"</div></td>");
                    out.println("   </tr> ");
                    out.println(" ");
                    //System.out.println();
                }else {                                                 // 如果有下一级单位                    out.println("   <tr>");
                    out.println("       <td>");
                    out.println("       <img  name=\""+strLayer+"img\" ID=\""+intDeptId+"\" style=\"cursor:'hand';\" onmouseup=\"clickEvent();\" src=\"../images/dot1.gif\" width=\"12\" height=\"12\" ></td>");
                    out.println("       <td align=left>");
                    out.println("       <div onClick=\"maingo('"+intDeptId+"',\'equipDept\','"+treeType+"','"+strDeptName+"')\" style=\"cursor:'hand'\"><img  name=\""+strLayer+"imgII\"  ID=\""+intDeptId+"II\" src=\"../images/close.gif\" >");
                    out.println("       "+ strDeptName +"</div></td>");
                    out.println("   </tr>");                    out.println("   <tr name=\""+strLayer+"\" ID=\""+intDeptId+"p\" STYLE=\"Display:'none'\">");
                    out.println("       <td ></td>");
                    out.println("       <td >");                    treePrint(con, intDeptId, "notop");
                    
                    out.println("       </td>");
                    out.println("   </tr>");
                    out.println(" ");                } // else
            } // while            out.println("</table>");
        }catch(Exception e){
                System.out.println(" equipDeptTree.java treePrint() Error is :: "+e);
        }    }
}