jsp中如何引用自编的JavaBeans？

Question

可能是你的resin配置有问题,打开resin下的conf,把resin.conf(文本编辑器打开)下的classpath改一下试试,我在http://www.csdn.net/expert/topic/109/109651.shtm中有回答

Answer 1

我用的是Tomcat，需要怎样设置呢？

Answer 2

把javabean的目录加到classpath中去
autoexec.bat

Answer 3

jsp下出现问题一般都是路径问题，江南说的对，你把路径设置一下，默认情况下，你所写的jsp
文件与bean是要放在某个目录下，要放到自己的目录下，往往要设置。

Answer 4

你的javabean有问题。 请贴出你的最简单的javabean。

Answer 5

<jsp:useBean id="jdbc" scope="session" class="hem.config" />
<%
String Driver     = jdbc.getLocalDriverStr();  /* Jdbc驱动器 */
String URL        = jdbc.getURL(jdbc.getLocalURLStr());

String Driver_R   = jdbc.getRemoteDriverStr();  /* Jdbc驱动器 */
String URL_R      = jdbc.getURL(jdbc.getRemoteURLStr());
%>
package hem;import java.io.*;
import java.sql.*;public class config
{
    String RemoteURLLine;
    String LocalURLLine;
    
    String LocalProtocol;
    
    Connection LocalConnection = null;
    Statement LocalStatement = null;
    Connection RemoteConnection = null;
    Statement RemoteStatement = null;    
    boolean UseRemoteDB = true;
    
    public config()
        throws  Exception
    {
    
     try
     {
       FileInputStream inDatabase = new FileInputStream("/config.txt");
       int databaseBytes = inDatabase.available();
       byte inDatabaseBuf[] = new byte[databaseBytes];
       int bytesRead = inDatabase.read(inDatabaseBuf,0,databaseBytes);
       LocalURLLine = new String(inDatabaseBuf);
     }
     catch(Exception e)
     {
       System.out.println("本地数据库配置文件出错!");
     }
     try
     {
       FileInputStream inDatabase = new FileInputStream("/remote.txt");
       int databaseBytes = inDatabase.available();
       byte inDatabaseBuf[] = new byte[databaseBytes];
       int bytesRead = inDatabase.read(inDatabaseBuf,0,databaseBytes);
       RemoteURLLine = new String(inDatabaseBuf);
     }    
     catch(Exception e)
     {
       System.out.println("远程数据库配置文件出错!");
     }
        /*
        FileReader IniFile;
        IniFile = new FileReader("/interhome.conf");
        LineNumberReader IniFileLines = new LineNumberReader(IniFile);
        RemoteURLLine = IniFileLines.readLine();
        LocalURLLine = IniFileLines.readLine();
     */
        //String Driver   = "oracle.jdbc.driver.OracleDriver";  /* Jdbc驱动器 */
        //String Driver = GetSubString(LocalURLLine,1,',');
        //Class.forName(Driver);
    }
    
    public String getLocalDriverStr()
    {
        return GetSubString(LocalURLLine,1,',');
    }        
    
    public String getLocalProtocol()
    {
        return GetSubString(LocalURLLine,2,',');
    } 
    
    public String getRemoteDriverStr()
    {
        return GetSubString(RemoteURLLine,1,',');
    }
    
    public String getLocalURLStr()
    {
        return LocalURLLine;
    }            public String getRemoteURLStr()
    {
        return RemoteURLLine;
    }            public Connection getRemoteConnection()
        throws SQLException
    {
        return DriverManager.getConnection(getURL(RemoteURLLine));
    }            public Connection getLocalConnection()
        throws SQLException
    {
        return DriverManager.getConnection(getURL(LocalURLLine));
    }            public String getURL(String DBURLLine)
    {
        
        String driver;
        String Protocol;
        String Port;
        String Host;
        String User;
        String Password;
        String Database;        Protocol = GetSubString(DBURLLine,2,',');
        Host = GetSubString(DBURLLine,3,',');
        Port = GetSubString(DBURLLine,4,',');
        
        Database = GetSubString(DBURLLine,5,',');
        User = GetSubString(DBURLLine,6,',');
        Password = GetSubString(DBURLLine,7,',');
        
        return Protocol+":"+User+"/"+Password+"@"+Host+":"+Port+":"+Database;
    }    String GetSubString(String DBURLLine,int SubNum, char Sign)
    {
        int CharIndex1 = -1;
        int CharIndex2 = 0;        for (int i = 1; i<SubNum; i++)
        {
            CharIndex2 = DBURLLine.indexOf(Sign,CharIndex1+1);
            CharIndex1 = CharIndex2;
        }        CharIndex2 = DBURLLine.indexOf(Sign,CharIndex1+2);
        if (CharIndex2 < 0)
        {
            return DBURLLine.substring(CharIndex1+1);
        }
        else
        {
            return DBURLLine.substring(CharIndex1+1,CharIndex2);
        }
    }
        
    public void OpenDB()
        throws Exception
    {
        if (LocalConnection == null)
        {
            LocalConnection = getLocalConnection();
            if (LocalStatement != null) 
                LocalStatement.close();
            LocalStatement = LocalConnection.createStatement();
        }
        LocalConnection.setAutoCommit(true);        if (UseRemoteDB)
        {
            if (RemoteConnection == null)
            {
                RemoteConnection = getRemoteConnection();
                if (RemoteStatement != null)
                    RemoteStatement.close(); 
                RemoteStatement = RemoteConnection.createStatement();
            }
            RemoteConnection.setAutoCommit(true);  
        }
    }
    
    public void OpenDBCommit()
        throws Exception
    {
        if (LocalConnection == null)
        {
            LocalConnection = getLocalConnection();
            if (LocalStatement != null) 
                LocalStatement.close();
            LocalStatement = LocalConnection.createStatement();
        }
        LocalConnection.setAutoCommit(false);        if (UseRemoteDB)
        {
            if (RemoteConnection == null)
            {
                RemoteConnection = getRemoteConnection();
                if (RemoteStatement != null)
                    RemoteStatement.close(); 
                RemoteStatement = RemoteConnection.createStatement();
            }
            RemoteConnection.setAutoCommit(false);
        }
    }
    
    public void CloseDB()
        throws Exception
    {
        if (LocalStatement != null)
        {
            LocalStatement.close();
            LocalStatement = null;
        }
        if (LocalConnection != null)
        {
            LocalConnection.close();
            LocalConnection = null;
        }        if (UseRemoteDB)
        {
            if (RemoteStatement != null)
            {
                RemoteStatement.close();
                RemoteStatement = null;
            }
            if (RemoteConnection != null)
            {
                RemoteConnection.close(); 
                RemoteConnection = null; 
            }
        }
    }
    
}
主要原因是 scope="session" ，或者你的 javabean有问题

Answer 6

设置了classpath之后，编译倒是通过了，可是运行时有新的问题，页面显示：
Internal Servlet Error:javax.servlet.ServletException: javadb/tjavabean
at java.lang.Throwable.(Throwable.java:96)
at java.lang.Exception.(Exception.java:44)
at javax.servlet.ServletException.(ServletException.java:161)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:399)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
at org.apache.tomcat.core.ServletWrapper.doService(ServletWrapper.java:404)
at org.apache.tomcat.core.Handler.service(Handler.java:286)
at org.apache.tomcat.core.ServletWrapper.service(ServletWrapper.java:372)
at org.apache.tomcat.core.ContextManager.internalService(ContextManager.java:797)
at org.apache.tomcat.core.ContextManager.service(ContextManager.java:743)
at org.apache.tomcat.service.http.HttpConnectionHandler.processConnection(HttpConnectionHandler.java:210)
at org.apache.tomcat.service.TcpWorkerThread.runIt(PoolTcpEndpoint.java:416)
at org.apache.tomcat.util.ThreadPool$ControlRunnable.run(ThreadPool.java:498)
at java.lang.Thread.run(Thread.java:498)Root cause: 
java.lang.NoClassDefFoundError: javadb/tjavabean
at java.lang.Class.newInstance0(Native Method)
at java.lang.Class.newInstance(Class.java:254)
at org.apache.jasper.servlet.JspServlet$JspServletWrapper.load(JspServlet.java:116)
at org.apache.jasper.servlet.JspServlet$JspServletWrapper.loadIfNecessary(JspServlet.java:154)
at org.apache.jasper.servlet.JspServlet$JspServletWrapper.service(JspServlet.java:164)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:318)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:391)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
at org.apache.tomcat.core.ServletWrapper.doService(ServletWrapper.java:404)
at org.apache.tomcat.core.Handler.service(Handler.java:286)
at org.apache.tomcat.core.ServletWrapper.service(ServletWrapper.java:372)
at org.apache.tomcat.core.ContextManager.internalService(ContextManager.java:797)
at org.apache.tomcat.core.ContextManager.service(ContextManager.java:743)
at org.apache.tomcat.service.http.HttpConnectionHandler.processConnection(HttpConnectionHandler.java:210)
at org.apache.tomcat.service.TcpWorkerThread.runIt(PoolTcpEndpoint.java:416)
at org.apache.tomcat.util.ThreadPool$ControlRunnable.run(ThreadPool.java:498)
at java.lang.Thread.run(Thread.java:498)
---------------------------------------------------------------------
下面是我的代码：
---------------------------------------------------------------------
javadb.jsp:<%@ page contentType = "text/html; charset=gb2312" %>
<%@ page import = "java.sql.*" %>
<jsp:useBean id="jdb" class="javadb.tjavabean" scope="session" />
<html>
   <head>
      <title>Test JDBC for MS SQL Server</title>
      <meta http-equiv="Content-Type" content="text/html; charset=gb2312">
   </head>
   <body>
      <!--
      <jsp:plugin type="applet" code="TJavaDB.class" codebase="/jsp" jreversion="1.3" width="200" height="75">
      <jsp:fallback> Your browser doesn't support OBJECT or EMBED </jsp:fallback>
      </jsp:plugin>
      -->
      <%
         /*
         ResultSet rset = jdb.Execute();
         out.println( rset );
         //*/
         jdb.Execute();
      %>
   </body>
</html>
-----------------------------------------------------------
tjavabean.java:package javadb;import java.io.*;public class tjavabean
{
   public tjavabean()
   {
      MsgStr = "HelloWorld !";
   }
   
   public void Execute()
   {
      System.out.println( MsgStr );
   }
   
   String MsgStr;
}

Answer 7

终于找到了解决的办法：
对于tomcat 3.2.1，如果是在用户自建的虚拟目录中使用JSP，则这个虚拟目录中应该建立WEB-INF目录，然后再WEB-INF目录下建立classes目录，JSP中需要引用的JavaBeans的class都存放于这个WEB-INF\classes目录中