JavaBean操作Oracle数据库

本文以一个完整的javabean数据库访问程序简要说明jsp操作数据库。
  本程序由3个bean组成，其中webconstants中定义全局变量，connectionmanager管理数据库连接，mainbean利用webconstants和connectionmanager操作数据库。

首先定义全局变量，如下：

package webrelease;

public interface webconstants
{
  public static final string driverclass ="driverclass";
  const userid is the user id to connect to database
  public static final string userid ="comm";
  const passwd is the user password to connect to database
  public static final string passwd ="comm123";
  const url is the url to connect to database
  public static final string url="jdbc:oracle:thin:@10.2.0.1:1521:orcl";
  public static final string selecttype ="select";
  public static final string connection ="connection";
  public static final string connerror ="conerror";
}

接着创建一个数据库连接管理bean，如下：

package webrelease;

import java.io.*;
import java.beans.*;
import java.util.*;
import java.sql.*;
import webrelease.webconstants;
import oracle.jdbc.driver.*;

public class connectionmanager implements webconstants
{
  private boolean debug = true;
  protected connection con;
  protected debugwriter writer;
  propertychangesupport pcs;
////////////////////////////////////////////////////////////////////////////////
  public connectionmanager()
  {
    pcs = new propertychangesupport(this);
    writer = new debugwriter();
  }
////////////////////////////////////////////////////////////////////////////////
  public void setdebug(string b)
  {
    debug = b.equals("true");
  }
////////////////////////////////////////////////////////////////////////////////
  public void addpropertychangelistener( propertychangelistener l)
  {
    pcs.addpropertychangelistener(l);
  }
////////////////////////////////////////////////////////////////////////////////
  public void removepropertychangelistener(propertychangelistener l)
  {
    pcs.removepropertychangelistener(l);
  }
////////////////////////////////////////////////////////////////////////////////
  public void login()
  {
    try
    {
      drivermanager.registerdriver(new oracle.jdbc.driver.oracledriver());
      class.forname("oracle.jdbc.driver.oracledriver");
    }
    catch(exception e)
    {
      if(debug) {  writer.writedebug("error setting driver:"+e.getmessage());}
    }
    try
    {
      con = drivermanager.getconnection(url,userid,passwd);
      pcs.firepropertychange(connection,null,con);
      if(debug)
      {
        writer.writedebug("connection succeded ! url:"+url+"user:"+userid+
                          "pwd:"+passwd);
      }
    }
    catch(exception e)
    {
      pcs.firepropertychange(connerror,null,e);
      if(debug)
      {
        writer.writedebug("connection failed ! url:"+url+"user:"+userid+
                          "pwd:"+passwd);
      }
    }

  }
}

在mainbean中，侦听数据库是否连接，如果连接则对数据库进行操作：

package webrelease;

import java.io.*;
import java.beans.*;
import java.util.*;
import java.sql.*;
import webrelease.*;

public class mainbean implements propertychangelistener ,webconstants
{
  private boolean debug = true;
  protected connection con;
  protected debugwriter writer;
////////////////////////////////////////////////////////////////////////////////
  public mainbean()
  {
  writer = new debugwriter();
  }
////////////////////////////////////////////////////////////////////////////////
  public void propertychange(propertychangeevent evt)
  {
  string prop = evt.getpropertyname();
 //see if we got a connection
  if(prop.equals(connection))
    {//ok so update the local connection
      try
      {
        //make sure it really is a connection
        con = (connection)evt.getnewvalue();
      }
      catch(exception e)
      {
        writer.writedebug("error connecting to database"+e.getmessage());
      }
    }
  }
////////////////////////////////////////////////////////////////////////////////
  public void setconnectionmanager(connectionmanager cm)
  {
    if(cm != null)
    {
      // to remove the old listener from cm
      // to avoid confusion in the mainbean
      cm.removepropertychangelistener(this);
      cm.addpropertychangelistener(this);
      if(debug)
      {
        writer.writedebug("mainbean;set connection manager"+ cm.tostring());
      }
    }
    else
    {
     if(debug)
      {
        writer.writedebug("mainbean;tried to set a null connection manager");
      }
    }
  }
////////////////////////////////////////////////////////////////////////////////
  public boolean isconnected()
  {
    //see if datatabe is connected
    return (con != null);
  }
////////////////////////////////////////////////////////////////////////////////
 public void processquery()
 {
 try
 {
  statement stmt=con.createstatement();
resultset rs=stmt.executequery("select * from hello order by id");
 writer.writedebug("select * from hello order by id");
while(rs.next())
{
writer.writedebug("next");
string str=rs.getstring("name");
writer.writedebug(str+"  &nbsp   ");
}
rs.close();
}
catch(exception e)
{
}