processnews.java

这是一个可以在手机客户端运行的选课系统 这个是客户端

package course.select;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import jdbc.*;
import java.sql.*;
import exception.*;

/**
 * @version 	1.0
 * @author
 */
public class ProcessNews extends HttpServlet implements Servlet {

	
	String [] category=null;
	DatabaseConnection connection=null;
	
	public ProcessNews()
	{
		try
		{
			connection=new DatabaseConnection();
			//产生与数据库连接的类的实例，可能抛出SQLException
			connection.connect();
		}
		catch(SQLException e)
		{
			e.printStackTrace();
		}
		catch(DriverException e)
		{
			e.printStackTrace();
		}
	}
	
	/**
	* @see javax.servlet.http.HttpServlet#void (javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse)
	*/
	public void doGet(HttpServletRequest req, HttpServletResponse resp)
		throws ServletException, IOException {
			processRequest(req,resp);
	}

	/**
	* @see javax.servlet.http.HttpServlet#void (javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse)
	*/
	public void doPost(HttpServletRequest req, HttpServletResponse resp)
		throws ServletException, IOException {
			processRequest(req,resp);
	}

	/**
	 * @param req
	 * @param resp
	 */
	private void processRequest(HttpServletRequest req, HttpServletResponse resp) throws IOException
		// TODO 自动生成方法存根
	{
		
		OutputStream os=resp.getOutputStream();
		DataOutputStream dos=new DataOutputStream(os);
		//获得向MIDlet返回所有信息的流
		
		int type=0;
		int target=0;
		try
		{
			type=Integer.parseInt(req.getParameter("type"));
			//查询的信息类型（分类列表，标题，详细信息）
		
			target=Integer.parseInt(req.getParameter("target"));
			
			try
			{
				switch(type)
				{
					case 1:getCategory(dos);break;
					case 2:getTitle(dos,target);break;
					case 3:getDetail(dos,target);break;
					default:break;
				}
				//connection.close();
			}
			catch(SQLException e)
			{
				throw e;
			}
			
		}
		catch(NumberFormatException e)
		{
			dos.writeInt(-8);
			//参数传递错误
		}
		catch(SQLException e)
		{
			dos.writeInt(-3);
			//-3代表连接数据库错误
				//返回提示信息
		}
		finally
		{
			dos.close();	
		}
		
		
		//调试用代码	
		/*
		int type=0;
		int target=0;
		type=Integer.parseInt(req.getParameter("type"));
		//查询的信息类型（分类列表，标题，详细信息）
		target=Integer.parseInt(req.getParameter("target"));
		PrintWriter out=resp.getWriter();
		out.println("type="+type);
		out.println("target="+target);
		try
		{
			category=connection.getCategory();
			out.println("length="+category.length);
			for(int i=0;i<category.length;i++)
				out.println(category[i]);
		}
		catch(SQLException e)
		{
			e.printStackTrace(out);
		}
		out.println(1);
		*/
	}
	
	protected void getCategory(DataOutputStream dos) throws SQLException,IOException
	{
		if(category==null)
			category=connection.getCategory();
		dos.writeUTF("length="+category.length);
		dos.writeInt(category.length);
		for(int i=0;i<category.length;i++)
			dos.writeUTF(category[i]);
	}
	
	protected void getTitle(DataOutputStream dos,int categoryID) throws SQLException,IOException
	{
		String [] title=null;
		int [] titleID=null;
		titleID=connection.getTitleID(category[categoryID-1]);
		title=connection.getTitle(category[categoryID-1]);
		dos.writeInt(titleID.length);
		for(int i=0;i<titleID.length;i++)
		{
			dos.writeInt(titleID[i]);
			dos.writeUTF(title[i]);
		}
	}
	
	protected void getDetail(DataOutputStream dos,int newsID) throws SQLException,IOException
	{
		String detail=null;
		detail=connection.getDetail(newsID);
		dos.writeInt(1);
		dos.writeUTF(detail);
	}

}