studentdbservlet.java

java 学生管理系统 applet/servlet应用

//  File:  StudentDBServlet.java
//  Listing 3
//
import javax.servlet.*;
import javax.servlet.http.*;

import java.io.*;

import java.util.*;

import shod.register.*;

/**
 *  This servlet provides data entry and retrieval of
 *  student data in a database. <p>
 *
 *  The server administrator/web-master can pass arguments to 
 *  the servlet at loading/intialization time by specifying the
 *  arguments as part of the server configuration. <p>
 *
 *  Servlet Parameters
 *  <ul>
 *    <li>dbDriver - name of the database driver class name (ie sun.jdbc.odbc.JdbcOdbcDriver)
 *    <li>dbURL - complete database URL (ie jdbc:odbc:StudentDatabase)
 *    <li>userid - user id
 *    <li>passwd - password
 *  </ul>
 *
 *  Default Servlet Parameters <br>
 *  These values will be used if not provided.
 *  <ul>
 *    <li>dbDriver - sun.jdbc.odbc.JdbcOdbcDriver
 *    <li>dbURL - jdbc:odbc:StudentDatabase
 *    <li>userid - <none>
 *    <li>passwd - <none>
 *  </ul>
 *
 *  @author Chad (shod) Darby,  [e-mail]
 *  @version 0.6, 5 Jan 1998 - 0.9, 31 July 1998
 *
 */
public class StudentDBServlet extends HttpServlet implements SingleThreadModel
{
    // data members
	private String dbDriver = "sun.jdbc.odbc.JdbcOdbcDriver";
    private String dbURL = "jdbc:odbc:StudentDatabase";
    private String userid = "";
    private String passwd = "";
    
    private StudentDataAccessor myDataAccessor = null;
    
    private String CR = "\n";
    
    /**
	 *  This method is called the first time the servlet is loaded.  Simply
	 *  makes a connection to the database.
	 */
    public void init(ServletConfig config) throws ServletException
    {
        super.init(config);

        System.out.println("StudentDBServlet init: Start");

		String value = null;
		
		// read in parameter value for dbDriver
		if ( (value = config.getInitParameter("dbDriver")) != null )
		{
			dbDriver = value;
		}

		// read in parameter value for dbDriver
		if ( (value = config.getInitParameter("dbURL")) != null )
		{
			dbURL = value;
		}

		// read in parameter value for used id
		if ( (value = config.getInitParameter("userid")) != null )
		{
			userid = value;
		}

		// read in parameter value for dbDriver
		if ( (value = config.getInitParameter("passwd")) != null )
		{
			passwd = value;
		}

        myDataAccessor = new StudentDataAccessor(dbDriver, dbURL, userid, passwd);
        
    }

	/**
	 *  This method is used for applets.
	 *
	 *  Receives and sends the data using object serialization.
	 *
	 *  Gets an input stream from the applet and reads a student object.  Then
	 *  registers the student using our data accessor.  Finally, sends a confirmation
	 *  message back to the applet.
	 */
    public void doPost(HttpServletRequest request,
                        HttpServletResponse response) 
           throws ServletException, IOException
    {
        ObjectInputStream inputFromApplet = null;
        Student aStudent = null;        
        PrintWriter out = null;
        BufferedReader inTest = null;
        
        try
        {  
            // get an input stream from the applet
	        inputFromApplet = new ObjectInputStream(request.getInputStream());
	        show("Connected");
	    
	        // read the serialized student data from applet        
	        show("Reading data...");
	        aStudent = (Student) inputFromApplet.readObject();
	        show("Finished reading.");
	        
	        inputFromApplet.close();
	        
	        // use our business object to register the student
	        // in the database
	        System.out.println(aStudent);
	        myDataAccessor.registerStudent(aStudent);
	        
	        show("Complete.");
	         
	        // send back a confirmation message to the applet
            out = new PrintWriter(response.getOutputStream());
            response.setContentType("text/plain");
            out.println("confirmed");
            out.flush();
            out.close();          
            
        }
        catch (Exception e)
        {
			e.printStackTrace();    
        }
    }
    
	/**
	 *  This method is used by HTML clients and applets.
	 *
	 *  Handles a request and reads information from HTML form data.
	 *
	 *  Figures out if the HTML form is sending a request to register
	 *  or display the students.  Also, handles a request from an applet
	 *  to simply display the students.
	 */
    public void doGet(HttpServletRequest request,
                        HttpServletResponse response) 
           throws ServletException, IOException
    {
        System.out.println("in doGet(...)");

        String userOption = null;
        
        userOption = request.getParameterValues("UserOption")[0];
        
        System.out.println("userOption == " + userOption);
        
        if (userOption == null)
        {
            // simply display the students
            show("Displaying the students");
            displayStudents(request, response);
        }        
        else if (userOption.equals("Register"))
        {
            // register a new student into the database
            registerStudent(request, response);
        }
        else if (userOption.equals("AppletDisplay"))
        {
            // begin applet communication to display students
            System.out.println("userOption = " + userOption);
            appletDisplayStudents(response);    
        }
    
    }
 
    /**
	 *  This method is used for applets.
	 *
	 *  Displays the students to the applet.  This is accomplished by
	 *  getting the student list and returning a vector of students.  This
	 *  vector is returned to the applet using object serialization.
	 */
    protected void appletDisplayStudents(HttpServletResponse response)
    {
        // build the student vector by accessing the database
        System.out.println("okay, building vector");
        Vector studentVector = myDataAccessor.getStudentList();
        
        // send the student vector back to the applet using 
        // object serialization
        System.out.println("sending response");
        sendStudentList(response, studentVector);
    }
    
	/**
	 *  This method is used for applets.
	 *
	 *  Performs the nuts and bolts of sending the student list.  The technique used is
	 *  object serialization.  The process is accomplished by opening an ObjectOutputStream
	 *  to the client connection.  This is accomplished via the HttpServletResponse parameter.
	 *  Next the object is written to the client followed by flushing and closing the stream.
	 *
	 */
    protected void sendStudentList(HttpServletResponse response, Vector studentVector)
    {
        ObjectOutputStream outputToApplet;
        
        try
        {
            outputToApplet = new ObjectOutputStream(response.getOutputStream());
            
            System.out.println("Sending student vector to applet...");
            outputToApplet.writeObject(studentVector);
            outputToApplet.flush();
            
            outputToApplet.close();
            System.out.println("Data transmission complete.");
        }
        catch (IOException e)
        {
			e.printStackTrace(); 
        }
    }
    
	/**
	 *
	 *  This method is used for HTML clients.
	 *
	 *  An HTML page is created that contains a list of students.  This method
	 *  is used to send back an HTML page to a servlet or CGI that requested a list
	 *  of students.
	 */
    protected void displayStudents(HttpServletRequest request,
                                HttpServletResponse response)
    {
        Student aStudent = null;
        
        try 
		{ 
            show("inside displaying students");
            
            // build the html page heading
            String htmlHead = "<html><head><title>List of Students</title></head>" + CR;
                       
            // build the html body
            String htmlBody = "<body><center>" + CR;
            htmlBody += "<h1>Student List</h1>" + CR;
            htmlBody += "<hr></center><p>" + CR;
            
            // build the table heading
            String tableHead = "<center><table border width=100% cellpadding=5>" + CR;
            tableHead += "<tr>" + CR;
            tableHead += "<th> </th>" + CR;
            tableHead += "<th>Student Name</th>" + CR;
            tableHead += "<th>E-mail</th>" + CR;
            tableHead += "<th>Company</th>" + CR;
            tableHead += "<th>Course Expectations</th>" + CR;
            tableHead += "</tr>" + CR;

            // execute the query to get a list of the students
            Vector studentVector = myDataAccessor.getStudentList();
            
            // build the table body
            String tableBody = "";

            int rowNumber = 1;
            
            Enumeration enum = studentVector.elements();
            
            while (enum.hasMoreElements())
            {
                aStudent = (Student) enum.nextElement();
                tableBody += aStudent.toTableString(rowNumber);
                rowNumber++;
            }
                                   
            // build the table bottom 
            String tableBottom = "</table></center>";
                      
            // build html page bottom
            String htmlBottom = "</body></html>";
            
            // build complete html page
            htmlBody += tableHead + tableBody + tableBottom;
            htmlBody += "<p><hr>";
            htmlBody += "<center><a href=/StudentDB/index.html>Return to Course Home Page</a>";
            htmlBody += "<p><i>" + this.getServletInfo() + "</i>";
            htmlBody += "</center>";
            String htmlPage = htmlHead + htmlBody + htmlBottom;
            
            // now let's send this dynamic data
            // back to the browser
            PrintWriter outputToBrowser =  new PrintWriter(response.getOutputStream());            
            response.setContentType("text/html");
            outputToBrowser.println(htmlPage);
            outputToBrowser.flush();
            outputToBrowser.close();
            
            show("finished");
            
        }
        catch (Exception e)
        {
            e.printStackTrace();
        }   
    }
    
	/**
	 *  Build a student object based on the form data
	 */
	protected Student buildStudent(HttpServletRequest request)	
	{
		Student theStudent = null;
		
		try
		{
			String lastName = request.getParameterValues("LastName")[0];
			String firstName = request.getParameterValues("FirstName")[0];
			String email = request.getParameterValues("Email")[0];
			String company = request.getParameterValues("Company")[0];

			String dateString = request.getParameterValues("CourseStartDate")[0];

			String courseTitle = request.getParameterValues("CourseTitle")[0];
			String courseLocation = request.getParameterValues("CourseLocation")[0];
			String expectations = request.getParameterValues("Expectations")[0];               

			theStudent = new Student(lastName, firstName, email, company,
									 dateString, courseTitle, courseLocation,
									 expectations);
		}
		catch (Exception e)
		{
			System.out.println(e);
		}
		
		return theStudent;
	}
	
	/**
	 *  This method is used for students.
	 *
	 *  Creates a new student based on the form data and registers the student
	 *  in the database.  Next, creates a confirmation page for the client.
	 */
    protected void registerStudent(HttpServletRequest request,
                                HttpServletResponse response)
    {
		// create a new student based on the form data
		Student aStudent = buildStudent(request);            

		// now use the business object to insert data into the database
		myDataAccessor.registerStudent(aStudent);

		// build confirmation page
		String htmlPage = "<html><head><title>Confirmation Page</title></head>";

		htmlPage += "<body>";
		htmlPage += "<center><h1>Confirmation Page</h1></center><hr>";
		htmlPage += "The following information was entered successfully";
		htmlPage += aStudent.toWebString();

		htmlPage += "<hr>";
		htmlPage += "<center><a href=/StudentDB/index.html>Return to Home Page</a> | ";
		htmlPage += "<a href=/servlet/StudentDBServlet>View Student List</a>";
		htmlPage += "<p><i>" + this.getServletInfo() + "</i>";
		htmlPage += "</center></body></html>";

		try
		{
			// now let's send this dynamic data
			// back to the browser
			PrintWriter outputToBrowser =  new PrintWriter(response.getOutputStream());

			response.setContentType("text/html");
			outputToBrowser.println(htmlPage);
			outputToBrowser.close();
		}
		catch (Exception e)
		{
			e.printStackTrace();   
		}
    }
    
	/**
	 *  Simply closes the database connection
	 */
    protected void cleanUp()
    {
        // close the database connections
        myDataAccessor.cleanUp();
    }
    
    /**
	 *  Destroys the servlet and calls cleanup to close the database connection
	 */
    public void destroy()
    {
        System.out.println("StudentDBServlet: destroy");
        cleanUp();
    }
    
	/**
	 *  Returns servlet information
	 */
    public String getServletInfo()
    {
        return "<i>Student Registration Servlet, v.06</i>";   
    }
    
	/**
	 *  Simple method for logging messages to the console.
	 */
    protected void show(String msg)
    {
        System.out.println(msg);    
    }
}