requesthandler.java

来自「JAVA Servlet2.3外文书籍源码」· Java 代码 · 共 152 行

package firewall.server;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import firewall.common.*;

import java.io.*;


/**
 * Title:        RequestHandler
 * Description:  Abstract base class for handling requests
 * Copyright:    Copyright (c) 2001
 * Company:
 * @author Andrew Harbourne-Thomas
 * @version 1.0
 */
public abstract class RequestHandler {


  /** HttpServletRequest from servlet containing request data for use
   *  by handlers
   */
  HttpServletRequest httpServletRequest;

  /** HttpServletResponse from servlet containing response data for use
   *  by handlers
   */
  HttpServletResponse httpServletResponse;

  /**
   * String location of files directory
   * Defaults to current location
   */
  static String stringFileBase = File.separator;

  /** File object representation of files directory */
  File fileBase;

  /**
   * Method returns an array of String objects corresponding to
   * files within files directory
   * @return Array of filenames within files directory
   */
  protected String[] getFileList() {
    String[] list = fileBase.list();
    return list;
  }

  /**
   * Method to create File object from String filename
   * @param fileName Name of file
   *
   * @return File object representing file identified by filename
   */
  protected File getFile(String fileName) {
    return new File(fileBase, fileName);
  }

  /**
   * Constructor to find the "Tomcat" home directory and hence the location for
   * our application and the files directory 'hidden' within the
   * WEB-INF directory
   */
  public RequestHandler() {
    fileBase = new File(stringFileBase);
  }

  /**
   * This method must be overridden in subclasses to perform the request
   * processing.
   *
   * @param baseRequest The BaseRequest object that specifes the
   *        request type
   */
  public abstract void respond(BaseRequest baseRequest);

  /**
   * Method sets the request and response object references for the handlers
   * from the servlet
   *
   * @param httpServletRequest Servlets HttpServletRequest object
   * @param httpServletResponse Servlets HttpServletResponse object
   */
  public void setHttpObjects(HttpServletRequest httpServletRequest,
                             HttpServletResponse httpServletResponse) {
    this.httpServletRequest = httpServletRequest;
    this.httpServletResponse = httpServletResponse;
  }

  /**
   * Method to send a file from the server to the client
   *
   * @param sendFile File to be sent to the client
   *
   * @throws IOException
   */
  public void sendFile(File sendFile) throws IOException {
    FileReader fileReader = new FileReader(sendFile);
    PrintWriter out = httpServletResponse.getWriter();
    char c[] = new char[4096];
    int read = 0;
    //Read until end of file and send to client
    while ((read = fileReader.read(c)) != -1) {
      out.write(c, 0, read);
    }

    //Close
    fileReader.close();
    out.close();
  }

  /**
   * Method to send an object from the servlet to the client
   *
   * @param sendObject Object to be sent to the client
   *
   * @throws IOException
   */
  public void sendSerializedObject(Object sendObject)
    throws IOException {
    OutputStream os = httpServletResponse.getOutputStream();
    ObjectOutputStream oos = new ObjectOutputStream(os);
    oos.writeObject(sendObject);
    oos.flush();
    os.flush();
    oos.close();
  }

  /**
   * Sets the response HTTP status code
   */
  public void setStatusCode(int statusCode) {
    httpServletResponse.setStatus(statusCode);
  }

  /**
   * Sets an error code and message for the response
   */
  public void sendError(int statusCode, String message)
    throws IOException {
    httpServletResponse.sendError(statusCode, message);
  }

  /**
   * Static method to set the location of the files
   */
  public static void setStringFileBase(String fileBase) {
    stringFileBase = fileBase;
  }
}