binaryservlet.java

21天学通java的示例程序源代码

import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.util.*;

public class BinaryServlet extends HttpServlet {
  private static final String defaultFilename = "image.gif";
  private String filename;

  public void init() {
    // Get the filename of the image file from the init parameter.
    Enumeration params = getInitParameterNames();
    filename = getInitParameter("filename");
    if (filename == null) {
      filename = defaultFilename;
    }
  }

  public void doGet(HttpServletRequest request,
                    HttpServletResponse response)
                    throws ServletException, IOException {

    // Must set the headers before starting the output stream
    File f = new File(filename);

    // Check to make sure the file specified by the init paramter exists.
    if (!f.exists()) {
      response.setContentType("text/plain");
      PrintWriter out = response.getWriter();
      out.println("Unable to find image file:" +f.getAbsolutePath());
      return;
    }

    response.setContentType("image/gif");
    response.setContentLength((int)f.length());

    OutputStream out = response.getOutputStream();
    // read the image data
    FileInputStream fis = new FileInputStream(f);
    byte [] data = new byte[(int)f.length()];
    fis.read(data);

    // write the image data to the client
    out.write(data);

  }
}