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6.3 A Front End to Various Search Engines

137

Listing 6.1 SearchEngines.java 

package coreservlets;

import java.io.*;

import javax.servlet.*;

import javax.servlet.http.*;

import java.net.*;

/** Servlet that takes a search string, number of results per

 *  page, and a search engine name, sending the query to

 *  that search engine. Illustrates manipulating

 *  the response status line. It sends a 302 response

 *  (via sendRedirect) if it gets a known search engine,

 *  and sends a 404 response (via sendError) otherwise.

 */

public class SearchEngines extends HttpServlet {

  public void doGet(HttpServletRequest request,

                    HttpServletResponse response)

      throws ServletException, IOException {

    String searchString = request.getParameter("searchString");

    if ((searchString == null) ||

        (searchString.length() == 0)) {

      reportProblem(response, "Missing search string.");

      return;

    }

    // The URLEncoder changes spaces to "+" signs and other

    // non alphanumeric characters to "%XY", where XY is the

    // hex value of the ASCII (or ISO Latin 1) character.

    // Browsers always URL encode form values, so the

    // getParameter method decodes automatically. But since

    // we're just passing this on to another server, we need to

    // re encode it.

    searchString = URLEncoder.encode(searchString);

    String numResults =

      request.getParameter("numResults");

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