@@ -0,0 +1,1342 @@
+package com.google.sps.servlets;%0A%0Aimport com.google.sps.data.OpportunitySignup;%0Aimport com.google.sps.utilities.CommonUtils;%0Aimport com.google.sps.utilities.DatabaseConstants;%0Aimport com.google.sps.utilities.SpannerTasks;%0Aimport java.io.IOException;%0Aimport java.util.Set;%0Aimport javax.servlet.annotation.WebServlet;%0Aimport javax.servlet.http.HttpServlet;%0Aimport javax.servlet.http.HttpServletRequest;%0Aimport javax.servlet.http.HttpServletResponse;%0A%0A/** Servlet to get all signups for a volunteering opportunity. */%0A@WebServlet(%22/event-volunteering-data%22)%0Apublic class OpportunitySignupDataServlet extends HttpServlet %7B%0A  private static final String OPPORTUNITY_ID = %22opportunity-id%22;%0A%0A  /**%0A   * Queries database for all opportunity signups that are for a specific volunteering opportunity.%0A   *%0A   * @param request servlet request%0A   * @param response servlet response%0A   * @throws IOException if Input/Output error occurs%0A   */%0A  @Override%0A  public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException %7B%0A    String opportunityId = request.getParameter(OPPORTUNITY_ID);%0A%0A    Set%3COpportunitySignup%3E opportunities = SpannerTasks.getSignupsByOpportunityId(opportunityId);%0A    %0A    response.setContentType(%22application/json;%22);%0A    response.getWriter().println(CommonUtils.convertToJson(opportunities));%0A  %7D%0A%7D%0A

Add servlet for retrieving signups by opportunity id.