package com.ajjpj.asysmon.servlet;
import com.ajjpj.abase.io.AJsonSerHelper;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.*;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Random;
/**
* This servlet_ class serves static resources and dispatches RESTful service calls
*
* @author arno
*/
public abstract class AbstractASysMonServlet extends HttpServlet {
public static final String ASYSMON_MARKER_SEGMENT = "/_$_asysmon_$_/";
public static final String ASYSMON_MARKER_STATIC = ASYSMON_MARKER_SEGMENT + "static/";
public static final String ASYSMON_MARKER_REST = ASYSMON_MARKER_SEGMENT + "rest/";
@Override protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
try {
final String uri = req.getRequestURI();
if(uri.contains(ASYSMON_MARKER_STATIC)) {
serveStaticResource(substringAfter(uri, ASYSMON_MARKER_STATIC), resp);
return;
}
if(uri.contains(ASYSMON_MARKER_REST)) {
try {
final String[] restPart = substringAfter(uri, ASYSMON_MARKER_REST).split("/");
if(!handleRestCall(new ArrayList<String>(Arrays.asList(restPart)), resp)) {
throw new IllegalArgumentException("unsupported REST call: " + uri);
}
return;
}
catch(Exception exc) {
try {
// special status code to indicate an exception that is reported as a JSON message
resp.setStatus(599);
writeExceptionToJson(new AJsonSerHelper(resp.getOutputStream()), exc);
}
catch(Exception e2) {
// throw the original exception if there is a problem in the special handling code
throw new ServletException(exc);
}
}
}
if(uri.contains(ASYSMON_MARKER_SEGMENT)) {
final String[] dynamicPart = substringAfter(uri, ASYSMON_MARKER_SEGMENT).split("/");
if(! handleDynamic(new ArrayList<String>(Arrays.asList(dynamicPart)), resp)) {
resp.setStatus(HttpServletResponse.SC_NOT_FOUND);
}
return;
}
if(! uri.endsWith("/")) {
resp.sendRedirect(uri + "/");
return;
}
serveStaticResource(getDefaultHtmlName(), resp);
}
catch (RuntimeException exc) {
throw exc;
}
catch (IOException exc) {
throw exc;
}
catch (ServletException exc) {
throw exc;
}
catch(Exception exc) {
throw new ServletException(exc);
}
}
private void writeExceptionToJson(AJsonSerHelper json, Exception exc) throws IOException {
json.startObject();
if(exc.getMessage() != null) {
json.writeKey("msg");
json.writeStringLiteral(exc.getMessage());
}
final StringWriter sw = new StringWriter();
final PrintWriter pw = new PrintWriter(sw);
exc.printStackTrace(pw);
pw.close();
json.writeKey("details");
json.startArray();
final BufferedReader br = new BufferedReader(new StringReader(sw.toString()));
String line;
while ((line = br.readLine()) != null) {
json.writeStringLiteral(line);
}
json.endArray();
json.endObject();
}
protected abstract String getDefaultHtmlName();
protected abstract boolean handleRestCall(List<String> pathSegments, HttpServletResponse resp) throws Exception;
protected boolean handleDynamic(List<String> pathSegments, HttpServletResponse resp) throws IOException {
return false;
}
private static String substringAfter(String s, String sub) {
final int idx = s.indexOf(sub);
return s.substring(idx + sub.length());
}
private void serveStaticResource(String resName, HttpServletResponse resp) throws IOException {
if(resName.contains("..") || resName.startsWith("/") || resName.contains("//")) {
throw new IllegalArgumentException("rejected resource request '" + resName + "' for security reasons");
}
final InputStream in = Thread.currentThread().getContextClassLoader().getResourceAsStream("asysmon-res/" + resName);
if(in == null) {
resp.setStatus(HttpServletResponse.SC_NOT_FOUND);
return;
}
resp.addHeader("Cache-Control", "max-age=36000");
final OutputStream out = resp.getOutputStream();
final byte[] buf = new byte[4096];
int numRead=0;
while((numRead = in.read(buf)) > 0) {
out.write(buf, 0, numRead);
}
}
}