com.brettonw.bedrock.service.Base Maven / Gradle / Ivy
package com.brettonw.bedrock.service;
import com.brettonw.bedrock.bag.*;
import com.brettonw.bedrock.bag.formats.MimeType;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import javax.servlet.ServletConfig;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;
import java.lang.reflect.Method;
import java.nio.charset.StandardCharsets;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;
import static java.util.stream.Collectors.joining;
public class Base extends HttpServlet {
private static final Logger log = LogManager.getLogger (Base.class);
public static final String CONTENT_TYPE = "Content-Type";
public static final String DESCRIPTION = "description";
public static final String DISPLAY_NAME = "display-name";
public static final String ERROR = "error";
public static final String EVENT = "event";
public static final String EVENTS = "events";
public static final String EXAMPLE = "example";
public static final String HELP = "help";
public static final String MULTIPLE = "multiple";
public static final String NAME = "name";
public static final String OK = "ok";
public static final String PARAMETERS = "parameters";
public static final String POM_NAME = "pom-name";
public static final String POM_VERSION = "pom-version";
public static final String POST_DATA = "post-data";
public static final String QUERY = "query";
public static final String REQUIRED = "required";
public static final String RESPONSE = "response";
public static final String SERVLET = "servlet";
public static final String STATUS = "status";
public static final String STRICT = "strict";
public static final String VERSION = "version";
public static final String SCHEMA = "schema";
private static ServletContext context;
public static ServletContext getContext () {
return context;
}
public static Object getAttribute (String key) {
return (context != null) ? context.getAttribute (key) : null;
}
public static Object setAttribute (String key, Object value) {
if (context != null) {
Object oldValue = context.getAttribute (key);
context.setAttribute (key, value);
return oldValue;
}
return null;
}
public static String getBedrockVersion () {
return Base.class.getPackage ().getImplementationVersion ();
}
private final Map handlers = new HashMap<> ();
private String configurationResourcePath = "/WEB-INF/configuration.json";
private BagObject configuration;
private BagObject schema;
protected BagObject getSchema () {
// return a deep copy so the user can't accidentally modify it
return new BagObject (schema);
}
protected BagObject getConfiguration () {
// if we already have the configuration, return it
if (configuration != null) {
return configuration;
}
// otherwise, check to see if the servlet has been initialized
if (context != null) {
// try to load the configuration from the specified file resource
String configurationPath = getContext ().getRealPath (configurationResourcePath);
log.info ("configuration path: " + configurationPath);
configuration = BagObjectFrom.inputStream (getContext ().getResourceAsStream (configurationResourcePath), () -> new BagObject ());
// common values for building the schema
String help = Key.cat (EVENTS, HELP);
// try to fetch the schema
if ((schema = configuration.getBagObject (SCHEMA)) != null) {
// remove the schema object from the configuration so it is protected
configuration.remove (SCHEMA);
// add a 'help' event if one isn't supplied
if (! schema.has (help)) {
schema.put (help, BagObjectFrom.resource (getClass (), "/help.json"));
}
// wire up the handlers specified in the schema - it is treated as authoritative so that
// only specified events are exposed
String[] eventNames = schema.getBagObject (EVENTS).keys ();
for (String eventName : eventNames) {
install (eventName);
}
} else {
// there is no schema, so report the warning
log.warn ("Starting service with no schema.");
// create a bootstrap schema and add the help descriptor
schema = BagObjectFrom.resource (getClass (), "/bootstrap.json");
schema.put (help, BagObjectFrom.resource (getClass (), "/help.json"));
// bootstrap/autowire... loop over all of the methods that match the target signature
// and install them as bootstraped generics
Method methods[] = this.getClass ().getMethods ();
for (Method method : methods) {
// if the method signature matches the event handler signature
if ((method.getName ().startsWith (Handler.HANDLER_PREFIX)) && (method.getParameterCount () == 1) && (method.getParameterTypes()[0] == Event.class)) {
// compute the event name (dash syntax), and install the handler
String[] elements = method.getName ().substring (Handler.HANDLER_PREFIX.length ()).split("(?=[A-Z])");
String eventName = Arrays.stream (elements).map (e -> e.toLowerCase ()).collect(joining("-"));
install (eventName);
// add a default schema entry if one isn't in the bootstrap so it passes
// basic validation
String schemaName = Key.cat (EVENTS, eventName);
if (!schema.has (schemaName)) {
log.info ("Adding bootstrap schema entry for '" + eventName + "'");
schema.put (schemaName, BagObject
.open (DESCRIPTION, "Bootstrap " + method.getName ())
.add (STRICT, false)
);
}
}
}
}
// if the schema didn't supply a name, add one
schema.put (NAME, getName ());
// return the built configuration
return configuration;
} else {
log.error ("Configuration requested before initialization.");
return null;
}
}
protected Base () {
}
protected Base (String configurationResourcePath) {
this.configurationResourcePath = configurationResourcePath;
}
public String getName () {
// if the configuration supplies a name,,,
String name = (configuration != null) ? configuration.getString (NAME) : null;
// or if the schema supplies a name...
if ((name == null) && (schema != null)) {
name = schema.getString (NAME);
}
// or if the POM has a name
if (name == null) {
name = getClass ().getPackage ().getImplementationTitle ();
}
// or if the web context supplies a name... this should be the last resort
if ((name == null) && (context != null) && (context.getServletContextName () != null)) {
name = context.getServletContextName ();
}
return (name != null) ? name : "[UNNAMED]";
}
public String getVersion () {
return getClass ().getPackage ().getImplementationVersion ();
}
@Override
public void init (ServletConfig config) throws ServletException {
super.init (config);
context = config.getServletContext ();
log.info ("STARTING " + getName () + " v." + getVersion () + " with Bedrock v." + getBedrockVersion ());
setAttribute (SERVLET, this);
// configure the application
getConfiguration ();
}
@Override
public void destroy () {
super.destroy ();
log.debug (getName () + " DESTROYING...");
}
@Override
public void doGet (HttpServletRequest request, HttpServletResponse response) throws IOException {
BagObject query = BagObjectFrom.string (request.getQueryString (), MimeType.URL, () -> new BagObject ());
handleRequest (query, request, response);
}
@Override
public void doPost (HttpServletRequest request, HttpServletResponse response) throws IOException {
// get the request data type, then tease out the response type (use a default if it's not present) and the
// charset (if given, otherwise default to UTF-8, because that's what it will be in Java)
String mimeType = MimeType.DEFAULT;
String contentTypeHeader = request.getHeader (CONTENT_TYPE);
if (contentTypeHeader != null) {
String[] contentType = contentTypeHeader.replace (" ", "").split (";");
mimeType = contentType[0];
log.debug ("'Content-Type' is (" + mimeType + ")");
} else {
log.warn ("'Content-Type' is not set by the requestor, using default (" + mimeType + ")");
}
// extract the bedrock data that's been posted, we do it this roundabout way because
// we don't know a priori if it's an object or array
SourceAdapter sourceAdapter = new SourceAdapterReader(request.getInputStream (), mimeType);
String requestString = sourceAdapter.getStringData ();
Bag postData = BagObjectFrom.string (requestString, mimeType);
if (postData == null) postData = BagArrayFrom.string (requestString);
// handle the query part normally, but add the post data to it (if any)
BagObject query = BagObjectFrom.string (request.getQueryString (), MimeType.URL, () -> new BagObject ())
.put (POST_DATA, postData);
handleRequest (query, request, response);
}
private void addCorsHeaders (HttpServletResponse response) {
// check to see if CORS is desired on this api
if (true) {
// the base CORS headers
response.setHeader ("Access-Control-Allow-Origin", "*");
response.setHeader ("Access-Control-Allow-Headers", "*");
response.setHeader ("Access-Control-Allow-Methods", "GET,POST,OPTIONS");
}
}
@Override
public void doOptions (HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
addCorsHeaders (response);
super.doOptions (request, response);
}
private void handleRequest (BagObject query, HttpServletRequest request, HttpServletResponse response) throws IOException {
// handle the event before we add headers and charsets so that exceptions are correctly
// reported back to the application container
Event event = handleEvent (query, request);
String UTF_8 = StandardCharsets.UTF_8.name ();
response.setContentType (MimeType.JSON + "; charset=" + UTF_8);
response.setCharacterEncoding (UTF_8);
// tell the browsers we know what we are returning (JSON is "protected")
response.setHeader ("X-Content-Type-Options", "nosniff");
addCorsHeaders (response);
PrintWriter out = response.getWriter ();
out.println (event.getResponse ().toString (MimeType.JSON));
out.close ();
}
private Event handleEvent (BagObject query, HttpServletRequest request) {
Event event = new Event (query, request);
if (schema != null) {
// create the event object around the request parameters, and validate that it is
// a known event
String eventName = event.getEventName ();
if (eventName != null) {
BagObject eventSpecification = schema.getBagObject (Key.cat (EVENTS, eventName));
if (eventSpecification != null) {
// validate the query parameters
BagObject parameterSpecification = eventSpecification.getBagObject (PARAMETERS);
boolean strict = eventSpecification.getBoolean (STRICT, () -> true);
BagArray validationErrors = new BagArray ();
if (strict) {
// loop over the query parameters to be sure they are all valid
String[] queryParameters = query.keys ();
for (int i = 0; i < queryParameters.length; ++i) {
String queryParameter = queryParameters[i];
if (!queryParameter.equals (EVENT)) {
if ((parameterSpecification == null) || (!parameterSpecification.has (queryParameter))) {
validationErrors.add ("Unspecified parameter: '" + queryParameter + "'");
}
}
}
}
// loop over the parameter specification to be sure all of the required ones are present
if (parameterSpecification != null) {
String[] expectedParameters = parameterSpecification.keys ();
for (int i = 0; i < expectedParameters.length; ++i) {
String expectedParameter = expectedParameters[i];
if (parameterSpecification.getBoolean (Key.cat (expectedParameter, REQUIRED), () -> false)) {
if (!query.has (expectedParameter)) {
validationErrors.add ("Missing required parameter: '" + expectedParameter + "'");
}
}
}
}
// if the validation passed
if (validationErrors.getCount () == 0) {
// get the handler, and try to take care of business...
Handler handler = handlers.get (eventName);
if (handler != null) {
// finally, do your business
handler.handle (event);
} else {
event.error ("No handler installed for '" + EVENT + "' (" + eventName + ")");
}
} else {
event.error (validationErrors);
}
} else {
event.error ("Unknown '" + EVENT + "' (" + eventName + ")");
}
} else {
event.error ("Missing '" + EVENT + "'");
}
} else {
// XXX what are the circumstances under which this happens? I ask because it shouldn't
event.error ("Missing API");
}
return event;
}
public boolean install (String eventName) {
try {
Handler handler = new Handler (eventName, this);
handlers.put (handler.getEventName (), handler);
log.info ("Installed handler '" + handler.getMethodName () + "' for '" + eventName + "'");
return true;
} catch (NoSuchMethodException exception) {
log.error ("Install '" + EVENT + "' failed for (" + eventName + ")", exception);
return false;
}
}
// default handlers
public void handleEventOk (Event event) {
event.ok ();
}
public void handleEventHelp (Event event) {
event.ok (schema);
}
public void handleEventVersion (Event event) {
event.ok (BagObject
.open (POM_VERSION, getVersion ())
.put (DISPLAY_NAME, getName ())
);
}
public void handleEventMultiple (Event event) {
BagArray eventsArray = event.getQuery ().getBagArray (POST_DATA);
if (eventsArray != null) {
int eventCount = eventsArray.getCount ();
BagArray results = new BagArray (eventCount);
for (int i = 0; i < eventCount; ++i) {
Event subEvent = handleEvent (eventsArray.getBagObject (i), event.getRequest ());
results.add (subEvent.getResponse ());
}
event.ok (results);
} else {
event.error ("No events found (expected an array in '" + POST_DATA + "')");
}
}
}
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