juneau-rest/juneau-rest-server/src/main/java/org/apache/juneau/rest/BasicRest.java

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// * to you under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance            *
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// *  http://www.apache.org/licenses/LICENSE-2.0                                                                             *
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// ***************************************************************************************************************************
package org.apache.juneau.rest;

import static org.apache.juneau.rest.annotation.HookEvent.*;

import java.io.*;
import java.lang.reflect.Method;
import java.text.*;
import java.util.*;
import java.util.function.*;
import java.util.logging.*;

import javax.servlet.*;
import javax.servlet.http.*;

import org.apache.juneau.cp.*;
import org.apache.juneau.cp.ResourceFinder;
import org.apache.juneau.dto.swagger.*;
import org.apache.juneau.html.annotation.*;
import org.apache.juneau.internal.*;
import org.apache.juneau.rest.annotation.*;
import org.apache.juneau.rest.config.*;
import org.apache.juneau.http.exception.*;

/**
 * Identical to {@link BasicRestServlet} but doesn't extend from {@link HttpServlet}.
 *
 * <p>
 * This is particularly useful in Spring Boot environments that auto-detect servlets to deploy in servlet containers,
 * but you want this resource to be deployed as a child instead.
 *
 * <ul class='seealso'>
 * 	<li class='link'>{@doc juneau-rest-server.Instantiation.BasicRest}
 * </ul>
 */
@Rest(
	// Allow OPTIONS requests to be simulated using ?method=OPTIONS query parameter.
	allowedMethodParams="OPTIONS"
)
@HtmlDocConfig(
	// Basic page navigation links.
	navlinks={
		"up: request:/..",
		"options: servlet:/?method=OPTIONS",
		"stats: servlet:/stats"
	}
)
public abstract class BasicRest implements BasicUniversalRest, BasicRestMethods, RestInfoProvider, RestCallLogger, RestResourceResolver, ResourceFinder {

	private Logger logger = Logger.getLogger(getClass().getName());
	private volatile RestContext context;
	private RestInfoProvider infoProvider;
	private RestCallLogger callLogger;
	private ResourceFinder resourceFinder;
	private RestResourceResolver resourceResolver = new BasicRestResourceResolver();

	/**
	 * [OPTIONS /*] - Show resource options.
	 *
	 * @param req The HTTP request.
	 * @return A bean containing the contents for the OPTIONS page.
	 */
	@Override /* BasicRestConfig */
	public Swagger getOptions(RestRequest req) {
		// Localized Swagger for this resource is available through the RestRequest object.
		return req.getSwagger();
	}

	/**
	 * [GET /options] - Show resource options.
	 *
	 * @param req The HTTP request.
	 * @return A bean containing the contents for the OPTIONS page.
	 */
	@Override /* BasicRestConfig */
	public Swagger getOptions2(RestRequest req) {
		// Localized Swagger for this resource is available through the RestRequest object.
		return req.getSwagger();
	}

	/**
	 * [* /error] - Error occurred.
	 *
	 * <p>
	 * Servlet chains will often automatically redirect to <js>"/error"</js> when any sort of error condition occurs
	 * (such as failed authentication) and will set appropriate response parameters (such as an <c>WWW-Authenticate</c>
	 * response header).
	 *
	 * <p>
	 * These responses should be left as-is without any additional processing.
	 */
	@Override /* BasicRestConfig */
	public void error() {}

	/**
	 * [GET /stats] - Timing statistics.
	 *
	 * <p>
	 * Timing statistics for method invocations on this resource.
	 *
	 * @return A collection of timing statistics for each annotated method on this resource.
	 */
	@Override /* BasicRestConfig */
	public RestContextStats getStats(RestRequest req) {
		return req.getContext().getStats();
	}

	//-----------------------------------------------------------------------------------------------------------------
	// Context methods.
	//-----------------------------------------------------------------------------------------------------------------

	/**
	 * Returns the read-only context object that contains all the configuration information about this resource.
	 *
	 * @return The context information on this servlet.
	 */
	protected synchronized RestContext getContext() {
		if (context == null)
			throw new InternalServerError("RestContext object not set on resource.");
		return context;
	}

	//-----------------------------------------------------------------------------------------------------------------
	// Convenience logger methods
	//-----------------------------------------------------------------------------------------------------------------

	/**
	 * Log a message at {@link Level#INFO} level.
	 *
	 * <p>
	 * Subclasses can intercept the handling of these messages by overriding {@link #doLog(Level, Throwable, Supplier)}.
	 *
	 * @param msg The message to log.
	 */
	public void log(String msg) {
		doLog(Level.INFO, null, () -> msg);
	}

	/**
	 * Log a message.
	 *
	 * <p>
	 * Subclasses can intercept the handling of these messages by overriding {@link #doLog(Level, Throwable, Supplier)}.
	 *
	 * @param msg The message to log.
	 * @param cause The cause.
	 */
	public void log(String msg, Throwable cause) {
		doLog(Level.INFO, null, () -> msg);
	}

	/**
	 * Log a message.
	 *
	 * <p>
	 * Subclasses can intercept the handling of these messages by overriding {@link #doLog(Level, Throwable, Supplier)}.
	 *
	 * @param level The log level.
	 * @param msg The message to log.
	 * @param args Optional {@link MessageFormat}-style arguments.
	 */
	public void log(Level level, String msg, Object...args) {
		doLog(level, null, () -> StringUtils.format(msg, args));
	}

	/**
	 * Log a message.
	 *
	 * <p>
	 * Subclasses can intercept the handling of these messages by overriding {@link #doLog(Level, Throwable, Supplier)}.
	 *
	 * @param level The log level.
	 * @param cause The cause.
	 * @param msg The message to log.
	 * @param args Optional {@link MessageFormat}-style arguments.
	 */
	public void log(Level level, Throwable cause, String msg, Object...args) {
		doLog(level, cause, () -> StringUtils.format(msg, args));
	}

	/**
	 * Main logger method.
	 *
	 * <p>
	 * The default behavior logs a message to the Java logger of the class name.
	 *
	 * <p>
	 * Subclasses can override this method to implement their own logger handling.
	 *
	 * @param level The log level.
	 * @param cause Optional throwable.
	 * @param msg The message to log.
	 */
	protected void doLog(Level level, Throwable cause, Supplier<String> msg) {
		logger.log(level, cause, msg);
	}

	//-----------------------------------------------------------------------------------------------------------------
	// Hook events
	//-----------------------------------------------------------------------------------------------------------------

	/**
	 * Method that gets called during servlet initialization.
	 *
	 * <p>
	 * This method is called from within the {@link Servlet#init(ServletConfig)} method after the {@link RestContextBuilder}
	 * object has been created and initialized with the annotations defined on the class, but before the
	 * {@link RestContext} object has been created.
	 *
	 * <p>
	 * An example of this is the <c>PetStoreResource</c> class that uses an init method to perform initialization
	 * of an internal data structure.
	 *
	 * <h5 class='figure'>Example:</h5>
	 * <p class='bcode w800'>
	 * 	<ja>@Rest</ja>(...)
	 * 	<jk>public class</jk> PetStoreResource <jk>extends</jk> ResourceJena {
	 *
	 * 		<jc>// Our database.</jc>
	 * 		<jk>private</jk> Map&lt;Integer,Pet&gt; <jf>petDB</jf>;
	 *
	 * 		<ja>@Override</ja>
	 * 		<jk>public void</jk> onInit(RestContextBuilder builder) <jk>throws</jk> Exception {
	 * 			<jc>// Load our database from a local JSON file.</jc>
	 * 			<jf>petDB</jf> = JsonParser.<jsf>DEFAULT</jsf>.parse(getClass().getResourceAsStream(<js>"PetStore.json"</js>), LinkedHashMap.<jk>class</jk>, Integer.<jk>class</jk>, Pet.<jk>class</jk>);
	 * 		}
	 * 	}
	 * </p>
	 *
	 * <ul class='notes'>
	 * 	<li>
	 * 		The default implementation of this method is a no-op.
	 * 	<li>
	 * 		Multiple INIT methods can be defined on a class.
	 * 		<br>INIT methods on parent classes are invoked before INIT methods on child classes.
	 * 		<br>The order of INIT method invocations within a class is alphabetical, then by parameter count, then by parameter types.
	 * 	<li>
	 * 		The method can throw any exception causing initialization of the servlet to fail.
	 * </ul>
	 *
	 * @param builder Context builder which can be used to configure the servlet.
	 * @throws Exception Any exception thrown will cause servlet to fail startup.
	 */
	@RestHook(INIT)
	public void onInit(RestContextBuilder builder) throws Exception {}

	/**
	 * Method that gets called immediately after servlet initialization.
	 *
	 * <p>
	 * This method is called from within the {@link Servlet#init(ServletConfig)} method after the {@link RestContext}
	 * object has been created.
	 *
	 * <ul class='notes'>
	 * 	<li>
	 * 		The default implementation of this method is a no-op.
	 * 	<li>
	 * 		Multiple POST_INIT methods can be defined on a class.
	 * 		<br>POST_INIT methods on parent classes are invoked before POST_INIT methods on child classes.
	 * 		<br>The order of POST_INIT method invocations within a class is alphabetical, then by parameter count, then by parameter types.
	 * 	<li>
	 * 		The method can throw any exception causing initialization of the servlet to fail.
	 * </ul>
	 *
	 * @param context The initialized context object.
	 * @throws Exception Any exception thrown will cause servlet to fail startup.
	 */
	@RestHook(POST_INIT)
	public void onPostInit(RestContext context) throws Exception {
		this.context = context;
		this.infoProvider = new BasicRestInfoProvider(context);
		this.callLogger = new BasicRestCallLogger(context);
		this.resourceFinder = new BasicResourceFinder();
	}

	/**
	 * Identical to {@link #onPostInit(RestContext)} except the order of execution is child-resources first.
	 *
	 * <p>
	 * Use this method if you need to perform any kind of initialization on child resources before the parent resource.
	 *
	 * <p>
	 * This method is called from within the {@link Servlet#init(ServletConfig)} method after the {@link RestContext}
	 * object has been created and after the {@link HookEvent#POST_INIT} methods have been called.
	 *
	 * <p>
	 * The only valid parameter type for this method is {@link RestContext} which can be used to retrieve information
	 * about the servlet.
	 *
	 * <ul class='notes'>
	 * 	<li>
	 * 		The default implementation of this method is a no-op.
	 * 	<li>
	 * 		Multiple POST_INIT_CHILD_FIRST methods can be defined on a class.
	 * 		<br>POST_INIT_CHILD_FIRST methods on parent classes are invoked before POST_INIT_CHILD_FIRST methods on child classes.
	 * 		<br>The order of POST_INIT_CHILD_FIRST method invocations within a class is alphabetical, then by parameter count, then by parameter types.
	 * 	<li>
	 * 		The method can throw any exception causing initialization of the servlet to fail.
	 * </ul>
	 *
	 * @param context The initialized context object.
	 * @throws Exception Any exception thrown will cause servlet to fail startup.
	 */
	@RestHook(POST_INIT_CHILD_FIRST)
	public void onPostInitChildFirst(RestContext context) throws Exception {}

	/**
	 * Method that gets called during servlet destroy.
	 *
	 * <p>
	 * This method is called from within the {@link Servlet#destroy()}.
	 *
	 * <h5 class='figure'>Example:</h5>
	 * <p class='bcode w800'>
	 * 	<ja>@Rest</ja>(...)
	 * 	<jk>public class</jk> PetStoreResource <jk>extends</jk> ResourceJena {
	 *
	 * 		<jc>// Our database.</jc>
	 * 		<jk>private</jk> Map&lt;Integer,Pet&gt; <jf>petDB</jf>;
	 *
	 * 		<ja>@Override</ja>
	 * 		<jk>public void</jk> onDestroy(RestContext context) {
	 * 			<jf>petDB</jf> = <jk>null</jk>;
	 * 		}
	 * 	}
	 * </p>
	 *
	 * <ul class='notes'>
	 * 	<li>
	 * 		The default implementation of this method is a no-op.
	 * 	<li>
	 * 		Multiple DESTROY methods can be defined on a class.
	 * 		<br>DESTROY methods on child classes are invoked before DESTROY methods on parent classes.
	 * 		<br>The order of DESTROY method invocations within a class is alphabetical, then by parameter count, then by parameter types.
	 * 	<li>
	 * 		In general, destroy methods should not throw any exceptions, although if any are thrown, the stack trace will be
	 * 		printed to <c>System.err</c>.
	 * </ul>
	 *
	 * @param context The initialized context object.
	 * @throws Exception Any exception thrown will cause stack trace to be printed to <c>System.err</c>.
	 */
	@RestHook(DESTROY)
	public void onDestroy(RestContext context) throws Exception {}

	/**
	 * A method that is called immediately after the <c>HttpServlet.service(HttpServletRequest, HttpServletResponse)</c>
	 * method is called.
	 *
	 * <p>
	 * Note that you only have access to the raw request and response objects at this point.
	 *
	 * <h5 class='figure'>Example:</h5>
	 * <p class='bcode w800'>
	 * 	<ja>@Rest</ja>(...)
	 * 	<jk>public class</jk> MyResource <jk>extends</jk> BasicRestServlet {
	 *
	 * 		<jc>// Add a request attribute to all incoming requests.</jc>
	 * 		<ja>@Override</ja>
	 * 		<jk>public void</jk> onStartCall(HttpServletRequest req, HttpServletResponse res) {
	 * 			req.setAttribute(<js>"foobar"</js>, <jk>new</jk> FooBar());
	 * 		}
	 * 	}
	 * </p>
	 *
	 * <ul class='notes'>
	 * 	<li>
	 * 		The default implementation of this method is a no-op.
	 * 	<li>
	 * 		Multiple START_CALL methods can be defined on a class.
	 * 		<br>START_CALL methods on parent classes are invoked before START_CALL methods on child classes.
	 * 		<br>The order of START_CALL method invocations within a class is alphabetical, then by parameter count, then by parameter types.
	 * 	<li>
	 * 		The method can throw any exception.
	 * 		<br>{@link HttpException HttpExceptions} can be thrown to cause a particular HTTP error status code.
	 * 		<br>All other exceptions cause an HTTP 500 error status code.
	 * </ul>
	 *
	 * @param req The HTTP servlet request object.
	 * @param res The HTTP servlet response object.
	 * @throws Exception Any exception.
	 */
	@RestHook(START_CALL)
	public void onStartCall(HttpServletRequest req, HttpServletResponse res) throws Exception {}

	/**
	 * Method that gets called immediately before the <ja>@RestMethod</ja> annotated method gets called.
	 *
	 * <p>
	 * At this point, the {@link RestRequest} object has been fully initialized, and all {@link RestGuard} and
	 * {@link RestMatcher} objects have been called.
	 *
	 * <ul class='notes'>
	 * 	<li>
	 * 		The default implementation of this method is a no-op.
	 * 	<li>
	 * 		Multiple PRE_CALL methods can be defined on a class.
	 * 		<br>PRE_CALL methods on parent classes are invoked before PRE_CALL methods on child classes.
	 * 		<br>The order of PRE_CALL method invocations within a class is alphabetical, then by parameter count, then by parameter types.
	 * 	<li>
	 * 		The method can throw any exception.
	 * 		<br>{@link HttpException HttpExceptions} can be thrown to cause a particular HTTP error status code.
	 * 		<br>All other exceptions cause an HTTP 500 error status code.
	 * 	<li>
	 * 		It's advisable not to mess around with the HTTP body itself since you may end up consuming the body
	 * 		before the actual REST method has a chance to use it.
	 * </ul>
	 *
	 * @param req The request object.
	 * @param res The response object.
	 * @throws Exception Any exception.
	 */
	@RestHook(PRE_CALL)
	public void onPreCall(RestRequest req, RestResponse res) throws Exception {}

	/**
	 * Method that gets called immediately after the <ja>@RestMethod</ja> annotated method gets called.
	 *
	 * <p>
	 * At this point, the output object returned by the method call has been set on the response, but
	 * {@link RestConverter RestConverters} have not yet been executed and the response has not yet been written.
	 *
	 * <ul class='notes'>
	 * 	<li>
	 * 		The default implementation of this method is a no-op.
	 * 	<li>
	 * 		Multiple POST_CALL methods can be defined on a class.
	 * 		<br>POST_CALL methods on parent classes are invoked before POST_CALL methods on child classes.
	 * 		<br>The order of POST_CALL method invocations within a class is alphabetical, then by parameter count, then by parameter types.
	 * 	<li>
	 * 		The method can throw any exception, although at this point it is too late to set an HTTP error status code.
	 * </ul>
	 *
	 * @param req The request object.
	 * @param res The response object.
	 * @throws Exception Any exception.
	 */
	@RestHook(POST_CALL)
	public void onPostCall(RestRequest req, RestResponse res) throws Exception {}

	/**
	 * Method that gets called right before we exit the servlet service method.
	 *
	 * <p>
	 * At this point, the output has been written and flushed.
	 *
	 * <p>
	 * The following attributes are set on the {@link HttpServletRequest} object that can be useful for logging purposes:
	 * <ul>
	 * 	<li><js>"Exception"</js> - Any exceptions thrown during the request.
	 * 	<li><js>"ExecTime"</js> - Execution time of the request.
	 * </ul>
	 *
	 * <ul class='notes'>
	 * 	<li>
	 * 		The default implementation of this method is a no-op.
	 * 	<li>
	 * 		Multiple END_CALL methods can be defined on a class.
	 * 		<br>END_CALL methods on parent classes are invoked before END_CALL methods on child classes.
	 * 		<br>The order of END_CALL method invocations within a class is alphabetical, then by parameter count, then by parameter types.
	 * 	<li>
	 * 		The method can throw any exception, although at this point it is too late to set an HTTP error status code.
	 * 	<li>
	 * 		Note that if you override a parent method, you probably need to call <code><jk>super</jk>.parentMethod(...)</code>.
	 * 		<br>The method is still considered part of the parent class for ordering purposes even though it's
	 * 		overridden by the child class.
	 * </ul>
	 *
	 * @param req The HTTP servlet request object.
	 * @param res The HTTP servlet response object.
	 * @throws Exception Any exception.
	 */
	@RestHook(END_CALL)
	public void onEndCall(HttpServletRequest req, HttpServletResponse res) throws Exception {}

	//-----------------------------------------------------------------------------------------------------------------
	// Other methods.
	//-----------------------------------------------------------------------------------------------------------------

	/**
	 * Returns the current HTTP request.
	 *
	 * @return The current HTTP request, or <jk>null</jk> if it wasn't created.
	 */
	public synchronized RestRequest getRequest() {
		return getContext().getRequest();
	}

	/**
	 * Returns the current HTTP response.
	 *
	 * @return The current HTTP response, or <jk>null</jk> if it wasn't created.
	 */
	public synchronized RestResponse getResponse() {
		return getContext().getResponse();
	}

	//-----------------------------------------------------------------------------------------------------------------
	// RestInfoProvider
	//-----------------------------------------------------------------------------------------------------------------

	@Override /* RestInfoProvider */
	public Swagger getSwagger(RestRequest req) throws Exception {
		return infoProvider.getSwagger(req);
	}

	@Override /* RestInfoProvider */
	public String getSiteName(RestRequest req) throws Exception {
		return infoProvider.getSiteName(req);
	}

	@Override /* RestInfoProvider */
	public String getTitle(RestRequest req) throws Exception {
		return infoProvider.getTitle(req);
	}

	@Override /* RestInfoProvider */
	public String getDescription(RestRequest req) throws Exception {
		return infoProvider.getDescription(req);
	}

	@Override /* RestInfoProvider */
	public String getMethodSummary(Method method, RestRequest req) throws Exception {
		return infoProvider.getMethodSummary(method, req);
	}

	@Override /* RestInfoProvider */
	public String getMethodDescription(Method method, RestRequest req) throws Exception {
		return infoProvider.getMethodDescription(method, req);
	}

	//-----------------------------------------------------------------------------------------------------------------
	// RestCallLogger
	//-----------------------------------------------------------------------------------------------------------------

	@Override /* RestCallLogger */
	public void log(RestCallLoggerConfig config, HttpServletRequest req, HttpServletResponse res) {
		callLogger.log(config, req, res);
	}

	//-----------------------------------------------------------------------------------------------------------------
	// ClasspathResourceFinder
	//-----------------------------------------------------------------------------------------------------------------

	@Override /* ClasspathResourceFinder */
	public InputStream findResource(Class<?> baseClass, String name, Locale locale) throws IOException {
		return resourceFinder.findResource(baseClass, name, locale);
	}

	//-----------------------------------------------------------------------------------------------------------------
	// RestResourceResolver
	//-----------------------------------------------------------------------------------------------------------------

	@Override /* RestResourceResolver */
	public <T> T resolve(Object parent, Class<T> c, Object... args) {
		return resourceResolver.resolve(parent, c, args);
	}

	@Override /* RestResourceResolver */
	public <T> T resolve(Object parent, Class<T> c, RestContextBuilder builder, Object... args) throws Exception {
		return resourceResolver.resolve(parent, c, builder, args);
	}
}