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

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package org.apache.juneau.rest;


import java.io.*;
import java.util.*;

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

/**
 * Class that handles the basic lifecycle of an HTTP REST call.
 *
 * <ul class='seealso'>
 * 	<li class='jf'>{@link RestContext#REST_callHandler}
 * </ul>
 */
public interface RestCallHandler {

	/**
	 * Represents no RestCallHandler.
	 *
	 * <p>
	 * Used on annotation to indicate that the value should be inherited from the parent class, and
	 * ultimately {@link BasicRestCallHandler} if not specified at any level.
	 */
	public interface Null extends RestCallHandler {}

	/**
	 * Creates a {@link RestRequest} object based on the specified incoming {@link HttpServletRequest} object.
	 *
	 * @param req The request object from the {@link #service(HttpServletRequest, HttpServletResponse)} method.
	 * @return The wrapped request object.
	 * @throws ServletException If any errors occur trying to interpret the request.
	 */
	public RestRequest createRequest(HttpServletRequest req) throws ServletException;

	/**
	 * Creates a {@link RestResponse} object based on the specified incoming {@link HttpServletResponse} object
	 * and the request returned by {@link #createRequest(HttpServletRequest)}.
	 *
	 * @param req The request object returned by {@link #createRequest(HttpServletRequest)}.
	 * @param res The response object from the {@link #service(HttpServletRequest, HttpServletResponse)} method.
	 * @return The wrapped response object.
	 * @throws ServletException If any errors occur trying to interpret the request or response.
	 */
	public RestResponse createResponse(RestRequest req, HttpServletResponse res) throws ServletException;

	/**
	 * The main service method.
	 *
	 * @param r1 The incoming HTTP servlet request object.
	 * @param r2 The incoming HTTP servlet response object.
	 * @throws ServletException Error occurred.
	 * @throws IOException Thrown by underlying stream.
	 */
	public void service(HttpServletRequest r1, HttpServletResponse r2) throws ServletException, IOException;

	/**
	 * The main method for serializing POJOs passed in through the {@link RestResponse#setOutput(Object)} method or
	 * returned by the Java method.
	 *
	 * @param req The HTTP request.
	 * @param res The HTTP response.
	 * @throws Exception Can be thrown if error occurred while handling response.
	 */
	public void handleResponse(RestRequest req, RestResponse res) throws Exception;

	/**
	 * Handle the case where a matching method was not found.
	 *
	 * @param rc The HTTP response code.
	 * @param req The HTTP request.
	 * @param res The HTTP response.
	 * @throws Exception Can be thrown if error occurred while handling response.
	 */
	public void handleNotFound(int rc, RestRequest req, RestResponse res) throws Exception;

	/**
	 * Method for handling response errors.
	 *
	 * @param req The servlet request.
	 * @param res The servlet response.
	 * @param e The exception that occurred.
	 * @throws Exception Can be thrown if error occurred while handling response.
	 */
	public void handleError(HttpServletRequest req, HttpServletResponse res, Throwable e) throws Exception;

	/**
	 * Method for converting thrown exceptions into other types before they are handled.
	 *
	 * @param t The thrown object.
	 * @return The converted thrown object.
	 */
	public Throwable convertThrowable(Throwable t);

	/**
	 * Returns the session objects for the specified request.
	 *
	 * @param req The REST request.
	 * @param res The REST response.
	 * @return The session objects for that request.
	 */
	public Map<String,Object> getSessionObjects(RestRequest req, RestResponse res);
}