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Java API for modeling web page content and relationships in a Servlet environment.
/*
* semanticcms-core-servlet - Java API for modeling web page content and relationships in a Servlet environment.
* Copyright (C) 2016, 2017, 2018, 2019, 2020, 2021, 2022 AO Industries, Inc.
* [email protected]
* 7262 Bull Pen Cir
* Mobile, AL 36695
*
* This file is part of semanticcms-core-servlet.
*
* semanticcms-core-servlet is free software: you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* semanticcms-core-servlet is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with semanticcms-core-servlet. If not, see
* HttpServletRequest, HttpServletResponse, and the response PrintWriter are frequently accessed
* while also frequently updated by elements for capture. It is tedious to pass these objects around
* all over. Also, with the lambda scoping in Java 8, it is easy to use the wrong object from a
* different scope (and possibly capturing context).
*
*
* Each context is intended to be established and used within a single servlet implementation.
* Do not assume correct management of PageContext between different pages, servlets, or files.
* If in doubt, skip this shortcut and pass explicit object references around.
*
*
* @see PageContextWriter
*/
public final class PageContext {
/** Make no instances, all is done through thread locals. */
private PageContext() {
throw new AssertionError();
}
static final ThreadLocal servletContext = new ThreadLocal<>();
static final ThreadLocal request = new ThreadLocal<>();
static final ThreadLocal response = new ThreadLocal<>();
static final ThreadLocal out = new ThreadLocal<>();
@FunctionalInterface
public static interface PageContextRunnable {
void run() throws ServletException, IOException;
}
public static void newPageContext(
ServletContext newServletContext,
HttpServletRequest newRequest,
HttpServletResponse newResponse,
PageContextRunnable target
) throws ServletException, IOException {
final ServletContext oldServletContext = servletContext.get();
final HttpServletRequest oldRequest = request.get();
final HttpServletResponse oldResponse = response.get();
final PrintWriter oldOut = out.get();
PrintWriter newOut = null;
try {
if (newServletContext != oldServletContext) {
servletContext.set(newServletContext);
}
if (newRequest != oldRequest) {
request.set(newRequest);
}
if (newResponse != oldResponse) {
response.set(newResponse);
out.remove();
} else {
newOut = oldOut;
}
target.run();
} finally {
if (newServletContext != oldServletContext) {
if (oldServletContext == null) {
servletContext.remove();
} else {
servletContext.set(oldServletContext);
}
}
if (newRequest != oldRequest) {
if (oldRequest == null) {
request.remove();
} else {
request.set(oldRequest);
}
}
if (newResponse != oldResponse) {
if (oldResponse == null) {
response.remove();
} else {
response.set(oldResponse);
}
}
if (newOut != oldOut) {
if (oldOut == null) {
out.remove();
} else {
out.set(oldOut);
}
}
}
}
@FunctionalInterface
public static interface PageContextCallable extends Callable {
@Override
V call() throws ServletException, IOException;
}
public static V newPageContext(
ServletContext newServletContext,
HttpServletRequest newRequest,
HttpServletResponse newResponse,
PageContextCallable target
) throws ServletException, IOException {
final ServletContext oldServletContext = servletContext.get();
final HttpServletRequest oldRequest = request.get();
final HttpServletResponse oldResponse = response.get();
final PrintWriter oldOut = out.get();
PrintWriter newOut = null;
try {
if (newServletContext != oldServletContext) {
servletContext.set(newServletContext);
}
if (newRequest != oldRequest) {
request.set(newRequest);
}
if (newResponse != oldResponse) {
response.set(newResponse);
out.remove();
} else {
newOut = oldOut;
}
return target.call();
} finally {
if (newServletContext != oldServletContext) {
if (oldServletContext == null) {
servletContext.remove();
} else {
servletContext.set(oldServletContext);
}
}
if (newRequest != oldRequest) {
if (oldRequest == null) {
request.remove();
} else {
request.set(oldRequest);
}
}
if (newResponse != oldResponse) {
if (oldResponse == null) {
response.remove();
} else {
response.set(oldResponse);
}
}
if (newOut != oldOut) {
if (oldOut == null) {
out.remove();
} else {
out.set(oldOut);
}
}
}
}
@FunctionalInterface
public static interface PageContextRunnableSkip {
void run() throws ServletException, IOException, SkipPageException;
}
/**
* Establishes a new page context.
* This usually does not need to be done directly as creating a page will
* establish the starting page context.
*/
public static void newPageContextSkip(
ServletContext newServletContext,
HttpServletRequest newRequest,
HttpServletResponse newResponse,
PageContextRunnableSkip target
) throws ServletException, IOException, SkipPageException {
final ServletContext oldServletContext = servletContext.get();
final HttpServletRequest oldRequest = request.get();
final HttpServletResponse oldResponse = response.get();
final PrintWriter oldOut = out.get();
PrintWriter newOut = null;
try {
if (newServletContext != oldServletContext) {
servletContext.set(newServletContext);
}
if (newRequest != oldRequest) {
request.set(newRequest);
}
if (newResponse != oldResponse) {
response.set(newResponse);
out.remove();
} else {
newOut = oldOut;
}
target.run();
} finally {
if (newServletContext != oldServletContext) {
if (oldServletContext == null) {
servletContext.remove();
} else {
servletContext.set(oldServletContext);
}
}
if (newRequest != oldRequest) {
if (oldRequest == null) {
request.remove();
} else {
request.set(oldRequest);
}
}
if (newResponse != oldResponse) {
if (oldResponse == null) {
response.remove();
} else {
response.set(oldResponse);
}
}
if (newOut != oldOut) {
if (oldOut == null) {
out.remove();
} else {
out.set(oldOut);
}
}
}
}
@FunctionalInterface
public static interface PageContextCallableSkip extends Callable {
@Override
V call() throws ServletException, IOException, SkipPageException;
}
/**
* Establishes a new page context.
* This usually does not need to be done directly as creating a page will
* establish the starting page context.
*/
public static V newPageContextSkip(
ServletContext newServletContext,
HttpServletRequest newRequest,
HttpServletResponse newResponse,
PageContextCallableSkip target
) throws ServletException, IOException, SkipPageException {
final ServletContext oldServletContext = servletContext.get();
final HttpServletRequest oldRequest = request.get();
final HttpServletResponse oldResponse = response.get();
final PrintWriter oldOut = out.get();
PrintWriter newOut = null;
try {
if (newServletContext != oldServletContext) {
servletContext.set(newServletContext);
}
if (newRequest != oldRequest) {
request.set(newRequest);
}
if (newResponse != oldResponse) {
response.set(newResponse);
out.remove();
} else {
newOut = oldOut;
}
return target.call();
} finally {
if (newServletContext != oldServletContext) {
if (oldServletContext == null) {
servletContext.remove();
} else {
servletContext.set(oldServletContext);
}
}
if (newRequest != oldRequest) {
if (oldRequest == null) {
request.remove();
} else {
request.set(oldRequest);
}
}
if (newResponse != oldResponse) {
if (oldResponse == null) {
response.remove();
} else {
response.set(oldResponse);
}
}
if (newOut != oldOut) {
if (oldOut == null) {
out.remove();
} else {
out.set(oldOut);
}
}
}
}
/**
* @param An arbitrary exception type that may be thrown
*/
@FunctionalInterface
public static interface PageContextRunnableSkipE {
void run() throws Ex, ServletException, IOException, SkipPageException;
}
/**
* @param An arbitrary exception type that may be thrown
*/
public static void newPageContextSkipE(
ServletContext newServletContext,
HttpServletRequest newRequest,
HttpServletResponse newResponse,
PageContextRunnableSkipE target
) throws Ex, ServletException, IOException, SkipPageException {
final ServletContext oldServletContext = servletContext.get();
final HttpServletRequest oldRequest = request.get();
final HttpServletResponse oldResponse = response.get();
final PrintWriter oldOut = out.get();
PrintWriter newOut = null;
try {
if (newServletContext != oldServletContext) {
servletContext.set(newServletContext);
}
if (newRequest != oldRequest) {
request.set(newRequest);
}
if (newResponse != oldResponse) {
response.set(newResponse);
out.remove();
} else {
newOut = oldOut;
}
target.run();
} finally {
if (newServletContext != oldServletContext) {
if (oldServletContext == null) {
servletContext.remove();
} else {
servletContext.set(oldServletContext);
}
}
if (newRequest != oldRequest) {
if (oldRequest == null) {
request.remove();
} else {
request.set(oldRequest);
}
}
if (newResponse != oldResponse) {
if (oldResponse == null) {
response.remove();
} else {
response.set(oldResponse);
}
}
if (newOut != oldOut) {
if (oldOut == null) {
out.remove();
} else {
out.set(oldOut);
}
}
}
}
/**
* @param An arbitrary exception type that may be thrown
*/
@FunctionalInterface
// TODO: Ex extends Throwable
public static interface PageContextCallableSkipE extends Callable {
@Override
V call() throws Ex, ServletException, IOException, SkipPageException;
}
/**
* @param An arbitrary exception type that may be thrown
*/
// TODO: Ex extends Throwable
public static V newPageContextSkipE(
ServletContext newServletContext,
HttpServletRequest newRequest,
HttpServletResponse newResponse,
PageContextCallableSkipE target
) throws Ex, ServletException, IOException, SkipPageException {
final ServletContext oldServletContext = servletContext.get();
final HttpServletRequest oldRequest = request.get();
final HttpServletResponse oldResponse = response.get();
final PrintWriter oldOut = out.get();
PrintWriter newOut = null;
try {
if (newServletContext != oldServletContext) {
servletContext.set(newServletContext);
}
if (newRequest != oldRequest) {
request.set(newRequest);
}
if (newResponse != oldResponse) {
response.set(newResponse);
out.remove();
} else {
newOut = oldOut;
}
return target.call();
} finally {
if (newServletContext != oldServletContext) {
if (oldServletContext == null) {
servletContext.remove();
} else {
servletContext.set(oldServletContext);
}
}
if (newRequest != oldRequest) {
if (oldRequest == null) {
request.remove();
} else {
request.set(oldRequest);
}
}
if (newResponse != oldResponse) {
if (oldResponse == null) {
response.remove();
} else {
response.set(oldResponse);
}
}
if (newOut != oldOut) {
if (oldOut == null) {
out.remove();
} else {
out.set(oldOut);
}
}
}
}
@FunctionalInterface
public static interface PageContextRunnableSkipEE {
void run() throws Ex1, Ex2, ServletException, IOException, SkipPageException;
}
public static void newPageContextSkipEE(
ServletContext newServletContext,
HttpServletRequest newRequest,
HttpServletResponse newResponse,
PageContextRunnableSkipEE target
) throws Ex1, Ex2, ServletException, IOException, SkipPageException {
final ServletContext oldServletContext = servletContext.get();
final HttpServletRequest oldRequest = request.get();
final HttpServletResponse oldResponse = response.get();
final PrintWriter oldOut = out.get();
PrintWriter newOut = null;
try {
if (newServletContext != oldServletContext) {
servletContext.set(newServletContext);
}
if (newRequest != oldRequest) {
request.set(newRequest);
}
if (newResponse != oldResponse) {
response.set(newResponse);
out.remove();
} else {
newOut = oldOut;
}
target.run();
} finally {
if (newServletContext != oldServletContext) {
if (oldServletContext == null) {
servletContext.remove();
} else {
servletContext.set(oldServletContext);
}
}
if (newRequest != oldRequest) {
if (oldRequest == null) {
request.remove();
} else {
request.set(oldRequest);
}
}
if (newResponse != oldResponse) {
if (oldResponse == null) {
response.remove();
} else {
response.set(oldResponse);
}
}
if (newOut != oldOut) {
if (oldOut == null) {
out.remove();
} else {
out.set(oldOut);
}
}
}
}
@FunctionalInterface
public static interface PageContextCallableSkipEE extends Callable {
@Override
V call() throws Ex1, Ex2, ServletException, IOException, SkipPageException;
}
public static V newPageContextSkipEE(
ServletContext newServletContext,
HttpServletRequest newRequest,
HttpServletResponse newResponse,
PageContextCallableSkipEE target
) throws Ex1, Ex2, ServletException, IOException, SkipPageException {
final ServletContext oldServletContext = servletContext.get();
final HttpServletRequest oldRequest = request.get();
final HttpServletResponse oldResponse = response.get();
final PrintWriter oldOut = out.get();
PrintWriter newOut = null;
try {
if (newServletContext != oldServletContext) {
servletContext.set(newServletContext);
}
if (newRequest != oldRequest) {
request.set(newRequest);
}
if (newResponse != oldResponse) {
response.set(newResponse);
out.remove();
} else {
newOut = oldOut;
}
return target.call();
} finally {
if (newServletContext != oldServletContext) {
if (oldServletContext == null) {
servletContext.remove();
} else {
servletContext.set(oldServletContext);
}
}
if (newRequest != oldRequest) {
if (oldRequest == null) {
request.remove();
} else {
request.set(oldRequest);
}
}
if (newResponse != oldResponse) {
if (oldResponse == null) {
response.remove();
} else {
response.set(oldResponse);
}
}
if (newOut != oldOut) {
if (oldOut == null) {
out.remove();
} else {
out.set(oldOut);
}
}
}
}
/**
* Gets the current servlet context.
*
* @throws IllegalStateException if no context set
*/
public static ServletContext getServletContext() throws IllegalStateException {
ServletContext s = servletContext.get();
if (s == null) {
throw new IllegalStateException("No page context");
}
return s;
}
/**
* Gets the current request.
*
* @throws IllegalStateException if no context set
*/
public static HttpServletRequest getRequest() throws IllegalStateException {
HttpServletRequest r = request.get();
if (r == null) {
throw new IllegalStateException("No page context");
}
return r;
}
/**
* Gets the current response.
*
* @throws IllegalStateException if no context set
*/
public static HttpServletResponse getResponse() throws IllegalStateException {
HttpServletResponse r = response.get();
if (r == null) {
throw new IllegalStateException("No page context");
}
return r;
}
/**
* Gets the current response writer.
*
* @throws IllegalStateException if no context set
*/
public static PrintWriter getOut() throws IllegalStateException, IOException {
PrintWriter o = out.get();
if (o == null) {
o = getResponse().getWriter();
out.set(o);
}
return o;
}
}