/*
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* Copyright 2002-2023 the original author or authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* https://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package org.springframework.web.context.request;
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import com.alibaba.ttl.TransmittableThreadLocal;
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import jakarta.faces.context.FacesContext;
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import org.springframework.lang.Nullable;
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import org.springframework.util.ClassUtils;
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/**
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* Holder class to expose the web request in the form of a thread-bound
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* {@link RequestAttributes} object. The request will be inherited
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* by any child threads spawned by the current thread if the
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* {@code inheritable} flag is set to {@code true}.
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*
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* <p>Use {@link RequestContextListener} or
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* {@link org.springframework.web.filter.RequestContextFilter} to expose
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* the current web request. Note that
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* already exposes the current request by default.
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*
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* 修改 spring 上下文存储方式 将 ThreadLocal 替换为 TransmittableThreadLocal
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* 支持线程上下文切换变量传递 异步获取 spring 上下文
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*
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* @author Juergen Hoeller
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* @author Rod Johnson
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* @since 2.0
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* @see RequestContextListener
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* @see org.springframework.web.filter.RequestContextFilter
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*/
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public abstract class RequestContextHolder {
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private static final boolean jsfPresent =
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ClassUtils.isPresent("jakarta.faces.context.FacesContext", RequestContextHolder.class.getClassLoader());
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// ThreadLocal 替换为 TransmittableThreadLocal
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private static final ThreadLocal<RequestAttributes> requestAttributesHolder =
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new TransmittableThreadLocal<>();
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private static final ThreadLocal<RequestAttributes> inheritableRequestAttributesHolder =
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new TransmittableThreadLocal<>();
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/**
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* Reset the RequestAttributes for the current thread.
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*/
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public static void resetRequestAttributes() {
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requestAttributesHolder.remove();
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inheritableRequestAttributesHolder.remove();
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}
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/**
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* Bind the given RequestAttributes to the current thread,
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* <i>not</i> exposing it as inheritable for child threads.
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* @param attributes the RequestAttributes to expose
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* @see #setRequestAttributes(RequestAttributes, boolean)
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*/
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public static void setRequestAttributes(@Nullable RequestAttributes attributes) {
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setRequestAttributes(attributes, false);
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}
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/**
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* Bind the given RequestAttributes to the current thread.
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* @param attributes the RequestAttributes to expose,
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* or {@code null} to reset the thread-bound context
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* @param inheritable whether to expose the RequestAttributes as inheritable
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* for child threads (using an {@link InheritableThreadLocal})
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*/
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public static void setRequestAttributes(@Nullable RequestAttributes attributes, boolean inheritable) {
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if (attributes == null) {
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resetRequestAttributes();
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}
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else {
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if (inheritable) {
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inheritableRequestAttributesHolder.set(attributes);
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requestAttributesHolder.remove();
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}
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else {
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requestAttributesHolder.set(attributes);
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inheritableRequestAttributesHolder.remove();
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}
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}
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}
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/**
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* Return the RequestAttributes currently bound to the thread.
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* @return the RequestAttributes currently bound to the thread,
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* or {@code null} if none bound
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*/
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@Nullable
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public static RequestAttributes getRequestAttributes() {
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RequestAttributes attributes = requestAttributesHolder.get();
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if (attributes == null) {
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attributes = inheritableRequestAttributesHolder.get();
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}
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return attributes;
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}
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/**
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* Return the RequestAttributes currently bound to the thread.
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* <p>Exposes the previously bound RequestAttributes instance, if any.
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* Falls back to the current JSF FacesContext, if any.
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* @return the RequestAttributes currently bound to the thread
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* @throws IllegalStateException if no RequestAttributes object
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* is bound to the current thread
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* @see #setRequestAttributes
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* @see ServletRequestAttributes
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* @see FacesRequestAttributes
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* @see jakarta.faces.context.FacesContext#getCurrentInstance()
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*/
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public static RequestAttributes currentRequestAttributes() throws IllegalStateException {
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RequestAttributes attributes = getRequestAttributes();
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if (attributes == null) {
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if (jsfPresent) {
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attributes = FacesRequestAttributesFactory.getFacesRequestAttributes();
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}
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if (attributes == null) {
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throw new IllegalStateException("No thread-bound request found: " +
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"Are you referring to request attributes outside of an actual web request, " +
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"or processing a request outside of the originally receiving thread? " +
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"If you are actually operating within a web request and still receive this message, " +
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"your code is probably running outside of DispatcherServlet: " +
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"In this case, use RequestContextListener or RequestContextFilter to expose the current request.");
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}
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}
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return attributes;
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}
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/**
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* Inner class to avoid hard-coded JSF dependency.
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*/
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private static class FacesRequestAttributesFactory {
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@Nullable
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public static RequestAttributes getFacesRequestAttributes() {
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try {
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FacesContext facesContext = FacesContext.getCurrentInstance();
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return (facesContext != null ? new FacesRequestAttributes(facesContext) : null);
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}
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catch (NoClassDefFoundError err) {
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// typically for com/sun/faces/util/Util if only the JSF API jar is present
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return null;
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}
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}
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}
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}
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