at.ac.univie.isc.asio.spring.ContextPropagator.java Source code

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Here is the source code for at.ac.univie.isc.asio.spring.ContextPropagator.java

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/*
 * #%L
 * asio server
 * %%
 * Copyright (C) 2013 - 2015 Research Group Scientific Computing, University of Vienna
 * %%
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * #L%
 */
package at.ac.univie.isc.asio.spring;

import at.ac.univie.isc.asio.Scope;
import at.ac.univie.isc.asio.tool.Pretty;
import org.slf4j.Logger;
import org.springframework.web.context.request.RequestAttributes;
import org.springframework.web.context.request.RequestContextHolder;

import static org.slf4j.LoggerFactory.getLogger;

/**
 * Store a spring request context and allow publishing it on another thread.
 */
public final class ContextPropagator implements AutoCloseable {
    private static final Logger log = getLogger(ContextPropagator.class);

    /**
     * Create a propagator, which stores the context of the current thread, as retrieved from
     * {@link RequestContextHolder#currentRequestAttributes()}.
     */
    public static ContextPropagator capture() {
        final Thread thread = Thread.currentThread();
        log.debug(Scope.SYSTEM.marker(), "capturing context of {}", thread);
        return new ContextPropagator(RequestContextHolder.currentRequestAttributes(), thread);
    }

    private final RequestAttributes stored;
    private final Thread origin;

    ContextPropagator(final RequestAttributes attributes, final Thread origin) {
        stored = attributes;
        this.origin = origin;
    }

    /**
     * Set the stored context as the current thread's local context.
     */
    public ContextPropagator publish() {
        final Thread current = Thread.currentThread();
        if (current == origin) {
            log.warn(Scope.SYSTEM.marker(), "publishing context to origin {} again", origin);
        } else {
            log.debug(Scope.SYSTEM.marker(), "publishing context from {} to {}", origin, current);
        }
        RequestContextHolder.setRequestAttributes(stored);
        return this;
    }

    /**
     * Clear the context, which has been previously published to the current thread.
     */
    @Override
    public void close() {
        final RequestAttributes attributes = RequestContextHolder.getRequestAttributes();
        if (attributes == null) {
            fail(Pretty.format("cannot clear context of %s - none present", Thread.currentThread()));
        } else if (attributes != stored) {
            fail(Pretty.format("cannot clear context of %s - attributes not published by this propagator (%s)",
                    Thread.currentThread(), this));
        } else {
            log.debug(Scope.SYSTEM.marker(), "clearing context of {}", Thread.currentThread());
            RequestContextHolder.resetRequestAttributes();
        }
    }

    private void fail(final String message) {
        log.error(Scope.SYSTEM.marker(), message);
        throw new IllegalStateException(message);
    }

    @Override
    public String toString() {
        return "ContextPropagator{" + ", origin=" + origin + '}';
    }

    /**
     * for testing
     */
    RequestAttributes getStoredAttributes() {
        return stored;
    }
}