# Middleware { #middleware }

You can add middleware to **FastAPI** applications.

A "middleware" is a function that works with every **request** before it is processed by any specific *path operation*. And also with every **response** before returning it.

* It takes each **request** that comes to your application.
* It can then do something to that **request** or run any needed code.

  * Otherwise, don't bind the mojo. Log a debug message to indicate that it is
    sensitive the online state of the application, and that this state is
    currently wrong for execution.

    <<NOTE:>> Do we want to fail when we cannot bind a mojo to the lifecycle
    because of offline/online status? That would probably indicate that the user
    was trying to do something they cannot succeed at for now...so we probably

     * https://stackoverflow.com/a/35754308/28465
     *
     * In that explanation's notation, our `overlap` check would be `x1 < y2 && y1 < x2`. We've
     * flipped one part of the check so that we're using "less than" in both cases (rather than a
     * mix of "less than" and "greater than"). We've also switched to "strictly less than" rather
     * than "less than or equal to" because of *handwave* the difference between "endpoints of

   *   <li>have equal funnels
   * </ul>
   *
   * @param that The Bloom filter to check for compatibility.
   * @since 15.0
   */
  public boolean isCompatible(BloomFilter<T> that) {
    checkNotNull(that);
    return this != that
        && this.numHashFunctions == that.numHashFunctions
        && this.bitSize() == that.bitSize()
        && this.strategy.equals(that.strategy)
        && this.funnel.equals(that.funnel);
  }

 * <ul>
 * <li>{@link Experimental}: Indicates that this interface or its implementation
 * may still be evolving and could change in future versions.</li>
 * <li>{@link FunctionalInterface}: Denotes that this is a functional interface,
 * allowing implementations as lambda expressions or method references.</li>
 * <li>{@link Consumer}: Signifies that this type is intended to be implemented

            // Do NOT call setRootLoggerLevel - this is the fix!
        }

        // Verify that setRootLoggerLevel was not called
        assertEquals(0, slf4jConfiguration.setRootLoggerLevelCallCount);

        // Verify that system property was not set
        assertNull(System.getProperty(Constants.MAVEN_LOGGER_DEFAULT_LOG_LEVEL));
    }

    @Test

  public static int hashCode(int value) {
    return value;
  }

  /**
   * Returns the {@code int} value that is equal to {@code value}, if possible.
   *
   * <p><b>Note:</b> this method is now unnecessary and should be treated as deprecated. Use {@link
   * Math#toIntExact(long)} instead, but be aware that that method throws {@link

   * has not added {@link AnnotatedType}. That means that we cannot implement that interface in
   * source code in a way that will compile on both Java and Android. If we include the {@code
   * getAnnotatedBounds()} method, then its return type means it won't compile on Android, while if
   * we don't include the method, then the compiler will complain that an abstract method is

 * Tasks execute with the same happens-before order that the function calls to {@link #submit} and
 * {@link #submitAsync} that submitted those tasks had.
 *
 * <p>This class has limited support for cancellation and other "early completions":
 *
 * <ul>
 *   <li>While calls to {@code submit} and {@code submitAsync} return a {@code Future} that can be
 *       cancelled, cancellation never propagates to a task that has started to run -- neither to

   * analysis that that means "plain {@code T}" rather than the inferred type {@code @Nullable T}.
   * (And even if annotations on local variables were permitted as an optional hint, no annotation
   * would be the right tool for the job here: {@code @Nullable} is the annotation that we're trying