/// info

Keep in mind that dataclasses can't do everything Pydantic models can do.

So, you might still need to use Pydantic models.

But if you have a bunch of dataclasses laying around, this is a nice trick to use them to power a web API using FastAPI. 🤓

///

## Dataclasses in `response_model` { #dataclasses-in-response-model }

You can also use `dataclasses` in the `response_model` parameter:

| `minio_node_cpu_avg_iowait_max`      | CPU ioWait time (max).                     |
| `minio_node_cpu_avg_nice`            | CPU nice time.                             |
| `minio_node_cpu_avg_nice_avg`        | CPU nice time (avg).                       |
| `minio_node_cpu_avg_nice_max`        | CPU nice time (max).                       |
| `minio_node_cpu_avg_steal`           | CPU steam time.                            |

With just that Python type declaration, **FastAPI** will:

* Read the body of the request as JSON.
* Convert the corresponding types (if needed).
* Validate the data.
    * If the data is invalid, it will return a nice and clear error, indicating exactly where and what was the incorrect data.
* Give you the received data in the parameter `item`.

   *     the size method
   */
  public static <T extends @Nullable Object> Collection<T> misleadingSizeCollection(int delta) {
    // It would be nice to be able to return a real concurrent
    // collection like ConcurrentLinkedQueue, so that e.g. concurrent
    // iteration would work, but that would not be GWT-compatible.

///

## Data validation { #data-validation }

But if you go to the browser at <a href="http://127.0.0.1:8000/items/foo" class="external-link" target="_blank">http://127.0.0.1:8000/items/foo</a>, you will see a nice HTTP error of:

```JSON
{
  "detail": [
    {
      "type": "int_parsing",
      "loc": [
        "path",
        "item_id"
      ],

      <activation>
        <property>
          <name>surefire.toolchain.version</name>
          <!-- the value provided by GitHub CI (which maybe we could even change, but supporting "8" seems nice for any users who try pass that value manually) -->
          <value>8</value>
        </property>
      </activation>
      <properties>
        <test.add.opens></test.add.opens>
      </properties>

      <activation>
        <property>
          <name>surefire.toolchain.version</name>
          <!-- the value provided by GitHub CI (which maybe we could even change, but supporting "8" seems nice for any users who try pass that value manually) -->
          <value>8</value>
        </property>
      </activation>
      <properties>
        <test.add.opens></test.add.opens>
      </properties>

         * unlikely that cancel() will be slow, so we can probably get away with calling it while
         * holding a lock. Still, it would be nice to avoid somehow.
         */
        lock.lock();
        try {
          currentFuture.cancel(mayInterruptIfRunning);
        } finally {
          lock.unlock();
        }
      }

         * unlikely that cancel() will be slow, so we can probably get away with calling it while
         * holding a lock. Still, it would be nice to avoid somehow.
         */
        lock.lock();
        try {
          currentFuture.cancel(mayInterruptIfRunning);
        } finally {
          lock.unlock();
        }
      }

 * but if it claims that an element is <i>not</i> contained in it, then this is definitely true.
 *
 * <p>If you are unfamiliar with Bloom filters, this nice <a
 * href="http://llimllib.github.io/bloomfilter-tutorial/">tutorial</a> may help you understand how
 * they work.
 *
 * <p>The false positive probability ({@code FPP}) of a Bloom filter is defined as the probability