By default, **FastAPI** would automatically convert that return value to JSON using the `jsonable_encoder` explained in [JSON Compatible Encoder](../tutorial/encoder.md){.internal-link target=_blank}.

/// tip

For new code and whenever possible, use `Annotated` as explained above. There are multiple advantages (explained below) and no disadvantages. 🍰

///

Because of that, it's now recommended to instead use the `lifespan` as explained above.

## Technical Details { #technical-details }

Just a technical detail for the curious nerds. 🤓

 * which contained the following notice:
 *
 * Written by Doug Lea with assistance from members of JCP JSR-166
 * Expert Group and released to the public domain, as explained at
 * http://creativecommons.org/publicdomain/zero/1.0/
 * Other contributors include Andrew Wright, Jeffrey Hayes,
 * Pat Fisher, Mike Judd.
 */

package com.google.common.util.concurrent;

### Return a Response Directly { #return-a-response-directly }

The most common case would be [returning a Response directly as explained later in the advanced docs](../advanced/response-directly.md){.internal-link target=_blank}.

{* ../../docs_src/response_model/tutorial003_02_py39.py hl[8,10:11] *}

This is because by default, FastAPI will inspect every item inside and make sure it is serializable as JSON, using the same [JSON Compatible Encoder](../tutorial/encoder.md){.internal-link target=_blank} explained in the tutorial. This is what allows you to return **arbitrary objects**, for example database models.

 * which contained the following notice:
 *
 * Written by Doug Lea with assistance from members of JCP JSR-166
 * Expert Group and released to the public domain, as explained at
 * http://creativecommons.org/publicdomain/zero/1.0/
 * Other contributors include Andrew Wright, Jeffrey Hayes,
 * Pat Fisher, Mike Judd.
 */

package com.google.common.util.concurrent;

 * Comparable#compareTo} or {@link Comparator#compare} instead of {@link Object#equals} to determine
 * equivalence of instances.
 *
 * <p><b>Warning:</b> The comparison must be <i>consistent with equals</i> as explained by the
 * {@link Comparable} class specification. Otherwise, the resulting multiset will violate the {@link
 * java.util.Collection} contract, which is specified in terms of {@link Object#equals}.
 *

/*
 * Written by Doug Lea with assistance from members of JCP JSR-166
 * Expert Group and released to the public domain, as explained at
 * http://creativecommons.org/publicdomain/zero/1.0/
 * Other contributors include Andrew Wright, Jeffrey Hayes,
 * Pat Fisher, Mike Judd.
 */

/*
 * Source:
 * http://gee.cs.oswego.edu/cgi-bin/viewcvs.cgi/jsr166/src/test/tck/JSR166TestCase.java?revision=1.90

 * Comparable#compareTo} or {@link Comparator#compare} instead of {@link Object#equals} to determine
 * equivalence of instances.
 *
 * <p><b>Warning:</b> The comparison must be <i>consistent with equals</i> as explained by the
 * {@link Comparable} class specification. Otherwise, the resulting multiset will violate the {@link
 * java.util.Collection} contract, which is specified in terms of {@link Object#equals}.
 *