## Official Guide { #official-guide }

Pydantic has an official [Migration Guide](https://docs.pydantic.dev/latest/migration/) from v1 to v2.

It also includes what has changed, how validations are now more correct and strict, possible caveats, etc.

You can read it to understand better what has changed.

## Tests { #tests }

Make sure you have [tests](../tutorial/testing.md) for your app and you run them on continuous integration (CI).

 *  Fix: Don't throw when converting an `HttpUrl` to a `java.net.URI`.
    Previously URLs with special characters like `|` and `[` would break when
    subjected to URI’s overly-strict validation.
 *  Fix: Don't re-encode `+` as `%20` in encoded URL query strings. OkHttp
    prefers `%20` when doing its own encoding, but will retain `+` when that is
    provided.

    know that it is application specific, it's not part of the specification.


    grant_type: the OAuth2 spec says it is required and MUST be the fixed string "password".
        This dependency is strict about it. If you want to be permissive, use instead the
        OAuth2PasswordRequestForm dependency class.
    username: username string. The OAuth2 spec requires the exact field name "username".

Bedenken Sie, dass Datenklassen nicht alles können, was Pydantic-Modelle können.

Daher müssen Sie möglicherweise weiterhin Pydantic-Modelle verwenden.

Wenn Sie jedoch eine Menge Datenklassen herumliegen haben, ist dies ein guter Trick, um sie für eine Web-API mithilfe von FastAPI zu verwenden. 🤓

///

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

Sie können `dataclasses` auch im Parameter `response_model` verwenden:

/// 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:

                alreadyEncoded = true,
                strict = true,
                plusIsSpace = true,
              )
          }
        }

        encodedFragment =
          encodedFragment?.canonicalize(
            encodeSet = FRAGMENT_ENCODE_SET_URI,
            alreadyEncoded = true,
            strict = true,
            unicodeAllowed = true,
          )
      }

        this.revision = revision;
        this.qualifier = qualifier == null ? null : Qualifier.of(qualifier);
    }

    /**
     * Parses the supplied string into an object.
     * @param s a version string in strict semver
     * @return a new instance
     */
    public static QualifiedVersion of(final String s) {
        Objects.requireNonNull(s);
        Matcher matcher = pattern.matcher(s);

            )
        return block_a["content"].copy()  # We don't handle mermaid code blocks for now

    code_block: list[str] = []
    for line_a, line_b in zip(block_a["content"], block_b["content"], strict=False):
        line_a_comment: str | None = None
        line_b_comment: str | None = None

        # Handle comments based on language
        if block_language in {
            "python",
            "py",

application/pagemaker          pm5 pt5 pm       # PageMaker
application/pdf                pdf              # Adobe Acrobat
application/postscript         ai eps ps        # Postscript File
application/rtf                rtf              # Rich Text File
application/toolbook           tbk              # Toolbook
application/wordperfect        wp               # WordPerfect
application/wordperfect5.1     wp5              # WordPerfect Version 5.1

import java.util.ArrayList;
import java.util.List;

/**
 * Signals one or more errors during settings building. The settings builder tries to collect as many problems as
 * possible before eventually failing to provide callers with rich error information. Use {@link #getProblems()} to
 * query the details of the failure.
 *
 * @deprecated since 4.0.0, use {@link org.apache.maven.api.services.SettingsBuilder} instead
 */
@Deprecated(since = "4.0.0")