# Extending OpenAPI { #extending-openapi }

There are some cases where you might need to modify the generated OpenAPI schema.

In this section you will see how.

## The normal process { #the-normal-process }

The normal (default) process, is as follows.

A `FastAPI` application (instance) has an `.openapi()` method that is expected to return the OpenAPI schema.

### Raise exceptions { #raise-exceptions }

These dependencies can `raise` exceptions, the same as normal dependencies:

{* ../../docs_src/dependencies/tutorial006_an_py310.py hl[10,15] *}

### Return values { #return-values }

And they can return values or not, the values won't be used.

  static final int SIGNIFICAND_BITS = 52;

  static final int EXPONENT_BIAS = 1023;

  /** The implicit 1 bit that is omitted in significands of normal doubles. */
  static final long IMPLICIT_BIT = SIGNIFICAND_MASK + 1;

  static long getSignificand(double d) {
    checkArgument(isFinite(d), "not a normal value");
    int exponent = getExponent(d);
    long bits = doubleToRawLongBits(d);
    bits &= SIGNIFICAND_MASK;

    }
  }

  @Test
  fun upgradesOnReusedConnection() {
    server.enqueue(MockResponse(body = "normal request"))
    client.newCall(Request(server.url("/"))).execute().use { response ->
      assertThat(response.body.string()).isEqualTo("normal request")
    }

    upgrade()

    assertThat(server.takeRequest().connectionIndex).isEqualTo(0)

import org.codehaus.plexus.classworlds.ClassWorld;

/**
 * Maven upgrade CLI "new-gen".
 */
public class MavenUpCling extends ClingSupport {
    /**
     * "Normal" Java entry point. Note: Maven uses ClassWorld Launcher and this entry point is NOT used under normal
     * circumstances.
     */
    public static void main(String[] args) throws IOException {
        int exitCode = new MavenUpCling().run(args, null, null, null, false);

Cache Events are exposed via the EventListener API.  Typical scenarios are below.

### Cache Hit

In the ideal scenario the cache can fulfill the request without any conditional call to the network.
This will skip the normal events such as DNS, connecting to the network, and downloading the response body.

As recommended by the HTTP RFC the max age of a document is defaulted to 10% of the

## The normal **FastAPI** app { #the-normal-fastapi-app }

Let's first see how the normal API app would look like before adding the callback.

It will have a *path operation* that will receive an `Invoice` body, and a query parameter `callback_url` that will contain the URL for the callback.

This part is pretty normal, most of the code is probably already familiar to you:

        LdapManager ldapManager = new LdapManager();
        ldapManager.init();

        // Edge cases
        assertEquals("", ldapManager.replaceWithUnderscores(""));
        assertEquals("normal", ldapManager.replaceWithUnderscores("normal"));
        // Input "//\\[]:;" has 8 special characters that should be replaced
        assertEquals("________", ldapManager.replaceWithUnderscores("//\\\\[]:;"));
    }

        }
        Path normal = Paths.get(javahome.getValue()).normalize();
        if (Files.exists(normal)) {
            jtc.setJavaHome(Paths.get(javahome.getValue()).normalize().toString());
        } else {
            throw new MisconfiguredToolchainException(
                    "Non-existing JDK home configuration at " + normal.toAbsolutePath());
        }

        return jtc;
    }

# 擴充 OpenAPI { #extending-openapi }

有些情況你可能需要修改自動產生的 OpenAPI 結構（schema）。

本章將示範如何做。

## 一般流程 { #the-normal-process }

一般（預設）的流程如下。

`FastAPI` 應用程式（實例）有一個 `.openapi()` 方法，會回傳 OpenAPI 結構。

在建立應用物件時，會同時註冊一個 `/openapi.json`（或你在 `openapi_url` 設定的路徑）的路徑操作（path operation）。

這個路徑只會回傳一個 JSON 回應，內容就是應用的 `.openapi()` 方法結果。

預設情況下，`.openapi()` 會先檢查 `.openapi_schema` 屬性是否已有內容，有的話就直接回傳。